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uWSGI log file...permission denied to read file

- by bkev

I have a server running Django/Nginx/uWSGI with uWSGI in emperor mode, and the error log for it (the vassal-level error log, not the emperor-level log) has a continual permissions error every time it spawns a new worker, like so: Tue Jun 26 19:34:55 2012 - Respawned uWSGI worker 2 (new pid: 9334) Error opening file for reading: Permission denied Problem is, I don't know what file it's having trouble opening; it's not the log file, obviously, since I'm looking at it and it's writing to that without issue. Any way to find out? I'm running the apt-get version of uWSGI 1.0.3-debian through Upstart on Ubuntu 12.04. The site is working successfully, aside from what seems like a memory leak...hence my looking at the log file. My Upstart conf file description "uWSGI" start on runlevel [2345] stop on runlevel [06] respawn env UWSGI=/usr/bin/uwsgi env LOGTO=/var/log/uwsgi/emperor.log exec $UWSGI \ --master \ --emperor /etc/uwsgi/vassals \ --die-on-term \ --auto-procname \ --no-orphans \ --logto $LOGTO \ --logdate My Vassal ini file: [uwsgi] # Variables base = /srv/env/mysiteenv # Generic Config uid = uwsgi gid = uwsgi socket = 127.0.0.1:5050 master = true processes = 2 reload-on-as = 128 harakiri = 60 harakiri-verbose = true auto-procname = true plugins = http,python cache = 2000 home = %(base) pythonpath = %(base)/mysite module = wsgi logto = /srv/log/mysite/uwsgi_error.log logdate = true

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The Incremental Architect’s Napkin - #5 - Design functions for extensibility and readability

- by Ralf Westphal

Originally posted on: http://geekswithblogs.net/theArchitectsNapkin/archive/2014/08/24/the-incremental-architectrsquos-napkin---5---design-functions-for.aspx The functionality of programs is entered via Entry Points. So what we´re talking about when designing software is a bunch of functions handling the requests represented by and flowing in through those Entry Points. Designing software thus consists of at least three phases: Analyzing the requirements to find the Entry Points and their signatures Designing the functionality to be executed when those Entry Points get triggered Implementing the functionality according to the design aka coding I presume, you´re familiar with phase 1 in some way. And I guess you´re proficient in implementing functionality in some programming language. But in my experience developers in general are not experienced in going through an explicit phase 2. “Designing functionality? What´s that supposed to mean?” you might already have thought. Here´s my definition: To design functionality (or functional design for short) means thinking about… well, functions. You find a solution for what´s supposed to happen when an Entry Point gets triggered in terms of functions. A conceptual solution that is, because those functions only exist in your head (or on paper) during this phase. But you may have guess that, because it´s “design” not “coding”. And here is, what functional design is not: It´s not about logic. Logic is expressions (e.g. +, -, && etc.) and control statements (e.g. if, switch, for, while etc.). Also I consider calling external APIs as logic. It´s equally basic. It´s what code needs to do in order to deliver some functionality or quality. Logic is what´s doing that needs to be done by software. Transformations are either done through expressions or API-calls. And then there is alternative control flow depending on the result of some expression. Basically it´s just jumps in Assembler, sometimes to go forward (if, switch), sometimes to go backward (for, while, do). But calling your own function is not logic. It´s not necessary to produce any outcome. Functionality is not enhanced by adding functions (subroutine calls) to your code. Nor is quality increased by adding functions. No performance gain, no higher scalability etc. through functions. Functions are not relevant to functionality. Strange, isn´t it. What they are important for is security of investment. By introducing functions into our code we can become more productive (re-use) and can increase evolvability (higher unterstandability, easier to keep code consistent). That´s no small feat, however. Evolvable code can hardly be overestimated. That´s why to me functional design is so important. It´s at the core of software development. To sum this up: Functional design is on a level of abstraction above (!) logical design or algorithmic design. Functional design is only done until you get to a point where each function is so simple you are very confident you can easily code it. Functional design an logical design (which mostly is coding, but can also be done using pseudo code or flow charts) are complementary. Software needs both. If you start coding right away you end up in a tangled mess very quickly. Then you need back out through refactoring. Functional design on the other hand is bloodless without actual code. It´s just a theory with no experiments to prove it. But how to do functional design? An example of functional design Let´s assume a program to de-duplicate strings. The user enters a number of strings separated by commas, e.g. a, b, a, c, d, b, e, c, a. And the program is supposed to clear this list of all doubles, e.g. a, b, c, d, e. There is only one Entry Point to this program: the user triggers the de-duplication by starting the program with the string list on the command line C:\>deduplicate "a, b, a, c, d, b, e, c, a" a, b, c, d, e …or by clicking on a GUI button. This leads to the Entry Point function to get called. It´s the program´s main function in case of the batch version or a button click event handler in the GUI version. That´s the physical Entry Point so to speak. It´s inevitable. What then happens is a three step process: Transform the input data from the user into a request. Call the request handler. Transform the output of the request handler into a tangible result for the user. Or to phrase it a bit more generally: Accept input. Transform input into output. Present output. This does not mean any of these steps requires a lot of effort. Maybe it´s just one line of code to accomplish it. Nevertheless it´s a distinct step in doing the processing behind an Entry Point. Call it an aspect or a responsibility - and you will realize it most likely deserves a function of its own to satisfy the Single Responsibility Principle (SRP). Interestingly the above list of steps is already functional design. There is no logic, but nevertheless the solution is described - albeit on a higher level of abstraction than you might have done yourself. But it´s still on a meta-level. The application to the domain at hand is easy, though: Accept string list from command line De-duplicate Present de-duplicated strings on standard output And this concrete list of processing steps can easily be transformed into code:static void Main(string[] args) { var input = Accept_string_list(args); var output = Deduplicate(input); Present_deduplicated_string_list(output); } Instead of a big problem there are three much smaller problems now. If you think each of those is trivial to implement, then go for it. You can stop the functional design at this point. But maybe, just maybe, you´re not so sure how to go about with the de-duplication for example. Then just implement what´s easy right now, e.g.private static string Accept_string_list(string[] args) { return args[0]; } private static void Present_deduplicated_string_list( string[] output) { var line = string.Join(", ", output); Console.WriteLine(line); } Accept_string_list() contains logic in the form of an API-call. Present_deduplicated_string_list() contains logic in the form of an expression and an API-call. And then repeat the functional design for the remaining processing step. What´s left is the domain logic: de-duplicating a list of strings. How should that be done? Without any logic at our disposal during functional design you´re left with just functions. So which functions could make up the de-duplication? Here´s a suggestion: De-duplicate Parse the input string into a true list of strings. Register each string in a dictionary/map/set. That way duplicates get cast away. Transform the data structure into a list of unique strings. Processing step 2 obviously was the core of the solution. That´s where real creativity was needed. That´s the core of the domain. But now after this refinement the implementation of each step is easy again:private static string[] Parse_string_list(string input) { return input.Split(',') .Select(s => s.Trim()) .ToArray(); } private static Dictionary<string,object> Compile_unique_strings(string[] strings) { return strings.Aggregate( new Dictionary<string, object>(), (agg, s) => { agg[s] = null; return agg; }); } private static string[] Serialize_unique_strings( Dictionary<string,object> dict) { return dict.Keys.ToArray(); } With these three additional functions Main() now looks like this:static void Main(string[] args) { var input = Accept_string_list(args); var strings = Parse_string_list(input); var dict = Compile_unique_strings(strings); var output = Serialize_unique_strings(dict); Present_deduplicated_string_list(output); } I think that´s very understandable code: just read it from top to bottom and you know how the solution to the problem works. It´s a mirror image of the initial design: Accept string list from command line Parse the input string into a true list of strings. Register each string in a dictionary/map/set. That way duplicates get cast away. Transform the data structure into a list of unique strings. Present de-duplicated strings on standard output You can even re-generate the design by just looking at the code. Code and functional design thus are always in sync - if you follow some simple rules. But about that later. And as a bonus: all the functions making up the process are small - which means easy to understand, too. So much for an initial concrete example. Now it´s time for some theory. Because there is method to this madness ;-) The above has only scratched the surface. Introducing Flow Design Functional design starts with a given function, the Entry Point. Its goal is to describe the behavior of the program when the Entry Point is triggered using a process, not an algorithm. An algorithm consists of logic, a process on the other hand consists just of steps or stages. Each processing step transforms input into output or a side effect. Also it might access resources, e.g. a printer, a database, or just memory. Processing steps thus can rely on state of some sort. This is different from Functional Programming, where functions are supposed to not be stateful and not cause side effects.[1] In its simplest form a process can be written as a bullet point list of steps, e.g. Get data from user Output result to user Transform data Parse data Map result for output Such a compilation of steps - possibly on different levels of abstraction - often is the first artifact of functional design. It can be generated by a team in an initial design brainstorming. Next comes ordering the steps. What should happen first, what next etc.? Get data from user Parse data Transform data Map result for output Output result to user That´s great for a start into functional design. It´s better than starting to code right away on a given function using TDD. Please get me right: TDD is a valuable practice. But it can be unnecessarily hard if the scope of a functionn is too large. But how do you know beforehand without investing some thinking? And how to do this thinking in a systematic fashion? My recommendation: For any given function you´re supposed to implement first do a functional design. Then, once you´re confident you know the processing steps - which are pretty small - refine and code them using TDD. You´ll see that´s much, much easier - and leads to cleaner code right away. For more information on this approach I call “Informed TDD” read my book of the same title. Thinking before coding is smart. And writing down the solution as a bunch of functions possibly is the simplest thing you can do, I´d say. It´s more according to the KISS (Keep It Simple, Stupid) principle than returning constants or other trivial stuff TDD development often is started with. So far so good. A simple ordered list of processing steps will do to start with functional design. As shown in the above example such steps can easily be translated into functions. Moving from design to coding thus is simple. However, such a list does not scale. Processing is not always that simple to be captured in a list. And then the list is just text. Again. Like code. That means the design is lacking visuality. Textual representations need more parsing by your brain than visual representations. Plus they are limited in their “dimensionality”: text just has one dimension, it´s sequential. Alternatives and parallelism are hard to encode in text. In addition the functional design using numbered lists lacks data. It´s not visible what´s the input, output, and state of the processing steps. That´s why functional design should be done using a lightweight visual notation. No tool is necessary to draw such designs. Use pen and paper; a flipchart, a whiteboard, or even a napkin is sufficient. Visualizing processes The building block of the functional design notation is a functional unit. I mostly draw it like this: Something is done, it´s clear what goes in, it´s clear what comes out, and it´s clear what the processing step requires in terms of state or hardware. Whenever input flows into a functional unit it gets processed and output is produced and/or a side effect occurs. Flowing data is the driver of something happening. That´s why I call this approach to functional design Flow Design. It´s about data flow instead of control flow. Control flow like in algorithms is of no concern to functional design. Thinking about control flow simply is too low level. Once you start with control flow you easily get bogged down by tons of details. That´s what you want to avoid during design. Design is supposed to be quick, broad brush, abstract. It should give overview. But what about all the details? As Robert C. Martin rightly said: “Programming is abot detail”. Detail is a matter of code. Once you start coding the processing steps you designed you can worry about all the detail you want. Functional design does not eliminate all the nitty gritty. It just postpones tackling them. To me that´s also an example of the SRP. Function design has the responsibility to come up with a solution to a problem posed by a single function (Entry Point). And later coding has the responsibility to implement the solution down to the last detail (i.e. statement, API-call). TDD unfortunately mixes both responsibilities. It´s just coding - and thereby trying to find detailed implementations (green phase) plus getting the design right (refactoring). To me that´s one reason why TDD has failed to deliver on its promise for many developers. Using functional units as building blocks of functional design processes can be depicted very easily. Here´s the initial process for the example problem: For each processing step draw a functional unit and label it. Choose a verb or an “action phrase” as a label, not a noun. Functional design is about activities, not state or structure. Then make the output of an upstream step the input of a downstream step. Finally think about the data that should flow between the functional units. Write the data above the arrows connecting the functional units in the direction of the data flow. Enclose the data description in brackets. That way you can clearly see if all flows have already been specified. Empty brackets mean “no data is flowing”, but nevertheless a signal is sent. A name like “list” or “strings” in brackets describes the data content. Use lower case labels for that purpose. A name starting with an upper case letter like “String” or “Customer” on the other hand signifies a data type. If you like, you also can combine descriptions with data types by separating them with a colon, e.g. (list:string) or (strings:string[]). But these are just suggestions from my practice with Flow Design. You can do it differently, if you like. Just be sure to be consistent. Flows wired-up in this manner I call one-dimensional (1D). Each functional unit just has one input and/or one output. A functional unit without an output is possible. It´s like a black hole sucking up input without producing any output. Instead it produces side effects. A functional unit without an input, though, does make much sense. When should it start to work? What´s the trigger? That´s why in the above process even the first processing step has an input. If you like, view such 1D-flows as pipelines. Data is flowing through them from left to right. But as you can see, it´s not always the same data. It get´s transformed along its passage: (args) becomes a (list) which is turned into (strings). The Principle of Mutual Oblivion A very characteristic trait of flows put together from function units is: no functional units knows another one. They are all completely independent of each other. Functional units don´t know where their input is coming from (or even when it´s gonna arrive). They just specify a range of values they can process. And they promise a certain behavior upon input arriving. Also they don´t know where their output is going. They just produce it in their own time independent of other functional units. That means at least conceptually all functional units work in parallel. Functional units don´t know their “deployment context”. They now nothing about the overall flow they are place in. They are just consuming input from some upstream, and producing output for some downstream. That makes functional units very easy to test. At least as long as they don´t depend on state or resources. I call this the Principle of Mutual Oblivion (PoMO). Functional units are oblivious of others as well as an overall context/purpose. They are just parts of a whole focused on a single responsibility. How the whole is built, how a larger goal is achieved, is of no concern to the single functional units. By building software in such a manner, functional design interestingly follows nature. Nature´s building blocks for organisms also follow the PoMO. The cells forming your body do not know each other. Take a nerve cell “controlling” a muscle cell for example:[2] The nerve cell does not know anything about muscle cells, let alone the specific muscel cell it is “attached to”. Likewise the muscle cell does not know anything about nerve cells, let a lone a specific nerve cell “attached to” it. Saying “the nerve cell is controlling the muscle cell” thus only makes sense when viewing both from the outside. “Control” is a concept of the whole, not of its parts. Control is created by wiring-up parts in a certain way. Both cells are mutually oblivious. Both just follow a contract. One produces Acetylcholine (ACh) as output, the other consumes ACh as input. Where the ACh is going, where it´s coming from neither cell cares about. Million years of evolution have led to this kind of division of labor. And million years of evolution have produced organism designs (DNA) which lead to the production of these different cell types (and many others) and also to their co-location. The result: the overall behavior of an organism. How and why this happened in nature is a mystery. For our software, though, it´s clear: functional and quality requirements needs to be fulfilled. So we as developers have to become “intelligent designers” of “software cells” which we put together to form a “software organism” which responds in satisfying ways to triggers from it´s environment. My bet is: If nature gets complex organisms working by following the PoMO, who are we to not apply this recipe for success to our much simpler “machines”? So my rule is: Wherever there is functionality to be delivered, because there is a clear Entry Point into software, design the functionality like nature would do it. Build it from mutually oblivious functional units. That´s what Flow Design is about. In that way it´s even universal, I´d say. Its notation can also be applied to biology: Never mind labeling the functional units with nouns. That´s ok in Flow Design. You´ll do that occassionally for functional units on a higher level of abstraction or when their purpose is close to hardware. Getting a cockroach to roam your bedroom takes 1,000,000 nerve cells (neurons). Getting the de-duplication program to do its job just takes 5 “software cells” (functional units). Both, though, follow the same basic principle. Translating functional units into code Moving from functional design to code is no rocket science. In fact it´s straightforward. There are two simple rules: Translate an input port to a function. Translate an output port either to a return statement in that function or to a function pointer visible to that function. The simplest translation of a functional unit is a function. That´s what you saw in the above example. Functions are mutually oblivious. That why Functional Programming likes them so much. It makes them composable. Which is the reason, nature works according to the PoMO. Let´s be clear about one thing: There is no dependency injection in nature. For all of an organism´s complexity no DI container is used. Behavior is the result of smooth cooperation between mutually oblivious building blocks. Functions will often be the adequate translation for the functional units in your designs. But not always. Take for example the case, where a processing step should not always produce an output. Maybe the purpose is to filter input. Here the functional unit consumes words and produces words. But it does not pass along every word flowing in. Some words are swallowed. Think of a spell checker. It probably should not check acronyms for correctness. There are too many of them. Or words with no more than two letters. Such words are called “stop words”. In the above picture the optionality of the output is signified by the astrisk outside the brackets. It means: Any number of (word) data items can flow from the functional unit for each input data item. It might be none or one or even more. This I call a stream of data. Such behavior cannot be translated into a function where output is generated with return. Because a function always needs to return a value. So the output port is translated into a function pointer or continuation which gets passed to the subroutine when called:[3]void filter_stop_words( string word, Action<string> onNoStopWord) { if (...check if not a stop word...) onNoStopWord(word); } If you want to be nitpicky you might call such a function pointer parameter an injection. And technically you´re right. Conceptually, though, it´s not an injection. Because the subroutine is not functionally dependent on the continuation. Firstly continuations are procedures, i.e. subroutines without a return type. Remember: Flow Design is about unidirectional data flow. Secondly the name of the formal parameter is chosen in a way as to not assume anything about downstream processing steps. onNoStopWord describes a situation (or event) within the functional unit only. Translating output ports into function pointers helps keeping functional units mutually oblivious in cases where output is optional or produced asynchronically. Either pass the function pointer to the function upon call. Or make it global by putting it on the encompassing class. Then it´s called an event. In C# that´s even an explicit feature.class Filter { public void filter_stop_words( string word) { if (...check if not a stop word...) onNoStopWord(word); } public event Action<string> onNoStopWord; } When to use a continuation and when to use an event dependens on how a functional unit is used in flows and how it´s packed together with others into classes. You´ll see examples further down the Flow Design road. Another example of 1D functional design Let´s see Flow Design once more in action using the visual notation. How about the famous word wrap kata? Robert C. Martin has posted a much cited solution including an extensive reasoning behind his TDD approach. So maybe you want to compare it to Flow Design. The function signature given is:string WordWrap(string text, int maxLineLength) {...} That´s not an Entry Point since we don´t see an application with an environment and users. Nevertheless it´s a function which is supposed to provide a certain functionality. The text passed in has to be reformatted. The input is a single line of arbitrary length consisting of words separated by spaces. The output should consist of one or more lines of a maximum length specified. If a word is longer than a the maximum line length it can be split in multiple parts each fitting in a line. Flow Design Let´s start by brainstorming the process to accomplish the feat of reformatting the text. What´s needed? Words need to be assembled into lines Words need to be extracted from the input text The resulting lines need to be assembled into the output text Words too long to fit in a line need to be split Does sound about right? I guess so. And it shows a kind of priority. Long words are a special case. So maybe there is a hint for an incremental design here. First let´s tackle “average words” (words not longer than a line). Here´s the Flow Design for this increment: The the first three bullet points turned into functional units with explicit data added. As the signature requires a text is transformed into another text. See the input of the first functional unit and the output of the last functional unit. In between no text flows, but words and lines. That´s good to see because thereby the domain is clearly represented in the design. The requirements are talking about words and lines and here they are. But note the asterisk! It´s not outside the brackets but inside. That means it´s not a stream of words or lines, but lists or sequences. For each text a sequence of words is output. For each sequence of words a sequence of lines is produced. The asterisk is used to abstract from the concrete implementation. Like with streams. Whether the list of words gets implemented as an array or an IEnumerable is not important during design. It´s an implementation detail. Does any processing step require further refinement? I don´t think so. They all look pretty “atomic” to me. And if not… I can always backtrack and refine a process step using functional design later once I´ve gained more insight into a sub-problem. Implementation The implementation is straightforward as you can imagine. The processing steps can all be translated into functions. Each can be tested easily and separately. Each has a focused responsibility. And the process flow becomes just a sequence of function calls: Easy to understand. It clearly states how word wrapping works - on a high level of abstraction. And it´s easy to evolve as you´ll see. Flow Design - Increment 2 So far only texts consisting of “average words” are wrapped correctly. Words not fitting in a line will result in lines too long. Wrapping long words is a feature of the requested functionality. Whether it´s there or not makes a difference to the user. To quickly get feedback I decided to first implement a solution without this feature. But now it´s time to add it to deliver the full scope. Fortunately Flow Design automatically leads to code following the Open Closed Principle (OCP). It´s easy to extend it - instead of changing well tested code. How´s that possible? Flow Design allows for extension of functionality by inserting functional units into the flow. That way existing functional units need not be changed. The data flow arrow between functional units is a natural extension point. No need to resort to the Strategy Pattern. No need to think ahead where extions might need to be made in the future. I just “phase in” the remaining processing step: Since neither Extract words nor Reformat know of their environment neither needs to be touched due to the “detour”. The new processing step accepts the output of the existing upstream step and produces data compatible with the existing downstream step. Implementation - Increment 2 A trivial implementation checking the assumption if this works does not do anything to split long words. The input is just passed on: Note how clean WordWrap() stays. The solution is easy to understand. A developer looking at this code sometime in the future, when a new feature needs to be build in, quickly sees how long words are dealt with. Compare this to Robert C. Martin´s solution:[4] How does this solution handle long words? Long words are not even part of the domain language present in the code. At least I need considerable time to understand the approach. Admittedly the Flow Design solution with the full implementation of long word splitting is longer than Robert C. Martin´s. At least it seems. Because his solution does not cover all the “word wrap situations” the Flow Design solution handles. Some lines would need to be added to be on par, I guess. But even then… Is a difference in LOC that important as long as it´s in the same ball park? I value understandability and openness for extension higher than saving on the last line of code. Simplicity is not just less code, it´s also clarity in design. But don´t take my word for it. Try Flow Design on larger problems and compare for yourself. What´s the easier, more straightforward way to clean code? And keep in mind: You ain´t seen all yet ;-) There´s more to Flow Design than described in this chapter. In closing I hope I was able to give you a impression of functional design that makes you hungry for more. To me it´s an inevitable step in software development. Jumping from requirements to code does not scale. And it leads to dirty code all to quickly. Some thought should be invested first. Where there is a clear Entry Point visible, it´s functionality should be designed using data flows. Because with data flows abstraction is possible. For more background on why that´s necessary read my blog article here. For now let me point out to you - if you haven´t already noticed - that Flow Design is a general purpose declarative language. It´s “programming by intention” (Shalloway et al.). Just write down how you think the solution should work on a high level of abstraction. This breaks down a large problem in smaller problems. And by following the PoMO the solutions to those smaller problems are independent of each other. So they are easy to test. Or you could even think about getting them implemented in parallel by different team members. Flow Design not only increases evolvability, but also helps becoming more productive. All team members can participate in functional design. This goes beyon collective code ownership. We´re talking collective design/architecture ownership. Because with Flow Design there is a common visual language to talk about functional design - which is the foundation for all other design activities. PS: If you like what you read, consider getting my ebook “The Incremental Architekt´s Napkin”. It´s where I compile all the articles in this series for easier reading. I like the strictness of Function Programming - but I also find it quite hard to live by. And it certainly is not what millions of programmers are used to. Also to me it seems, the real world is full of state and side effects. So why give them such a bad image? That´s why functional design takes a more pragmatic approach. State and side effects are ok for processing steps - but be sure to follow the SRP. Don´t put too much of it into a single processing step. ? Image taken from www.physioweb.org ? My code samples are written in C#. C# sports typed function pointers called delegates. Action is such a function pointer type matching functions with signature void someName(T t). Other languages provide similar ways to work with functions as first class citizens - even Java now in version 8. I trust you find a way to map this detail of my translation to your favorite programming language. I know it works for Java, C++, Ruby, JavaScript, Python, Go. And if you´re using a Functional Programming language it´s of course a no brainer. ? Taken from his blog post “The Craftsman 62, The Dark Path”. ?

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Nginx + uWSGI on a fresh Ubuntu install - bind error port 80

- by knuckfubuck

I know this is a common problem usually having to do with apache or another service already running on port 80 and I have done a lot of searching and running netstat and still have not figured out why I am getting this error. I rebuilt my slice, did a fresh install of Ubuntu 10.04 and setup nginx + uwsgi. It worked and I was able to see my Django site. I then installed Postgres8.4 and the rest of the stack needed for Geodjango from this link. After that was done I tried to restart nginx and I get this error: sudo /etc/init.d/nginx start Starting nginx: the configuration file /usr/local/nginx/conf/nginx.conf syntax is ok configuration file /usr/local/nginx/conf/nginx.conf test is successful [emerg]: bind() to 0.0.0.0:80 failed (98: Address already in use) [emerg]: bind() to 0.0.0.0:80 failed (98: Address already in use) [emerg]: bind() to 0.0.0.0:80 failed (98: Address already in use) [emerg]: bind() to 0.0.0.0:80 failed (98: Address already in use) [emerg]: bind() to 0.0.0.0:80 failed (98: Address already in use) [emerg]: still could not bind() I have nginx set to listen 80. Here's an output from netstat -l --numeric-ports | grep 80: tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:8000 0.0.0.0:* LISTEN Output from sudo lsof +M -i4: nginx 2330 root 8u IPv4 3195 0t0 TCP *:www (LISTEN) nginx 2331 www-data 8u IPv4 3195 0t0 TCP *:www (LISTEN) uwsgi 2335 s 4u IPv4 3259 0t0 TCP localhost:8000 (LISTEN) uwsgi 2352 s 4u IPv4 3259 0t0 TCP localhost:8000 (LISTEN) uwsgi 2353 s 4u IPv4 3259 0t0 TCP localhost:8000 (LISTEN) uwsgi 2354 s 4u IPv4 3259 0t0 TCP localhost:8000 (LISTEN) uwsgi 2355 s 4u IPv4 3259 0t0 TCP localhost:8000 (LISTEN) Anyone have any other ideas how I can figure out what is blocking port 80? edit Paste of my /etc/init.d/nginx script here: http://dpaste.com/hold/400937/

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What open source ecommerce webshops offer #1: usability, #2: PayPal integration, and #3: ease of administration and use

- by Jonathan Hayward

I've spent several days trying to deploy Satchmo, in the process asking several questions about deployment (http://stackoverflow.com/questions/11277407/can-anyone-explain-this-error-message-deploying-a-satchmo-project-under-gunicorn, http://stackoverflow.com/questions/11277685/is-there-a-howto-to-fcgi-for-deploying-satchmo, and http://stackoverflow.com/questions/11278295/what-is-the-most-stable-release-of-satchmo). Django's tagline is "The web framework for perfectionists with deadlines," and Satchmo's tagline is equally forceful: "The webshop for perfectionists with deadlines." I'm looking more to set up, configure, design, etc., rather than code for this one, and I'm taking a bit of a hint that for me at least the "with deadlines" bit is something that I cannot manage. Deployment has been a time sink. So, taking a step back, I don't specifically need to edit and extend the source code; what I want are first, good usability and a clean experience for the end-user, then being easy to deploy/install/manage/maintain, and enough so that even if you're having a slow day it should at most be one day's work to install, one day's work to get running, and one day's work to rebrand as white label (for simple branding). What ecommerce webshops should I be looking at?

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deploy LAMP config to new boxes with low/no effort

- by user1444233

I'm spending a lot of time setting up new Centos 6 instances. I use a VCS (Subversion) for most of the config files and all of the webapp source files (Github), but even with excellent package managers (like yum, npm, easy_install, etc.) it still takes time. I'd like to get to the point where I could try out a new potential web host by just signing up for an account, logging in and automatically sucking my standardised config onto the box. I know there are a set of tools that can help: Puppet Chef Vagrant and a set of services that sell solutions: [Jumpbox] http://www.jumpbox.com/ [BitNami Cloud] http://bitnami.org/cloud I don't mind investing time in learning a new tool, but as a no-budget start-up, I'm keen to keep monthly costs down. My biggest concern is that time spent on the server config is time away from the codebase, and that's where I think my team and I should be investing our energy, at least until we get funded and scale up a bit. I'd be grateful of some recommendations for which way to jump on config: stick with SSH and manual deploys, at least until you get big. bite the bullet and learn [say] puppet. You may only use it 8-10 times, but it pays to have such an easy tunable server bootstrap. don't bother, just pay the $100/month for a standard config service. It'll cost you $1000/year, but you should focus on the code. Other questions in this domain I use quite a complex stack (Drupal, Zend Server, MySQL, PHP, MongoDB, Python, django), but are there standard(ish) setups that include these or that I could build upon more quickly? Are the configs optimised for small, medium, large VPS (1GB, 4GB, 16GB)? How secure are they?

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Apache2 MPM-prefork MPM-worker multiple instances on same Ubuntu host machine possible?

- by user60985

I have a live Apache2/MPM-Worker instance running Django. I want to also run an Apache2/MPM-prefork instance to run some Drupal6 applications on the same host machine and utilize a vast selection of PHP modules that run on the prefork model. I plan to use my MPM-worker instance to reverse proxy to the Apache2-prefork instance for URLS starting with myhost.com/drupal6/. It seems theoretically doable/configurable by having the second Apache2-prefork instance configured to listen on an internal port, say 127.0.0.1:8080 and having my current Apache2-worker configured to proxy pass and reverse pass to it for the 'drupal6' URLs. However, how do I compile or install the apache2-prefork version so it has a different executable name than /usr/sbin/apache2, for example /usr/sbin/apache2p, and so apache2ctl has a different name, say apache2pctl, and that apache2pctl invokes the /usr/sbin/apache2p instead of /usr/sbin/apache2... and so on down the line (eg /etc/apache2p) so I can start and restart my two instances independently? As I understand it, no one executable of 'apache2' can be compiled with both the MPM-prefork and MPM-worker modules, so it seems I need two separate versions of the apache2 MPM flavors. But then I need to invoke and control them by separate names, I assume. I looked at the configuration options for apache2 and I am a bit queasy about compiling a second apache2 version with prefork because I am not sure I can set all the options so that none of my current apache2 files is overwritten. Is there a way? Is there a standard solution to separately installing and controlling prefork and worker apache2 executables on the same machine without them stepping on each other during installation or operation?

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apache2: ssl_error_rx_record_too_long when visiting port 80? help!

- by John

Hi, I have an Ubuntu 10 x64 server edition machine. I got a second IP and configured /etc/network/interfaces like so (actual IPs and gateways removed): [code] auto lo iface lo inet loopback iface eth0 inet dhcp auto eth0 auto eth0:0 iface eth0 inet static address [ my first IP ] netmask 255.255.255.0 gateway [ my first gateway ] iface eth0:0 inet static address [ my second IP ] netmask 255.255.255.0 gateway [ my second gateway ] [/code] /etc/apache2/ports.conf: [code] Listen 80 NameVirtualHost [ my first IP ]:80 NameVirtualHost [ my second IP ]:80 # If you add NameVirtualHost *:443 here, you will also have to change # the VirtualHost statement in /etc/apache2/sites-available/default-ssl # to # Server Name Indication for SSL named virtual hosts is currently not # supported by MSIE on Windows XP. Listen 443 NameVirtualHost [ my first IP - some site is running SSL successfully using it ]:443 Listen 443 [/code] /etc/apache2/sites-enabled/mysite.conf: [code] ServerName mysite.com Include /var/www/mysite.com/djangoproject/apache/django.conf [/conf] [/code] Then when visiting http[mysite].com:80 or http[mysite].com (:// removed because serverfault doesn't allow me to post hyperlinks), I get: [code] An error occurred during a connection to [mysite].com. SSL received a record that exceeded the maximum permissible length. (Error code: ssl_error_rx_record_too_long) [/code] My guess is that the configuration file is not being picked up, and apache is therefore looking for the default-ssl file, which is not in conf-enabled. If I were to configure that file properly, it seems I would successfully connect to whatever default directory is specified in the default-ssl file. But I want to connect to my website. Any ideas? Thanks in advance!

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Mac OS X 10.6.3: how does Apache config work?

- by w-

Just got a MacBook Pro 15" so I'm unfamiliar with how the filesystem is laid out. I noticed when in my filesystem that I've got a few paths specifying httpd.conf: /etc/apache2/httpd.conf /opt/local/apache2/conf/httpd.conf /private/etc/apache2/httpd.conf The config files are different in lots of ways (user, group, server_root, modules that are loaded, etc.) The apache2 folders themselves also greatly differ. It seems that the one getting used is either /etc/apache2/httpd.conf or /private/etc/apache2/httpd.conf I'm wondering if I might have messed up my system after installing some packages (php5, django, etc) via macports and maybe ended up with 2 apache2 instances. My questions are hence: which httpd.conf is the one being used ? what are the other files for? thanks --update-- To clarify, I didn't explicitly install apache2 via macports. I'm wondering if it was installed because it was a dependency. After more hunting around I'm learning I never should've installed php to begin with because Snow Leopard already includes php 5.3 from the get go. http://serverfault.com/questions/82410/apache-2-and-php-5-3-via-macports I'll need to open another question that asks about how the Mac filesystem works. Thanks all for replies.

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Apache debugging: where to find error logs?

- by AP257

I'm new to Apache and web serving generally, so apologies if this is a very stupid question. I want to configure a new sub-domain on a working site and install a forum there. I'm using a Debian server that already has Apache, mod_wsgi and a bunch of virtual hosts successfully running on it. I first installed my forum app (Django's OSQA). Following the OSQA instructions, I then created an Apache config file that specified ServerName as the new sub-domain. I also created a .wsgi file for the app, and pointed WSGIScriptAlias at it. I then restarted Apache. However, when I go to the new sub-domain, I get a 404 error message. Two questions: Is there a step missing above? Or is simply creating a new Apache config file in sites-available enough to 'tell' Apache about a new sub-domain? If there's something else going wrong, how can I debug it? The ErrorLog and CustomLog specified in the config file are both blank. apache2.conf, which I guess is Apache-wide configuration, specifies ErrorLog /var/log/apache2/error.log, but this is yet another blank file.

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Extending Oracle CEP with Predictive Analytics

- by vikram.shukla(at)oracle.com

Introduction: OCEP is often used as a business rules engine to execute a set of business logic rules via CQL statements, and take decisions based on the outcome of those rules. There are times where configuring rules manually is sufficient because an application needs to deal with only a small and well-defined set of static rules. However, in many situations customers don't want to pre-define such rules for two reasons. First, they are dealing with events with lots of columns and manually crafting such rules for each column or a set of columns and combinations thereof is almost impossible. Second, they are content with probabilistic outcomes and do not care about 100% precision. The former is the case when a user is dealing with data with high dimensionality, the latter when an application can live with "false" positives as they can be discarded after further inspection, say by a Human Task component in a Business Process Management software. The primary goal of this blog post is to show how this can be achieved by combining OCEP with Oracle Data Mining® and leveraging the latter's rich set of algorithms and functionality to do predictive analytics in real time on streaming events. The secondary goal of this post is also to show how OCEP can be extended to invoke any arbitrary external computation in an RDBMS from within CEP. The extensible facility is known as the JDBC cartridge. The rest of the post describes the steps required to achieve this: We use the dataset available at http://blogs.oracle.com/datamining/2010/01/fraud_and_anomaly_detection_made_simple.html to showcase the capabilities. We use it to show how transaction anomalies or fraud can be detected. Building the model: Follow the self-explanatory steps described at the above URL to build the model. It is very simple - it uses built-in Oracle Data Mining PL/SQL packages to cleanse, normalize and build the model out of the dataset. You can also use graphical Oracle Data Miner® to build the models. To summarize, it involves: Specifying which algorithms to use. In this case we use Support Vector Machines as we're trying to find anomalies in highly dimensional dataset.Build model on the data in the table for the algorithms specified. For this example, the table was populated in the scott/tiger schema with appropriate privileges. Configuring the Data Source: This is the first step in building CEP application using such an integration. Our datasource looks as follows in the server config file. It is advisable that you use the Visualizer to add it to the running server dynamically, rather than manually edit the file. <data-source> <name>DataMining</name> <data-source-params> <jndi-names> <element>DataMining</element> </jndi-names> <global-transactions-protocol>OnePhaseCommit</global-transactions-protocol> </data-source-params> <connection-pool-params> <credential-mapping-enabled></credential-mapping-enabled> <test-table-name>SQL SELECT 1 from DUAL</test-table-name> <initial-capacity>1</initial-capacity> <max-capacity>15</max-capacity> <capacity-increment>1</capacity-increment> </connection-pool-params> <driver-params> <use-xa-data-source-interface>true</use-xa-data-source-interface> <driver-name>oracle.jdbc.OracleDriver</driver-name> <url>jdbc:oracle:thin:@localhost:1522:orcl</url> <properties> <element> <value>scott</value> <name>user</name> </element> <element> <value>{Salted-3DES}AzFE5dDbO2g=</value> <name>password</name> </element> <element> <name>com.bea.core.datasource.serviceName</name> <value>oracle11.2g</value> </element> <element> <name>com.bea.core.datasource.serviceVersion</name> <value>11.2.0</value> </element> <element> <name>com.bea.core.datasource.serviceObjectClass</name> <value>java.sql.Driver</value> </element> </properties> </driver-params> </data-source> Designing the EPN: The EPN is very simple in this example. We briefly describe each of the components. The adapter ("DataMiningAdapter") reads data from a .csv file and sends it to the CQL processor downstream. The event payload here is same as that of the table in the database (refer to the attached project or do a "desc table-name" from a SQL*PLUS prompt). While this is for convenience in this example, it need not be the case. One can still omit fields in the streaming events, and need not match all columns in the table on which the model was built. Better yet, it does not even need to have the same name as columns in the table, as long as you alias them in the USING clause of the mining function. (Caveat: they still need to draw values from a similar universe or domain, otherwise it constitutes incorrect usage of the model). There are two things in the CQL processor ("DataMiningProc") that make scoring possible on streaming events. 1. User defined cartridge function Please refer to the OCEP CQL reference manual to find more details about how to define such functions. We include the function below in its entirety for illustration. <?xml version="1.0" encoding="UTF-8"?> <jdbcctxconfig:config xmlns:jdbcctxconfig="http://www.bea.com/ns/wlevs/config/application" xmlns:jc="http://www.oracle.com/ns/ocep/config/jdbc"> <jc:jdbc-ctx> <name>Oracle11gR2</name> <data-source>DataMining</data-source> <function name="prediction2"> <param name="CQLMONTH" type="char"/> <param name="WEEKOFMONTH" type="int"/> <param name="DAYOFWEEK" type="char" /> <param name="MAKE" type="char" /> <param name="ACCIDENTAREA" type="char" /> <param name="DAYOFWEEKCLAIMED" type="char" /> <param name="MONTHCLAIMED" type="char" /> <param name="WEEKOFMONTHCLAIMED" type="int" /> <param name="SEX" type="char" /> <param name="MARITALSTATUS" type="char" /> <param name="AGE" type="int" /> <param name="FAULT" type="char" /> <param name="POLICYTYPE" type="char" /> <param name="VEHICLECATEGORY" type="char" /> <param name="VEHICLEPRICE" type="char" /> <param name="FRAUDFOUND" type="int" /> <param name="POLICYNUMBER" type="int" /> <param name="REPNUMBER" type="int" /> <param name="DEDUCTIBLE" type="int" /> <param name="DRIVERRATING" type="int" /> <param name="DAYSPOLICYACCIDENT" type="char" /> <param name="DAYSPOLICYCLAIM" type="char" /> <param name="PASTNUMOFCLAIMS" type="char" /> <param name="AGEOFVEHICLES" type="char" /> <param name="AGEOFPOLICYHOLDER" type="char" /> <param name="POLICEREPORTFILED" type="char" /> <param name="WITNESSPRESNT" type="char" /> <param name="AGENTTYPE" type="char" /> <param name="NUMOFSUPP" type="char" /> <param name="ADDRCHGCLAIM" type="char" /> <param name="NUMOFCARS" type="char" /> <param name="CQLYEAR" type="int" /> <param name="BASEPOLICY" type="char" /> <return-component-type>char</return-component-type> <sql><![CDATA[ SELECT to_char(PREDICTION_PROBABILITY(CLAIMSMODEL, '0' USING *)) AS probability FROM (SELECT :CQLMONTH AS MONTH, :WEEKOFMONTH AS WEEKOFMONTH, :DAYOFWEEK AS DAYOFWEEK, :MAKE AS MAKE, :ACCIDENTAREA AS ACCIDENTAREA, :DAYOFWEEKCLAIMED AS DAYOFWEEKCLAIMED, :MONTHCLAIMED AS MONTHCLAIMED, :WEEKOFMONTHCLAIMED, :SEX AS SEX, :MARITALSTATUS AS MARITALSTATUS, :AGE AS AGE, :FAULT AS FAULT, :POLICYTYPE AS POLICYTYPE, :VEHICLECATEGORY AS VEHICLECATEGORY, :VEHICLEPRICE AS VEHICLEPRICE, :FRAUDFOUND AS FRAUDFOUND, :POLICYNUMBER AS POLICYNUMBER, :REPNUMBER AS REPNUMBER, :DEDUCTIBLE AS DEDUCTIBLE, :DRIVERRATING AS DRIVERRATING, :DAYSPOLICYACCIDENT AS DAYSPOLICYACCIDENT, :DAYSPOLICYCLAIM AS DAYSPOLICYCLAIM, :PASTNUMOFCLAIMS AS PASTNUMOFCLAIMS, :AGEOFVEHICLES AS AGEOFVEHICLES, :AGEOFPOLICYHOLDER AS AGEOFPOLICYHOLDER, :POLICEREPORTFILED AS POLICEREPORTFILED, :WITNESSPRESNT AS WITNESSPRESENT, :AGENTTYPE AS AGENTTYPE, :NUMOFSUPP AS NUMOFSUPP, :ADDRCHGCLAIM AS ADDRCHGCLAIM, :NUMOFCARS AS NUMOFCARS, :CQLYEAR AS YEAR, :BASEPOLICY AS BASEPOLICY FROM dual) ]]> </sql> </function> </jc:jdbc-ctx> </jdbcctxconfig:config> 2. Invoking the function for each event. Once this function is defined, you can invoke it from CQL as follows: <?xml version="1.0" encoding="UTF-8"?> <wlevs:config xmlns:wlevs="http://www.bea.com/ns/wlevs/config/application"> <processor> <name>DataMiningProc</name> <rules> <query id="q1"><![CDATA[ ISTREAM(SELECT S.CQLMONTH, S.WEEKOFMONTH, S.DAYOFWEEK, S.MAKE, : S.BASEPOLICY, C.F AS probability FROM StreamDataChannel [NOW] AS S, TABLE(prediction2@Oracle11gR2(S.CQLMONTH, S.WEEKOFMONTH, S.DAYOFWEEK, S.MAKE, ..., S.BASEPOLICY) AS F of char) AS C) ]]></query> </rules> </processor> </wlevs:config> Finally, the last stage in the EPN prints out the probability of the event being an anomaly. One can also define a threshold in CQL to filter out events that are normal, i.e., below a certain mark as defined by the analyst or designer. Sample Runs: Now let's see how this behaves when events are streamed through CEP. We use only two events for brevity, one normal and other one not. This is one of the "normal" looking events and the probability of it being anomalous is less than 60%. Event is: eventType=DataMiningOutEvent object=q1 time=2904821976256 S.CQLMONTH=Dec, S.WEEKOFMONTH=5, S.DAYOFWEEK=Wednesday, S.MAKE=Honda, S.ACCIDENTAREA=Urban, S.DAYOFWEEKCLAIMED=Tuesday, S.MONTHCLAIMED=Jan, S.WEEKOFMONTHCLAIMED=1, S.SEX=Female, S.MARITALSTATUS=Single, S.AGE=21, S.FAULT=Policy Holder, S.POLICYTYPE=Sport - Liability, S.VEHICLECATEGORY=Sport, S.VEHICLEPRICE=more than 69000, S.FRAUDFOUND=0, S.POLICYNUMBER=1, S.REPNUMBER=12, S.DEDUCTIBLE=300, S.DRIVERRATING=1, S.DAYSPOLICYACCIDENT=more than 30, S.DAYSPOLICYCLAIM=more than 30, S.PASTNUMOFCLAIMS=none, S.AGEOFVEHICLES=3 years, S.AGEOFPOLICYHOLDER=26 to 30, S.POLICEREPORTFILED=No, S.WITNESSPRESENT=No, S.AGENTTYPE=External, S.NUMOFSUPP=none, S.ADDRCHGCLAIM=1 year, S.NUMOFCARS=3 to 4, S.CQLYEAR=1994, S.BASEPOLICY=Liability, probability=.58931702982118561 isTotalOrderGuarantee=true\nAnamoly probability: .58931702982118561 However, the following event is scored as an anomaly with a very high probability of 89%. So there is likely to be something wrong with it. A close look reveals that the value of "deductible" field (10000) is not "normal". What exactly constitutes normal here?. If you run the query on the database to find ALL distinct values for the "deductible" field, it returns the following set: {300, 400, 500, 700} Event is: eventType=DataMiningOutEvent object=q1 time=2598483773496 S.CQLMONTH=Dec, S.WEEKOFMONTH=5, S.DAYOFWEEK=Wednesday, S.MAKE=Honda, S.ACCIDENTAREA=Urban, S.DAYOFWEEKCLAIMED=Tuesday, S.MONTHCLAIMED=Jan, S.WEEKOFMONTHCLAIMED=1, S.SEX=Female, S.MARITALSTATUS=Single, S.AGE=21, S.FAULT=Policy Holder, S.POLICYTYPE=Sport - Liability, S.VEHICLECATEGORY=Sport, S.VEHICLEPRICE=more than 69000, S.FRAUDFOUND=0, S.POLICYNUMBER=1, S.REPNUMBER=12, S.DEDUCTIBLE=10000, S.DRIVERRATING=1, S.DAYSPOLICYACCIDENT=more than 30, S.DAYSPOLICYCLAIM=more than 30, S.PASTNUMOFCLAIMS=none, S.AGEOFVEHICLES=3 years, S.AGEOFPOLICYHOLDER=26 to 30, S.POLICEREPORTFILED=No, S.WITNESSPRESENT=No, S.AGENTTYPE=External, S.NUMOFSUPP=none, S.ADDRCHGCLAIM=1 year, S.NUMOFCARS=3 to 4, S.CQLYEAR=1994, S.BASEPOLICY=Liability, probability=.89171554529576691 isTotalOrderGuarantee=true\nAnamoly probability: .89171554529576691 Conclusion: By way of this example, we show: real-time scoring of events as they flow through CEP leveraging Oracle Data Mining.how CEP applications can invoke complex arbitrary external computations (function shipping) in an RDBMS.

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Which database to use and system/db administration by layman [closed]

- by blah

So my friend and I got briliant ;) idea for a business. Since it is not predictable whether it will work out or not, we decided to keep cost as low as possible to start with, in particular not to hire anyone. If it will work out as expected it will generate enough profit to hire professionals in few months. But for the first few months we'll be doing everything by ourselfs. He's a business/finance major, and I'm a software developer, so obviously I have to take care of IT :) It will be a webapp, written in python/django. My questions regarding this project: 1) What database should I choose? I'm experienced with oracle, and have been working with SQL Server for a while, but both of them are too expensive(at least now). It's a developer experience, I've never done any dba stuff. I'm looking for something free(as in beer). Looks like MySql or PostgreSQL are most popular in this sector. I would appreciate any comments on which db to choose. I'm open to any suggestions(it doesn't have to be MySql or Postgre). Here's what I know about data: It will be almost dates and numbers, a little bit of text. Searched mainly by dates. Data will almost never be updated, mostly inserted and browsed. From 30k to 300k new records/month. 2) Servers. My idea is to rent two dedicated servers. During normal operation one would be a web server(debian/apache), other would be a db server(debian/?). My recovery plan is to install everything on both, and in case of trouble with one of machines just run everything on the other one. Does it even makes sense? Any other tips appreciated. Thanks.

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How to set the VirtualDocumentRoot based on the files within

- by Chuck Vose

I'm trying to set up Apache to use the VirtualDocumentRoot directive but my sites aren't all exactly the same. Most of the sites have a drupal folder which should be the root but there are a few really old drupal sites, a few rails sites, some django sites, etc. that want the Document root to be / or some other folder. Is there a way to set up VirtualDocumentRoot based on a conditional or is there a way to use RewriteRule/Cond to detect that / is the incorrect folder if there is a drupal folder or a public folder? Here's what I have so far: <VirtualHost *:80> # Wildcard ServerAlias, this is the default vhost if no specific vhost matches first. ServerAlias *.unicorn.devserver.com # Automatic ServerName, based on the HTTP_HOST header. UseCanonicalName Off # Automatic DocumentRoot. This uses the 4th level domain name as the document root, # for example http://bar.foo.baz.com/ would respond with /Users/vosechu/Sites/bar/drupal. VirtualDocumentRoot /Users/vosechu/Sites/%-4/drupal </VirtualHost> Thanks in advance! -Chuck

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How do I only dp or do just the lines, not the entire block in Vim diff?

- by hobbes3

I'm currently using MacVim (Snapshot 64) "Split Diff by..." menu option. The file is Django's my settings.py from version 1.3.1 to a fresh file from version 1.4. (Open the image on a separate window/tab to enlarge.) I know two basic commands do to "obtain" (and replace) a block from the other side. dp to "put" (and replace) a block to the other side. But those two commands writes the entire block, which in MacVim is the purple highlights. If you look at the 2nd block, you can see that from line 2 and 3 only has 2 words that are different: mysite and hobbes3. I just want to replace per line not the entire block. So what is there a command to replace do do and dp per line as oppose to an entire block or do I have to manually type it out? Bonus question: I noticed that once I manually edit a block, I lose the purple highlighting. How do I "refresh" the diff again to include the highlights without reopening the file? Please try to keep the answers Vim-general as oppose to MacVim-specific. Thanks!

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Routing a single request through multiple nginx backend apps

- by Jonathan Oliver

I wanted to get an idea if anything like the following scenario was possible: Nginx handles a request and routes it to some kind of authentication application where cookies and/or other kinds of security identifiers are interpreted and verified. The app perhaps makes a few additions to the request (appending authenticated headers). Failing authentication returns an HTTP 401. Nginx then takes the request and routes it through an authorization application which determines, based upon identity and the HTTP verb (put, delete, get, etc.) and URL in question, whether the actor/agent/user has permission to performed the intended action. Perhaps the authorization application modifies the request somewhat by appending another header, for example. Failing authorization returns 403. (Wash, rinse, repeat the proxy pattern for any number of services that want to participate in the request in some fashion.) Finally, Nginx routes the request into the actual application code where the request is inspected and the requested operations are executed according to the URL in question and where the identity of the user can be captured and understood by the application by looking at the altered HTTP request. Ideally, Nginx could do this natively or with a plugin. Any ideas? The alternative that I've considered is having Nginx hand off the initial request to the authentication application and then have this application proxy the request back through to Nginx (whether on the same box or another box). I know there are a number of applications frameworks (Django, RoR, etc.) that can do a lot of this stuff "in process", but I was trying to make things a little more generic and self contained where different applications could "hook" the HTTP pipeline of Nginx and then participate in, short circuit, and even modify the request accordingly. If Nginx can't do this, is anyone aware of other web servers that will perform in the manner described above?

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apache2: ssl_error_rx_record_too_long when visiting port 80?

- by John

Hi, I have an Ubuntu 10 x64 server edition machine. I got a second IP and configured /etc/network/interfaces like so (actual IPs and gateways removed): auto lo iface lo inet loopback #iface eth0 inet dhcp auto eth0 auto eth0:0 iface eth0 inet static address [ my first IP ] netmask 255.255.255.0 gateway [ my first gateway ] iface eth0:0 inet static address [ my second IP ] netmask 255.255.255.0 gateway [ my second gateway ] /etc/apache2/ports.conf: Listen 80 NameVirtualHost [ my first IP ]:80 NameVirtualHost [ my second IP ]:80 <IfModule mod_ssl.c> # If you add NameVirtualHost *:443 here, you will also have to change # the VirtualHost statement in /etc/apache2/sites-available/default-ssl # to <VirtualHost *:443> # Server Name Indication for SSL named virtual hosts is currently not # supported by MSIE on Windows XP. Listen 443 NameVirtualHost [ my first IP - some site is running SSL successfully using it ]:443 </IfModule> <IfModule mod_gnutls.c> Listen 443 </IfModule> /etc/apache2/sites-enabled/mysite.conf: <VirtualHost [my second IP ]:80> ServerName mysite.com Include /var/www/mysite.com/djangoproject/apache/django.conf </VirtualHost> Then when visiting http[mysite].com:80 or http[mysite].com (:// removed because serverfault doesn't allow me to post hyperlinks), I get: An error occurred during a connection to [mysite].com. SSL received a record that exceeded the maximum permissible length. (Error code: ssl_error_rx_record_too_long) My guess is that the configuration file is not being picked up, and apache is therefore looking for the default-ssl file, which is not in conf-enabled. If I were to configure that file properly, it seems I would successfully connect to whatever default directory is specified in the default-ssl file. But I want to connect to my website. Any ideas? Thanks in advance!

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Cannot connect to postgres installed on Ubuntu

- by Assaf

I installed the Bitnami Django stack which included PostgreSQL 8.4. When I run psql -U postgres I get the following error: psql: could not connect to server: No such file or directory Is the server running locally and accepting connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"? PG is definitely running and the pg_hba.conf file looks like this: # TYPE DATABASE USER CIDR-ADDRESS METHOD # "local" is for Unix domain socket connections only local all all md5 # IPv4 local connections: host all all 127.0.0.1/32 md5 # IPv6 local connections: host all all ::1/128 md5 What gives? "Proof" that pg is running: root@assaf-desktop:/home/assaf# ps axf | grep postgres 14338 ? S 0:00 /opt/djangostack-1.3-0/postgresql/bin/postgres -D /opt/djangostack-1.3-0/postgresql/data -p 5432 14347 ? Ss 0:00 \_ postgres: writer process 14348 ? Ss 0:00 \_ postgres: wal writer process 14349 ? Ss 0:00 \_ postgres: autovacuum launcher process 14350 ? Ss 0:00 \_ postgres: stats collector process 15139 pts/1 S+ 0:00 \_ grep --color=auto postgres root@assaf-desktop:/home/assaf# netstat -nltp | grep 5432 tcp 0 0 127.0.0.1:5432 0.0.0.0:* LISTEN 14338/postgres tcp6 0 0 ::1:5432 :::* LISTEN 14338/postgres root@assaf-desktop:/home/assaf#

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How to have SSL on Amazon Elastic Load Balancer with a Gunicorn EC2 server?

- by Riegie Godwin

I'm a self taught back end engineer so I'm learning all of this stuff as I go along. For the longest time, I've been using basic authentication for my users. Many developers are advising against this approach since each request will contain the username & password in clear text. Anyone with the right skills can sniff on the connection between my iOS application and my Django/Gunicorn Server and obtain their password. I wouldn't want to put my user's credentials at risk so I would like to implement a more secure way of authentication. SSL seems to be the most viable option. My server doesn't serve any static content or anything crazy of that sort. All the server does is send and receive "json" responses from and to my iOS application. Here is my current topology. iOS application ------ Amazon Elastic Load Balancer ------- EC2 Instances running HTTP Gunicorn. Gunicorn runs on port 8000. I have a CNAME record from GoDaddy for the Amazon Elastic Load Balancer DNS. So instead of using the long DNS to make requests, I just use server.example.com. To interact with my servers I send and receive requests to server.example.com:8000/ This setup works and has been solid. However I need to have a more secure way. I would like to setup SSL between my iOS application and my Elastic Load Balancer. How can I go about doing this? Since I am only sending json responses to my application, do I really need to buy a certificate from a CA or can I create my own? (since browsers will not be interacting with my servers. My servers are only designed to send json responses to my iOS application).

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nginx: SSI working on Apache backend, but not on gunicorn backend

- by j0nes

I have nginx in front of an Apache server and a gunicorn server for different parts of my website. I am using the SSI module in nginx to display a snippet in every page. The websites include a snippet in this form: For static pages served by nginx everything is working fine, the same goes for the Apache-generated pages - the SSI include is evaluated and the snippet is filled. However for requests to my gunicorn backend running a Python app in Django, the SSI include does not get evaluated. Here is the relevant part of the nginx config: location /cgi-bin/script.pl { ssi on; proxy_pass http://default_backend/cgi-bin/script.pl; include sites-available/aspects/proxy-default.conf; } location /directory/ { ssi on; limit_req zone=directory nodelay burst=3; proxy_pass http://django_backend/directory/; include sites-available/aspects/proxy-default.conf; } Backends: upstream django_backend { server dynamic.mydomain.com:8000 max_fails=5 fail_timeout=10s; } upstream default_backend { server dynamic.mydomain.com:80; server dynamic2.mydomain.com:80; } proxy_default.conf: proxy_redirect off; proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; What is the cause for this behaviour? How can I get SSI includes working for my pages generated on gunicorn? How can I debug this further?

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Apache crashes a few seconds after the start.

- by Nacho

Hi, i've got a problem with apache. When i try to start it (/etc/init.d/apache2 start) it dies after a few seconds. It shows up on "ps aux" consuming a lot of memory and then dies. I don't know what could be causing apache to consume this amount of memory: USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 13379 1.0 0.3 14376 3908 ? Ss 22:31 0:00 /usr/sbin/apache2 -k start www-data 13383 0.0 0.4 197316 4196 ? Sl 22:31 0:00 /usr/sbin/apache2 -k start www-data 13390 0.0 0.3 172728 4172 ? Sl 22:31 0:00 /usr/sbin/apache2 -k start www-data 13396 0.0 0.3 156336 4160 ? Sl 22:31 0:00 /usr/sbin/apache2 -k start www-data 13400 0.0 0.3 148140 4156 ? Sl 22:31 0:00 /usr/sbin/apache2 -k start www-data 13403 0.0 0.3 131748 4148 ? Sl 22:31 0:00 /usr/sbin/apache2 -k start Here is a htop screenshot: http://i.imgur.com/N4Chh.png It happened suddenly, no change had been made to server config, so i don't know whats causing it. The error log of my virtual servers shows this: [Sun Jan 30 22:19:50 2011] [alert] (11)Resource temporarily unavailable: mod_wsgi (pid=9685): Couldn't create worker thread 11 in daemon process 'fb.ebookmetafinder.com'. [Sun Jan 30 22:19:55 2011] [alert] (11)Resource temporarily unavailable: mod_wsgi (pid=9685): Couldn't create worker thread 19 in daemon process 'fb.ebookmetafinder.com'. [Sun Jan 30 22:29:40 2011] [alert] (11)Resource temporarily unavailable: mod_wsgi (pid=12009): Couldn't create worker thread 18 in daemon process 'fb.ebookmetafinder.com'. [Sun Jan 30 22:31:06 2011] [alert] (11)Resource temporarily unavailable: mod_wsgi (pid=13396): Couldn't create worker thread 15 in daemon process 'fb.ebookmetafinder.com'. [Sun Jan 30 22:35:02 2011] [alert] (11)Resource temporarily unavailable: mod_wsgi (pid=14009): Couldn't create worker thread 16 in daemon process 'fb.ebookmetafinder.com'. [Sun Jan 30 22:35:07 2011] [alert] (11)Resource temporarily unavailable: mod_wsgi (pid=14009): Couldn't create worker thread 17 in daemon process 'fb.ebookmetafinder.com'. I'm on a ubuntu server vps and i use mod_wsgi with django. Thanks.

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how to go about scaling a web-application ?

- by phoenix24

for someone whoes been primarily a web-application developer, and know not much about scaling/scalability techniques. I'll start by stating my application is written in Python, using Django; a fairly standard setup. I currently use Apache 2.2 for my webserver, and MySql for my database server; both running on the same vps server. Up until now, it was basically a prototype and merely 15-30 concurrent users at any given time; so I had no issues, but now since we'll be adding more users we'll have severe performance issues. So my question is how do i go about scaling my web-application? and my plan is as follows. Now I have just one vps server running, apache + mysql. Next, I plan to add another vps server, to run only MySql; so i'll have one web-server and one db server. Next, I'll add Memcache to the webserver for caching data; and taking some load off mysql. Next, another web-server for serving all the static content; Next, a vps server for load-balancing (nginx/varnish) behind which would be my two web-servers and then db-server. Does that sound like a workable strategy, please guide me around here.

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Configuring wsgi for a simple Python based site

- by jbbarnes

I have an Ubuntu 10.04 server that already has apache and wsgi working. I also have a python script that works just fine using the make_server command: if __name__ == '__main__': from wsgiref.simple_server import make_server srv = make_server('', 8080, display_status) srv.serve_forever() Now I would like to have the page always active without having to run the script manually. I looked at what Moin is doing. I found these lines in apache2.conf: WSGIScriptAlias /wiki /usr/local/share/moin/moin.wsgi WSGIDaemonProcess moin user=www-data group=www-data processes=5 threads=10 maximum-requests=1000 umask=0007 WSGIProcessGroup moin And moin.wsgi is as listed: import sys, os sys.path.insert(0, '/usr/local/share/moin') from MoinMoin.web.serving import make_application application = make_application(shared=True) QUESTION: Can I create a similar section in apache2.conf pointing to another wsgi file? Like this: WSGIScriptAlias /status /mypath/status.wsgi WSGIDaemonProcess status user=www-data group=www-data processes=5 threads=10 maximum-requests=1000 umask=0007 WSGIProcessGroup status And if so, what is required to convert my simple_server script into a daemonized process? Most of the information I find about wsgi is related to using it with frameworks like Django. I haven't found a simple howto detailing how to make this work. Thanks.

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sudo fdisk in a live session does not show all hard drives

- by cornbread

I am having Grub2 issues in my Ubuntu 10.04 dual boot, 2 hard drive system. So I am attempting to follow the standard grub2 reinstallation guide (cant post link because of spam filters allowing only one... ?_?) Don't know if this is the root of my problem, but my speedy internal HD with my OS on it is not showing up anywhere in a live session. Not in nautilus, behind fdisk.... no where. When I can get the main system to boot, there is no issue seeing all available partitions. But the live session sees only the 1TB internal media/backup hard drive. I need access to the other hard drive and it's partitions to finish the grub2 re-installation but I am not sure anymore that is the underlying issue. Anyone have experience with this? The issue I have identified as a grub2 issue is fully described here. SandPvvr describes it exactly. Some notes: I do not see the grub2 menu for my os's holding down the shift key after my bios screen works maybe 10% of the time Not related to reinstalling a windows os. havent been touched in a year do some web development. issue may have started when I was playing with ruby and django. not sure on this. Could a dev environment do this? fdisk in live session ubuntu@ubuntu:~$ sudo fdisk -l Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x0001d518 Device Boot Start End Blocks Id System /dev/sdb2 1 121601 976759939 5 Extended /dev/sdb5 487 110765 885816036 83 Linux /dev/sdb6 110766 121601 87040138+ b W95 FAT32 /dev/sdb7 1 486 3903700+ 82 Linux swap / Solaris Partition table entries are not in disk order

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Merely installing PHP5 causes my AWS Ubuntu server to die minutes later from a massive CPU spike

- by Mark Amery

I have an AWS server with Ubuntu 11.04 as the OS that is running an Apache2 webserver (incidentally Python-based and using Django). We recently needed to add support for php5 to let us use a third party PHP library (incidentally for serving minified versions of js and css files). However, for no reason any of us can discern, if we simply run sudo apt-get install php5 on the server, then the install appears to finish successfully but, without us taking any further action (including not yet running sudo apt-get install libapache2-mod-php5, which I think would be the next step for us if everything worked), or actually running any PHP scripts on the server, a few minutes later the server becomes impossible to connect to, and looking at the 'Monitoring' tab for the server in the EC2 Management Console reveals that a while after the installation, CPU usage spikes to 100% and stays there permanently (until we reboot the server from the AWS Console). After rebooting, the server also reliably dies within a few (between 0 and 10) minutes. We restored the server to a pre-PHP state from an AMI Image, observed that it was stable, and then tried installing PHP5 again and observed the server die in exactly the same way, so we're pretty much certain that installing PHP5 is what causes the symptoms. What on earth could be causing this behaviour, and how can we get PHP installed on the server without it dying?

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Apache using 100% CPU, once again

- by CBenni

Recently, apache2 started using 100% of CPU power: top gives me From other, similar threads, I took the tip to use mod_status. Aside from HUGE amounts of NULL requests, it gives: CPU Usage: u2.16 s1.32 cu0 cs0 - .0835% CPU load 1.2 requests/sec - 17.6 kB/second - 14.6 kB/request 8 requests currently being processed, 42 idle workers The access and error logs do not show anything surprising or intriguing at all. Note the .8% CPU usage. Another tip was to use strace: root@server:~# strace -p 1956 Process 1956 attached - interrupt to quit restart_syscall(<... resuming interrupted call ...> And remains like this for at least half an hour, without producing any additional output. Restarting apache fixed the problem for less than a second The server runs a few custom python scripts aswell as a django-powered website on apache2 (up-to-date), but even turning the scripts off (or not having them active in the first place) did not change anything. After I stopped apache and powered my server off, powered it on a few minutes afterwards and restarted all my services, the CPU usage remained low for several hours, just in order to pop up again randomly (?) The DigitalOcean CPU stats on my server are: You can see how the CPU usage was super high for almost half a day until I restarted the bot - just to remain stable for several hours and then pop up again. I am completely at a loss of words and don't know what I could do to find out what piece of my code is giving me these problems or if apache itself is the cause... Therefore I would greatly appreciate any hints to the questions: What else can I try to do? Which things might I not have checked? Is this definitely in my own code? How do you find what part of python code crashes an app via a infinite loop or similar?

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What kind of hosting do I need? [closed]

- by Robert Smith

I have been trying to answer this question but I haven't found an specific answer to my situation. As I want to pay for what I need, I thought I could get a good answer here. I have custom made forum (rather than a built-in forum like the ones you can find as plugins, e.g. WP-Forum or phpBB type of software) in Django. I don't want to use Apache and modwsgi because it's usually very memory-hungry and I can't afford a big server. I prefer a combination of nginx and gunicorn which I think is very efficient (maybe you can also tell me what you think about that). I'm expecting to receive 10,000 to 20,000 visits each month with 15,000 to 30,000 page impressions. I have reviewed some cloud services like Amazon EC2 or Rackspace and other more traditional services (Linodo). This site won't use videos or big images and I certainly don't need a huge amount of bandwidth (200GB would be definitely too much). I need shell access so shared hosting is out of the question. What do I need to run a website like that without problems? What about RAM? 256MB would be enough (that's the amount of RAM offered by small instances in Amazon and Rackspace)? Do you know of any alternative to those I mentioned? If you need more information to provide a useful answer, please don't hesitate to ask. Thanks a lot.

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