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• Webcrawler, feedback?

  - by Jan Kuboschek

  Hey folks, every once in a while I have the need to automate data collection tasks from websites. Sometimes I need a bunch of URLs from a directory, sometimes I need an XML sitemap (yes, I know there is lots of software for that and online services). Anyways, as follow up to my previous question I've written a little webcrawler that can visit websites. Basic crawler class to easily and quickly interact with one website. Override "doAction(String URL, String content)" to process the content further (e.g. store it, parse it). Concept allows for multi-threading of crawlers. All class instances share processed and queued lists of links. Instead of keeping track of processed links and queued links within the object, a JDBC connection could be established to store links in a database. Currently limited to one website at a time, however, could be expanded upon by adding an externalLinks stack and adding to it as appropriate. JCrawler is intended to be used to quickly generate XML sitemaps or parse websites for your desired information. It's lightweight. Is this a good/decent way to write the crawler, provided the limitations above? http://pastebin.com/VtgC4qVE - Main.java http://pastebin.com/gF4sLHEW - JCrawler.java http://pastebin.com/VJ1grArt - HTMLUtils.java Thanks for your feedback in advance! :)

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• Ideas on frameworks in .NET that can be used for job processing and notifications

  - by Rajat Mehta

  Scenario: We have one instance of WCF windows service which exposes contracts like: AddNewJob(Job job), GetJobs(JobQuery query) etc. This service is consumed by 70-100 instances of client which is Windows Form based .NET app. Typically the service has 50-100 inward calls/minute to add or query jobs that are stored in a table on Sql Server. The same service is also responsible for processing these jobs in real time. It queries database every 5 seconds picks up the queued jobs and starts processing them. A job has 6 states. Queued, Pre-processing, Processing, Post-processing, Completed, Failed, Locked. Another responsibility on this service is to update all clients on every state change of every job. This means almost 200+ callbacks to clients per second. Question: This whole implementation is done using WCF Duplex bindings and works perfectly fine on small number of parallel jobs. Problem arises when we scale it up to 1000 jobs at a time. The notifications don't work as expected, it leads to memory overflow etc. Is there any standard framework that can provide a clean infrastructure for handling this scenario?? Apologies for the long explanation!

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• ASP.NET MVC Posted date field comes in as 1/1/0001

  - by engil

  Just started working with .NET and MVC(1). I'm having a problem wherein in my add action the entered date for some reason ends up as 1/1/0001 instead of what is entered thus causing a date overflow. In my model, this field ("Added") is is of type datetime and does not allow nulls. In my controller I have: public ActionResult Add() { Instance instance = new Instance() { Added = DateTime.Now, Active = true }; return View(instance); } [AcceptVerbs(HttpVerbs.Post)] public ActionResult Add(Instance instance) { if (ModelState.IsValid) { try { System.Diagnostics.Trace.Write("test"); instanceRepository.Add(instance); instanceRepository.Save(); return RedirectToAction("Details", new { id = instance.InstanceID }); } catch { ModelState.AddRuleViolations(instance.GetRuleViolations()); } } return View(instance); } And in my view I have: <div class="editor-label"> <%= Html.LabelFor(model => model.Added) %> </div> <div class="editor-field"> <%= Html.TextBoxFor(model => model.Added,String.Format("{0:g}",Model.Added))%> <%= Html.ValidationMessageFor(model => model.Added) %> When I first go to Instances/Add the default value is set correctly, however as soon as I submit the date turns into 1/1/0001 (from my understanding this indicates that it was either null or in an unrecognizable format) When I debug and palce a watch on Request.Form I see the date coming in encoded ie Request.Form {Added=4%2f9%2f2010+8%3a24%3a39+AM} - is this an issue? I know its probably not enough information to make a conlusive determination on why this is failing, but if someone could provide some good debugging tips on how to determine where the submitted date is getting munged I'd really appreciate it.

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• What's the pattern for a JSONP method that was initiated from a jQuery plugin?

  - by michielvoo

  I'm writing a jQuery plugin to render data retrieved from another domain in an element on the page. I follow the typical pattern for my jQuery plugin: $(selector).Plugin(options); In the plugin I get external data using jQuery.getScript(url, [success]). The external data source allows me to define the name of a method and it will wrap the data in a call to that method (JSONP): $.getScript("http://www.example.com/data?callback=global_callback", instance_callback); This effectively results in: <script type="text/javascript"> global_callback(data); </script> The scope of global_callback limits what the Plugin instance can do with the data. And the global_callback method has no knowledge of the selector or options that the plugin was instantiated with. I was thinking that global_callback would just store the data, and the plugin would retrieve the data in instance_callback. But I need to make sure that instance_callback will retrieve the correct data, I foresee a problem with multiple instances of the Plugin. How can I handle this? Thanks!

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• Migration solution for singletons in an OSGI environment

  - by Ido

  I'm working in a JEE Environment in which each application is in a war file of its own. In the WEB-INF/lib of each application war file there is a common jar that is shared by all applications. This common jar contains several Singletons which are accessed from many points in the code. Because of the war-file boundaries each application has its own instances of the Singletons. Which is how we operate today, since we want to configure some of the singletons differently in each application. Now we are moving towards an OSGi environment, where this solution will no longer work since each bundle has its own class loader, so if I try to access MySingleton which resides in bundle "common.jar" from bundle "appA.jar" or from bundle "appB.jar" I will get the same instance. Remember I "want" a different instance of a singleton per bundle. (as ironic as it sounds) Now I realize the ideal solution would be to fix the code to not rely on those singletons, however due to a tight schedule I was wondering if you guys can suggest some sort of a migration solution that would allow me to use bundle-wide singletons so each of them could be configured per bundle.

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• Alternative way of implementation of a code

  - by vikramjb

  The title is not exactly meaningful, but I am not share what else to name it. I wrote a TOC Generation code sometime later. Based on this I was writing code to check for duplicates also. The code is as follows curNumber = getTOCReference(selItem.SNo, IsParent); CheckForDuplicates(curNumber, IsParent,out realTOCRef); curNumber = realTOCRef; And the code for CheckForDuplicates is ListViewItem curItem = this.tlvItems.FindItemWithText(curNumber); if (curItem != null) { curNumber = this.getTOCReference(curNumber, !IsParent); CheckForDuplicates(curNumber, IsParent,out realTOCRef); } else { realTOCRef= curNumber; } What this code does, it gets a TOC and tries it find if it already exists in the ObjectListView and gets a new TOC if there is a existing TOC. Once it determines that the generated TOC is not there in the list it stores it in realTOCRef and sends it back to the main calling code. I have used "out" to return the last generated TOC, which is something I did not want to do. The reason why I did it was after the non duplicate TOC was generated the return was not going back to the calling code instead it looped through the previous instances then it returned back. When the looping back happened the TOC that was to be returned also got reset. I would appreciate any help on this.

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• problem when cloning jQuery UI datepicker

  - by h3

  I have a div in which there is a datepicker. I use something like this to clone it: mydiv = $('#someDiv'); // works fine so far mydiv.find('input.datefield').datepicker(); // clone without the events and insert newDiv = myDiv.clone(false).insertAfter(myDiv); // datepicker won't re-init if this class is present newDiv.find('.hadDatepicker').removeClass('hadDatepicker'); // reinitialize datepicker newDiv.find('input.datefield').datepicker(); This is a stripped down version of my code. It works and the calendar shows up as expected where it is expected .. but when a date is clicked, the previous datepicker's value gets updated.. (the one from which it was cloned). I've tried to destroy the (inexisting) instance before like this: newDiv.find('input.datefield').datepicker('destroy').datepicker(); No luck .. I've checked how it keeps track of instances and manually cleared the data like this: newDiv.find('input.datefield').data('datepicker', false).datepicker('destroy').datepicker(); Still no luck. What I don't understand is that only the date selection behavior is buggy, everything else works as expected. I really don't know what else to check now ..

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• Switching textstorage of NSTextViews back and forth

  - by Jakob Dam Jensen

  I'm trying to make a feature in a product which gives the user the ability to split a textview into two. The way this is done is by removing the textview from it's superview, making a NSSplitView and adding the textview as well as a new NSTextView instance to this splitview. Lastly I make these two textviews share the same textstorage in order to make them share the same content. It works great. But the problem is when I want to make one of the two textviews change textstorage. The replaceTextStorage method in NSLayoutManager causes both NSTextView to change textStorage. The API documentation states: replaceTextStorage: All NSLayoutManager objects sharing the original NSTextStorage object then share the new one. This method makes all the adjustments necessary to keep these relationships intact, unlike setTextStorage:. So it makes sense that it would do this. But the question is how do I make it possible to have two (or more) textviews first share the same storage and after that having them using their own? I've tried replacing the layoutManager and even making new instances of NSTextViews but no luck... Any suggestions?

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• Java Process.waitFor() and IO streams

  - by lynks

  I have the following code; String[] cmd = { "bash", "-c", "~/path/to/script.sh" }; Process p = Runtime.getRuntime().exec(cmd); PipeThread a = new PipeThread(p.getInputStream(), System.out); PipeThread b = new PipeThread(p.getErrorStream(), System.err); p.waitFor(); a.die(); b.die(); The PipeThread class is quite simple so I will include it in full; public class PipeThread implements Runnable { private BufferedInputStream in; private BufferedOutputStream out; public Thread thread; private boolean die = false; public PipeThread(InputStream i, OutputStream o) { in = new BufferedInputStream(i); out = new BufferedOutputStream(o); thread = new Thread(this); thread.start(); } public void die() { die = true; } public void run() { try { byte[] b = new byte[1024]; while(!die) { int x = in.read(b, 0, 1024); if(x > 0) out.write(b, 0, x); else die(); out.flush(); } } catch(Exception e) { e.printStackTrace(); } try { in.close(); out.close(); } catch(Exception e) { } } } My problem is this; p.waitFor() blocks endlessly, even after the subprocess has terminated. If I do not create the pair of PipeThread instances, then p.waitFor() works perfectly. What is it about the piping of io streams that is causing p.waitFor() to continue blocking? I'm confused as I thought the IO streams would be passive, unable to keep a process alive, or to make Java think the process is still alive.

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• Why does Microsoft advise against readonly fields with mutable values?

  - by Weeble

  In the Design Guidelines for Developing Class Libraries, Microsoft say: Do not assign instances of mutable types to read-only fields. The objects created using a mutable type can be modified after they are created. For example, arrays and most collections are mutable types while Int32, Uri, and String are immutable types. For fields that hold a mutable reference type, the read-only modifier prevents the field value from being overwritten but does not protect the mutable type from modification. This simply restates the behaviour of readonly without explaining why it's bad to use readonly. The implication appears to be that many people do not understand what "readonly" does and will wrongly expect readonly fields to be deeply immutable. In effect it advises using "readonly" as code documentation indicating deep immutability - despite the fact that the compiler has no way to enforce this - and disallows its use for its normal function: to ensure that the value of the field doesn't change after the object has been constructed. I feel uneasy with this recommendation to use "readonly" to indicate something other than its normal meaning understood by the compiler. I feel that it encourages people to misunderstand the meaning of "readonly", and furthermore to expect it to mean something that the author of the code might not intend. I feel that it precludes using it in places it could be useful - e.g. to show that some relationship between two mutable objects remains unchanged for the lifetime of one of those objects. The notion of assuming that readers do not understand the meaning of "readonly" also appears to be in contradiction to other advice from Microsoft, such as FxCop's "Do not initialize unnecessarily" rule, which assumes readers of your code to be experts in the language and should know that (for example) bool fields are automatically initialised to false, and stops you from providing the redundancy that shows "yes, this has been consciously set to false; I didn't just forget to initialize it". So, first and foremost, why do Microsoft advise against use of readonly for references to mutable types? I'd also be interested to know: Do you follow this Design Guideline in all your code? What do you expect when you see "readonly" in a piece of code you didn't write?

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• How can I move TinyMCE's toolbar into a modal popup?

  - by Nate Wagar

  I'm using TinyMCE & jQuery and am having a problem moving TinyMCE's external toolbar to another location in the DOM. To further complicate things, there are multiple TinyMCE instances on the page. I only want the toolbar for the one that's currently being edited. Here's some sample code: $(textarea).tinymce({ setup: function(ed) {setupMCEToolbar(ed, componentID, displaySettingsPane)} ,script_url: '/clubs/data/shared/scripts/tiny_mce/tiny_mce.js' ,theme : "advanced" ,plugins : "safari,pagebreak,style,layer,table,save,advhr,advimage,advlink,emotions,iespell,inlinepopups,insertdatetime,preview,media,searchreplace,print,contextmenu,paste,directionality,fullscreen,noneditable,visualchars,nonbreaking,xhtmlxtras,template" ,theme_advanced_buttons1 : "save,newdocument,|,bold,italic,underline,strikethrough,|,justifyleft,justifycenter,justifyright,justifyfull,styleselect,formatselect,fontselect,fontsizeselect" ,theme_advanced_buttons2 : "cut,copy,paste,pastetext,pasteword,|,search,replace,|,bullist,numlist,|,outdent,indent,blockquote,|,undo,redo,|,link,unlink,anchor,image,cleanup,help,code,|,insertdate,inserttime,preview,|,forecolor,backcolor" ,theme_advanced_buttons3 : "tablecontrols,|,hr,removeformat,visualaid,|,sub,sup,|,charmap,emotions,iespell,media,advhr,|,print,|,ltr,rtl,|,fullscreen" ,theme_advanced_buttons4 : "insertlayer,moveforward,movebackward,absolute,|,styleprops,|,cite,abbr,acronym,del,ins,attribs,|,visualchars,nonbreaking,template,pagebreak" ,theme_advanced_toolbar_location : "external" ,theme_advanced_toolbar_align : "left" ,theme_advanced_statusbar_location : "bottom" ,theme_advanced_resizing : true }); var setupMCEToolbar = function (mce, componentID, displaySettingsPane) { mce.onClick.add(function(ed,e){ displaySettingsPane($('#' + componentID)); $('#' + componentID).fetch('.mceExternalToolbar').eq(0).appendTo('#settingsPaneContent'); }); } Basically, it seems as though the setupMCEToolbar function cannot track down the mceExternalToolbar to move it. Has anyone ever had success trying to do something like this? EDIT It's a Monday alright... it couldn't find the external toolbar because I was using children() instead of fetch(). There's still an issue in that: 1) Moving it is incredibly slow and 2) Once it moves, TinyMCE breaks. EDIT 2 A bit more clarification: The modal is draggable, thus making any purely-CSS workarounds a bit awkward...

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• MySql: Query multiple identical dynamic tables.

  - by JYelton

  I have a database with 500+ tables, each with identical structure, that contain historical data from sensors. I am trying to come up with a query that will locate, for example, all instances where sensor n exceeds x. The problem is that the tables are dynamic, the query must be able to dynamically obtain the list of tables. I can query information_schema.tables to get a list of the tables, like so: SELECT table_name FROM information_schema.tables WHERE table_schema = 'database_name'; I can use this to create a loop in the program and then query the database repeatedly, however it seems like there should be a way to have MySql do the multiple table search. I have not been able to make a stored procedure that works, but the examples I can find are generally for searching for a string in any column. I want to specifically find data in a specific column that exists in all tables. I admit I do not understand how to properly use stored procedures nor if they are the appropriate solution to this problem. An example query inside the loop would be: SELECT device_name, sensor_value FROM device_table WHERE sensor_value > 10; Trying the following does not work: SELECT device_name, sensor_value FROM ( SELECT table_name FROM information_schema.tables WHERE table_schema = 'database_name' ) WHERE sensor_value > 10; It results in an error: "Every derived table must have its own alias." The goal is to have a list of all devices that have had a given sensor value occur anywhere in their log (table). Ultimately, should I just loop in my program once I've obtained a list of tables, or is there a query structure that would be more efficient?

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• xPath Groupings how?

  - by David

  OK So, I'm learning/using xpath for a basic application thats effectively ripping data off another website. I need to gain the knowledge of each persons Countryy/Suburb/area. In some instances you can get Australia/Victoria/melborne for instance. Others may just be Australia/Melbourne. Or even just Melbourne OR just AUSTRALIA. who knows. So I'm current able to view the below code and rip all of the information with the string xpath search:@" //table/tr/td/tabke/tr/td/font/a, this returns every entry, but what I really want is to group each lot separately. I hope someone out there on planet earth knows what I just tried to explain... and can help... Good day! <font face="arial" size="2"> <strong>Location:</strong> <a href="http://maps.google.com/maps?q=Australia" target="mapblast" style="text-decoration:none">Australia</a>, <a href='http://maps.google.com/maps?q=Australia%20Victoria'target="mapblast" style='text-decoration:none'>Victoria</a>, <a href='http://maps.google.com/maps?q=Australia%20Melbourne%20Victoria'target="mapblast" style='text-decoration:none'>Melbourne</a> </font> </td> </tr>

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• What is the form_for syntax for nested resources?

  - by Kris

  I am trying to create a form for a nested resource. Here is my route: map.resources :websites do |website| website.resources :domains end Here are my attempts and the errors: <% form_for(@domain, :url => website_domains_path(@website)) do | form | %> <%= form.text_field :name %> # ArgumentError: wrong number of arguments (1 for 0) # form_helper.rb:290:in 'respond_to?' # form_helper.rb:290:in 'apply_form_for_options!' # form_helper.rb:277:in 'form_for' <% form_for([@website, @domain]) do | form | %> <%= form.text_field :name %> # ArgumentError: wrong number of arguments (1 for 0) # form_helper.rb:290:in 'respond_to?' # form_helper.rb:290:in 'apply_form_for_options!' # form_helper.rb:277:in 'form_for' <% form_for(:domain, @domain, :url => website_domains_path(@website)) do | form | %> <%= form.text_field :name %> # ArgumentError: wrong number of arguments (1 for 0) # wrapper.rb:14:in 'respond_to?' # wrapper.rb:14:in 'wrap' # active_record_helper.rb:174:in 'error_messages_for' <% form_for(:domain, [@website, @domain]) do | form | %> <%= form.text_field :name %> # UndefinedMethodError 'name' for #<Array:0x40fa498> I have confirmed both @website and @domain contain instances of the correct class. The routes also generate correctly is used like this for example, so I dont think their is an issue with the route or url helpers. <%= website_domains_path(1) %> <%= website_data_source_path(1, 1) %> Rails 2.3.5

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• iPhone: Leak with UIWebView loading Office documents. Any ideas how to avoid it?

  - by Thomas Tempelmann

  While there are already quite a few posts about leaks around UIWebView, mine is a bit more special, I believe, and thus deserves its own post here. I see a reproducible large leak every time I load a Office document such as a Word or Excel file. For instance, every time I display a 180KB .doc file, I get a 100KB leak. And that happens with both the simulator and an actual device, running OS 3.1.3. The leak is not visible with the Leaks instrument but only by looking at the malloc instances via the ObjectAlloc instrument. Here's a picture from the instruments trace: I've also made a demo project, UIWebView-Leak.zip, so you can verify this yourself. To see the leak, use the ObjectAlloc instrument, switch to the view where you see individual allocation objects, and sort by size so that you see the large ones in a group, just like in my picture above. Then view a Office document a few times and find the Malloc objects that keep staying "Live" even after the actual UIWebView has been freed. Is this a known bug? Or is there any way I can avoid these leaks? I.e, have you successfully shown Office documents on an iPhone withing getting such leaks? Note: I've reported this as a bug to Apple now, too (ID 7950594) I am still waiting for someone (including Apple) to confirm this as a true leak or show why it isn't (i.e. that I do something wrong or make wrong assumptions)

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• Password hashing, salt and storage of hashed values

  - by Jonathan Leffler

  Suppose you were at liberty to decide how hashed passwords were to be stored in a DBMS. Are there obvious weaknesses in a scheme like this one? To create the hash value stored in the DBMS, take: A value that is unique to the DBMS server instance as part of the salt, And the username as a second part of the salt, And create the concatenation of the salt with the actual password, And hash the whole string using the SHA-256 algorithm, And store the result in the DBMS. This would mean that anyone wanting to come up with a collision should have to do the work separately for each user name and each DBMS server instance separately. I'd plan to keep the actual hash mechanism somewhat flexible to allow for the use of the new NIST standard hash algorithm (SHA-3) that is still being worked on. The 'value that is unique to the DBMS server instance' need not be secret - though it wouldn't be divulged casually. The intention is to ensure that if someone uses the same password in different DBMS server instances, the recorded hashes would be different. Likewise, the user name would not be secret - just the password proper. Would there be any advantage to having the password first and the user name and 'unique value' second, or any other permutation of the three sources of data? Or what about interleaving the strings? Do I need to add (and record) a random salt value (per password) as well as the information above? (Advantage: the user can re-use a password and still, probably, get a different hash recorded in the database. Disadvantage: the salt has to be recorded. I suspect the advantage considerably outweighs the disadvantage.) There are quite a lot of related SO questions - this list is unlikely to be comprehensive: Encrypting/Hashing plain text passwords in database Secure hash and salt for PHP passwords The necessity of hiding the salt for a hash Clients-side MD5 hash with time salt Simple password encryption Salt generation and Open Source software I think that the answers to these questions support my algorithm (though if you simply use a random salt, then the 'unique value per server' and username components are less important).

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• Working with extra fields in an Inline form - save_model, save_formset, can't make sense of the diff

  - by magicrebirth

  Suppose I am in the usual situation where there're extra fields in the many2many relationship: class Person(models.Model): name = models.CharField(max_length=128) class Group(models.Model): name = models.CharField(max_length=128) members = models.ManyToManyField(Person, through='Membership') class Membership(models.Model): person = models.ForeignKey(Person) group = models.ForeignKey(Group) date_joined = models.DateField() invite_reason = models.CharField(max_length=64) # other models which are unrelated to the ones above.. class Trip(models.Model): placeVisited = models.ForeignKey(Place) visitor = models.ForeignKey(Person) pleasuretrip = models.Boolean() class Place(models.Model): name = models.CharField(max_length=128) I want to add some extra fields in the Membership form that gets displayed through the Inline. These fields basically are a shortcut to the instantiation of another model (Trip). Trip can have its own admin views, but these shortcuts are needed because when my project partners are entering 'Membership' data in the system they happen to have also the 'Trip' information handy (and also because some of the info in Membership can just be copied over to Trip etc. etc.). So all I want to have is two extra fields in the Membership Inline - placeVisited and pleasuretrip - which together with the Person instance will let me instantiate the Trip model in the background... I found out I can easily add extra fields to the inline view by defining my own form. But once the data have been entered, how and when to reference to them in order to perform the save operations I need to do? class MyForm(forms.ModelForm): place = forms.ModelChoiceField(required=False, queryset=Place.objects.all(), label="place",) pleasuretrip = forms.BooleanField(required=False, label="...") class MembershipInline(admin.TabularInline): model = Membership form = MyForm def save_model(self, request, obj, form, change): place = form.place pleasuretrip = form.pleasuretrip person = form.person .... # now I can create Trip instances with those data .... obj.save() class GroupAdmin(admin.ModelAdmin): model = Group .... inlines = (MembershipInline,) This doesn't seem to work... I'm also a bit puzzled by the save_formset method... maybe is that the one I should be using? Many thanks in advance for the help!!!!

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• What setting needs to be made to make .Net Automation responsive?

  - by Greg

  Have an app that is looking for application windows being created on the desktop using class Unresponsive { private StructureChangedEventHandler m_UIAeventHandler = new StructureChangedEventHandler(OnStructureChanged); public Unresponsive() { Automation.AddStructureChangedEventHandler(AutomationElement.RootElement, TreeScope.Children, m_UIAeventHandler); } private void OnStructureChanged(object sender, StructureChangedEventArgs e) { Debug.WriteLine("Change event"); } } You can see the same issue using UISpy.exe, selecting the desktop and configuring scope for children and just the structure changed event. The problem I'm trying to resolve is that the events are not raised in a timely manner, there seems to be some grouping/delay which makes the app appear to be non responsive. If you start a new app with 1 window and wait a second you get the event, seems alright. If you start the same app several times without delay (say clicking on quickstart), it's not until all of the instances of the app get 'initialised' by the AutomationProxies that you get the notice for the first app (and in short order the other apps/windows). I've sat watching task manager as each instance of the app starts to grow as it is initialised, waiting until the last app is done and then seeing the events all come in. Similarly any time any apps are starting windows within a timeframe there seems to be some blocking. I can't see how to configure this timeframe, or get each structure changed event to be sent on as soon as it happens. Also, this process of listening for structure changed events seems to be leaking, just by listening there is a leak in native memory. (visible in UISpy and my app)

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• Systems design question: DB connection management in load-balanced n-tier

  - by aoven

  I'm wondering about the best approach to designing a DB connection manager for a load-balanced n-tier system. Classic n-tier looks like this: Client -> BusinessServer -> DBServer A load-balancing solution as I see it would then look like this: +--> ... +--+ +--> BusinessServer +--+--> SessionServer --+ Client -> Gateway --+--> BusinessServer +--| +--> DBServer +--> BusinessServer +--+--------------------+ +--> ... +--+ As pictured, the business server component is being load-balanced via multiple instances, and a hardware gateway is distributing the load among them. Session server probably needs to be situated outside the load-balancing array, because it manages state, which mustn't be duplicated. Barring any major errors in design so far, what is the best way to implement DB connection management? I've come up with a couple of options, but there may be others I'm not aware of: Introduce a new Broker component between the DBServer and the other components and let it handle the DB connections. The upside is that all the connections can be managed from a single point, which is very convenient. The downside is that now there is an additional "single point of failure" in the system. Other components must go through it for every request that involves DB in some way, which also makes this a bottleneck. Move the DB connection management into BusinessServer and SessionServer components and let each handle its own DB connections. The upside is that there is no additional "single point of failure" or bottleneck components. The downside is that there is also no control over possible conflicts and deadlocks apart from what DBServer itself can provide. What else can be done? FWIW: Technology is .NET, but none of the vendor-specific stacks are used (e.g. no WCF, MSMQ or the like).

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• Using StructureMap to create classes by a name?

  - by Bevan

  How can I use StructureMap to resolve to an appropriate implementation of an interface based on a name stored in an attribute? In my project, I have many different kinds of widgets, each descending from IWidget, and each decorated with an attribute specifying the kind of associated element. To illustrate: [Configuration("header")] public class HeaderWidget : IWidget { } [Configuration("linegraph")] public class LineGraphWidget : IWidget { } When processing my (XML) configuration file, I want to obtain an instance of the appropriate concrete class based on the name of the element I'm processing. public IWidget CreateWidget(XElement definition) { var kind = definition.Name.LocalName; var widget = // What goes here? widget.Configure(definition); return widget; } Each definition should result in a different widget being created - I don't need or want the instances to be shared. In the past I've written plenty of code to do this kind of thing manually, including writing a custom "roll-your-own" IoC container for one project. However, one of my goals with this project is to become proficient with StructureMap instead of reinventing the wheel. I think I've already managed to set up automatic scanning of assemblies so that StructureMap knows about all my IWidget implementations: public class WidgetRegistration : Registry { public WidgetRegistration() { Scan( scanner => { scanner.AssembliesFromApplicationBaseDirectory(); scanner.AddAllTypesOf<IWidget>(); }); } } However, this isn't registering the names of my widgets with StructureMap. What do I need to add to make my scenario work? (While I am trying to use StructureMap in this project, an answer showing me how to solve this problem with a different DI/IoC tool would still be valuable.)

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• Suggested (simple) approach for drawing large numbers of visual elements in WPF?

  - by Ender

  I'm writing an interface that features a large (~50000px width) "canvas"-type area that is used to display a lot of data in a fairly novel way. This involves lots of lines, rectangles, and text. The user can scroll around to explore the entire canvas. At the moment I'm just using a standard Canvas panel with various Shapes placed on it. This is nice and easy to do: construct a shape, assign some coordinates, and attach it to the Canvas. Unfortunately, it's pretty slow (to construct the children, not to do the actual rendering). I've looked into some alternatives, it's a bit intimidating. I don't need anything fancy - just the ability to efficiently construct and place objects in a coordinate plane. If all I get are lines, colored rectangles, and text, I'll be happy. Do I need Geometry instances inside of Geometry Groups inside of GeometryDrawings inside of some Panel container? Note: I'd like to include text and graphics (i.e. colored rectangles) in the same space, if possible.

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• Parse usable Street Address, City, State, Zip from a string

  - by Rob Allen

  Problem: I have an address field from an Access database which has been converted to Sql Server 2005. This field has everything all in one field. I need to parse out the individual sections of the address into their appropriate fields in a normalized table. I need to do this for approximately 4,000 records and it needs to be repeatable. Here are the rules for this exercise: 1 - no whining about how this should have been separate fields in the first place, we are often confronted with less than ideal situations and have to make the best of them 2- for this post, use any language you want 3- feel free to play code golf 4 - Assume an address in the US (for now) 5 - assume that the input string will sometimes contain an addressee (the person being addressed) and/or a second street address (i.e. Suite B) 6 - states may be abbreviated 7 - zip code could be standard 5 digit or zip+4 8 - there are typos in some instances UPDATE: In response to the questions posed, standards were not universally followed, I need need to store the individual values, not just geocode and errors means typo (corrected above) Sample Data: A. P. Croll & Son 2299 Lewes-Georgetown Hwy, Georgetown, DE 19947 11522 Shawnee Road, Greenwood DE 19950 144 Kings Highway, S.W. Dover, DE 19901 Intergrated Const. Services 2 Penns Way Suite 405 New Castle, DE 19720 Humes Realty 33 Bridle Ridge Court, Lewes, DE 19958 Nichols Excavation 2742 Pulaski Hwy Newark, DE 19711 2284 Bryn Zion Road, Smyrna, DE 19904 VEI Dover Crossroads, LLC 1500 Serpentine Road, Suite 100 Baltimore MD 21 580 North Dupont Highway Dover, DE 19901 P.O. Box 778 Dover, DE 19903

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• Parallel.Foreach loop creating multiple db connections throws connection errors?

  - by shawn.mek

  Login failed. The login is from an untrusted domain and cannot be used with Windows authentication I wanted to get my code running in parallel, so I changed my foreach loop to a parallel foreach loop. It seemed simple enough. Each loop connects to the database, looks up some stuff, performs some logic, adds some stuff, closes the connection. But I get the above error? I'm using my local sql server and entity framework (each loop uses it's own context). Is there some problem with connecting multiple times using the same local login or something? How did I get around this? I have (before trying to covert to a parallel.foreach loop) split my list of objects that I am foreach looping through into four groups (separate csv files) and run four concurrent instances of my program (which ran faster overall than just one, thus the idea for parallel). So it seems connecting to the db shouldn't be a problem? Any ideas? EDIT: Here's before var gtgGenerator = new CustomGtgGenerator(); var connectionString = ConfigurationManager.ConnectionStrings["BioEntities"].ConnectionString; var allAccessionsFromObs = _GetAccessionListFromDataFiles(collectionId); ForEach(cloneIdAndAccessions in allAccessionsFromObs) DoWork(gtgGenerator, taxonId, organismId, cloneIdAndAccessions, connectionString)); after var gtgGenerator = new CustomGtgGenerator(); var connectionString = ConfigurationManager.ConnectionStrings["BioEntities"].ConnectionString; var allAccessionsFromObs = _GetAccessionListFromDataFiles(collectionId); Parallel.ForEach(allAccessionsFromObs, cloneIdAndAccessions => DoWork(gtgGenerator, taxonId, organismId, cloneIdAndAccessions, connectionString)); Inside the DoWork I use the BioEntities using (var bioEntities = new BioEntities(connectionString)) {...}

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• Tips on designing a .NET API for future use with F#

  - by Drew Noakes

  I'm in the process of designing a .NET API to allow developers to create RoboCup agents for the 3D simulated soccer league. I'm pretty happy with how the API work with C# code, however I would like to use this project to improve my F# skill (which is currently based on reading rather than practice). So I would like to ask what kinds of things I should consider when designing an API that is to be consumed by both C# and F# code. Some points. I make fairly heavy use of matrix and vector math. These are currently immutable classes/structs. The API currently defines a few interfaces with the consumer implements (eg: IAgent), using instances of their implementations (eg: MyAgent) to construct other API classes (eg: new Client(myAgent)). The API fires events. The API exposes a few delegate types. The API includes several enums. I'd like to release a version of the API as soon as possible and don't want to make major changes to it later if I realise it's too difficult to work with from F#. Any advice is appreciated.

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• SSIS Transaction with Sql Transaction

  - by Mike

  I started with a package to make sure Transactions are working correctly. The package level transaction is set to Required. I have two Execute Sql Task, one deletes rows from a table and one does 1/0, to throw the error. Both task are set to supported transaction level and Serializable IsolationLevel. That works. Now when I replace my two sql task to two separate procedure calls, the first one, ChargeInterest, runs successful but the second one, PaymentProcess, fails always saying. [Execute SQL Task] Error: Executing the query "Exec [proc_xx_NotesReceivable_PaymentProcess] ..." failed with the following error: "Uncommittable transaction is detected at the end of the batch. The transaction is rolled back.". Possible failure reasons: Problems with the query, "ResultSet" property not set correctly, parameters not set correctly, or connection not established correctly. PaymentProcess being the second stored procedure. Both procedures have there own BEGIN, COMMIT AND ROLLBACKS inside the SP. I believe that the transactions are being successfully handed in the Charge Interest because I can run the following without issues or the dreaded you started with 0 and now have 1 transaction. EXEC [proc_XX_NotesReceivable_ChargeInterest] 'NR', 'M', 186, 300 EXEC [proc_XX_NotesReceivable_PaymentProcess] 'NR', 186, 300 --OR GO BEGIN TRAN EXEC [proc_XX_NotesReceivable_ChargeInterest] 'NR', 'M', 186, 300 EXEC [proc_XX_NotesReceivable_PaymentProcess] 'NR', 186, 300 ROLLBACK TRAN Now I have noticed that DTC does get kicked off in both instances? Why I am not sure because it is using the same connection. In the live example I can see the transaction get started but disappears if I put a breakpoint on the PreExecute event of the second stored procedure. What is the correct way to mingle SP transactions with SSIS transactions?

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