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RavenDB On Linux–Status Update

Ayende @ Rahien - 16 hours 23 min ago

imageSeveral months ago we decided to ramp up the RavenDB on Linux migration effort, and hired a full time developer to do just that.

We started this with great hopes, mostly because we were able to get Voron to run on Linux in a reasonable amount of time. But RavenDB is several orders of magnitude bigger than Voron, and we run into a lot more complexities along the way.

In particular, and I am not quite sure how to put it nicely, the entire environment is pretty unstable. Our target was Mono – 4.3.0, MonoDevelop 5.10 and Ubuntu 14.04. And it takes really no effort at all to break pretty much everything there.

For example, SLEEP_DURATION_BEFORE_ABORT will, if you are running inside a debugger, or just running GC, sometimes, it will intentionally crash if certain operations takes longer than 200ms.

But in general, it feels like Mono just isn’t nearly stable enough for a production platform. Sometimes it would work fine, other time, you get horrible crashes in the process that required us to debug the mono runtime to figure out what is going on. Sometimes it was us doing stupid things, other times it was real bugs in the Mono runtime. Other issues related to missing websockets implementation (it appears to be there and then removed, for some reason), missing chunked encoding support etc.

As an aside, MonoDevelop in particular is… quite uncomfortable IDE, and it doesn’t compare well in pretty much any level of experience to the experience you get from other IDEs. That just exacerbate the problem, to be frank.

In other words, porting RavenDB to mono is a lot of hard work. But that was pretty much expected. What I didn’t really expect was how much work it would be not to port it, but to actually fill in missing / incomplete parts of the framework itself.

Now, there are plenty of other problems in there even without Mono. Typically Windows –> Linux port, anything from file paths to case sensitivity to finding different ways to do various things (from finding how busy the CPU is to getting low memory notifications to … well, you get the drift). Those are the kind of problems that we expected, and the kinds that frankly, we wanted to be solving.

But the instability of the mono runtime environment make it really expensive to port any non trivial software without spending most of the time debugging Mono. Even if the error is in our code, the only way to verify that is to actually debug Mono itself. And that puts a much higher cost on the actual porting effort. More to the point, this also means frightening things for trying to support this in production. I don’t relish the thought of having to go to a customer and tell them that a particular issue is caused by a GC bug and that fixing that will require a new custom runtime. Leaving aside the actual cost of such a support call.

So we stopped, and looked at the CoreCLR. I have a much higher expectation of quality from Microsoft, given the track record of the .NET framework. The problem is that the CoreCLR, while it is supposed to have an RC out in November, it still quite problematic on Linux. For example, you can’t use Unix paths in Uris, which broke us pretty early in the process. That was annoying, but expected for the time being, and while this issue (and other stuff we run into, I’m only pointing this out as a simple example, nitpickers, don’t get hang up on this) are surmountable, the major issue is that the CoreCLR require a lot more than just a few #ifdef, it require quite a lot of work. Probably restructuring the project (some dependencies are now nuget packages, different structure for projects and build system, etc).

Therefor, what we intend to do now is wait a bit until the CoreCLR next release, probably September, and then start seeing what it takes to run RavenDB (both server & client) under the CoreCLR on Windows. The idea is that we have much better tooling for working with .NET code on Windows, and hopefully the bulk of the work to actually run on the CoreCLR runtime there, then just deal with everything we need to run on Linux, and not have to worry about debugging the runtime as well.

Now, to deal with the nitpickers:

Mono is Open Source, you can fix any issues you find and submit pull requests.

That is correct, but let me talk about a few of the issues we have run into.

The class library is partial / bad.  I think that we would have done much better if we were building on Mono from the get go, we would know what pieces to avoid. But when a call to a ZipFile.Open will crash with SIGSEGV and no indication of why that is happening (ended up being stack overflow in the Mono BCL implementation), the fix was a single line but finding the root cause took a long while.

With the actual runtime, a GC issue caused a segmentation fault, that took about a month to figure out.

Now, we aren’t expert in Mono. So when we got in trouble  we reached out to the members in the Mono team, and were recommended a company that had the required expertise. I’m very happy with the service provided by them, but the fact of the matter is, it took a month to narrow down a big problem to something that would be fixed by a couple of lines of code. Not because they weren’t good, but because the problem was pretty tough to figure out.

So we contributed some stuff back, and we would be happy to continue doing so if the process wasn’t so hard (and quite expensive). Even relative simple issues had a very high threshold.

The RavenDB codebase is close to a million lines of code. It is doing some pretty advanced stuff, and changing the foundation underneath it means that we invalidate a lot of silent assumptions. If the trivial stuff breaks so badly, I don’t want to think about the cost of the really complex stuff. The GC issue was bad enough.

If we were working from scratch, we would know what to avoid, but with such a big codebase, that isn’t feasible. And again, even if we did manage to get it working properly, we still have the issue of how to support it. We provide production support to our customers, and the ability to accurately and quickly pinpoint problems and troubleshoot them is key. Taking on the support burden on Mono is very risky.

Note that the worry I have isn’t based around vague fears. The GC issue we had would cause random crashes, typically far after the relevant code would run, and only under very specific scenarios. In 99% of the cases, it would run just fine (well, not fine, but it wouldn’t be crashing). A production system with this type of behavior would be a nightmare, even escalating to the Mono core team, figuring out where and how this is happening is nasty, and it won’t happen in the time frames that we want to provide to customers who have production support contracts with us.

What about the CoreCLR, it is Open Source too, why not contribute to it?

The current plan, as I said, is to first see what it takes to move to the CoreCLR on Windows. That is a much smaller step, but it will let us get familiar both with the way the CoreCLR is structured and the new dependencies. We are actively looking at the project, and to say that I’m excited is not nearly enough. This require a lot of work on our side, before we get to the point where we are actually getting to figure out if there is stuff that needs fixing there too.

Once we have that, we are going to go back to Linux and get to working on running on a different OS, with all the implications of that. I’m actually looking forward to this. That is the kind of problem that I want to tackle.

If you want to look at the current state of our work (RavenDB on Linux using Mono), you can check it out here. We still have a full time developer for this, we are just going to divert him until the next beta of CoreCLR is out, and then we are going to restart the process as I described above.

Categories: Blogs

You should not be using WebComponents yet

Decaying Code - Maxime Rouiller - 18 hours 7 min ago

Have you read about WebComponents? It sounds like something that we all tried to achieve on the web since... well... a long time.

If you take a look at the specification, it's hosted on the W3C website. It smell like a real specification. It looks like a real specification.

The only issue is that Web Components is really four specifications. Let's take a look at all four of them.

Reviewing the specificationsHTML Templates


This specific specification is not part of the "Web components" section. It has been integrated in HTML5. Henceforth, this one is safe.

Custom Elements


This specification is for review and not for implementation!

Alright no let's not touch this yet.

Shadow DOM


This specification is for review and not for implementation!

Wow. Okay so this is out of the window too.

HTML Imports


This one is still a working draft so it hasn't been retired or anything yet. Sounds good!

Getting into more details

So open all of those specifications. Go ahead. I want you to read one section in particular and it's the author/editors section. What do we learn? That those specs were draft, edited and all done by the Google Chrome Team. Except maybe HTML Templates which has Tony Ross (previously PM on the Internet Explorer Team).

What about browser support?

Chrome has all the spec already implemented.

Firefox implemented it but put it behind a flag (about:config, search for properties dom.webcomponents.enabled)

Internet Explorer, they are all Under Consideration

What that tells us

Google is pushing for a standard. Hard. They built the spec, pushing the spec also very hary since all of this is available in Chrome STABLE right now. No other vendors has contributed to the spec itself. Polymer is also a project that is built around WebComponents and it's built by... well the Chrome team.

That tells me that nobody right now should be implementing this in production. If you want to contribute to the spec, fine. But WebComponents are not to be used.

Otherwise, we're only getting in the same issue we were in 10-20 years ago with Internet Explorer and we know it's a painful path.

What is wrong right now with WebComponents

First, it's not cross platform. We handled that in the past. That's not something to stop us.

Second, the current specification is being implemented in Chrome as if it was recommended by the W3C (it is not). Which may lead us to change in the specification which may render your current implementation completely inoperable.

Third, there's no guarantee that the current spec is going to even be accepted by the other browsers. If we get there and Chrome doesn't move, we're back to Internet Explorer 6 era but this time with Chrome.

What should I do?

As for what "Production" is concerned, do not use WebComponents directly. Also, avoid Polymer as it's only a simple wrapper around WebComponents (even with the polyfills).

Use other framework that abstract away the WebComponents part. Frameworks like X-Tag or Brick. That way you can benefit from the feature without learning a specification that may be obsolete very quickly or not implemented at all.

Categories: Blogs

Fix: Error occurred during a cryptographic operation.

Decaying Code - Maxime Rouiller - 18 hours 7 min ago

Have you ever had this error while switching between projects using the Identity authentication?

Are you still wondering what it is and why it happens?

Clear your cookies. The FedAuth cookie is encrypted using the defined machine key in your web.config. If there is none defined in your web.config, it will use a common one. If the key used to encrypt isn't the same used to decrypt?

Boom goes the dynamite.

Categories: Blogs

Renewed MVP ASP.NET/IIS 2015

Decaying Code - Maxime Rouiller - 18 hours 7 min ago

Well there it goes again. It was just confirmed that I am renewed as an MVP for the next 12 months.

Becoming an MVP is not an easy task. Offline conferences, blogs, Twitter, helping manage a user group. All of this is done in my free time and it requires a lot of time.But I'm so glad to be part of the big MVP family once again!

Thanks to all of you who interacted with me last year, let's do it again this year!

Categories: Blogs

Failed to delete web hosting plan Default: Server farm 'Default' cannot be deleted because it has sites assigned to it

Decaying Code - Maxime Rouiller - 18 hours 7 min ago

So I had this issue where I was moving web apps between hosting plans. As they were all transferred, I wondered why it refused to delete them with this error message.

After a few click left and right and a lot of wasted time, I found this blog post that provides a script to help you debug and the exact explanation as to why it doesn't work.

To make things quick, it's all about "Deployment Slots". Among other things, they have their own serverFarm setting and they will not change when you change their parents in Powershell (haven't tried by the portal).

Here's a copy of the script from Harikharan Krishnaraju for future references:

Switch-AzureMode AzureResourceManager
$Resource = Get-AzureResource

foreach ($item in $Resource)
	if ($item.ResourceType -Match "Microsoft.Web/sites/slots")
		$plan=(Get-AzureResource -Name $item.Name -ResourceGroupName $item.ResourceGroupName -ResourceType $item.ResourceType -ParentResource $item.ParentResource -ApiVersion 2014-04-01).Properties.webHostingPlan;
		write-host "WebHostingPlan " $plan " under site " $item.ParentResource " for deployment slot " $item.Name ;

	elseif ($item.ResourceType -Match "Microsoft.Web/sites")
		$plan=(Get-AzureResource -Name $item.Name -ResourceGroupName $item.ResourceGroupName -ResourceType $item.ResourceType -ApiVersion 2014-04-01).Properties.webHostingPlan;
		write-host "WebHostingPlan " $plan " under site " $item.Name ;
Categories: Blogs

Switching Azure Web Apps from one App Service Plan to another

Decaying Code - Maxime Rouiller - 18 hours 7 min ago

So I had to do some change to App Service Plan for one of my client. The first thing I was looking for was to do it under the portal. A few clicks and I'm done!

But before I get into why I need to move one of them, I'll need to tell you about why I needed to move 20 of them.

Consolidating the farm

First, my client had a lot of WebApps deployed left and right in different "Default" ServicePlan. Most were created automatically by scripts or even Visual Studio. Each had different instance size and difference scaling capabilities.

We needed a way to standardize how we scale and especially the size on which we deployed. So we came down with a list of different hosting plans that we needed, the list of apps that would need to be moved and on which hosting plan they currently were.

That list went to 20 web apps to move. The portal wasn't going to cut it. It was time to bring in the big guns.


Powershell is the Command Line for Windows. It's powered by awesomeness and cats riding unicorns. It allows you to do thing like remote control Azure, import/export CSV files and so much more.

CSV and Azure is what I needed. Since we built a list of web apps to migrate in Excel, CSV was the way to go.

The Code or rather, The Script

What follows is what is being used. It's heavily inspired of what was found online.

My CSV file has 3 columns: App, ServicePlanSource and ServicePlanDestination. Only two are used for the actual command. I could have made this command more generic but since I was working with apps in EastUS only, well... I didn't need more.

This script should be considered as "Works on my machine". Haven't tested all the edge cases.


Switch-AzureMode AzureResourceManager
$rgn = 'Default-Web-EastUS'

$allAppsToMigrate = Import-Csv $filename
foreach($app in $allAppsToMigrate)
    if($app.ServicePlanSource -ne $app.ServicePlanDestination)
        $appName = $app.App
		    $source = $app.ServicePlanSource
		    $dest = $app.ServicePlanDestination
        $res = Get-AzureResource -Name $appName -ResourceGroupName $rgn -ResourceType Microsoft.Web/sites -ApiVersion 2014-04-01
        $prop = @{ 'serverFarm' = $dest}
        $res = Set-AzureResource -Name $appName -ResourceGroupName $rgn -ResourceType Microsoft.Web/sites -ApiVersion 2014-04-01 -PropertyObject $prop
        Write-Host "Moved $appName from $source to $dest"
Categories: Blogs

Microsoft Virtual Academy Links for 2014

Decaying Code - Maxime Rouiller - 18 hours 7 min ago

So I thought that going through a few Microsoft Virtual Academy links could help some of you.

Here are the links I think deserve at least a click. If you find them interesting, let me know!

Categories: Blogs

Temporarily ignore SSL certificate problem in Git under Windows

Decaying Code - Maxime Rouiller - 18 hours 7 min ago

So I've encountered the following issue:

fatal: unable to access 'https://myurl/myproject.git/': SSL certificate problem: unable to get local issuer certificate

Basically, we're working on a local Git Stash project and the certificates changed. While they were working to fix the issues, we had to keep working.

So I know that the server is not compromised (I talked to IT). How do I say "ignore it please"?

Temporary solution

This is because you know they are going to fix it.

PowerShell code:

$env:GIT_SSL_NO_VERIFY = "true"

CMD code:


This will get you up and running as long as you don’t close the command window. This variable will be reset to nothing as soon as you close it.

Permanent solution

Fix your certificates. Oh… you mean it’s self signed and you will forever use that one? Install it on all machines.

Seriously. I won’t show you how to permanently ignore certificates. Fix your certificate situation because trusting ALL certificates without caring if they are valid or not is juts plain dangerous.

Fix it.


Categories: Blogs

The Yoda Condition

Decaying Code - Maxime Rouiller - 18 hours 7 min ago

So this will be a short post. I would like to introduce a word in my vocabulary and yours too if it didn't already exist.

First I would like to credit Nathan Smith for teaching me that word this morning. First, the tweet:

Chuckling at "disallowYodaConditions" in JSCS… — Awesome way of describing it.

— Nathan Smith (@nathansmith) November 12, 2014

So... this made me chuckle.

What is the Yoda Condition?

The Yoda Condition can be summarized into "inverting the parameters compared in a conditional".

Let's say I have this code:

string sky = "blue";if(sky == "blue) {    // do something}

It can be read easily as "If the sky is blue". Now let's put some Yoda into it!

Our code becomes :

string sky = "blue";	if("blue" == sky){    // do something}

Now our code read as "If blue is the sky". And that's why we call it Yoda condition.

Why would I do that?

First, if you're missing an "=" in your code, it will fail at compile time since you can't assign a variable to a literal string. It can also avoid certain null reference error.

What's the cost of doing this then?

Beside getting on the nerves of all the programmers in your team? You reduce the readability of your code by a huge factor.

Each developer on your team will hit a snag on every if since they will have to learn how to speak "Yoda" with your code.

So what should I do?

Avoid it. At all cost. Readability is the most important thing in your code. To be honest, you're not going to be the only guy/girl maintaining that app for years to come. Make it easy for the maintainer and remove that Yoda talk.

The problem this kind of code solve isn't worth the readability you are losing.

Categories: Blogs

Do you have your own Batman Utility Belt?

Decaying Code - Maxime Rouiller - 18 hours 7 min ago
Just like most of us on any project, you (yes you!) as a developer must have done the same thing over and over again. I'm not talking about coding a controller or accessing the database.

Let's check out some concrete examples shall we?

  • Have you ever setup HTTP Caching properly, created a class for your project and call it done?
  • What about creating a proper Web.config to configure static asset caching?
  • And what about creating a MediaTypeFormatter for handling CSV or some other custom type?
  • What about that BaseController that you rebuild from project to project?
  • And those extension methods that you use ALL the time but rebuild for each projects...

If you answered yes to any of those questions... you are in great risk of having to code those again.

Hell... maybe someone already built them out there. But more often than not, they will be packed with other classes that you are not using. However, most of those projects are open source and will allow you to build your own Batman utility belt!

So once you see that you do something often, start building your utility belt! Grab those open source classes left and right (make sure to follow the licenses!) and start building your own class library.


Once you have a good collection that is properly separated in a project and that you seem ready to kick some monkey ass, the only way to go is to use NuGet to pack it together!

Checkout the reference to make sure that you do things properly.

NuGet - Publishing

OK you got a steamy new hot NuGet package that you are ready to use? You can either push it to the main repository if your intention is to share it with the world.

If you are not ready quite yet, there are multiple way to use a NuGet package internally in your company. The easiest? Just create a Share on a server and add it to your package source! As simple as that!

Now just make sure to increment your version number on each release by using the SemVer convention.

Reap the profit

OK, no... not really. You probably won't be money anytime soon with this library. At least not in real money. Where you will gain however is when you are asked to do one of those boring task yet over again in another project or at another client.

The only thing you'll do is import your magic package, use it and boom. This task that they planned would take a whole day? Got finished in minutes.

As you build up your toolkit, more and more task will become easier to accomplish.

The only thing left to consider is what NOT to put in your toolkit.

Last minute warning

If you have an employer, make sure that your contract allows you to reuse code. Some contracts allows you to do that but double check with your employer.

If you are a company, make sure not to bill your client for the time spent building your tool or he might have the right to claim them as his own since you billed him for it.

In case of doubt, double check with a lawyer!

Categories: Blogs

Software Developer Computer Minimum Requirements October 2014

Decaying Code - Maxime Rouiller - 18 hours 7 min ago

I know that Scott Hanselman and Jeff Atwood have already done something similar.

Today, I'm bringing you the minimum specs that are required to do software development on a Windows Machine.

P.S.: If you are building your own desktop, I recommend PCPartPicker.


Intel: Intel Core i7-4790K

AMD: AMD FX-9590

Unless you use a lot of software that supports multi-threading, a simple 4 core here will work out for most needs.


Minimum 8GB. 16GB is better.

My minimum requirement here is 8GB. I run a database engine and Visual Studio. SQL Server can easily take 2Gb with some big queries. If you have extensions installed for Visual Studio, it will quickly raise to 1GB of usage per instance and finally... Chrome. With multiple extensions and multiple pages running... you will quickly reach 4GB.

So get 8GB as the bare minimum. If you are running Virtual Machines, get 16GB. It won't be too much. There's no such thing as too much RAM when doing software development.


512 GB SSD drive

I can't recommend enough an SSD. Most tools that you use on a development machine will require a lot of I/O. Especially random read. When a compiler starts and retrieve all your source code to compile, it will need to read from all those file. Same thing if you have tooling like ReSharper or CodeRush. I/O speed is crucial. This requirement is even more important on a laptop. Traditionally, PC maker put a 5200RPM HDD on a laptop to reduce power usage. However, 5200 RPM while doing development will be felt everywhere.

Get an SSD.

If you need bigger storage (terabytes), you can always get a second hard-drive of the HDD type instead. Slower but capacities are also higher. On most laptop, you will need external storage for this hard drive so make sure it is USB3 compatible.

Graphic Card

Unless you do graphic rendering or are working with graphic tools that require a beast of a card... this is where you will put the less amount of money.

Make sure to get enough of them for your amount of monitors and that they can provide the right resolution/refresh rate.


My minimum requirement nowadays is 22 inches. 4K is nice but is not part of the "minimum" requirement. I enjoy a 1920x1080 resolution. If you are buying them for someone else, make sure they can be rotated. Some developers like to have a vertical screen when reading code.

To Laptop or not to Laptop

Some company go Laptop for everyone. Personally, if the development machine never need to be taken out of the building, you can go desktop. You will save a bit on all the required accessories (docking port, wireless mouse, extra charger, etc.).

My personal scenario takes me to clients all over the city as well as doing presentations left and right. Laptop it is for me.

Categories: Blogs

"Napa" Office 365 Development Tools in SharePoint 2013 & Office 365 - Part 1

C-Sharpcorner - Latest Articles - 18 hours 23 min ago
In this article you will learn about Napa Office 365 Development Tools in SharePoint 2013 & Office 365.
Categories: Communities

Bind Data in ListView Controls using Database in ASP.NET

C-Sharpcorner - Latest Articles - 18 hours 23 min ago
This article shows how to bind data in ListView controls with using any database and also shows paging on controls on linkbutton click.
Categories: Communities

Create Custom Table for HTML Helper in MVC

C-Sharpcorner - Latest Articles - 18 hours 23 min ago
In this article you will learn how to create Custom Table for HTML Helper in MVC.
Categories: Communities

"Napa" Office 365 Development Tools in SharePoint 2013 & Office 365

C-Sharpcorner - Latest Articles - 18 hours 23 min ago
In this article you will learn about "Napa" Office 365 Development Tools in SharePoint 2013 & Office 365.
Categories: Communities

Learn MVVM Pattern

C-Sharpcorner - Latest Articles - 18 hours 23 min ago
In this article you will learn about the MVVM Pattern.
Categories: Communities

Write Download Code For PDF From GridView in ASP.Net Using Ionic.Zip

C-Sharpcorner - Latest Articles - Thu, 07/30/2015 - 08:00
In this article I’ll show you how to write download code for downloading a PDF from a GridView in ASP.NET using C#.
Categories: Communities

Routing System in Web API

C-Sharpcorner - Latest Articles - Thu, 07/30/2015 - 08:00
This article explains how to use routing in the Web API.
Categories: Communities

Build Events in Visual Studio

C-Sharpcorner - Latest Articles - Thu, 07/30/2015 - 08:00
In this article you will learn how to use Build Events in Visual Studio.
Categories: Communities