RavenDB is a bad choice for Asp.Net Session Provider

I was considering using RavenDb as a custom session state provider in a web application.  Essentially I am looking for a document database that works as a session state provider and also serves other application needs.  NServiceBus bundles this database, so I thought I don't have to use one more document database.

This is my first encounter with RavenDb.  I read lot of good things about this database.  I wanted give a try to see if this fits in to my requirements.

With a little bit of googling,  you can find few session state provider implementation for RavenDb here, and here.  All these implementations are based on Microsoft's ODBC session state provider sample here.

All the important methods you need to implement for your own provider are explained here.

Session State Provider is little tricky to implement.  In the context of session asp.net can server three types of page requests.

• Pages that require no session
• Pages that require read-only session
• Pages that require writable session

All these requests can concurrently reach your provider.  Thanks to ajax calls.
All these three types of calls have the potential to update the session document concurrently.

Now the writable session pages attempt to use 'LockId' and 'Locked' properties to protect session data corruption from concurrent write calls.

Pages that require no session data just extend the expiry time of the session.  Pages that required read-only sessions should be able to retrieve the session data given a session id and they will wait for the releasing lock.

All of the above RavenDb session state provider implementations buckle at concurrent user loads.  These providers try to work around RavendDb limitations for this scenario.

Queries require Indexes

You cannot use RavenDb queries to get the session document(s).  This is because RavenDb queries require indexes and these indexes run in the back ground.  Under a heavy load these indexing yields stale documents. And if you wait for the indexing to finish you will run in to timeouts.

No Find And Modify Support

RavenDb won't support find and modify operations over a collection.  Following type of query is not possible.  Now you are left with loading the session by its id and then modifying its partsby examining its properties.

UPDATE Sessions SET Locked = true WHERE Id = 'xyz' and Locked = false

With out using indexes, and without the support for atomic operations as above, you are forced to write the following code.

var doc = sessionStateDoc.Load<SessionState>("xyz");

if(!doc.Locked){

// other code

}

This kid of code increases the chances for concurrency.

Optimistic Concurrency

Pages that doesn't requie session attempts update the "Expires" property of session document, at the same time a page that requires writable session might attempt to update the "LockId" property of session document.  

Even though they are totally different properties of the same document, we are forced to deal with the concurrency.  There might be a way to do fine grained concurrency based on specific fields, I find it way too much trouble than necessary.

When session module calls GetItemExclusive method, if it runs in to concurrency problems, we can simply return null by indicating session module to retry getting the document.  But how many times we should do this?  This slows down the pages.

You can probably attempt to use RavenDb patch command update "Expires" property, thus avoiding concurrency conflicts.  But soon you will find that this idea fails when we try to use RavenDb Expires Bundle.

Expiring documents

RavenDb comes with an expiration bundle that allows you to remove expired session documents.  In order to make this bundle work, you need to make use of the metadata constructs like the following. Unfortunately you must include this setter as part of the unit of work.  

db.Advanced.GetMetadataFor(session)["Raven-Expiration-Date"] = DateTime.UtcNow.AddMinutes(20)

sessionStateDoc.Expires = DateTime.UtcNow.AddMinutes(20)
sessionStateDoc.SaveChanges();

This prevents us from doing partial updates to the document. This metata data update must be done every time you update the collection. 

Other minor but annoying issues  

• As of build #2261 there are still bugs. 
• Master-Master replication won't work when you use API Keys.  
• Expiration bundle randomly deletes session documents.  
• Raven Studio doesn't give you a comfortable feeling of using a professional grade database.

Following changes gave me a relatively stable implementation of RavenDb Session Provider under higher loads.

• Do not use expiration bundle.  Use a server side trigger or a scheduled task to expire documents. This allows us to do path command for updating "Expires" property in "ResetTimeOut" method. 
• Do not use concurrency checks while removing the item, saving the session data, and while releasing exclusive locks.  These calls must succeed, if they fail you might get in to logic errors in the app. 
• Use optimistic concurrency check only in GetItemExclusive/GetItem routines.  If the concurrency check fails, simply return null, this will force session module make calls to these methods.

All in all I am not happy about the friction.  I smell maintenance head aches.

I would like to try another document database to see if that fits better for this usecase.

Typescript is neat

javascript is not picky about line endings.  Following code looks fine but causes trouble.

   1: function func() {

   2:     return 

   3:     {

   4:         greet: "Hello World"

   5:     };

   6: }

   7: console.log(func().greet);

Line number 7 prints, undefined.  This is because return statement at line number 2 has line ending.  Now if you use the first code snipped in typescript, you can avoid this error.  Typescript marks the usage of greet in line number 7 as an error.

   1: Error    1    Expected var, class, interface, or module   …\TypeScript1\TypeScript1\app.ts    7    13    app.ts

May be they can do better with the error message. 

This problem can be fixed by moving opening curly brace at line 3 to line 2.

   1: function func() {

   2:     return {

   3:         greet: "Hello World"

   4:     };

   5: }

   6: console.log(func().greet);

Now the error goes away, and also you will get intellisense  for the string property “greet” after func().  in line 6.

Tips for windows developer working on Mac–Tip # 2

Many times you want to run a text editor from terminal.  May be you want to edit a .bashrc file or a .gitignore file.  I use my favorite editor that works on both windows and mac, Sublime Text

ln -s "/Applications/Sublime Text 2.app/Contents/SharedSupport/bin/subl" /usr/local/bin

once you typed that command from terminal, you can now open files using sublime directly from your terminal by typing

subl ~/.bashrc

Tips for windows developer working on Mac–Tip # 1

Files/folder with names starting with period are hidden by default in Finder.  So files like .bashrc or .gitignore are not can’t be found.  Running following commands from the terminal fixes that issue

defaults write com.apple.finder AppleShowAllFiles TRUE

killall Finder

Second command restarts the finder.

Running Asp.Net MVC controller actions on STA threads

Recently while we were converting a legacy asp application (Yes they still exist) to asp.net mvc, we had to work with a set of 3rd party business critical components.

These components were legacy COM components.  In load testing we found that controller actions that contain calls to these components were crashing w3wp process almost every minute.   A little bit of research around this problem yielded the following article.

Running ASMX Web Services on STA Threads

The summary of the problem is, MVC action methods run in COM multithreaded apartment (MTA) threads.  These legacy components were being created from MTA threads are being serialized and are being processed by single STA thread.  On top of that these components are loading tons of data in to memory and the load is causing the memory corruption.

So the solution is to make the MVC action method to run on STA thread, thus allowing COM to place the object instances on the creator’s thread.

Here is an MSDN thread that ties up the STA with asp.net mvc

AspCompat=true does not work with MVC

The above solution doesn’t support asp.net sessions and also was written for asp.net mvc 1.0

Here is the asp.net mvc 3.0 adjusted solution.

First the RouteHandler, it derives from MVCRouteHandler and instantiate a IHttpHandler derived class.

public class STARouteHandler : MvcRouteHandler
{
   protected override IHttpHandler GetHttpHandler(RequestContext requestContext)
   {
       return new STARequestHandler(requestContext);
   }
}

Next the STARequestHandler,  the key to this entire magic to work is in the BeginProcessRequest and EndProcessRequest methods. These two methods create an aspnet compat wrapper around the actual execution of action method.  This handler also implements IRequiresSessionState marker interface to support the sessions.

public class STARequestHandler : Page, IHttpAsyncHandler, IRequiresSessionState
{
    public STARequestHandler(RequestContext requestContext)
    {
        if (requestContext == null)
            throw new ArgumentNullException("requestContext");
        this.RequestContext = requestContext;
    }

    private ControllerBuilder _controllerBuilder;

    internal ControllerBuilder ControllerBuilder
    {
        get { return this._controllerBuilder ?? (this._controllerBuilder = ControllerBuilder.Current);}
    }

    public RequestContext RequestContext { get; set; }

    protected override void OnInit(EventArgs e)
    {
        string requiredString = this.RequestContext.RouteData.GetRequiredString("controller");
        var controllerFactory = this.ControllerBuilder.GetControllerFactory();
        var controller = controllerFactory.CreateController(this.RequestContext, requiredString);
        if (controller == null)
            throw new InvalidOperationException("Could not find controller: " + requiredString);
        try
        {
            controller.Execute(this.RequestContext);
        }
        finally
        {
            controllerFactory.ReleaseController(controller);
        }
        this.Context.ApplicationInstance.CompleteRequest();
    }

    public override void ProcessRequest(HttpContext httpContext)
    {
        throw new NotSupportedException("This should not get called for an STA");
    }

    public IAsyncResult BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData)
    {
        return this.AspCompatBeginProcessRequest(context, cb, extraData);
    }

    public void EndProcessRequest(IAsyncResult result)
    {
        this.AspCompatEndProcessRequest(result);
    }

    void IHttpHandler.ProcessRequest(HttpContext httpContext)
    {
        this.ProcessRequest(httpContext);
    }
}

 And lastly the usage of this handler.

While creating a route for the action method, simply attach this handler to the route definition.

context.MapRoute("STARoute", "{controller/{action}",
                    new { controller = "Home", action = "Index")
                    .RouteHandler = new STARouteHandler();

You can test the apartment state by calling the following line of code in the action method.

Thread.CurrentThread.ApartmentState.ToString();

MongoDB mapreduce for stackoverflow.com recent tags

I was playing with MongoDB's mapreduce, and wanted to write a query that simulates the list of 'Recent Tags' feature on stackoveflow home page.

I am using mongo-csharp-driver for this experiment.

Here I am taking a guess at stackoverflow's domain model. Here is the Question model with enough properties to demonstrate the mapreduce query.
Every question is associated with a list of Tags and has a CreatedOn property.

public class Question{
public ObjectId Id { get; set; }
public DateTime CreatedOn { get; set; }
public ICollection Tags { get; set; }
}

Create a database with some name and add 'Questions' collection to the mongodb.

We are going to make the following call to find the recent tags.

var recentTags = questions.MapReduce(map, reduce).GetResultsAs<ResentTagResult>();

RecentTagResult holds the results of the mapreduce query and defined as

public class RecentTagResult {

public string Id;
[BsonElement("value")]
public RecentTag Value;

}

MongoDb's mapreduce call outputs a result set with two properties _id and value. So here I am defining a mapper class with a property 'Id' and property 'Value' of type RecentTag. BsonElement attribute in the above code simply maps lower case property 'value' from the result set to title case property 'Value'. _id property from result is automatically mapped to Id by 'GetResultsAs' call.

RecentTag is defined as follows. Here I am expecting that the query results are going to contain Tag, count of tags, last time when a question was created with this tag. As you can guess our map/reduce functions must emit the values that match the following class definition.

public class RecentTag {

public string Tag { get; set; }
public int Count { get; set; }
public DateTime LastSeenOn { get; set; }

}

Now coming to the meat of the problem. A question can have more than one tag. We are looking for a list of tags used by questions asked in the last month. Here is the definition of the map function (which is completely written in javascript) that goes over entire collection of questions and emits a result each time a tag is found if that question is asked in the last month.

private string map =
@"function() {
if(this.CreatedOn >= new Date('Oct 1, 2011') && this.CreatedOn {
var lastseen = this.CreatedOn;
this.Tags.forEach(function(tag) {emit(tag, {Tag: tag, LastSeenOn:lastseen, Count: 1});});
}}";

It is very important that the emit function's value should match our RecentTag type definition.

emit(tag, {Tag: tag, LastSeenOn:lastseen, Count: 1})

Now coming to reduce, we have a bunch of emitted results from map function and we simply count them to find the total count of each tag found in last month.
A tag might appear more than once in the last month. If the tag appears only once, reduce function will never be called.

private string reduce =
@"function (key, arr_values) {
var dates = [];
arr_values.forEach(function(val) {dates.push(val.lastseenon)});
var result = {Tag: key, LastSeenOn: new Date(Math.max.apply(Math, dates )), Count:0};
for(var i in arr_values)
{
temp = arr_values[i];
result.Count += temp.Count;
}
return result;
}}";

Here att_values contain all emits for a single tag. Again it is important that our return type must match with ResultTag definition similar to the map function.
We start with that definition first

var result = {Tag: '', LastSeenOn: new Date(Math.max.apply(Math, dates )), Count:0};

And then iterate through arr_values and simply increment the count to get the final result.

Filling LastSeenOn property is little tricky. Here we are trying to find out the Max of the CreatedOn property of all emitted values of a single tag.

var dates = [];
arr_values.forEach(function(val) {dates.push(val.lastseenon)});

Here we are gathering all the dates from lastseenon property in to an array. And then while defining the result we are applying the javascrpt's Math.Max function to find the last seen date.

LastSeenOn: new Date(Math.max.apply(Math, dates )

That is all to it.

Open Source Dependencies

Total Cost of Ownership is a critical metric which I would like to pay attention to in software development. A project with lots of open source dependencies can become very difficult to maintain.
With advent of modern package systems like gems, Nuget and CDNs it has never been this easy to use open source in software projects. As of this writing there are thousands of JQuery plugins, hundreds of ruby gems, and hundreds of Nuget packages. I have seen developers arguing about their favorite ORM tool. I have not seen enough arguments about which JQuery light box plug-in should be used for the user interface. If you try to take a stock of all dependencies (both commercial/open source) on your code, you might be surprised to see the list.

I surveyed few .Net web applications. A single web application can have following list of components, without counting the major dependencies like Object Relational Mapper

1. PDF
2. Charting
3. Ajax
4. Half a dozen JQuery plugins/other JavaScript alternatives
5. Spread sheet
6. Dashboard
7. Social networking
8. Payment gateway
9. Reporting
10. Other value added services like support, feedback, live help
11. External web services
12. Scheduling
13. Email
14. JSON
15. Mocking
16. Unit Testing

.. and the list goes on.

Now imagine using a open source component for each one of these dependencies. That is a lot of code to maintain!

All non-trivial abstractions, to some degree, are leaky

At one point or the other your team needs to know internals of every open source library used in your project. Some of these libraries have hard dependencies, with a potential of preventing the future upgrades.

Never under estimate the testing burden. Take the example of a JQuery plugins. Usually these plugins depend on JQuery. When you upgrade JQuery, you are forced to upgrade the dependent plugins. Depending on quality of the plugin, many times you end of spending hours in debugging why a web page is failing to find the correct version of plugin that works. Cross browser testing is also time killer. All this can become very complex when all you trying to do is upgrading JQuery to its latest version, which itself is a trivial task.

You might not see this kind of risk with popular open source libraries. As they operate similar to commercial offerings. But not all of the open source projects are popular.

Some tips to control the proliferation of these dependencies in to your projects

1. Always maintain a list of open source dependencies. Make it available to QA team and developers.
2. Create a test suite to test all these dependencies. And run the tests with every deployment.
3. Always check-in the source code for the open source project in to source control.
4. Try to keep these dependencies to minimum. Remember that your team needs to re-learn these dependencies on every upgrade or major functionality rewrite.
5. If possible try to stick to a known set of controls from a single vendor.
6. While choosing the libraries weigh in your team’s skill set, team’s composition and future direction. If you don’t have dedicated resources to focus on Ajax work of the website, it is better to stick to a commercial solution than using a laundry list of multiple open source offerings.

The Upgrade Dilemma

If you are working on a project that uses 3rd party products you should be facing this dilemma regarding upgrades, regularly. It could be a core system upgrade such as .Net framework version or a SQL Server database version or a significant 3rd party component upgrade. Usually these upgrades proposals come from tech teams.

Assuming that cost of the software that is being upgraded itself is not prohibitive, most of the arguments are centered on the work that needs to be done by the team to stabilize the product with the upgraded version

Arguments

1. Arguments in favor of the upgrade

a. If we don’t upgrade now, when would we upgrade? After we acquired another 1000 customers?
b. It would be an incentive for the developers. It will help with both hiring and retaining good developers, since they tend to want to work on the latest and greatest.
c. We could get rid of some of the nagging bugs in the product, as the new upgrade solves them
d. New upgrade contains significant and important changes and we should take advantage of them
e. If we are up to date with the latest version, our product won’t become obsolete

2. Arguments against the upgrade

a. There aren’t many useful features in the new version
b. Everything works now so why should we unnecessarily disturb the code base?
c. What is in it for customers, since they didn’t ask for the upgrade?
d. If we upgrade component A, component B will not work
e. We will need to test the whole product, which would be very expensive. We might miss some parts which can put the product at risk
f. The whole process could be exhaustive and we may burn out the team
Most of the arguments against the upgrade are centered on changing the code base, and the fact that changing code could be a risky affair. However, I usually favor staying as current as possible, because the speed with which new upgrades are being released to the market is extremely fast, and if we fail to stay current, the product will end up becoming stale and will almost certainly require a big rewrite in the future.

Process – What Not To Do

Upgrade by committee

It is very tempting to gather all parties involved and conduct formal meetings, get all of their buy ins, create and manage a project plan. This means lot of meetings, follow ups, emails and creates inevitable creation of heroes who will end up taking on the bulk of the work to meet some arbitrary deadline. It may sound logical, and works most of the time. But this is a very expensive process, and usually involves lots of meetings. These meetings are the breeding grounds for “Fear, Uncertainty, Doubt (“FUD”). Any one person in these meetings can derail the attempt or significantly delay the process. After one such upgrade experience you will lose the appetite for any future attempts.

Process – What To Do

If you are really looking ways for successfully convince the organization or your boss for an upgrade here is a summary of what worked for me.

1. Build confidence

Your organization must have faith in your team. They should believe that your team can deliver. They should know that you can fix issues fast and that you care about the success of both the business and the product. This won’t come in a single day. You need to build that confidence every day. One trick that works is to constantly solve simple problems. These kinds of problems won’t take much time. They don’t need big project plans. They come from all parts of the organization. Solving them proves that you are for continuous improvement.
Try to tackle troubled areas of the products. These are the parts of the software that attract frequent bugs, frequent code churns. Try to take initiative and make that area trouble free. Once you successfully solve such problems, you are guaranteed to gain the support in any of your future upgrade proposals.

2. Build safety net

If you don’t have them already, you should start writing tests for important areas of your application. These tests when written properly help you in two ways. They help you identify the problem quickly and also help serve as a repository of business knowledge. You must run these tests with every code check-in.

3. QA is your friend

The most important help you can get from you QA team is in the form of exploratory tests and also from testing tedious, non-automated parts of the application. A tester with an intention to solve the problem is the best resource than a tester with an intention to just report a problem. Have them involved in every non trivial decision your team makes.

4. Research

If the upgrade is going to have big impact on your product, wait for about 6 months after the release date of the upgrade. Go through the release notes, breaking changes, write small prototypes to test the areas of the concern.
Most importantly go through the product support forums to understand the quality of the version you are upgrading. Even if you decide not to upgrade, this research helps you decide the future direction of your product.

5. Build excitement within the team

Try to lay out the broad plan for the upgrade. Take your team’s consensus. Understand possible real problems. Tell them why the upgrade is important. A self-organizing, motivated team can make the whole upgrade process a trivial affair. As a team, you should try to think through and anticipate every major problem, and come up with possible options. Consider other major projects your team is dealing with to make sure that they are not being unnecessarily burdened. Come up with a possible time line.

6. Sell the proposal

Get the major stake holders in a room and sell your proposal. If you did your homework properly this should go well.

7. Appoint a facilitator

Find someone in the team (a PM, BA, team lead etc.) who can act as glue with all the team members. Their job is to continuously update all stake holders (management, team, end users etc.) about the team’s decisions, choices and find answers.

8. Short but to the point standup meetings

Meet twice a day to talk about the most important issues that you team is facing that day. This helps the team to share the work, gather questions, seek answers and inform stake holders about problems.
I too often here developers complaining that their organization is not good at keeping at the top of the latest technology trends. I believe that this is mostly due to the lack of effort from the software teams themselves.

Routes with non optional parameters

You can define restful routes in asp.net mvc applications. I recently ran into an interesting problem.

I defined the following route.

routes.MapRoute("MemberDetail", "Member/{memberId}", new { controller = "Employee", action = "Details" });

Here I am defining a route named "MemberDetails", that allows user to use urls similar to Member/1234 to get a member's detail.

This route works fine. However somewhere else in the code, when I try to output the route url in a page, by doing the following

UrlHelper.RouteUrl("MemberDetail")

To my surprise I saw an empty string in the page output. I wrote a test to see the problem.

[Test]
public void MemberDetailRoute()
{
Assert.IsNotNull(_mockedUrlHelper.RouteUrl("MemberDetail"))
}

Yes that test fails. It turns out that in case of non optional parameters, I must pass their values for MVC framework to identify the route. So the following test passes.

[Test]
public void MemberDetailRoute()
{
Assert.AreEqual("/Member/123", _mockedUrlHelper.RouteUrl("MemberDetail", new {memberId = 123}))
}

And in a view, if you ever want to dynamically construct the above url using javascript, you could do the following
Here we are using jquery to bind a click event to a button, that grabs the user entered value and gets the member detail url.

<script type="text/javascript">
var memberUrl = '<%: HttpUtility.UrlDecode(Url.RouteUrl("MemberDetail", new {memberId = {0}) )%>';
$('#Go').click(function() {
var memberId = $('#memberId').val(); // get the member id from a textbox
window.location.href = HttpUtility.UrlEncode(url.replace("{0}", memberId));
});
</script>

Here I am passing a dummy value {0} to get the correct url and then replacing that value with the memberId entered by user.
Note that Url.RouteUrl method always encodes the url string.

Reference

Microsoft Patterns and Practices Content

Connecting to a windows 7 printer from Mac

It seems that I am ending up searching for these instructions many times, just so I don't forget these steps

On the Windows 7 PC

1. In Windows 7 Control Panel

2. Select "Programs and Features" pane

3. Click "Turn Windows Features on or off"

4. Click on the "LPD Print Service". Under "Print and Document Services"

5. Ensure printer(s) are shared

On the Mac

1. Open "System Preferences" - "Print & Fax"

2. Click "+" to add a printer

3. Right click -> tool bar to customize and add "Advanced" button

4. Select "Advanced"

5. In the "Type:" field select "LPD/LPR Host or Printer"

6. In the "URL:" field enter lpd://ipaddressofwindows7machine/PrinterShareName

Using lpd://ServeName/PrinterShareName does not work, the IP address must replace ServerName

The IP address is the address of your PC, the one assigned by your router

7. Click the "Add" button

If nothing works, just reset the print system on your mac.  This would delete the existing printers allowing you to start fresh.

Asp.net WebSite Administration Tool

Asp.net allows to quickly setup a security for the site using WebSite Administration tool, which can be instantiated from visual studio.  If that tool throws an error, there is no place find what went wrong.

I ran into one such case with the following cryptic error.

"An error was encountered. Please return to the previous page and try again."

I found a work around for this problem.  I needed to hit F5 (run the site in the debug mode) and then click the "WebSite Administration tool" icon from solution explorer to get rid of the above error.

Conference Videos

OreDev 2010 Videos
OreDev Archives

Norwegian Developers Conference Videos

Skills Matter Video PodCasts

Microsoft TechEd Videos

MIX 2011

Rendering asp.net controls with dynamic ids

You have a legacy asp application with lots of html and server side code.

And you you have a loop in which you are trying to add server controls and you want their ids to be dynamically generated.

You want the mark up to look like the following.  Here for this blog post purposes I am using textbox.

<input name="0" type="text" id="0" />
 <br />
<input name="1" type="text" id="1" />
 <br />
<input name="2" type="text" id="2" />
 <br />
<input name="3" type="text" id="3" />
 <br />
<input name="4" type="text" id="4" />

You might intuitively try the following

<%  for (var i = 0 ; i <5; i++){ %>
 <asp:TextBox runat="server" id="<%# i %>" />
<% } %>

But this results in to the following error

The ID property of a control can only be set using the ID attribute in the tag and a simple value. Example: <asp:Button runat="server" id="Button1" />

Workaround for this issue is as follows.

First the Markup.

<% for (var i = 0; i < 5; i++) {

AddTextBox(i);

} %>

Here we are adding 5 text boxes dynamically to the page in place.

This kind of code gets executed at the rendering stage of the page life cycle.  Trick is get the html out of the text box and just render in place.

And code for AddTextBox method

void AddTextBox(int i){

    var ctrl = new TextBox() { ID = i.ToString() };

    var sb = new StringBuilder();

    using (var sw = new StringWriter(sb)){

        using (var textWriter = new HtmlTextWriter(sw)){

            ctrl.RenderControl(textWriter);

        }

    }

    Response.Write(sb.ToString());

}

Here we are creating a new TextBox control and setting its id property dynamically.   And then using RenderControl method, we are populating the StringBuilder instance.  And then outputting the value to response stream.

This can easily be turned in to an extension method.  Then the usage looks like the following

<%= TextBox.ToHtml(id, val) %>

Windows Live Writer and WordPress problem solved

While I was trying to set up windows live writer to post to this site, I got the following error.

Invalid Server Response - The response to the blogger.getUsersBlogs method received from the weblog server was invalid

Googling didn't help to find a solution to this problem.  I fired up fiddler to see what is going on with the response.  Fiddler showed the following as the first line in the response.

b>Warning</b>:  include(./wp-load.php) [<a href='function.include'>function.include</a>]: failed to open stream: No such file or directory in ........

The above line is coming from xmlrpc.php.
ah..ha.. This blog was set up as a root folder.  Somehow WordPress assumes that all blogs must be in a sub-folder of the root site.

Changing that include line from

include('./wp-load.php');

to

include('wp-load.php');

solved the issue. 

And this blog post is from Windows Live Writer!

:)

ubuntu - rails TCPServer Error: Address already in use

When you try to start the rails server with the following command

rails s

and if webrick doesn't start and throws "Address already in use" error, following are the directions on ubuntu to kill all ready running

Type the following from terminal

lsof|grep 3000

This gives a list of running processses that are using 3000 port.  Find a line that starts with ruby, and note the process id

ruby  12345 ....

Type the following command at terminal

kill -9 12345

And your webrick server should start fine now

Rails for windows developer

I have been working in the Microsoft world for too many years.  Every time I attempt to venture in to learning ruby on rails, I end up setting up every thing from scratch and spend tons of time to get started.  And leave all of that to only start again after few months.  It feels like I am doing this over and over again.  Finally I decided to write down the instructions needed to set up Rails development environment on Ubuntu virtual machine.

• Do not use windows environment to develop on Rails.  You cannot stand the friction after a while.  Not much support in the community if you are struck.


• I found it best to use Ubuntu on a virtual machine. I tried to use  Wubi, which is a fantastic tool. But duel booting means rails environment is not a click away.  And a number one reason for not spending much time on rails learning.


• If you are taking rails seriously you mush be comfortable with either mac or unix environments.


• I decided to use ubuntu as I would like to have rails on my windows machine via vmware workstation.  VirtualBox will do fine.


• I tried multiple IDEs and finally settled on RubyMine.  This choice is a no-brainer as I am used to Resharper on visual studio.

Setup instructions

• Install vmware workstation


• Insall ubuntu on vmware.  Grab the iso files from ubuntu.  I used 10.1 beta.   15GB space and 1GB RAM


• Create a shortcut for Terminal on the panel.  You will be using this a lot.

Installing ruby, rvm and rails

Open the terminal and type the following at the prompt

sudo apt-get install curl git-core ruby

Install rvm by typing the following

bash < <( curl http://rvm.beginrescueend.com/releases/rvm-install-head )

At the end of the installation, change the .bashrc file.  Type the following at the command prompt

gedit .bashrc

Replace the following text in .bashrc file

[ -z "$PS1" ] && return

with

if [[ -n "$PS1" ]]; then

And add the following to the end of the file

if [[ -s $HOME/.rvm/scripts/rvm ]] ; then source $HOME/.rvm/scripts/rvm ; fi

fi

Verify the installation of rvm by typing

rvm -v

Close the terminal and reopen it

Install ruby 1.92 packages by typing the following at prompt

sudo aptitude install build-essential bison openssl libreadline5 libreadline-dev curl git-core zlib1g zlib1g-dev
libssl-dev vim libsqlite3-0 libsqlite3-dev sqlite3 libreadline-dev libxml2-dev git-core subversion autoconf

Use rvm to install ruby 1.9.2 by typing the following command

rvm install 1.9.2-head

Set default ruby version in rvm

rvm --default 1.9.2-head

Type the following at the prompt

ruby -v

You should see the following

ruby 1.9.2p0 .....

Now ruby set up is done.  Type the following at the prompt to install Rails

gem install rails

That is it!  Rails is now installed on your ubuntu setup

Installing RubyMine IDE

I used 2.5 EAP version of RubyMine

Grab RubyMine-<version>.tar.gz file.  And extract that to a known folder using default ubuntu archiver

Move the unpacked rubymine to /opt/rubymine by typing the following command at prompt

sudo mv RubyMine-96.1085 /opt/rubymine

Create an app launcher on the panel bar.  Right click on the panel and choose add to panel and create custom application launcher

Set the command option to opt/rubymine/bin/rubymine.sh

Choose the icon from opt/rubymine/bin/rubymine.png

Installing Sun Java

RubyMine needs sun java, which is not installed on ubuntu.

Open System --> Administration --> Software sources --> Other Software

Check all the check boxes pointing to http://archive.canonical.com/ubuntu maverick

Open Applications -> Ubuntu Software Center and search for sun java

Install sun-java6-bin, sun-java6-jre, sun-java6-fonts,  , sun-java6-jdk, sun-java6-plugin

Type which java at command prompt.  It should show /user/bin/java

Rubymine needs a symbolic link for java in bin folder.  Type the following command at the prompt

sudo ln -s /usr/bin/java /bin/java

Now you should be able to start RubyMine

Asp.Net MVC Multi Area Projects and Intellisense

If your MVC project is divided in to multiple area projects and if you are using portable areas feature of MVCContrib, and if the view pages are stronly typed, intellisense on the view pages might not work.

Only way I was able to make this work is

a. Copy the main web.config file in to the area project

b. Copy the Views\Web.Config in to the areas project under views folder

c. Do not select 'Copy Local' option on System.Web.MVC dll.

Using TestDriven.Net and NCover to boost your team to write more tests

Having a large number of unit tests and sizable number of integrations tests is essential for maintaining a software project or product.  Apart from the quality of those tests, the quantity is some indication that the teams are in the right direction.

I see the following clear benefits of tests among many.

• If your working code is the truth, tests are the validators of that truth.  Tests are the code's knowledge base.


• They take out the fear of unknown.  This encourage the developers to refactor the code and improve it instead of merely maitaining it.


• Tests essentially improve the design of the code


• Tests helps new developers to come up to speed with the code base quickly

TestDriven.Net is a visual studio plugin that makes it super easy to run the tests right from the IDE.  This plugin integrates well with NUnit GUI and also NCover.

NCover is a code coverage tool.  It shows how much of your source code is covered by the tests.  Once you run the tests using NCover, it produces a report of which parts of the source code is not covered by the tests in percentages.

I found that these numbers play an important role in the developer psyche.  Once developers looks at these numbers, and know that how much of their code is not being tested at all, they can't resist from writing more tests.  I have seen this happening all the time. If stackoverflow.com's success is any proof that developers like numbers, scores, this makes complete sense.

Declare a target coverage percentage to the team and announce which parts of the code reached the target in the daily team meetings.  Like every other thing in development large number of poorly written tests could become a maintenance headache.  Once your team gets in to the track of writing tests, it is very important to review the tests.

Happy testing!

MVC Portable Areas and WebForms

MvcContrib project has a neat little feature called portable areas.  This allows us to develop features as independent units of work in asp.net mvc.

Eric Hester wrote a detailed post on how to use areas in an MVC project.  Jeffery Palermo wrote on how to use portable areas in a webforms project.

Portable areas projects stores all the views in the assembly as enbedded resources.  Normally asp.net runtime look for the page in the file system.  We can change this behavior by making the following call in the application start event of the global.asax file.

HostingEnvironment.RegisterVirtualPathProvider (YourVirtualPathProvider);

Portable areas feature in MVCContrib simply does that.  MvcContrib profject supplies a VirtualPathProvider called AssemblyResourceProvider.

However the above call will fail quietly if your website is precompiled.   This behavior is documented in an MSDN article.  So in order to use the portable areas in your webforms project, you should not use precompile option in the website project.