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• What are five things you hate about your favorite language?

  - by brian d foy

  There's been a cluster of Perl-hate on Stackoverflow lately, so I thought I'd bring my "Five things you hate about your favorite language" question to StackOverflow. Take your favorite language and tell me five things you hate about it. Those might be things that just annoy you, admitted design flaws, recognized performance problems, or any other category. You just have to hate it, and it has to be your favorite language. Don't compare it to another language, and don't talk about languages that you already hate. Don't talk about the things you like in your favorite language. I just want to hear the things that you hate but tolerate so you can use all of the other stuff, and I want to hear it about the language you wished other people would use. I ask this whenever someone tries to push their favorite language on me, and sometimes as an interview question. If someone can't find five things to hate about his favorite tool, he don't know it well enough to either advocate it or pull in the big dollars using it. He hasn't used it in enough different situations to fully explore it. He's advocating it as a culture or religion, which means that if I don't choose his favorite technology, I'm wrong. I don't care that much which language you use. Don't want to use a particular language? Then don't. You go through due diligence to make an informed choice and still don't use it? Fine. Sometimes the right answer is "You have a strong programming team with good practices and a lot of experience in Bar. Changing to Foo would be stupid." This is a good question for code reviews too. People who really know a codebase will have all sorts of suggestions for it, and those who don't know it so well have non-specific complaints. I ask things like "If you could start over on this project, what would you do differently?" In this fantasy land, users and programmers get to complain about anything and everything they don't like. "I want a better interface", "I want to separate the model from the view", "I'd use this module instead of this other one", "I'd rename this set of methods", or whatever they really don't like about the current situation. That's how I get a handle on how much a particular developer knows about the codebase. It's also a clue about how much of the programmer's ego is tied up in what he's telling me. Hate isn't the only dimension of figuring out how much people know, but I've found it to be a pretty good one. The things that they hate also give me a clue how well they are thinking about the subject.

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• Linq to SQL Repository ~theory~ - Generic but now uses Linq to Objects?

  - by Matt Tolliday

  The project I am currently working on used Linq to SQL as an ORM data access technology. Its an MVC3 Web app. The problem I faced was primarily due to the inability to mock (for testing) the DataContext which gets autogenerated by the DBML designer. So to solve this issue (after much reading) I refactored the repository system which was in place - single repository with seperate and duplicated access methods for each table which ended up with something like 300 methods only 10 of which were unique - into a single repository with generic methods taking the table and returning more generic types to the upper reaches of the application. My question revolves more around the design I've used to get thus far and the differences I'm noticing in the structure of the app. 1) Having refactored the code from the dark ages which used classic Linq to SQL queries: public Billing GetBilling(int id) { var result = ( from bil in _bicDc.Billings where bil.BillingId == id select bil).SingleOrDefault(); return (result); } it now looks like: public T GetRecordWhere<T>(Expression<Func<T, bool>> predicate) where T : class { T result; try { result = _dataContext.GetTable<T>().Where(predicate).SingleOrDefault(); } catch (Exception ex) { throw ex; } return result; } and is used by the controller with a query along the lines of: _repository.GetRecordWhere<Billing>(x => x.BillingId == 1); which is fine, and precisely what I wanted to achieve. ...however.... I'm also having to do the following to get precisely the result set i require in the controller class (the highest point of the app in essence)... viewModel.RecentRequests = _model.GetAllRecordsWhere<Billing>(x => x.BillingId == 1) .Where(x => x.BillingId == Convert.ToInt32(BillingType.Submitted)) .OrderByDescending(x => x.DateCreated). Take(5).ToList(); This - as far as my understanding is correct - is now using Linq to Objects rather than the Linq to SQL queries I was previously? Is this okay practise? It feels wrong to me but I dont know why. Probably because the logic of the queries is in the very highest tier of the app, rather than the lowest, but... I defer to you good people for advice. One of the issues I considered was bringing the entire table into memory but I understand that using the Iqeryable return type the where clause is taken to the database and evaluated there. Thus returning only the resultset i require... i may be wrong. And if you've made it this far, well done. Thank you, and if you have any advice it is very much appreciated!!

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• C#, AES encryption check!

  - by Data-Base

  I have this code for AES encryption, can some one verify that this code is good and not wrong? it works fine, but I'm more concern about the implementation of the algorithm // Plaintext value to be encrypted. //Passphrase from which a pseudo-random password will be derived. //The derived password will be used to generate the encryption key. //Password can be any string. In this example we assume that this passphrase is an ASCII string. //Salt value used along with passphrase to generate password. //Salt can be any string. In this example we assume that salt is an ASCII string. //HashAlgorithm used to generate password. Allowed values are: "MD5" and "SHA1". //SHA1 hashes are a bit slower, but more secure than MD5 hashes. //PasswordIterations used to generate password. One or two iterations should be enough. //InitialVector (or IV). This value is required to encrypt the first block of plaintext data. //For RijndaelManaged class IV must be exactly 16 ASCII characters long. //KeySize. Allowed values are: 128, 192, and 256. //Longer keys are more secure than shorter keys. //Encrypted value formatted as a base64-encoded string. public static string Encrypt(string PlainText, string Password, string Salt, string HashAlgorithm, int PasswordIterations, string InitialVector, int KeySize) { byte[] InitialVectorBytes = Encoding.ASCII.GetBytes(InitialVector); byte[] SaltValueBytes = Encoding.ASCII.GetBytes(Salt); byte[] PlainTextBytes = Encoding.UTF8.GetBytes(PlainText); PasswordDeriveBytes DerivedPassword = new PasswordDeriveBytes(Password, SaltValueBytes, HashAlgorithm, PasswordIterations); byte[] KeyBytes = DerivedPassword.GetBytes(KeySize / 8); RijndaelManaged SymmetricKey = new RijndaelManaged(); SymmetricKey.Mode = CipherMode.CBC; ICryptoTransform Encryptor = SymmetricKey.CreateEncryptor(KeyBytes, InitialVectorBytes); MemoryStream MemStream = new MemoryStream(); CryptoStream CryptoStream = new CryptoStream(MemStream, Encryptor, CryptoStreamMode.Write); CryptoStream.Write(PlainTextBytes, 0, PlainTextBytes.Length); CryptoStream.FlushFinalBlock(); byte[] CipherTextBytes = MemStream.ToArray(); MemStream.Close(); CryptoStream.Close(); return Convert.ToBase64String(CipherTextBytes); } public static string Decrypt(string CipherText, string Password, string Salt, string HashAlgorithm, int PasswordIterations, string InitialVector, int KeySize) { byte[] InitialVectorBytes = Encoding.ASCII.GetBytes(InitialVector); byte[] SaltValueBytes = Encoding.ASCII.GetBytes(Salt); byte[] CipherTextBytes = Convert.FromBase64String(CipherText); PasswordDeriveBytes DerivedPassword = new PasswordDeriveBytes(Password, SaltValueBytes, HashAlgorithm, PasswordIterations); byte[] KeyBytes = DerivedPassword.GetBytes(KeySize / 8); RijndaelManaged SymmetricKey = new RijndaelManaged(); SymmetricKey.Mode = CipherMode.CBC; ICryptoTransform Decryptor = SymmetricKey.CreateDecryptor(KeyBytes, InitialVectorBytes); MemoryStream MemStream = new MemoryStream(CipherTextBytes); CryptoStream cryptoStream = new CryptoStream(MemStream, Decryptor, CryptoStreamMode.Read); byte[] PlainTextBytes = new byte[CipherTextBytes.Length]; int ByteCount = cryptoStream.Read(PlainTextBytes, 0, PlainTextBytes.Length); MemStream.Close(); cryptoStream.Close(); return Encoding.UTF8.GetString(PlainTextBytes, 0, ByteCount); } Thank you

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• mdadm raid5 recover double disk failure - with a twist (drive order)

  - by Peter Bos

  Let me acknowledge first off that I have made mistakes, and that I have a backup for most but not all of the data on this RAID. I still have hope of recovering the rest of the data. I don't have the kind of money to take the drives to a recovery expert company. Mistake #0, not having a 100% backup. I know. I have a mdadm RAID5 system of 4x3TB. Drives /dev/sd[b-e], all with one partition /dev/sd[b-e]1. I'm aware that RAID5 on very large drives is risky, yet I did it anyway. Recent events The RAID become degraded after a two drive failure. One drive [/dev/sdc] is really gone, the other [/dev/sde] came back up after a power cycle, but was not automatically re-added to the RAID. So I was left with a 4 device RAID with only 2 active drives [/dev/sdb and /dev/sdd]. Mistake #1, not using dd copies of the drives for restoring the RAID. I did not have the drives or the time. Mistake #2, not making a backup of the superblock and mdadm -E of the remaining drives. Recovery attempt I reassembled the RAID in degraded mode with mdadm --assemble --force /dev/md0, using /dev/sd[bde]1. I could then access my data. I replaced /dev/sdc with a spare; empty; identical drive. I removed the old /dev/sdc1 from the RAID mdadm --fail /dev/md0 /dev/sdc1 Mistake #3, not doing this before replacing the drive I then partitioned the new /dev/sdc and added it to the RAID. mdadm --add /dev/md0 /dev/sdc1 It then began to restore the RAID. ETA 300 mins. I followed the process via /proc/mdstat to 2% and then went to do other stuff. Checking the result Several hours (but less then 300 mins) later, I checked the process. It had stopped due to a read error on /dev/sde1. Here is where the trouble really starts I then removed /dev/sde1 from the RAID and re-added it. I can't remember why I did this; it was late. mdadm --manage /dev/md0 --remove /dev/sde1 mdadm --manage /dev/md0 --add /dev/sde1 However, /dev/sde1 was now marked as spare. So I decided to recreate the whole array using --assume-clean using what I thought was the right order, and with /dev/sdc1 missing. mdadm --create /dev/md0 --assume-clean -l5 -n4 /dev/sdb1 missing /dev/sdd1 /dev/sde1 That worked, but the filesystem was not recognized while trying to mount. (It should have been EXT4). Device order I then checked a recent backup I had of /proc/mdstat, and I found the drive order. md0 : active raid5 sdb1[0] sde1[4] sdd1[2] sdc1[1] 8790402048 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/4] [UUUU] I then remembered this RAID had suffered a drive loss about a year ago, and recovered from it by replacing the faulty drive with a spare one. That may have scrambled the device order a bit...so there was no drive [3] but only [0],[1],[2], and [4]. I tried to find the drive order with the Permute_array script: https://raid.wiki.kernel.org/index.php/Permute_array.pl but that did not find the right order. Questions I now have two main questions: I screwed up all the superblocks on the drives, but only gave: mdadm --create --assume-clean commands (so I should not have overwritten the data itself on /dev/sd[bde]1. Am I right that in theory the RAID can be restored [assuming for a moment that /dev/sde1 is ok] if I just find the right device order? Is it important that /dev/sde1 be given the device number [4] in the RAID? When I create it with mdadm --create /dev/md0 --assume-clean -l5 -n4 \ /dev/sdb1 missing /dev/sdd1 /dev/sde1 it is assigned the number [3]. I wonder if that is relevant to the calculation of the parity blocks. If it turns out to be important, how can I recreate the array with /dev/sdb1[0] missing[1] /dev/sdd1[2] /dev/sde1[4]? If I could get that to work I could start it in degraded mode and add the new drive /dev/sdc1 and let it resync again. It's OK if you would like to point out to me that this may not have been the best course of action, but you'll find that I realized this. It would be great if anyone has any suggestions.

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• Find optimal/good-enough strategy and AI for the game 'Proximity'?

  - by smci

  'Proximity' is a strategy game of territorial domination similar to Othello, Go and Risk. Two players, uses a 10x12 hex grid. Game invented by Brian Cable in 2007. Seems to be a worthy game for discussing a) optimal algorithm then b) how to build an AI. Strategies are going to be probabilistic or heuristic-based, due to the randomness factor, and the insane branching factor (20^120). So it will be kind of hard to compare objectively. A compute time limit of 5s per turn seems reasonable. Game: Flash version here and many copies elsewhere on the web Rules: here Object: to have control of the most armies after all tiles have been placed. Each turn you received a randomly numbered tile (value between 1 and 20 armies) to place on any vacant board space. If this tile is adjacent to any ally tiles, it will strengthen each tile's defenses +1 (up to a max value of 20). If it is adjacent to any enemy tiles, it will take control over them if its number is higher than the number on the enemy tile. Thoughts on strategy: Here are some initial thoughts; setting the computer AI to Expert will probably teach a lot: minimizing your perimeter seems to be a good strategy, to prevent flips and minimize worst-case damage like in Go, leaving holes inside your formation is lethal, only more so with the hex grid because you can lose armies on up to 6 squares in one move low-numbered tiles are a liability, so place them away from your main territory, near the board edges and scattered. You can also use low-numbered tiles to plug holes in your formation, or make small gains along the perimeter which the opponent will not tend to bother attacking. a triangle formation of three pieces is strong since they mutually reinforce, and also reduce the perimeter Each tile can be flipped at most 6 times, i.e. when its neighbor tiles are occupied. Control of a formation can flow back and forth. Sometimes you lose part of a formation and plug any holes to render that part of the board 'dead' and lock in your territory/ prevent further losses. Low-numbered tiles are obvious-but-low-valued liabilities, but high-numbered tiles can be bigger liabilities if they get flipped (which is harder). One lucky play with a 20-army tile can cause a swing of 200 (from +100 to -100 armies). So tile placement will have both offensive and defensive considerations. Comment 1,2,4 seem to resemble a minimax strategy where we minimize the maximum expected possible loss (modified by some probabilistic consideration of the value ß the opponent can get from 1..20 i.e. a structure which can only be flipped by a ß=20 tile is 'nearly impregnable'.) I'm not clear what the implications of comments 3,5,6 are for optimal strategy. Interested in comments from Go, Chess or Othello players. (The sequel ProximityHD for XBox Live, allows 4-player -cooperative or -competitive local multiplayer increases the branching factor since you now have 5 tiles in your hand at any given time, of which you can only play one. Reinforcement of ally tiles is increased to +2 per ally.)

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• What was your the most impressive technical programming achievement performed to impress a romantic

  - by DVK

  OK, so the archetypal human story is for a guy to go out and impress the girl with some wonderful achievement like slaying a dragon or building a monument or conquering neighboring tribe. This being enlightened 21st century on SO, let's morph this into a: StackOverflower performing a feat of programming to impress a romantic interest. There are two ways to do this: Technical achievement: Impressing a person with suitable background/understanding of programming with actual coding powerss you displayed. A dumb movie example would be that kid in "Hackers" move showing off his hacking skills in front of Angeline Jolie. Artistic achievement: Impressing a person with a result of running said code, whether they understand just how incredible the code itself is. An example is the animated ANSI rose (for a guy who actually wrote the ANSI code) This question is only about the first kind (technical achievements) - e.g. the person of interest was presented with impressive code/design that (s)he was able to properly appreciate. Rules (what doesn't qualify): The target audience must have been a person of romantic interest (prospective or present significant other or random hook-up). E.g. showing your program to your sister who's also a software developer doesn't count. The achievement must have been done specifically with the goal to impress such a person. However, it is OK if the achievement was done to impress a generic qualifying person, not someone specific. Although... if you write code to impress girls in general, I'd say "get a better idea of the opposite sex" The achievement must have been done with the goal of impressing the person. In other words, if you would have done it without romantic interest's knowledge anyway, it doesn't count. As examples, the following does not count: programming for your job. Programming for a coding contest. Open Source program that you'd have done anyway. The precise nature of the awesomeness of the achievement is somewhat irrelevant - from learning entire J2EE in 2 days to writing fancy game engine to implementing Python compiler in LOGO. As long as it's programming/software development related. The achievement should preferably be something other people would rank highly as well. If your date was impressed with your skill at calculating Fibonacci sequence without recursive function calls, it doesn't mean most developers will be. But it does mean you need to start finding better things to do on dates ;)

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• CDI SessionScoped Bean instance remains unchanged when login with different user

  - by Jason Yang

  I've been looking for the workaround of this problem for rather plenty of time and no result, so I ask question here. Simply speaking, I'm using a CDI SessionScoped Bean User in my project to manage user information and display them on jsf pages. Also container-managed j_security_check is used to resolve authentication issue. Everything is fine if first logout with session.invalidate() and then login in the same browser tab with a different user. But when I tried to directly login (through login.jsf) with a new user without logout beforehand, I found the user information remaining unchanged. I debugged and found the User bean, as well as the HttpSession instance, always remaining the same if login with different users in the same browser, as long as session.invalidate() not invoked. But oddly, the session id did modified, and I've both checked in Java code and Firebug. org.apache.catalina.session.StandardSessionFacade@5d7b4092 StandardSession[c69a71d19f369d08b5dddbea2ef0] attrName = org.jboss.weld.context.conversation.ConversationIdGenerator : attrValue=org.jboss.weld.context.conversation.ConversationIdGenerator@583c9dd8 attrName = org.jboss.weld.context.ConversationContext.conversations : attrValue = {} attrName = org.jboss.weld.context.http.HttpSessionContext#org.jboss.weld.bean-Discipline-ManagedBean-class com.netease.qa.discipline.profile.User : attrValue = Bean: Managed Bean [class com.netease.qa.discipline.profile.User] with qualifiers [@Any @Default @Named]; Instance: com.netease.qa.discipline.profile.User@c497c7c; CreationalContext: org.jboss.weld.context.CreationalContextImpl@739efd29 attrName = javax.faces.request.charset : attrValue = UTF-8 org.apache.catalina.session.StandardSessionFacade@5d7b4092 StandardSession[c6ab4b0c51ee0a649ef696faef75] attrName = org.jboss.weld.context.conversation.ConversationIdGenerator : attrValue = org.jboss.weld.context.conversation.ConversationIdGenerator@583c9dd8 attrName = com.sun.faces.renderkit.ServerSideStateHelper.LogicalViewMap : attrValue = {-4968076393130137442={-7694826198761889564=[Ljava.lang.Object;@43ff5d6c}} attrName = org.jboss.weld.context.ConversationContext.conversations : attrValue = {} attrName = org.jboss.weld.context.http.HttpSessionContext#org.jboss.weld.bean-Discipline-ManagedBean-class com.netease.qa.discipline.profile.User : attrValue = Bean: Managed Bean [class com.netease.qa.discipline.profile.User] with qualifiers [@Any @Default @Named]; Instance: com.netease.qa.discipline.profile.User@c497c7c; CreationalContext: org.jboss.weld.context.CreationalContextImpl@739efd29 attrName = javax.faces.request.charset : attrValue = UTF-8 Above block contains two successive logins and their Session info. We can see that the instance(1st row) the same while session id(2nd row) different. Seems that session object is reused to contain different session id and CDI framework manages session bean life cycle in accordance with the session object only(?). I'm wondering whether there could be only one server-side session object within the same browser unless invalidated? Since I'm adopting j_security_check I fancy intercepting it and invalidating old session is not so easy. So is it possible to accomplish the goal without altering the CDI+JSF+j_security_check design that one can relogin with different account in the same or different tab within the same browser? Really look forward for your response. More info: Glassfish v3.1 is my appserver.

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• C# - How to override GetHashCode with Lists in object

  - by Christian

  Hi, I am trying to create a "KeySet" to modify UIElement behaviour. The idea is to create a special function if, eg. the user clicks on an element while holding a. Or ctrl+a. My approach so far, first lets create a container for all possible modifiers. If I would simply allow a single key, it would be no problem. I could use a simple Dictionary, with Dictionary<Keys, Action> _specialActionList If the dictionary is empty, use the default action. If there are entries, check what action to use depending on current pressed keys And if I wasn't greedy, that would be it... Now of course, I want more. I want to allow multiple keys or modifiers. So I created a wrapper class, wich can be used as Key to my dictionary. There is an obvious problem when using a more complex class. Currently two different instances would create two different key, and thereby he would never find my function (see code to understand, really obvious) Now I checked this post: http://stackoverflow.com/questions/638761/c-gethashcode-override-of-object-containing-generic-array which helped a little. But my question is, is my basic design for the class ok. Should I use a hashset to store the modifier and normal keyboardkeys (instead of Lists). And If so, how would the GetHashCode function look like? I know, its a lot of code to write (boring hash functions), some tips would be sufficient to get me started. Will post tryouts here... And here comes the code so far, the Test obviously fails... public class KeyModifierSet { private readonly List<Key> _keys = new List<Key>(); private readonly List<ModifierKeys> _modifierKeys = new List<ModifierKeys>(); private static readonly Dictionary<KeyModifierSet, Action> _testDict = new Dictionary<KeyModifierSet, Action>(); public static void Test() { _testDict.Add(new KeyModifierSet(Key.A), () => Debug.WriteLine("nothing")); if (!_testDict.ContainsKey(new KeyModifierSet(Key.A))) throw new Exception("Not done yet, help :-)"); } public KeyModifierSet(IEnumerable<Key> keys, IEnumerable<ModifierKeys> modifierKeys) { foreach (var key in keys) _keys.Add(key); foreach (var key in modifierKeys) _modifierKeys.Add(key); } public KeyModifierSet(Key key, ModifierKeys modifierKey) { _keys.Add(key); _modifierKeys.Add(modifierKey); } public KeyModifierSet(Key key) { _keys.Add(key); } }

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• being able to solve google code jam problem sets

  - by JPro

  This is not a homework question, but rather my intention to know if this is what it takes to learn programming. I keep loggin into TopCoder not to actually participate but to get the basic understand of how the problems are solved. But to my knowledge I don't understand what the problem is and how to translate the problem into an algorithm that can solve it. Just now I happen to look at ACM ICPC 2010 World Finals which is being held in china. The teams were given problem sets and one of them is this: Given at most 100 points on a plan with distinct x-coordinates, find the shortest cycle that passes through each point exactly once, goes from the leftmost point always to the right until it reaches the rightmost point, then goes always to the left until it gets back to the leftmost point. Additionally, two points are given such that the the path from left to right contains the first point, and the path from right to left contains the second point. This seems to be a very simple DP: after processing the last k points, and with the first path ending in point a and the second path ending in point b, what is the smallest total length to achieve that? This is O(n^2) states, transitions in O(n). We deal with the two special points by forcing the first path to contain the first one, and the second path contain the second one. Now I have no idea what I am supposed to solve after reading the problem set. and there's an other one from google code jam: Problem In a big, square room there are two point light sources: one is red and the other is green. There are also n circular pillars. Light travels in straight lines and is absorbed by walls and pillars. The pillars therefore cast shadows: they do not let light through. There are places in the room where no light reaches (black), where only one of the two light sources reaches (red or green), and places where both lights reach (yellow). Compute the total area of each of the four colors in the room. Do not include the area of the pillars. Input * One line containing the number of test cases, T. Each test case contains, in order: * One line containing the coordinates x, y of the red light source. * One line containing the coordinates x, y of the green light source. * One line containing the number of pillars n. * n lines describing the pillars. Each contains 3 numbers x, y, r. The pillar is a disk with the center (x, y) and radius r. The room is the square described by 0 = x, y = 100. Pillars, room walls and light sources are all disjoint, they do not overlap or touch. Output For each test case, output: Case #X: black area red area green area yellow area Is it required that people who program should be should be able to solve these type of problems? I would apprecite if anyone can help me interpret the google code jam problem set as I wish to participate in this years Code Jam to see if I can do anthing or not. Thanks.

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• Hidden Features of PHP?

  - by George Mauer

  EDIT: This didn't really start as a hidden features of PHP topic, but thats what it ended up as, so go nuts. I know this sounds like a point-whoring question but let me explain where I'm coming from. Out of college I got a job at a PHP shop. I worked there for a year and a half and thought that I had learned all there was to learn about programming. Then I got a job as a one-man internal development shop at a sizable corporation where all the work was in C#. In my commitment to the position I started reading a ton of blogs and books and quickly realized how wrong I was to think I knew everything. I learned about unit testing, dependency injection and decorator patterns, the design principle of loose coupling, the composition over inheritance debate, and so on and on and on - I am still very much absorbing it all. Needless to say my programming style has changed entirely in the last year. Now I find myself picking up a php project doing some coding for a friend's start-up and I feel completely constrained as opposed to programming in C#. It really bothers me that all variables at a class scope have to be referred to by appending '$this-' . It annoys me that none of the IDEs that I've tried have very good intellisense and that my SimpleTest unit tests methods have to start with the word 'test'. It drives me crazy that dynamic typing keeps me from specifying implicitly which parameter type a method expects, and that you have to write a switch statement to do method overloads. I can't stand that you can't have nested namespaces and have to use the :: operator to call the base class's constructor. Now I have no intention of starting a PHP vs C# debate, rather what I mean to say is that I'm sure there are some PHP features that I either don't know about or know about yet fail to use properly. I am set in my C# universe and having trouble seeing outside the glass bowl. So I'm asking, what are your favorite features of PHP? What are things you can do in it that you can't or are more difficult in the .Net languages?

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• TripleDES in Perl/PHP/ColdFusion

  - by Seidr

  Recently a problem arose regarding hooking up an API with a payment processor who were requesting a string to be encrypted to be used as a token, using the TripleDES standard. Our Applications run using ColdFusion, which has an Encrypt tag - that supports TripleDES - however the result we were getting back was not what the payment processor expected. First of all, here is the resulting token the payment processor were expecting. AYOF+kRtg239Mnyc8QIarw== And below is the snippet of ColdFusion we were using, and the resulting string. <!--- Coldfusion Crypt (here be monsters) ---> <cfset theKey="123412341234123412341234"> <cfset theString = "username=test123"> <cfset strEncodedEnc = Encrypt(theString, theKey, "DESEDE", "Base64")> <!--- resulting string(strEncodedEnc): tc/Jb7E9w+HpU2Yvn5dA7ILGmyNTQM0h ---> As you can see, this was not returning the string we were hoping for. Seeking a solution, we ditched ColdFusion for this process and attempted to reproduce the token in PHP. Now I'm aware that various languages implement encryption in different ways - for example in the past managing encryption between a C# application and PHP back-end, I've had to play about with padding in order to get the two to talk, but my experience has been that PHP generally behaves when it comes to encryption standards. Anyway, on to the PHP source we tried, and the resulting string. /* PHP Circus (here be Elephants) */ $theKey="123412341234123412341234"; $theString="username=test123"; $strEncodedEnc=base64_encode(mcrypt_ecb (MCRYPT_3DES, $theKey, $theString, MCRYPT_ENCRYPT)); /* resulting string(strEncodedEnc): sfiSu4mVggia8Ysw98x0uw== */ As you can plainly see, we've got another string that differs from both the string expected by the payment processor AND the one produced by ColdFusion. Cue head-against-wall integration techniques. After many to-and-fro communications with the payment processor (lots and lots of reps stating 'we can't help with coding issues, you must be doing it incorrectly, read the manual') we were finally escalated to someone with more than a couple of brain-cells to rub together, who was able to step back and actually look at and diagnose the issue. He agreed, our CF and PHP attempts were not resulting in the correct string. After a quick search, he also agreed that it was not neccesarily our source, but rather how the two languages implemented their vision of the TripleDES standard. Coming into the office this morning, we were met by an email with a snippet of source code, in Perl. This is was the code they were directly using on their end to produce the expected token. #!/usr/bin/perl # Perl Crypt Calamity (here be...something) use strict; use CGI; use MIME::Base64; use Crypt::TripleDES; my $cgi = CGI->new(); my $param = $cgi->Vars(); $param->{key} = "123412341234123412341234"; $param->{string} = "username=test123"; my $des = Crypt::TripleDES->new(); my $enc = $des->encrypt3($param->{string}, $param->{key}); $enc = encode_base64($enc); $enc =~ s/\n//gs; # resulting string (enc): AYOF+kRtg239Mnyc8QIarw== So, there we have it. Three languages, three implementations of what they quote in the documentation as TripleDES Standard Encryption, and three totally different resulting strings. My question is, from your experience of these three languages and their implementations of the TripleDES algorithm, have you been able to get any two of them to give the same response, and if so what tweaks to the code did you have to make in order to come to the result? I understand this is a very drawn out question, but I wanted to give clear and precise setting for each stage of testing that we had to perform. I'll also be performing some more investigatory work on this subject later, and will post any findings that I come up with to this question, so that others may avoid this headache.

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• Is the Scala 2.8 collections library a case of "the longest suicide note in history" ?

  - by oxbow_lakes

  First note the inflammatory subject title is a quotation made about the manifesto of a UK political party in the early 1980s. This question is subjective but it is a genuine question, I've made it CW and I'd like some opinions on the matter. Despite whatever my wife and coworkers keep telling me, I don't think I'm an idiot: I have a good degree in mathematics from the University of Oxford and I've been programming commercially for almost 12 years and in Scala for about a year (also commercially). I have just started to look at the Scala collections library re-implementation which is coming in the imminent 2.8 release. Those familiar with the library from 2.7 will notice that the library, from a usage perspective, has changed little. For example... > List("Paris", "London").map(_.length) res0: List[Int] List(5, 6) ...would work in either versions. The library is eminently useable: in fact it's fantastic. However, those previously unfamiliar with Scala and poking around to get a feel for the language now have to make sense of method signatures like: def map[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That For such simple functionality, this is a daunting signature and one which I find myself struggling to understand. Not that I think Scala was ever likely to be the next Java (or /C/C++/C#) - I don't believe its creators were aiming it at that market - but I think it is/was certainly feasible for Scala to become the next Ruby or Python (i.e. to gain a significant commercial user-base) Is this going to put people off coming to Scala? Is this going to give Scala a bad name in the commercial world as an academic plaything that only dedicated PhD students can understand? Are CTOs and heads of software going to get scared off? Was the library re-design a sensible idea? If you're using Scala commercially, are you worried about this? Are you planning to adopt 2.8 immediately or wait to see what happens? Steve Yegge once attacked Scala (mistakenly in my opinion) for what he saw as its overcomplicated type-system. I worry that someone is going to have a field day spreading fud with this API (similarly to how Josh Bloch scared the JCP out of adding closures to Java). Note - I should be clear that, whilst I believe that Josh Bloch was influential in the rejection of the BGGA closures proposal, I don't ascribe this to anything other than his honestly-held beliefs that the proposal represented a mistake.

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• How to break a Hibernate session?

  - by Péter Török

  In the Hibernate reference, it is stated several times that All exceptions thrown by Hibernate are fatal. This means you have to roll back the database transaction and close the current Session. You aren’t allowed to continue working with a Session that threw an exception. One of our legacy apps uses a single session to update/insert many records from files into a DB table. Each recourd update/insert is done in a separate transaction, which is then duly committed (or rolled back in case an error occurred). Then for the next record a new transaction is opened etc. But the same session is used throughout the whole process, even if a HibernateException was caught in the middle. We are using Oracle 9i btw with Hibernate 3.24.sp1 on JBoss 4.2. Reading the above in the book, I realized that this design may fail. So I refactored the app to use a separate session for each record update. In a unit test with a mock session factory, I could prove that it is now requesting a new session for each record update. So far, so good. However, we found no way to reproduce the session failure while testing the whole app (would this be a stress test btw, or ...?). We thought of shutting down the listener of the DB but we realized that the app is keeping a bunch of connections open to the DB, and the listener would not affect those connections. (This is a web app, activated once every night by a scheduler, but it can also be activated via the browser.) Then we tried to kill some of those connections in the DB while the app was processing updates - this resulted in some failed updates, but then the app happily continued. Apparently Hibernate is clever enough to reopen broken connections under the hood without breaking the whole session. So this might not be a critical issue, as our app seems to be robust enough even in its original form. However, the issue keeps bugging me. I would like to know: Under what circumstances does the Hibernate session really become unusable after a HibernateException was thrown? How to reproduce this in a test? (What's the proper term for such a test?)

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• How to write a cctor and op= for a factory class with ptr to abstract member field?

  - by Kache4

  I'm extracting files from zip and rar archives into raw buffers. I created the following to wrap minizip and unrarlib: Archive.hpp #include "ArchiveBase.hpp" #include "ArchiveDerived.hpp" class Archive { public: Archive(string path) { /* logic here to determine type */ switch(type) { case RAR: archive_ = new ArchiveRar(path); break; case ZIP: archive_ = new ArchiveZip(path); break; case UNKNOWN_ARCHIVE: throw; break; } } Archive(Archive& other) { archive_ = // how do I copy an abstract class? } ~Archive() { delete archive_; } void passThrough(ArchiveBase::Data& data) { archive_->passThrough(data); } Archive& operator = (Archive& other) { if (this == &other) return *this; ArchiveBase* newArchive = // can't instantiate.... delete archive_; archive_ = newArchive; return *this; } private: ArchiveBase* archive_; } ArchiveBase.hpp class ArchiveBase { public: // Is there any way to put this struct in Archive instead, // so that outside classes instantiating one could use // Archive::Data instead of ArchiveBase::Data? struct Data { int field; }; virtual void passThrough(Data& data) = 0; /* more methods */ } ArchiveDerived.hpp "Derived" being "Zip" or "Rar" #include "ArchiveBase.hpp" class ArchiveDerived : public ArchiveBase { public: ArchiveDerived(string path); void passThrough(ArchiveBase::Data& data); private: /* fields needed by minizip/unrarlib */ // example zip: unzFile zipFile_; // example rar: RARHANDLE rarFile_; } ArchiveDerived.cpp #include "ArchiveDerived.hpp" ArchiveDerived::ArchiveDerived(string path) { //implement } ArchiveDerived::passThrough(ArchiveBase::Data& data) { //implement } Somebody had suggested I use this design so that I could do: Archive archiveFile(pathToZipOrRar); archiveFile.passThrough(extractParams); // yay polymorphism! How do I write a cctor for Archive? What about op= for Archive? What can I do about "renaming" ArchiveBase::Data to Archive::Data? (Both minizip and unrarlib use such structs for input and output. Data is generic for Zip & Rar and later is used to create the respective library's struct.)

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• Putting update logic in your migrations

  - by Daniel Abrahamsson

  A couple of times I've been in the situation where I've wanted to refactor the design of some model and have ended up putting update logic in migrations. However, as far as I've understood, this is not good practice (especially since you are encouraged to use your schema file for deployment, and not your migrations). How do you deal with these kind of problems? To clearify what I mean, say I have a User model. Since I thought there would only be two kinds of users, namely a "normal" user and an administrator, I chose to use a simple boolean field telling whether the user was an adminstrator or not. However, after I while I figured I needed some third kind of user, perhaps a moderator or something similar. In this case I add a UserType model (and the corresponding migration), and a second migration for removing the "admin" flag from the user table. And here comes the problem. In the "add_user_type_to_users" migration I have to map the admin flag value to a user type. Additionally, in order to do this, the user types have to exist, meaning I can not use the seeds file, but rather create the user types in the migration (also considered bad practice). Here comes some fictional code representing the situation: class CreateUserTypes < ActiveRecord::Migration def self.up create_table :user_types do |t| t.string :name, :nil => false, :unique => true end #Create basic types (can not put in seed, because of future migration dependency) UserType.create!(:name => "BASIC") UserType.create!(:name => "MODERATOR") UserType.create!(:name => "ADMINISTRATOR") end def self.down drop_table :user_types end end class AddTypeIdToUsers < ActiveRecord::Migration def self.up add_column :users, :type_id, :integer #Determine type via the admin flag basic = UserType.find_by_name("BASIC") admin = UserType.find_by_name("ADMINISTRATOR") User.all.each {|u| u.update_attribute(:type_id, (u.admin?) ? admin.id : basic.id)} #Remove the admin flag remove_column :users, :admin #Add foreign key execute "alter table users add constraint fk_user_type_id foreign key (type_id) references user_types (id)" end def self.down #Re-add the admin flag add_column :users, :admin, :boolean, :default => false #Reset the admin flag (this is the problematic update code) admin = UserType.find_by_name("ADMINISTRATOR") execute "update users set admin=true where type_id=#{admin.id}" #Remove foreign key constraint execute "alter table users drop foreign key fk_user_type_id" #Drop the type_id column remove_column :users, :type_id end end As you can see there are two problematic parts. First the row creation part in the first model, which is necessary if I would like to run all migrations in a row, then the "update" part in the second migration that maps the "admin" column to the "type_id" column. Any advice?

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• Using the HTML 'label' tag with radio buttons

  - by GlenPeterson

  Does the label tag work with radio buttons? If so, how do you use it? I have a form that displays like this: First Name: (text field) Hair Color: (color drop-down) Description: (text area) Salutation: (radio buttons for Mr., Mrs., Miss) I'd like to use the label tag for each label in the left column to define its connection to the appropriate control in the right column. But If I use a radio button, the spec seems to indicate that suddenly the actual "Salutation" label for the form control no longer belongs in the label tag, but rather the options "Mr., Mrs., etc." go in the label tag. I've always been a fan of accessibility and the semantic web, but this design doesn't make sense to me. The label tag explicitly declares labels. The option tag selection options. How do you declare a label on the actual label for a set of radio buttons? UPDATE: Here is an example with code: <tr><th><label for"sc">Status:</label></th> <td>&#160;</td> <td><select name="statusCode" id="sc"> <option value="ON_TIME">On Time</option> <option value="LATE">Late</option> </select></td></tr> This works great. But unlike other form controls, radio buttons have a separate field for each value: <tr><th align="right"><label for="???">Activity:</label></th> <td>&#160;</td> <td align="left"><input type="radio" name="es" value="" id="es0" /> Active &#160; <input type="radio" name="es" value="ON_TIME" checked="checked" id="es1" /> Completed on Time &#160; <input type="radio" name="es" value="LATE" id="es2" /> Completed Late &#160; <input type="radio" name="es" value="CANCELED" id="es3" /> Canceled</td> </tr> What to do?

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• Spring/RMI server error

  - by 4herpsand7derpsago

  We have a Spring MVC web app (WAR) deploying to Tomcat (6.0.35) that launches a thread inside a separate JVM at deploy time (don't ask why - not my design) and then communicates with that thread via RMI over port 8888. Despite being totally convoluded, this was working perfectly fine up until yesterday, and now the thread is failing at startup and despite our best efforts to add logging into the mix, we are hitting a wall. This is the only exception we are able to find in the logs: Jun 12, 2012 3:11:36 AM com.ourapp.ImageController destroy SEVERE: Shutdown Error: Lookup of RMI stub failed; nested exception is java.rmi.ConnectException: Connection refused to host: localhost; nested exception is: java.net.ConnectException: Connection refused Jun 12, 2012 3:11:37 AM org.apache.catalina.core.StandardContext listenerStop SEVERE: Exception sending context destroyed event to listener instance of class org.springframework.web.context.ContextLoaderListener java.lang.NoClassDefFoundError: org/springframework/web/context/ContextCleanupListener at org.springframework.web.context.ContextLoaderListener.contextDestroyed(ContextLoaderListener.java:80) at org.apache.catalina.core.StandardContext.listenerStop(StandardContext.java:3973) at org.apache.catalina.core.StandardContext.stop(StandardContext.java:4577) at org.apache.catalina.startup.HostConfig.checkResources(HostConfig.java:1165) at org.apache.catalina.startup.HostConfig.check(HostConfig.java:1271) at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:296) at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119) at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1337) at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1601) at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1610) at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1590) at java.lang.Thread.run(Thread.java:662) Caused by: java.lang.ClassNotFoundException: org.springframework.web.context.ContextCleanupListener at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1387) at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1233) ... 12 more The ImageController is the Spring MVC Controller that is responsible for kicking off this daemon/spawned RMI thread. Based on the verbage of this error, does anybody have any idea what might be causing this "connection refused" error? Running a netstat -an | grep 8888 (this is a Linux machine) produces no output which means nothing is listening on that port. Thanks in advance for any ideas/suggestions that lead to a fix. Edit: Here's another ConnectionException we're seeing: Caused by: java.net.ConnectException: Connection refused at java.net.PlainSocketImpl.socketConnect(Native Method) at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:351) at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:213) at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:200) at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366) at java.net.Socket.connect(Socket.java:529) at java.net.Socket.connect(Socket.java:478) at java.net.Socket.<init>(Socket.java:375) at java.net.Socket.<init>(Socket.java:189) at sun.rmi.transport.proxy.RMIDirectSocketFactory.createSocket(RMIDirectSocketFactory.java:22) at sun.rmi.transport.proxy.RMIMasterSocketFactory.createSocket(RMIMasterSocketFactory.java:128) at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:595) ... 74 more

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• Problem with memset after an instance of a user defined class is created and a file is opened

  - by Liberalkid

  I'm having a weird problem with memset, that was something to do with a class I'm creating before it and a file I'm opening in the constructor. The class I'm working with normally reads in an array and transforms it into another array, but that's not important. The class I'm working with is: #include <vector> #include <algorithm> using namespace std; class PreProcess { public: PreProcess(char* fileName,char* outFileName); void SortedOrder(); private: vector< vector<double > > matrix; void SortRow(vector<double> &row); char* newFileName; vector< pair<double,int> > rowSorted; }; The other functions aren't important, because I've stopped calling them and the problem persists. Essentially I've narrowed it down to my constructor: PreProcess::PreProcess(char* fileName,char* outFileName):newFileName(outFileName){ ifstream input(fileName); input.close(); //this statement is inconsequential } I also read in the file in my constructor, but I've found that the problem persists if I don't read in the matrix and just open the file. Essentially I've narrowed it down to if I comment out those two lines the memset works properly, otherwise it doesn't. Now to the context of the problem I'm having with it: I wrote my own simple wrapper class for matrices. It doesn't have much functionality, I just need 2D arrays in the next part of my project and having a class handle everything makes more sense to me. The header file: #include <iostream> using namespace std; class Matrix{ public: Matrix(int r,int c); int &operator()(int i,int j) {//I know I should check my bounds here return matrix[i*columns+j]; } ~Matrix(); const void Display(); private: int *matrix; const int rows; const int columns; }; Driver: #include "Matrix.h" #include <string> using namespace std; Matrix::Matrix(int r,int c):rows(r),columns(c) { matrix=new int[rows*columns]; memset(matrix,0,sizeof(matrix)); } const void Matrix::Display(){ for(int i=0;i<rows;i++){ for(int j=0;j<columns;j++) cout << (*this)(i,j) << " "; cout << endl; } } Matrix::~Matrix() { delete matrix; } My main program runs: PreProcess test1(argv[1],argv[2]); //test1.SortedOrder(); Matrix test(10,10); test.Display(); And when I run this with the input line uncommented I get: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -1371727776 32698 -1 0 0 0 0 0 6332656 0 -1 -1 0 0 6332672 0 0 0 0 0 0 0 0 0 0 0 0 0 -1371732704 32698 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 I really don't have a clue what's going on in memory to cause this, on a side note if I replace memset with: for(int i=0;i<rows*columns;i++) *(matrix+i) &= 0x0; Then it works perfectly, it also works if I don't open the file. If it helps I'm running GCC 64-bit version 4.2.4 on Ubuntu.I assume there's some functionality of memset that I'm not properly understanding.

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• Learning to create beautiful /next-generation GUI

  - by ShaChris23

  I really want to create a stunning-looking GUI desktop application that looks like, for example: Mac OS X interface Picasa desktop client on windows IPhone apps Office 2007 I've mostly been programming GUI using Qt/Swing/WinForm and I'm tired of creating so plain looking GUI, lol. So I was thinking about diving into stuff like: jQuery WPF/C# iPhone SDK Silverlight Adobe Air/Flex Just to get some ideas on how to create really cool looking UI. Does that sound like a good list? Any developers here that could share what platform they use to create very cool looking desktop app? On a sidenote, I really wonder what developers at Apple / Microsoft use to develop their own cool-looking software. EDIT A lot of responses talk about the importance of usability over "cool-looking".. I totally agree that usability and simplicity are the most important aspects of user interface design. I've been doing GUI development for a while now ( 3 years), so that I understand. But using cool-looking UI also improves user experience + it could make big difference on whether or not your software sells. I mean, otherwise why would Microsoft/Apple try to make their OS UI look "cooler" everytime there's a new version? Why would websites like pragprog.com, or versionsapp.com. make their websites look like that? Basically you kill 2 birds with one stone: stunnning-looking UI + super usability (because it looks simple and intuitive). That is what I'm striving for. And as far as I know, I cannot achieve that using Qt/Winform. Most of the books I have read just show you how to make average-looking (read: 1990's) UI. I want to learn how to create cool-looking UI. And the only place I see cool-looking UIs these days are the technology I list above. I'm not enamored with any technology; but I just want to know how things are done in other technology to see if I could apply them to the technology I'm using, or see if I could use those technology in my line of work. An example: if I were to pick between this UI and this UI, I probably would pick the latter, if just based on looks alone. Functionally, they are just the same UI; they both allow you to keep track of your time. They both contain buttons and textboxes, etc. But the fact that they look different, also differentiate them in terms of attractiveness. So in all, I think the "ice on the cake" is very important. I would say it's the thing you strive for after you are certain you have a totally intuitive, usable UI.

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• Does this MSDN article violate MVVM?

  - by rasx

  This may be old news but back in March 2009, this article, “Model-View-ViewModel In Silverlight 2 Apps,” has a code sample that includes DataServiceEntityBase: // COPIED FROM SILVERLIGHTCONTRIB Project for simplicity /// <summary> /// Base class for DataService Data Contract classes to implement /// base functionality that is needed like INotifyPropertyChanged. /// Add the base class in the partial class to add the implementation. /// </summary> public abstract class DataServiceEntityBase : INotifyPropertyChanged { /// <summary> /// The handler for the registrants of the interface's event /// </summary> PropertyChangedEventHandler _propertyChangedHandler; /// <summary> /// Allow inheritors to fire the event more simply. /// </summary> /// <param name="propertyName"></param> protected void FirePropertyChanged(string propertyName) { if (_propertyChangedHandler != null) { _propertyChangedHandler(this, new PropertyChangedEventArgs(propertyName)); } } #region INotifyPropertyChanged Members /// <summary> /// The interface used to notify changes on the entity. /// </summary> event PropertyChangedEventHandler INotifyPropertyChanged.PropertyChanged { add { _propertyChangedHandler += value; } remove { _propertyChangedHandler -= value; } } #endregion What this class implies is that the developer intends to bind visuals directly to data (yes, a ViewModel is used but it defines an ObservableCollection of data objects). Is this design diverging too far from the guidance of MVVM? Now I can see some of the reasons Why would we go this way: what we can do with DataServiceEntityBase is this sort of thing (which is intimate with the Entity Framework): // Partial Method to support the INotifyPropertyChanged interface public partial class Game : DataServiceEntityBase { #region Partial Method INotifyPropertyChanged Implementation // Override the Changed partial methods to implement the // INotifyPropertyChanged interface // This helps with the Model implementation to be a mostly // DataBound implementation partial void OnDeveloperChanged() { base.FirePropertyChanged("Developer"); } partial void OnGenreChanged() { base.FirePropertyChanged("Genre"); } partial void OnListPriceChanged() { base.FirePropertyChanged("ListPrice"); } partial void OnListPriceCurrencyChanged() { base.FirePropertyChanged("ListPriceCurrency"); } partial void OnPlayerInfoChanged() { base.FirePropertyChanged("PlayerInfo"); } partial void OnProductDescriptionChanged() { base.FirePropertyChanged("ProductDescription"); } partial void OnProductIDChanged() { base.FirePropertyChanged("ProductID"); } partial void OnProductImageUrlChanged() { base.FirePropertyChanged("ProductImageUrl"); } partial void OnProductNameChanged() { base.FirePropertyChanged("ProductName"); } partial void OnProductTypeIDChanged() { base.FirePropertyChanged("ProductTypeID"); } partial void OnPublisherChanged() { base.FirePropertyChanged("Publisher"); } partial void OnRatingChanged() { base.FirePropertyChanged("Rating"); } partial void OnRatingUrlChanged() { base.FirePropertyChanged("RatingUrl"); } partial void OnReleaseDateChanged() { base.FirePropertyChanged("ReleaseDate"); } partial void OnSystemNameChanged() { base.FirePropertyChanged("SystemName"); } #endregion } Of course MSDN code can seen as “toy code” for educational purposes but is anyone doing anything like this in the real world of Silverlight development?

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• fd partitions gone from 2 discs, md happy with it and resyncs. How to recover ?

  - by d0nd

  Hey gurus, need some help badly with this one. I run a server with a 6Tb md raid5 volume built over 7*1Tb disks. I've had to shut down the server lately and when it went back up, 2 out of the 7 disks used for the raid volume had lost its conf : dmesg : [ 10.184167] sda: sda1 sda2 sda3 // System disk [ 10.202072] sdb: sdb1 [ 10.210073] sdc: sdc1 [ 10.222073] sdd: sdd1 [ 10.229330] sde: sde1 [ 10.239449] sdf: sdf1 [ 11.099896] sdg: unknown partition table [ 11.255641] sdh: unknown partition table All 7 disks have same geometry and were configured alike : dmesg : Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x1e7481a5 Device Boot Start End Blocks Id System /dev/sdb1 1 121601 976760001 fd Linux raid autodetect All 7 disks (sdb1, sdc1, sdd1, sde1, sdf1, sdg1, sdh1) were used in a md raid5 xfs volume. When booting, md, which was (obviously) out of sync kicked in and automatically started rebuilding over the 7 disks, including the two "faulty" ones; xfs tried to do some shenanigans as well: dmesg : [ 19.566941] md: md0 stopped. [ 19.817038] md: bind<sdc1> [ 19.817339] md: bind<sdd1> [ 19.817465] md: bind<sde1> [ 19.817739] md: bind<sdf1> [ 19.817917] md: bind<sdh> [ 19.818079] md: bind<sdg> [ 19.818198] md: bind<sdb1> [ 19.818248] md: md0: raid array is not clean -- starting background reconstruction [ 19.825259] raid5: device sdb1 operational as raid disk 0 [ 19.825261] raid5: device sdg operational as raid disk 6 [ 19.825262] raid5: device sdh operational as raid disk 5 [ 19.825264] raid5: device sdf1 operational as raid disk 4 [ 19.825265] raid5: device sde1 operational as raid disk 3 [ 19.825267] raid5: device sdd1 operational as raid disk 2 [ 19.825268] raid5: device sdc1 operational as raid disk 1 [ 19.825665] raid5: allocated 7334kB for md0 [ 19.825667] raid5: raid level 5 set md0 active with 7 out of 7 devices, algorithm 2 [ 19.825669] RAID5 conf printout: [ 19.825670] --- rd:7 wd:7 [ 19.825671] disk 0, o:1, dev:sdb1 [ 19.825672] disk 1, o:1, dev:sdc1 [ 19.825673] disk 2, o:1, dev:sdd1 [ 19.825675] disk 3, o:1, dev:sde1 [ 19.825676] disk 4, o:1, dev:sdf1 [ 19.825677] disk 5, o:1, dev:sdh [ 19.825679] disk 6, o:1, dev:sdg [ 19.899787] PM: Starting manual resume from disk [ 28.663228] Filesystem "md0": Disabling barriers, not supported by the underlying device [ 28.663228] XFS mounting filesystem md0 [ 28.884433] md: resync of RAID array md0 [ 28.884433] md: minimum _guaranteed_ speed: 1000 KB/sec/disk. [ 28.884433] md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for resync. [ 28.884433] md: using 128k window, over a total of 976759936 blocks. [ 29.025980] Starting XFS recovery on filesystem: md0 (logdev: internal) [ 32.680486] XFS: xlog_recover_process_data: bad clientid [ 32.680495] XFS: log mount/recovery failed: error 5 [ 32.682773] XFS: log mount failed I ran fdisk and flagged sdg1 and sdh1 as fd. I tried to reassemble the array but it didnt work: no matter what was in mdadm.conf, it still uses sdg and sdh instead of sdg1 and sdh1. I checked in /dev and I see no sdg1 and and sdh1, shich explains why it wont use it. I just don't know why those partitions are gone from /dev and how to readd those... blkid : /dev/sda1: LABEL="boot" UUID="519790ae-32fe-4c15-a7f6-f1bea8139409" TYPE="ext2" /dev/sda2: TYPE="swap" /dev/sda3: LABEL="root" UUID="91390d23-ed31-4af0-917e-e599457f6155" TYPE="ext3" /dev/sdb1: UUID="2802e68a-dd11-c519-e8af-0d8f4ed72889" TYPE="mdraid" /dev/sdc1: UUID="2802e68a-dd11-c519-e8af-0d8f4ed72889" TYPE="mdraid" /dev/sdd1: UUID="2802e68a-dd11-c519-e8af-0d8f4ed72889" TYPE="mdraid" /dev/sde1: UUID="2802e68a-dd11-c519-e8af-0d8f4ed72889" TYPE="mdraid" /dev/sdf1: UUID="2802e68a-dd11-c519-e8af-0d8f4ed72889" TYPE="mdraid" /dev/sdg: UUID="2802e68a-dd11-c519-e8af-0d8f4ed72889" TYPE="mdraid" /dev/sdh: UUID="2802e68a-dd11-c519-e8af-0d8f4ed72889" TYPE="mdraid" fdisk -l : Disk /dev/sda: 40.0 GB, 40020664320 bytes 255 heads, 63 sectors/track, 4865 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x8c878c87 Device Boot Start End Blocks Id System /dev/sda1 * 1 12 96358+ 83 Linux /dev/sda2 13 134 979965 82 Linux swap / Solaris /dev/sda3 135 4865 38001757+ 83 Linux Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x1e7481a5 Device Boot Start End Blocks Id System /dev/sdb1 1 121601 976760001 fd Linux raid autodetect Disk /dev/sdc: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0xc9bdc1e9 Device Boot Start End Blocks Id System /dev/sdc1 1 121601 976760001 fd Linux raid autodetect Disk /dev/sdd: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0xcc356c30 Device Boot Start End Blocks Id System /dev/sdd1 1 121601 976760001 fd Linux raid autodetect Disk /dev/sde: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0xe87f7a3d Device Boot Start End Blocks Id System /dev/sde1 1 121601 976760001 fd Linux raid autodetect Disk /dev/sdf: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0xb17a2d22 Device Boot Start End Blocks Id System /dev/sdf1 1 121601 976760001 fd Linux raid autodetect Disk /dev/sdg: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x8f3bce61 Device Boot Start End Blocks Id System /dev/sdg1 1 121601 976760001 fd Linux raid autodetect Disk /dev/sdh: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0xa98062ce Device Boot Start End Blocks Id System /dev/sdh1 1 121601 976760001 fd Linux raid autodetect I really dont know what happened nor how to recover from this mess. Needless to say the 5TB or so worth of data sitting on those disks are very valuable to me... Any idea any one? Did anybody ever experienced a similar situation or know how to recover from it ? Can someone help me? I'm really desperate... :x

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• Asynchronous vs Synchronous vs Threading in an iPhone App

  - by Coocoo4Cocoa

  I'm in the design stage for an app which will utilize a REST web service and sort of have a dilemma in as far as using asynchronous vs synchronous vs threading. Here's the scenario. Say you have three options to drill down into, each one having its own REST-based resource. I can either lazily load each one with a synchronous request, but that'll block the UI and prevent the user from hitting a back navigation button while data is retrieved. This case applies almost anywhere except for when your application requires a login screen. I can't see any reason to use synchronous HTTP requests vs asynchronous because of that reason alone. The only time it makes sense is to have a worker thread make your synchronous request, and notify the main thread when the request is done. This will prevent the block. The question then is bench marking your code and seeing which has more overhead, a threaded synchronous request or an asynchronous request. The problem with asynchronous requests is you need to either setup a smart notification or delegate system as you can have multiple requests for multiple resources happening at any given time. The other problem with them is if I have a class, say a singleton which is handling all of my data, I can't use asynchronous requests in a getter method. Meaning the following won't go: - (NSArray *)users { if(users == nil) users = do_async_request // NO GOOD return users; } whereas the following: - (NSArray *)users { if(users == nil) users == do_sync_request // OK. return users; } You also might have priority. What I mean by priority is if you look at Apple's Mail application on the iPhone, you'll notice they first suck down your entire POP/IMAP tree before making a second request to retrieve the first 2 lines (the default) of your message. I suppose my question to you experts is this. When are you using asynchronous, synchronous, threads -- and when are you using either async/sync in a thread? What kind of delegation system do you have setup to know what to do when a async request completes? Are you prioritizing your async requests? There's a gamut of solutions to this all too common problem. It's simple to hack something out. The problem is, I don't want to hack and I want to have something that's simple and easy to maintain.

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• Is there a way to handle the dynamic change of a dropdown for a single row in a grid-based datawindo

  - by TomatoSandwich

  Is there a way to handle the dynamic change of a dropdown for a single row in a grid-based datawindow? Example: NAME LIKABILITY PURCHASED IN COLOUR (Text) (DropDown*) (Text) (Text) Bananas [Good] Hands Yellow [Bad] [Bananas are good] Apples [Good] Bags Red [Bad] Given the above is a grid-based datawindow, where the fields 'NAME','PURCHASED IN' and 'COLOUR' are text fields, where as the 'LIKABILITY' field is a dropdown*. I say dropdown* because the same visual representation can be created by using a DropDownList (hardcoded within the datawindow element at design time), or a DropDownDW (or DDDW, a select statement that can be based on other elements in the datawindow). However, there is no way I can get 'Bananas' having it's 3 dropdowns, while Apples has only 2. If I enter multiple rows of 'Bananas', then all rows have 3 dropdowns, but as soon as I add an Apples row, all dropdowns revert to 2 selections. To attempt to achieve this functionality, I have tried the following options: -- 1) dw_1.Object.likability.values("Good~tG/Bad~tB/Bananas are good~tDRWHO") on ue_itemchange when editing NAME. FAILS: edits all instances of LIKABILITY instead of the current row. -- 2) Duplicate Dropdowns, having one filtered, one unfiltered selection list per row, visible based on NAME selection. FAILS: can't set visibility/overlapping columns on grid-based datawindow. (Source) -- 3) Hard-code display value as Database value, or Vice Versa. Have 'GOOD','BAD','BANANASAREGOOD' as the display and database values, and change handling of options from G, B, DRWHO to these new values. FAILS: 3rd option appears for all rows, still selectable on Apple rows, which is wrong. -- 4) DDDW retrieve list of options for dropdown. Create a DDDW that uses the value of NAME to determine what selections it should have for the dropdown. FAILS: edits all instances of the dropdown, not just the current row. -- 5) DDDW retrieve counter of options available (if B then 3 else 2), then have duplicate dropdown columns that protect/unprotect based on DDDW counter. FAILS: Can't autoselect dddw value to populate column to cause protect on other two columns, ugly solution in any case. -- There is now a bounty on this question for anyone who can give me a solution that will enable me to edit a dropdown column for a single row on a grid-based datawindow in PB 10.5

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• Adding a generic image field onto a ModelForm in django

  - by Prairiedogg

  I have two models, Room and Image. Image is a generic model that can tack onto any other model. I want to give users a form to upload an image when they post information about a room. I've written code that works, but I'm afraid I've done it the hard way, and specifically in a way that violates DRY. Was hoping someone who's a little more familiar with django forms could point out where I've gone wrong. Update: I've tried to clarify why I chose this design in comments to the current answers. To summarize: I didn't simply put an ImageField on the Room model because I wanted more than one image associated with the Room model. I chose a generic Image model because I wanted to add images to several different models. The alternatives I considered were were multiple foreign keys on a single Image class, which seemed messy, or multiple Image classes, which I thought would clutter my schema. I didn't make this clear in my first post, so sorry about that. Seeing as none of the answers so far has addressed how to make this a little more DRY I did come up with my own solution which was to add the upload path as a class attribute on the image model and reference that every time it's needed. # Models class Image(models.Model): content_type = models.ForeignKey(ContentType) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey('content_type', 'object_id') image = models.ImageField(_('Image'), height_field='', width_field='', upload_to='uploads/images', max_length=200) class Room(models.Model): name = models.CharField(max_length=50) image_set = generic.GenericRelation('Image') # The form class AddRoomForm(forms.ModelForm): image_1 = forms.ImageField() class Meta: model = Room # The view def handle_uploaded_file(f): # DRY violation, I've already specified the upload path in the image model upload_suffix = join('uploads/images', f.name) upload_path = join(settings.MEDIA_ROOT, upload_suffix) destination = open(upload_path, 'wb+') for chunk in f.chunks(): destination.write(chunk) destination.close() return upload_suffix def add_room(request, apartment_id, form_class=AddRoomForm, template='apartments/add_room.html'): apartment = Apartment.objects.get(id=apartment_id) if request.method == 'POST': form = form_class(request.POST, request.FILES) if form.is_valid(): room = form.save() image_1 = form.cleaned_data['image_1'] # Instead of writing a special function to handle the image, # shouldn't I just be able to pass it straight into Image.objects.create # ...but it doesn't seem to work for some reason, wrong syntax perhaps? upload_path = handle_uploaded_file(image_1) image = Image.objects.create(content_object=room, image=upload_path) return HttpResponseRedirect(room.get_absolute_url()) else: form = form_class() context = {'form': form, } return direct_to_template(request, template, extra_context=context)

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• I don't understand how work call_once

  - by SABROG

  Please help me understand how work call_once Here is thread-safe code. I don't understand why this need Thread Local Storage and global_epoch variables. Variable _fast_pthread_once_per_thread_epoch can be changed to constant/enum like {FAST_PTHREAD_ONCE_INIT, BEING_INITIALIZED, FINISH_INITIALIZED}. Why needed count calls in global_epoch? I think this code can be rewriting with logc: if flag FINISH_INITIALIZED do nothing, else go to block with mutexes and this all. #ifndef FAST_PTHREAD_ONCE_H #define FAST_PTHREAD_ONCE_H #include #include typedef sig_atomic_t fast_pthread_once_t; #define FAST_PTHREAD_ONCE_INIT SIG_ATOMIC_MAX extern __thread fast_pthread_once_t _fast_pthread_once_per_thread_epoch; #ifdef __cplusplus extern "C" { #endif extern void fast_pthread_once( pthread_once_t *once, void (*func)(void) ); inline static void fast_pthread_once_inline( fast_pthread_once_t *once, void (*func)(void) ) { fast_pthread_once_t x = *once; /* unprotected access */ if ( x _fast_pthread_once_per_thread_epoch ) { fast_pthread_once( once, func ); } } #ifdef __cplusplus } #endif #endif FAST_PTHREAD_ONCE_H Source fast_pthread_once.c The source is written in C. The lines of the primary function are numbered for reference in the subsequent correctness argument. #include "fast_pthread_once.h" #include static pthread_mutex_t mu = PTHREAD_MUTEX_INITIALIZER; /* protects global_epoch and all fast_pthread_once_t writes */ static pthread_cond_t cv = PTHREAD_COND_INITIALIZER; /* signalled whenever a fast_pthread_once_t is finalized */ #define BEING_INITIALIZED (FAST_PTHREAD_ONCE_INIT - 1) static fast_pthread_once_t global_epoch = 0; /* under mu */ __thread fast_pthread_once_t _fast_pthread_once_per_thread_epoch; static void check( int x ) { if ( x == 0 ) abort(); } void fast_pthread_once( fast_pthread_once_t *once, void (*func)(void) ) { /*01*/ fast_pthread_once_t x = *once; /* unprotected access */ /*02*/ if ( x _fast_pthread_once_per_thread_epoch ) { /*03*/ check( pthread_mutex_lock(µ) == 0 ); /*04*/ if ( *once == FAST_PTHREAD_ONCE_INIT ) { /*05*/ *once = BEING_INITIALIZED; /*06*/ check( pthread_mutex_unlock(µ) == 0 ); /*07*/ (*func)(); /*08*/ check( pthread_mutex_lock(µ) == 0 ); /*09*/ global_epoch++; /*10*/ *once = global_epoch; /*11*/ check( pthread_cond_broadcast(&cv;) == 0 ); /*12*/ } else { /*13*/ while ( *once == BEING_INITIALIZED ) { /*14*/ check( pthread_cond_wait(&cv;, µ) == 0 ); /*15*/ } /*16*/ } /*17*/ _fast_pthread_once_per_thread_epoch = global_epoch; /*18*/ check (pthread_mutex_unlock(µ) == 0); } } This code from BOOST: #ifndef BOOST_THREAD_PTHREAD_ONCE_HPP #define BOOST_THREAD_PTHREAD_ONCE_HPP // once.hpp // // (C) Copyright 2007-8 Anthony Williams // // Distributed under the Boost Software License, Version 1.0. (See // accompanying file LICENSE_1_0.txt or copy at // http://www.boost.org/LICENSE_1_0.txt) #include #include #include #include "pthread_mutex_scoped_lock.hpp" #include #include #include namespace boost { struct once_flag { boost::uintmax_t epoch; }; namespace detail { BOOST_THREAD_DECL boost::uintmax_t& get_once_per_thread_epoch(); BOOST_THREAD_DECL extern boost::uintmax_t once_global_epoch; BOOST_THREAD_DECL extern pthread_mutex_t once_epoch_mutex; BOOST_THREAD_DECL extern pthread_cond_t once_epoch_cv; } #define BOOST_ONCE_INITIAL_FLAG_VALUE 0 #define BOOST_ONCE_INIT {BOOST_ONCE_INITIAL_FLAG_VALUE} // Based on Mike Burrows fast_pthread_once algorithm as described in // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2444.html template void call_once(once_flag& flag,Function f) { static boost::uintmax_t const uninitialized_flag=BOOST_ONCE_INITIAL_FLAG_VALUE; static boost::uintmax_t const being_initialized=uninitialized_flag+1; boost::uintmax_t const epoch=flag.epoch; boost::uintmax_t& this_thread_epoch=detail::get_once_per_thread_epoch(); if(epoch #endif I right understand, boost don't use atomic operation, so code from boost not thread-safe?

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