The 80s just called - they want their telnet client back

Telnet has been around ever since I was born. No..really..it was developed in 1968 and the very first protocol used on the ARPAnet. That’s right kids, when grandpa wanted to send an email, he used telnet.

I don’t think I have used Telnet for its intended use since the late nineties, but for years and years, enabling the stock Microsoft telnet client has been part of my routine setup script for any windows box I work with.

dism /Online /Get-FeatureInfo /FeatureName:telnet-client

For me and many of my colleagues, this is often the simplest, albeit crude, tool to help determine if a remote machine is listening on a specific port. Its certainly not the only tool, but one is nearly guaranteed that this can be found on any windows OS.  

On linux, Netcat is a similarly ubiquitous tool that is typically installed with most distributions:

nc -z -w1 boxstarter.com 80;echo $?

This will return 0, if the specified host is listening on port 80.

Why is this important?

Perhaps you are a web developer and your web site goes down. One key troubleshooting step is to determine if the web server is even up and listening on port 80. Or maybe SSL traffic is broken and you are wondering if the server is listening to port 443. The answer to these questions may very well tell you which of many possible paths is the best to pursue in finding the root of your problem.

So you whip out your command line console and simply run:

telnet myhost.com 80

If the machine is in fact listening on port 80, I will likely get a blank screen. Otherwise, the command will hang and eventually timeout. This always felt clunky, but it worked. Oh sure, since powershell became available, I could write a script that worked with the .net library to construct a raw socket to reach an endpoint and thereby get the same information. But that’s just more code to write.

A better way

Since powershell version 4 which ships with Windows 8.1 and server 2012R2, there is a new cmdlet that provides a much more elegant means of getting this information.

C:\dev\WinRM [v1.3]> Test-NetConnection -ComputerName boxstarter.org -Port 80
WARNING: Ping to boxstarter.org failed -- Status: TimedOut
ComputerName           : boxstarter.org
RemoteAddress          : 168.62.20.37
RemotePort             : 80
InterfaceAlias         : vEthernet (Virtual External Switch)
SourceAddress          : 192.168.1.7
PingSucceeded          : False
PingReplyDetails (RTT) : 0 ms
TcpTestSucceeded       : True
C:\dev\WinRM [v1.3]>

So now I have the same information plus some other bits of useful data given to me in a much more easily consumable format. Not only can I see that a site is responding to TCP port 80 requests, I see the IP address that the host name resolves to and I notice that the server is configured not to respond to ping requests.

Some may complain that Test-NetConnection requires far too many key strokes. Well there is a built in alias that points to this cmdlet allowing you to shorten the above command to:

TNC boxstarter.org -port 80

And if you don’t like having to include the -Port parameter name, the -CommonTCPPort is the next parameter in the default parameter order which takes the possible values of "HTTP,RDP,SMB,WINRM". So this means you get the same result as the command above using:

TNC boxstarter.org HTTP

So lose the telnet, and remember TNC – and welcome to the twenty first century!

Help raise the Chocolatey experiment to the Chocolatey experience and support the Chocolatey Kickstarter!

Mmm…Chocolatey…

As described on the homepage of Chocolatey.org, Chocolatey is like Apt-Get for windows. Now to some, that will immediately paint a clear picture of what Chocolatey is and why it puts the “awesome” into windows just like it does on my winawesomedows system. Others may be asking, “what get?” Or maybe, “that’s ok. I’m not in the market for an apartment right now.” For those who are not familiar with package management systems on other operating systems, Chocolatey makes it easy to find, download and install software. I cant remember the last time I searched for the windows git installer and went through all the screens in the install wizard. I just pop open a command line and type: ‘cinst git’. Curious what you can install via chocolatey? Check out chocolatey.org and you’ll find the over 2300 packages available for download and install.

Beyond this immediate value of installation ease, Chocolatey makes it easy to create packages and provides a platform that anyone can leverage to support private and alternate repositories other than the public community feed on chocolatey.org.

Chocolatey launches a Kickstarter

About a week and a half ago, Rob Reynolds (@ferventcoder) and team launched a kickstarter for chocolatey to help raise funds to not only preserve the value chocolatey currently provides to many many windows users but to help fund some greatly needed enhancements.

Chocolatey costs

While the benefits of chocolatey are free to anyone with access to a windows command line (or powershell console), there is a cost. Hosting these packages entails monthly storage and bandwidth expenses. There is also a huge time investment on the part of Chocolatey contributors and especially Rob Reynolds to address support questions and add features. I’m personally on the chocolatey email groups and I can tell you that I see a constant stream of emails from Rob every day addressing issues, merging PRs, and announcing new features. Gary Park (@gep13) is another individual who immediately comes to mind as an avid supporter. While no one has officially stated this, I can only imagine that asking Rob (husband and father of two) to continue to personally front the recurring costs and invest this amount of time is not sustainable and certainly not scalable.

Professional level offering

In addition to recurring expenses and some first-line support assistance, there are a slew of “professional grade” features the team would like to add to make Chocolatey a more polished experience for those needing to support an enterprise or other business critical infrastructure. These would include, enhanced security, better support for private feeds and other slick features as described in this image from the kickstarter:

New feature: Package moderation

Unrelated to the kickstarter but adding to the evidence that funding can only make things better is a new feature just launched the afternoon prior to this writing – package moderation. One of the most prevelant criticisms of Chocolatey is the fact that it potentially exposes users to malware. This is absolutely true. When you download a chocolatey package, you are downloading software over the open internet and you likely do not know the individual who created the package. The package may state that it installs one thing, but nothing stops it from doing something else or generally doing a sloppy job of installing what it is advertising.

To be clear, I do not believe that this truth implies that chocolatey should not be included in ones tool set. Its not the only package management system with these flaws and there are steps individuals and businesses can take today to protect themselves like pinning to known good package versions or hosting their own chocolatey feed.

Package moderation is one of many other features that stand to enhance the overall security story of Chocolatey. New packages, including package updates must now be approved by a Chocolatey moderator in order to be publicly visible and available to others. Here are some criteria that moderators use to deem a package approved:

1. Is the package named appropriately? 
2. Is the title appropriate? 
3. Does it have all the links? ProjectUrl at the very least. 
4. Is the description sufficient to explain the software? 
5. Are the authors pointed to the actual authors and not the package maintainers? 
6. Does the package look generally safe for consumption? 
7. Are links in the package to download software using the appropriate location? 
8. Does the package generally meet the guidelines set forth? 
9. Does the install and uninstall scripts make sense or are there variables being used that don't work? 
10. Does the package actually work?

Of course this feature does incur more time on the part of the core chocolatey team and is an example of another area of Chocolatey that this kickstarter aims to support.

Call to action!

So in the spirit of this blog, HurryUpAndWait, I encurage you to hurry up and offer what you feel comfortable contributing and then wait for the success of this kickstrarter! Do you work for a business that uses chocolatey? Perhaps it uses the chocolatey chef cookbook or the chocolatey puppet module. If you have access to those who make financial decisions in these organizations, let them know about how they can help to make chocolatey a more business friendly option that stands to improve its ability to automate.

Cloud Automation in a Windows World via InfoQ

This week InfoQ published an article I wrote entitled "Cloud Automation in a Windows World." The article could just as well been given the title "Automation in a Windows World" since there is nothing exclusive to cloud in the article. The article is a survey of automation strategies and tools used for windows provisioning and environment definition and management.

When it comes to compute resource automation, windows has not traditionally been known to be a leader in that space. This article discusses this historical gap and illustrates some of the ways in which it is closing.

I discuss ways in which we automate windows at CenturyLink Cloud and I point to a variety of tools that anyone can use today to assist in windows environment automation, be it a cloud or your grandma's PC. Among other technologies I mention Chef, Powershell DSC, Chocolatey, Boxstarter, Vagrant, and the future of windows containers.

If this all sounds interesting, please give it a read.

Configure and test windows infrastructure using Powershell technologies DSC and Pester running from Chef and Test-Kitchen

Update: see this post for the latest update on getting up and running with Test-Kitchen on windows.

About a week ago I attended the 2014 Chef Summit. I got to meet a bunch of new and interesting people and also met several who I had interacted with online but had never seen in person. One new person I met was Jay Mundrawala (@jdmundrawala). Jay works for chef and built a Test-Kitchen Busser for Pester (as a personal oss contribution and not as part of his job at Chef). You might ask…a What for What? Well this post is going to attempt to answer that and explain why I think it is important.

Pester

Pester is a unit testing framework for Powershell. It was originally created by Scott Muc (@scottmuc) a few years back. I joined in in 2012 to add support for Mocking and now development has largely been taken over by Dave Wyatt (@MSH_Dave). It is a BDD style approach to writing and running unit tests for powershell. However, as we will see here, you can write more than just unit tests. You can write a suite of tests to ensure your infrastructure is built and runs as intended.

The whole idea of writing tests for powershell is new to a lot of long time scripters. However, as just mentioned, this framework has been around for a few years but is just now starting to gain some popularity among the powershell community and in fact the Powershell team at Microsoft is now beginning to use it themselves.

Many entrenched in the Chef ecosystem have undoubtedly been exposed to rspec and rspec derivative tools for writing tests for their chef recipes and other ruby gems. Pester is very much inspired by rspec and many familiar with rspec who take a first look at Pester may not immediately notice the difference. There are indeed several differences but the primary difference is one is written in and for ruby and the other powershell.

Test-Kitchen

Test kitchen is a tool that is widely used within the Chef community but can also be used by other Configuration management tools like Puppet. Test kitchen is not a test framework per se but it is a sort of meta framework that provides a plugin architecture around configuration management scripts that makes it easy to use one or more of many testing frameworks with your infrastructure management scripts.

There are issues specific to configuration management that make such a tool as Test-kitchen very useful. In addition to simply running tests, Test-Kitchen can manage the creation and destruction of a VM or other computing resource where tests can be run in a repeatable, disposable and rebuildable manner. Again, this is managed by another plugin family of provisioners. Some may use the vagrant driver, others docker, vsphere, EC2, etc. Using Test-kitchen, I can watch as an instance is provisioned, built, tested ad then destroyed without any side effects impacting my local environment.

The plugin that manages different test frameworks is called the busser. This plugin is responsible for “bussing” code from your local machine to a virtual test instance. Jay’s busser, like all the others simply make sure that Pester gets installed on the system where you want your tests to run. Since Pester is a powershell based tool. You are typically going to be running Pester tests on a windows machine and the cool thing here is that you can write them in “pure” powershell. No need to wrap all of your powershell inside of ruby language constructs. Its all 100% powershell here.

Enter DSC – Microsoft’s Desired State Configuration

This is an interesting one because it is both a product (or API) of a specific technology vendor and a long time philosophical approach to infrastructure management. Some also incorrectly interpret it as a competitor trying to unseat  tools like chef or Puppet. There is indeed some overlap between DSC and other configuration management tools but the easiest way to groc how DSC fits into the CM landscape is as an API for writing resources specifically for windows infrastructure. Chef, Puppet and other tools provide a broad range of features to help you oversee and codify your infrastructure. The DSC surface area is really much simpler. DSC as it stands today consists of a constantly growing set of resources that can be leveraged in your configuration management tool of choice.

What do I mean by “resource?” Resource is a ubiquitous term in the popular CM tools used to provide an abstraction or DSL over a concrete piece of infrastructure (user, group, machine, file, firewall rule, etc) The resource descries how you want this infrastructure to look and does so in code that can be reviewed, tested, linted and source controlled.

You can use straight up DSC to execute these resources which offers a bare bones approach, or you can wrap them inside of a Chef recipe that can live alongside of non-DSC resources. Now the DSC resource for your windows roles and features, sql server HA, registry keys sits inside of your larger Chef infrastructure of nodes, environments, attributes, etc.

Chef making it easy to execute DSC resources

An initial reaction to this by many would be users of DSC is, why would I use Chef? Don’t I have to learn Ruby to work with that? Well because Chef is a full featured, mature configuration management solution, you get access to all of the great reporting, and server management features of chef. If you have a mixed windows/linux shop, you can manage everything with chef. Finally, it can be a bit unwieldy using raw DSC on its own. Before you can execute DSC resources, they must be downloaded and installed. Chef makes that super easy. And as we will see with test-kitchen, now you can plug your powershell based tests right into your chef workflow.

A real world example of executing DSC resources with chef and testing with Pester

We are going to follow a typical chef workflow of writing a cookbook to build a server. In our case it will be an IIS powered web server that hosts a Nuget package feed. Nuget is a windows package management specification very similar to ruby Gems. Its also the same specification behind windows Chocolatey packages similar to apt-get/yum/rpm for linux. Our web server will provide a rest based feed similar to rubygems.org that one can use to discover nuget packages.

Welcome to the bleeding edge

Before we get started let me point out that testing cookbooks on windows has not historically been well supported but there is more interest than ever in it today. There is very active development that is driving to make this possible but it is still not available from the latest stable version of Test-Kitchen. During this year’s Chef Summit, this exact topic was discussed. The creator and maintainer of Test-Kitchen, Fletcher Nichols was present as well as several others either interested in windows support  or actively working to provide first class support for windows like Salim Afiune. I was there as well and I think everyone left with a clear understanding that this work needs to come together in a future version of Test-Kitchen in the near future. I blogged on the current state of this tooling just a couple months ago. This may be seen as a continuation of that post with a specific bend towards powershell and DSC.

I will walk you through how to get your environment configured so that you can do this testing today and I will certainly update this post once the tooling is officially released.

Environment setup

I am going to assume that you do not have any of the necessary tools needed to run through the sample cookbook I am about to show. So you can pick and choose what you need to add to your system. I am also assuming you are using the ruby embedded with chefDK. If you have another ruby versioning environment, chances are you know what to do. Note: this environment does not need to be a windows box.

ChefDK

First and foremost you need chef. The easiest way to get chef along with many of the popular tools in its ecosystem like test-kitchen is to install the Chef development kit. There are downloads available for windows, mac and several linux distributions.

Vagrant

This tutorial will use Vagrant to instantiate a machine to run the cookbook and execute the tests. You can download vagrant from VagrantUp and like chef, it has downloads for all of the popular platforms.

A hypervisor

You will need something that your vagrant flavored VM can run in. Many prefer the free and feature complete VirtualBox. If you run on windows and are currently using versions 8/2012 and above, you may use Hyper-V already on your box. Note you cannot run both on the same boot instance.

Git

You will be using git to download some of the tools I am about to mention.

The WinRM Test-Kitchen fork

This will eventually and hopefully soon be merged into the authoritative test-kitchen repo. This fork has been largely developed by Salim Afiune and can be found here. There is still active development here. Currently I have my own fork of this fork working to improve performance of winrm based file transfers. My fork hopes to dramatically improve upload times of cookbooks to the test instance. The cookbook in this tutorial should just take a couple minutes to upload using my fork compared to nearly an hour and we hope to get the perf much more faster than that. Note that WinRM has no equivalent SCP functionality so implementing this is a bit crude. Here is how you can use and install my fork:

git clone -b one_session https://github.com/mwrock/test-kitchen
copy-item test-kitchen\lib `
  C:\opscode\chefdk\embedded\apps\test-kitchen `
  -recurse -force
copy-item test-kitchen\support `
  C:\opscode\chefdk\embedded\apps\test-kitchen `
  -recurse -force
cd test-kitchen
C:\opscode\chefdk\embedded\bin\gem build test-kitchen.gemspec
C:\opscode\chefdk\embedded\bin\gem install test-kitchen-1.3.0.gem

The Winrm based Kitchen-Vagrant plugin fork

Salim has also ported his enhancements to the popular Kitchen-Vagrant Test-Kitchen plugin. Since this tutorial uses vagrant, you will need this fork. Note that if you plan to use Hyper-V or a non VirtualBox hypervisor, please use my fork that includes recent changes to make vagrant and the winrm test kitchen work outside of VirtualBox. Here is how to get and install this:

git clone -b Transport https://github.com/mwrock/kitchen-vagrant
cd kitchen-vagrant
C:\opscode\chefdk\embedded\bin\gem build kitchen-vagrant.gemspec
C:\opscode\chefdk\embedded\bin\gem install kitchen-vagrant-0.16.0.gem

The dsc_nugetserver repository containing a sample cookbook and pester tests

This can simply be cloned from https://github.com/mwrock/dsc_nugetserver.

DSC in a chef recipe

Similar to the WinRM Test-Kitchen work, the DSC recipe work done by the folks at chef is still in fairly early development. There is a dsc_script resource available in the latest chef client release as of this post. There is also a community cookbook that represents a prototype of work that will be evolved into the core chef client. This cookbook contains the dsc_resource resource.

I intentionally wrote the dsc_nugetserver cookbook almost entirely from DSC resources. Lets take a look in the default recipe and observe the two flavors of the dsc resource.

dsc_script

dsc_script  "webroot" do
  code <<-EOH
    File webroot
    {
      DestinationPath="C:\\web"
      Type="Directory"
    }
  EOH
end

This is what is currently supported by the official chef-client and ships with the latest version. They really just wrap the DSC Configuration syntax supported by powershell today. The benefit that you get using it inside of a chef recipe are that you can now use the dsc_script as just another resource in your wider library of cookbooks. Chef also does some leg work for you. You do not need to worry about where the resource is installed and you do not need to compile the resource before use.

dsc_resource

dsc_resource "http firewall rule" do
  resource_name :xfirewall
  property :name, "http"
  property :ensure, "Present"
  property :state, "Enabled"
  property :direction, "Inbound"
  property :access, "Allow"
  property :protocol, "TCP"
  property :localport, "80"
end

This is really similar if not the same as dsc_scipt just with different syntax. Note the use of the property DSL. dsc_resource also does a much better job at finding the correct resource. While I believe that dsc_script only works with the official microsoft preinstalled resources, the community dsc cookbook can locate the newer experimental resources that are being distributed as part of the community resource kit waves.

Using the resource_kit recipe to download and install all of the current resource wave kit modules

I have included a recipe that will download the latest batch of resource wave dsc resources. I basically just copied this from one of chef’s own cookbook examples and replaced the download url with the latest resource wave. Once this recipe runs, literally all dsc resources are available for you to use.

Whatif Bug affecting most resources used within chef

There is a bug in both of the dsc resource flavors that will cause most resources to crash. If the dsc resource either does not support ShouldProcess of if the underlying call to powershell DSC’s Set-TargetResource results in the function throwing an error, these chef resources currently to not provide graceful failure for these scenarios. So as is, the resource will break when called. The chef team knows about this and has a fix that will be released in a future release.

In the meantime, I have forked the community dsc_resource in the dsc cookbook and commented out a single line. I can consume this fork from any cookbook by adding this to the Berksfile:

source "https://supermarket.getchef.com"

metadata

cookbook 'dsc' , git: 'https://github.com/mwrock/dsc'

Converging the recipe

The sample cookbook comes with both a .kitchen.yml file that includes a pointer to an evaluation copy of windows 8.1 for testing. I would have included a 2012 box instead but my 2012 vagrant box is Hyper-V only and I have not had time to add virtual box.

So running:

kitchen converge

Should create a windows box for testing and converge that box to run the sample recipe.

[2014-10-13T02:34:38-07:00] INFO: Getting PowerShell DSC resource 'xfirewall'
[2014-10-13T02:35:26-07:00] INFO: DSC Resource type 'xfirewall' Configuration completed successfully
[2014-10-13T02:35:29-07:00] INFO: Chef Run complete in 534.665725 seconds
[2014-10-13T02:35:29-07:00] INFO: Removing cookbooks/dsc_nugetserver/files/default/NugetServer.zip from the cache; it is no longer needed by chef-client.
[2014-10-13T02:35:29-07:00] INFO: Running report handlers
[2014-10-13T02:35:29-07:00] INFO: Report handlers complete
Finished converging <default-windows-81> (13m6.61s).
-----> Kitchen is finished. (13m11.87s)
C:\dev\dsc_nugetserver [master]>

Note that there is a chance the kitchen converge will fail shortly after creating the box and just before downloading the chef client. My suspicion is that this is because the windows 8.1 box is hard at work installing updates and the initial winrm call times out. I have always had success immediately calling kitchen converge again.

So once this completes, you should be able to open a local browser and point at your test box to see the nuget server informational home page:

Testing the recipe with Pester

Here are the tests we will run with Pester:

describe "default recipe" {

  it "should expose a nuget packages feed" {
    $packages = Invoke-RestMethod -Uri "http://localhost/nuget/Packages"
    $packages.Count | should not be 0
    $packages[0].Title.InnerText | should be 'elmah'
  }

  context "firewall" {

    $rule = Get-NetFirewallRule | ? { $_.InstanceID -eq 'http' }
    $filter = Get-NetFirewallPortFilter | ? { $_.InstanceID -eq 'http' }

    it "should filter port 80" {
      $filter.LocalPort | should be 80
    }
    it "should be enabled" {
      $rule.Enabled | should be $true
    }
    it "should allow traffic" {
      $rule.Action | should be "Allow"
    }
    it "should apply to inbound traffic" {
      $rule.Direction | should be "Inbound"
    }    
  }
}

This is 100% powershell. No ruby to see here.

This is first going to test our nuget server website. If all went as we intended, an http call to the root of localhost should reach our nuget server and it should behave like a nuget feed. So here we expect the Packages feed to return some packages and knowing what the first package should be, we test that its name is what we expect.

Because Test-Kitchen runs tests on the converged node, we need to be sure that the outside world can reach our entry point. So we go ahead and test that we opened the firewall correctly.

kitchen verify

The kitchen Pester busser now installs Pester:

C:\dev\dsc_nugetserver [master]> kitchen verify
-----> Starting Kitchen (v1.3.0)
-----> Setting up <default-windows-81>...
       Successfully installed thor-0.19.0
       Successfully installed busser-0.6.2
       2 gems installed
       Plugin pester installed (version 0.0.6)
-----> Running postinstall for pester plugin
-----> [pester] Installing PsGet
Downloading        PsGet from https://github.com/psget/psget/raw/master/PsGet/PsGet.psm1
PsGet is installed and ready to use
       USAGE:
           PS> import-module PsGet
           PS> install-module PsUrl

       For more details:
           get-help install-module
       Or visit http://psget.net
-----> [pester] Installing Pester

Then it runs our tests:

-----> Running pester test suite
-----> [pester] Running
Executing all tests in 'C:\tmp\busser\suites\pester'Describing        default recipe
[+] should expose a nuget packages feed 4.02s   Context        firewall
[+] should filter port 80 3.18s           
[+] should be enabled 16ms
[+] should allow traffic 12ms
[+] should apply to inbound traffic 13ms
Tests completed in 7.23s
       Passed: 5 Failed: 0
       Finished verifying <default-windows-81> (0m22.55s).
-----> Kitchen is finished. (0m59.74s)
C:\dev\dsc_nugetserver [master]>

Bugs regarding Execution Policy

One issue I ran into both with the dsc_resource resource and the Pester busser was a failure to bypass the ExecutionPolicy of the Powershell.exe process. This means if no one has explicitly set an execution policy on the box which they would not have if this is a newly provisioned machine and unless this is windows server 2012R2 which implements a new default ExecutionPolicy of RemoteSigned instead of Undefined, the converge will fail complaining that the execution of scripts are not allowed to run. Since the test vagrant box used here is windows 8.1, it is susceptible to this bug.

You can work around this by setting the execution policy in the recipe as is done in the sample:

powershell_script "set execution policy" do
  code <<-EOH
    Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Force
    if(Test-Path "$env:SystemRoot\\SysWOW64") {
      Start-Process "$env:SystemRoot\\SysWOW64\\WindowsPowerShell\\v1.0\\powershell.exe" -verb runas -wait -argumentList "-noprofile -WindowStyle hidden -noninteractive -ExecutionPolicy bypass -Command `"Set-ExecutionPolicy RemoteSigned`""
    }
    EOH
end

We set the policy for both the 64 and 32 bit shells since chef-client is a 32 bit process.

I have filed an issue with the dsc cookbook here and submitted a pull request for the busser here.

Testing on windows keeps getting better

We are still not where we need to be but we are making progress. This is a big step I think to adding accesibility to the work coming out of the Microsoft DSC initiatives. Here you have all the tools you need to not only execute DSC resources but also test them. A big thanks to Jay and Salim for their work here with Test Kitchen and the Pester busser!

If you want to learn more about DSC or Chef and particularly DSC in Chef. Pay attention to Steven Murawski's blog. Steven is a Chef Community manager and has done a ton of work with DSC at his previous employer Stack Exchange, the home of StackOverflow.com.

Chef Cookbook dependency management and the environment cookbook pattern

Last week I discussed how we at CenturyLink Cloud are approaching the versioning of cookbooks, environments and data bags focusing on our strategy of generating version numbers using git commit counts. In this post I’d like to explore one of the concrete values these version numbers provide in your build pipeline. We’ll explore how these versions can eliminate surprise breaks when cookbook dependencies in production may be different from the cookbooks you used in your tests. You are testing your cookbooks right?

A cookbook is its own code plus the sum of its dependencies

My build pipeline must be able to guarantee to the furthest extent possible that my build conditions match the same conditions of production. So if I test a cookbook with a certain set of dependencies and the tests pass, I want to have a high level of confidence that this same cookbook will converge successfully on production environments. However, if I promote the cookbook to production but my production environment has different versions of the dependent cookbooks, this confidence is lost because my tests accounted for different circumstances.

Even if these different versions are just at the patch level (the third level version number in the semantic version numbering schema), I still consider this an important difference. I know that only changes of the major build number should include breaking changes but lets just see a show of hands of those who have deployed a bug fix patch that regressed elsewhere…I thought so. You can put your hands down now everyone. Regardless, it can be quite simple to allow major version changes to slip in if your build process does not account for this.

Common dependency breakage scenarios

We will assume that you are using Berkshelf to manage dependencies and that you keep your Berksfile.lock files synced and version controlled. Lets explore why this is not enough to protect from dependency change creep.

Relaxed version constraints

Even if you have rigorously ensured that your metadata.rb files include explicit version constraints, there is never any guarantee that some downstream community cookbook has not specified any constraints in its metadata.rb file. You might think this is exactly where the Berksfile.lock saves you. A Berksfile.lock will snap the entire dependency graph to the exact version of the last sync. If this lock file is in source control, you can be assured that fellow teammates and your build system are testing the top level cookbook with all the same dependency versions. So far so good.

Now you upload the cookbooks to the chef server and when its time for a node to converge against your cookbook changes, where is your Berksfile.lock now? Unless you have something in place to account for this, chef-client is simply going to get the highest available version for cookbook dependencies without constraints. If anyone at any time uploads a higher version of a community cookbook to the chef server that is used by other cookbooks that had been tested against lesser versions, a break can easily occur.

Dependency islands in the same environment

This is related to the scenario just described above and explains how cookbook dependencies can be uploaded from one successful cookbook test run that can break sibling cookbooks in the same environment.

The Berksfile.lock file generates the initial dependency graph upon the very first berks install. Therefore you can create two cookbooks that have all of the same cookbook dependencies but if you build the Berksfile.lock file even hours apart, there is a perfectly reasonable possibility that the two cookbooks will have different versioned dependencies in their respective Berksfile.lock files.

Once both sets are uploaded to the chef server and unless an explicit version constraint is specified, the highest eligible version wins and this may be a different version than some of the cookbooks that use this dependency were tested against. So now you can only hope that everything works when nodes start converging.

Poorly timed application of cookbook constraints

You may be thinking the obvious remedy to all of these dependency issues is to add cookbook constraints to your environment files. I think you are definitely on the right track. This will eliminate the mystery version creep scenarios and you can look at your environment file and know exactly what versions of which cookbooks will be used. However in order for this to work, it has to be carefully managed. If I promote a cookbook version along with all of its dependencies by updating the version constraints in my environment, can I be guaranteed that all other cookbooks in the environment with the same downstream dependencies  have been tested with any new versions being updated?

I do believe that constraining environment versions is important. These constraints can serve the same function as your Berksfile.lock file within any chef server environment. Unless the entire matrix of constraints matches up against what has been tested, these constraints provide inadequate safety.

Safety guidelines for cookbook constraints in an environment

A constraint for every cookbook

Not only your internal top level cookbooks should be constrained. All dependent cookbooks should also include constraints. Any cookbook missing a constraint introduces the possibility that an untested dependency graph will be introduced.

All constraints point to exact versions (no pessimistic constraints)

I do think pessimistic constraints are fine in your Berksfile.lock or metadata.rb files. This basically says you are ok with upgrading dependencies within dev/test scenarios, but once you need to establish a baseline of a known set of good cookbooks, you want that known group to be declared rigidly. Unless you point to precise versions, you are stating that you are ok with “inflight” change and that’s the change that can bring down your system.

Test all changes and all cookbooks potentially affected by changes

You will need to be able to identify what cookbooks that had no direct changes applied but are part of the same graph undergoing change. In other words if both cookbook A and B depend on C and C gets bumped as you are developing A, you must be able to automatically identify that B is potentially affected and must be tested to validate your changes to A even though no direct changes were made to B. Not until A, B, and C all converge successfully can you consider the changes to be included in your environment.

Leveraging the environment cookbook pattern to keep your tree whole

The environment cookbook pattern was introduced by Jamie Windsor in this post. The environment cookbook can be thought of as the trunk or root of your environment. You may have several top level cookbooks that have no direct dependencies on one another and therefore you are subject to the dependency islands referred to above. However if you have a common root declaring a dependency on all your top level cookbooks, you now have a single coherent graph that can represent all cookbooks.

The environment cookbook pattern prescribes the inclusion of an additional cookbook for every environment you want to apply this versioning rigor. This cookbook is called the environment cookbook and includes only four files:

README.md

Providing thorough documentation of the cookbook’s usage.

metadata.rb

Includes one dependency for each top level cookbook in your environment.

Berksfile and Berksfile.lock

These express the canonical dependency graph of your chef environment. Jamie suggests that this is the only Berksfile.lock you need to keep in source control. While I agree it’s the only one that “needs” to be in source control, I do see value in keeping the others. I think by keeping “child” Berksfile.lock files in sync the top level dependencies may fluctuate less often and provide a bit more stability during development.

Generating cookbook constraints against an environment cookbook

Some will suggest using berks apply in the environment cookbook and point to the environment you want to constrain. I personally do not like this method because it simply uploads the constraints to the environment on the chef server. I just want to generate it locally first where I can run tests and version control the environment file first.

At CenturyLink Cloud we have steps in our CI pipeline that I believe not only adds the correct constraints but allows us to identify all cookbooks impacted by the constraints and also ensures that all impacted cookbooks are then tested against the exact same set of dependencies. Here is the flow we are currently using:

Generating new cookbook versions for changed cookbooks

As included in the safety guidelines above, this not only means that cookbooks with changed code get a version bump, it also means that any cookbook that takes a dependency on one of these changed cookbooks also gets a bump. Please refer to my last post which describes the version numbering strategy. This is a three step process:

1. Initial versioning of all cookbooks in the environment. This results in all directly changed cookbooks getting bumped.
2. Sync all individual Berksfile.lock files. This will effectively change the Berksflie.locks of all dependent cookbooks.
3. A second versioning pass that ensures that all cookbooks affected by the Berksfile.lock updates also get a version bump.

Generate master list of cookbook constraints against the environment cookbook

Using the Berksfile of the environment cookbook, we will apply the new cookbook versions to a test environment file:

def constrain_environment(environment_name, cookbook_name)
  dependencies = environment_dependencies(cookbook_name)
  env_file = File.join(config.environment_directory, 
    "#{environment_name}.json")
  content = JSON.parse(File.read(env_file))
  content['cookbook_versions'] = {}
  dependencies.each do | dep |
    content['cookbook_versions'][dep.name] = dep.locked_version.to_s
  end

  File.open(env_file, 'w') do |out|
    out << JSON.pretty_generate(content)
  end
  dependencies
end

def environment_dependencies(cookbook_name)
  berks_name = File.join(config.cookbook_directory, 
    cookbook_name, "Berksfile")
  berksfile = Berkshelf::Berksfile.from_file(berks_name)
  berksfile.list
end

This will result in a test.json environment file getting all of the cookbook constraints for the environment. Another positive byproduct of this code is that it will force a build failure in the event of version conflicts.

It is very possible that one cookbook will declare a dependency with an explicit version while another cookbook declares the same cookbook dependency but with a different version constraint. In these cases the Berkshelf list command invoked above will fail because it cannot satisfy both constraints. Its good that it fails now so you can align the versions before the final constraint is locked and potentially causing a version conflict during a chef node client run.

Run kitchen tests for impacted cookbooks against the test.json environment

How do we identify the impacted cookbooks? Well as we saw above, every cookbook that was either directly changed or impacted via a transitive dependency got a version bump. Therefore it’s a matter of comparing a cookbook’s new version to the version of the last known good tested environment. I've created an is_dirty function to determine if a cookbook needs to be tested:

def is_dirty(environment_name, cookbook_name, environment_cookbook)
  dependencies = environment_dependencies(environment_cookbook)
  
  cb_dependency = (
    dependencies.select { |dep| dep.name == cookbook_name })[0]

  env_file = File.join(config.environment_directory, 
    "#{environment_name}.json")
    
  content = JSON.parse(File.read(env_file))
  if content.has_key?('cookbook_versions')
    if content['cookbook_versions'].has_key?(cookbook_name)
      curr_version = cb_dependency.locked_version.to_s
      curr_version != content['cookbook_versions'][cookbook_name]
    else
      true
    end
  end
end

This method takes the environment that represents my last known good environment (the one where all the tests passed), the cookbook to check for dirty status and the environment cookbook. If the cookbook is clean, it effectively passes this build step.

In a future post I may go into detail regarding how we utilize our build server to run all of these tests concurrently from the same git commit and aggregate the results into a single master integration result.

Create a new Last Known Good environment

If any test fails, the entire build fails and it all stops for further investigation. If all tests pass, we run through the above constrain_environment method again to produce the final cookbook constraints of our Last Known Good environment which serves as a release candidate of cookbooks that can converge our canary deployment group. The deployment process is a topic for a separate post.

The Kitchen-Environment provisioner driver

One problem we hit early on was that when test-kitchen generated the Berksfile dependencies to ship to the test instance, the versions it generated may differ from the versions in the environment file. This was because Test-Kitchen’s chef-zero driver as well as most the other chef provisioner drivers, run a berks vendor against the Berksfile of the individual cookbook under test. These may produce different versions than a berks vendor against the environment cookbook and it also illustrates why we are following this pattern. When this happens, it means that the individual cookbook on its own runs with a different dependency than it may in a chef server.

What we needed was a way for the provisioner to run berks vendor against the environment cookbook. The following custom provisioner driver does just this.

require "kitchen/provisioner/chef_zero"

module Kitchen

  module Provisioner

    class Environment < ChefZero

      def create_sandbox
        super
        prepare_environment_dependencies
      end

      private

      def prepare_environment_dependencies
          tmp_env = "TMP_ENV"
          path = File.join(tmpbooks_dir, tmp_env)
          env_berksfile = File.expand_path(
            "../#{config[:environment_cookbook]}/Berksfile", 
            config[:kitchen_root])    

          info("Vendoring environment cookbook")    
          ::Berkshelf.set_format :null

          Kitchen.mutex.synchronize do
             Berkshelf::Berksfile.from_file(env_berksfile).vendor(path)

              # we do this because the vendoring converts metadayta.rb
              # to json. any subsequent berks command on the 
              # vendored cookbook will fail
              FileUtils.rm_rf Dir.glob("#{path}/**/Berksfile*")

              Dir.glob(File.join(tmpbooks_dir, "*")).each do | dir |
                cookbook = File.basename(dir)
                if cookbook != tmp_env
                  env_cookbook = File.join(path, cookbook)
                  if File.exist?(env_cookbook)
                    debug("copying #{env_cookbook} to #{dir}")
                    FileUtils.copy_entry(env_cookbook, dir)
                  end
                end
              end
              FileUtils.rm_rf(path)
          end
      end

      def tmpbooks_dir
        File.join(sandbox_path, "cookbooks")
      end

    end
  end
end

Environments as cohesive units

This is all about treating any chef environment as a cohesive unit wherein any change introduced must be considered upon all parts involved. One may find this to be overly rigid or change adverse. One belief I have regarding continuous deployment is that in order to be fluid and nimble, you must have rigor. There is no harm in a high bar for build success as long as it is all automated and therefore easy to apply the rigor. Having a test framework that guides us toward success is what can separate a continuous deployment pipeline from a continuous hot fix fire drill.