Traditional configuration management systems perform operations on the target systems they manage after doing topological sorting of the operations that need to be performed.

The operations that need to be performed on the systems are usually described as a directed acyclic graph, which is also known as a dependency graph.

The result of a successful topological sort gives the proper order of execution for the operations that need to be performed, that is which operation gets executed first, which is next, and so on.

In case of any errors while doing a topological sort they are also able to determine and pinpoint circular dependencies in the graph, which indicates an impossible evaluation of the dependency graph.

Successful topological sort of the graph often results in a serialized or sequential execution of operations, where only one operation gets executed at any given time.

As you might guess, the more operations we have to perform results in more time required for the whole execution to complete.

In this post we will see how two different configuration management systems perform operations in terms of speed and concurrency.

First on the list is Puppet - a very popular and well established configuration management system with a rich library of features and third party modules available at the Puppet Forge.

The second one is Gru - a relatively new project, described as a distributed orchestration & configuration management framework, which is written in Go and uses Lua as the DSL language.

The focus of Gru is to be a simple, fast and concurrent framework for doing orchestration and configuration management.

While tradional configuration management systems execute operations sequentially, Gru tries it’s best to determine which operations can be executed concurrently, thus reducing the overall amount of time, required for an execution run to complete.

In this post we will see how both systems compare to each other in terms of speed and concurrency by looking into some examples.

The system that was used for the tests below has 2 CPUs, 4GB of memory and is running CentOS Linux release 7.2.1511 (Core).

This is the version of Puppet that was used.

$ puppet --version 4.6.1

And this is the version of Gru.

$ gructl --version gructl version 0.4.0

Let’s start off with a simple resource for managing a single file.

This is the Puppet code that we use for this test. Note that we don’t use any classes or modules here in order to keep things simple.

file { '/tmp/foo' : ensure => 'present' , owner => 'root' , group => 'root' , }

The same configuration written in the Lua-based DSL of Gru looks like this.

-- Create a new file resource foo = resource . file . new ( "/tmp/foo" ) foo . state = "present" foo . owner = "root" foo . group = "root" -- Add the resource to the catalog catalog : add ( foo )

Measuring the Puppet run gives us the following result.

$ time puppet apply --verbose init.pp Notice: Compiled catalog for <fqdn> in environment production in 0.12 seconds Info: Applying configuration version '1472481236' Notice: /Stage[main]/Main/File[/tmp/foo]/ensure: created Notice: Applied catalog in 0.02 seconds real 0m2.403s user 0m2.171s sys 0m0.166s

Running the Gru code gives us the following result.

$ time gructl apply site.lua 2016/08/29 17:34:39 Loaded 1 resources 2016/08/29 17:34:39 Starting 2 goroutines for concurrent processing 2016/08/29 17:34:39 file[/tmp/foo] is concurrent 2016/08/29 17:34:39 file[/tmp/foo] is absent, should be present 2016/08/29 17:34:39 file[/tmp/foo] creating resource 2016/08/29 17:34:39 Applied 1 resources, 0 of which have failed and 1 have succeeded real 0m0.009s user 0m0.005s sys 0m0.006s

This was a simple test, but it does show one of the key features of Gru - it is fast, and it is concurrent.

The next test extends upon the previous example by adding a few more resources.

The Puppet code that we use for the next test relies on the puppetlabs/stdlib module, from which we use the range function.

$ puppet module install puppetlabs/stdlib Notice: Preparing to install into /etc/puppetlabs/code/environments/production/modules ... Notice: Downloading from https://forgeapi.puppetlabs.com ... Notice: Installing -- do not interrupt ... /etc/puppetlabs/code/environments/production/modules └── puppetlabs-stdlib ( v4.12.0 )

The Puppet code below creates resources for managing five files.

range ( '1' , '5' ) . each | $i | { file { "/tmp/foo ${i} " : ensure => 'present' , owner => 'root' , group => 'root' , } }

And the Lua code that we use for the Gru module looks like this.

for i = 1 , 5 do f = resource . file . new ( "/tmp/foo" .. i ) f . state = "present" f . owner = "root" f . group = "root" catalog : add ( f ) end

Running the Puppet code produces the following results.

$ time puppet apply --verbose init.pp Info: Loading facts Notice: Compiled catalog for <fqdn> in environment production in 0.13 seconds Info: Applying configuration version '1472541787' Notice: /Stage[main]/Main/File[/tmp/foo1]/ensure: created Notice: /Stage[main]/Main/File[/tmp/foo2]/ensure: created Notice: /Stage[main]/Main/File[/tmp/foo3]/ensure: created Notice: /Stage[main]/Main/File[/tmp/foo4]/ensure: created Notice: /Stage[main]/Main/File[/tmp/foo5]/ensure: created Notice: Applied catalog in 0.05 seconds real 0m4.017s user 0m3.085s sys 0m0.266s

And this is the result of running the Lua code from Gru.

$ time gructl apply site.lua 2016/08/30 10:24:52 Loaded 5 resources 2016/08/30 10:24:52 Starting 2 goroutines for concurrent processing 2016/08/30 10:24:52 file[/tmp/foo2] is concurrent 2016/08/30 10:24:52 file[/tmp/foo1] is concurrent 2016/08/30 10:24:52 file[/tmp/foo2] is absent, should be present 2016/08/30 10:24:52 file[/tmp/foo2] creating resource 2016/08/30 10:24:52 file[/tmp/foo1] is absent, should be present 2016/08/30 10:24:52 file[/tmp/foo1] creating resource 2016/08/30 10:24:52 file[/tmp/foo3] is concurrent 2016/08/30 10:24:52 file[/tmp/foo3] is absent, should be present 2016/08/30 10:24:52 file[/tmp/foo3] creating resource 2016/08/30 10:24:52 file[/tmp/foo4] is concurrent 2016/08/30 10:24:52 file[/tmp/foo4] is absent, should be present 2016/08/30 10:24:52 file[/tmp/foo4] creating resource 2016/08/30 10:24:52 file[/tmp/foo5] is concurrent 2016/08/30 10:24:52 file[/tmp/foo5] is absent, should be present 2016/08/30 10:24:52 file[/tmp/foo5] creating resource 2016/08/30 10:24:52 Applied 5 resources, 0 of which have failed and 5 have succeeded real 0m0.010s user 0m0.009s sys 0m0.005s

One thing to note here, is that the file resources in this Lua code are concurrent. That is because the file resource has support for concurrency of multiple instances of the same type and since these resources have no forward or reverse dependencies in the dependency graph, they are scheduled for concurrent execution by Gru.

In this particular example it wouldn’t matter much if the resources were concurrent or not, since the time required to execute the same operation in a serialized way would result in the same amount of time, but it does show one of the key strengths of Gru - its support for concurrent execution of operations.

You can read more about how Gru determines whether a resource is a good candidate for concurrent execution in the catalog package.

Another resource which supports concurrent execution of multiple instances from the same type is the shell resource.

In order to illustrate better the concurrency features of Gru, let’s see another example, which will create five resources, each sleeping for five seconds. We will use the sleep command in order to simulate some work being done by our resources.

range ( '1' , '5' ) . each | $i | { $cmd = "command- ${i} " notify { "running ${cmd} " : } exec { $cmd : command => '/usr/bin/sleep 5' , } }

The above Puppet code creates five exec resources, each sleeping for five seconds.

And this is the Lua code that we use for the Gru module.

for i = 1 , 5 do s = resource . shell . new ( "sleep-command-" .. i ) s . command = "/usr/bin/sleep 5" catalog : add ( s ) end

Running the Puppet code produces the following result.

$ time puppet apply --verbose init.pp Info: Loading facts Notice: Compiled catalog for <fqdn> in environment production in 0.20 seconds Info: Applying configuration version '1472544399' Notice: running command-1 Notice: /Stage[main]/Main/Notify[running command-1]/message: defined 'message' as 'running command-1' Notice: /Stage[main]/Main/Exec[command-1]/returns: executed successfully Notice: running command-2 Notice: /Stage[main]/Main/Notify[running command-2]/message: defined 'message' as 'running command-2' Notice: /Stage[main]/Main/Exec[command-2]/returns: executed successfully Notice: running command-3 Notice: /Stage[main]/Main/Notify[running command-3]/message: defined 'message' as 'running command-3' Notice: /Stage[main]/Main/Exec[command-3]/returns: executed successfully Notice: running command-4 Notice: /Stage[main]/Main/Notify[running command-4]/message: defined 'message' as 'running command-4' Notice: /Stage[main]/Main/Exec[command-4]/returns: executed successfully Notice: running command-5 Notice: /Stage[main]/Main/Notify[running command-5]/message: defined 'message' as 'running command-5' Notice: /Stage[main]/Main/Exec[command-5]/returns: executed successfully Notice: Applied catalog in 25.09 seconds real 0m28.943s user 0m3.317s sys 0m0.275s

Due to the way that Puppet executes resources in a serialized way, this results in at least a 25 seconds execution run as we can see from the output above.

And this is the result of running the Lua module using Gru.

$ time gructl apply site.lua 2016/08/30 11:08:49 Loaded 5 resources 2016/08/30 11:08:49 Starting 2 goroutines for concurrent processing 2016/08/30 11:08:49 shell[sleep-command-2] is concurrent 2016/08/30 11:08:49 shell[sleep-command-2] is absent, should be present 2016/08/30 11:08:49 shell[sleep-command-2] executing command 2016/08/30 11:08:49 shell[sleep-command-3] is concurrent 2016/08/30 11:08:49 shell[sleep-command-3] is absent, should be present 2016/08/30 11:08:49 shell[sleep-command-3] executing command 2016/08/30 11:08:54 shell[sleep-command-2] 2016/08/30 11:08:54 shell[sleep-command-4] is concurrent 2016/08/30 11:08:54 shell[sleep-command-4] is absent, should be present 2016/08/30 11:08:54 shell[sleep-command-4] executing command 2016/08/30 11:08:54 shell[sleep-command-3] 2016/08/30 11:08:54 shell[sleep-command-5] is concurrent 2016/08/30 11:08:54 shell[sleep-command-5] is absent, should be present 2016/08/30 11:08:54 shell[sleep-command-5] executing command 2016/08/30 11:08:59 shell[sleep-command-4] 2016/08/30 11:08:59 shell[sleep-command-1] is concurrent 2016/08/30 11:08:59 shell[sleep-command-1] is absent, should be present 2016/08/30 11:08:59 shell[sleep-command-1] executing command 2016/08/30 11:08:59 shell[sleep-command-5] 2016/08/30 11:09:04 shell[sleep-command-1] 2016/08/30 11:09:04 Applied 5 resources, 0 of which have failed and 5 have succeeded real 0m15.014s user 0m0.007s sys 0m0.015s

The output above shows that Gru has used only two goroutines for executing concurrent resources. This results in a reduced overall time for the whole execution run compared to the Puppet run, but still this is a lot of time and we can do much better than that.

Raising the concurrency level means we will have more goroutines processing resources concurrently. Let’s do that now and run our Lua code again.

In order to set the concurrency level we use the --concurrency flag of the gructl apply command.

$ time gructl apply --concurrency = 10 site.lua 2016/08/30 11:15:39 Loaded 5 resources 2016/08/30 11:15:39 Starting 10 goroutines for concurrent processing 2016/08/30 11:15:39 shell[sleep-command-2] is concurrent 2016/08/30 11:15:39 shell[sleep-command-5] is concurrent 2016/08/30 11:15:39 shell[sleep-command-2] is absent, should be present 2016/08/30 11:15:39 shell[sleep-command-2] executing command 2016/08/30 11:15:39 shell[sleep-command-5] is absent, should be present 2016/08/30 11:15:39 shell[sleep-command-5] executing command 2016/08/30 11:15:39 shell[sleep-command-3] is concurrent 2016/08/30 11:15:39 shell[sleep-command-3] is absent, should be present 2016/08/30 11:15:39 shell[sleep-command-3] executing command 2016/08/30 11:15:39 shell[sleep-command-4] is concurrent 2016/08/30 11:15:39 shell[sleep-command-1] is concurrent 2016/08/30 11:15:39 shell[sleep-command-4] is absent, should be present 2016/08/30 11:15:39 shell[sleep-command-4] executing command 2016/08/30 11:15:39 shell[sleep-command-1] is absent, should be present 2016/08/30 11:15:39 shell[sleep-command-1] executing command 2016/08/30 11:15:44 shell[sleep-command-3] 2016/08/30 11:15:44 shell[sleep-command-2] 2016/08/30 11:15:44 shell[sleep-command-4] 2016/08/30 11:15:44 shell[sleep-command-1] 2016/08/30 11:15:44 shell[sleep-command-5] 2016/08/30 11:15:44 Applied 5 resources, 0 of which have failed and 5 have succeeded real 0m5.022s user 0m0.006s sys 0m0.012s

As you can see from the output above now we have enough goroutines to handle all of the resources at the same time, which results in much less time required to complete the whole execution run.

Hopefully these short examples gave you an idea of how Gru can help you on the configuration management side of things by providing you a fast and concurrent orchestration and configuration management framework.

Of course configuration management is not just about speed and concurrency. While Gru clearly outperforms Puppet in terms of speed and concurrency support, in other areas Puppet stands much better - and that is the number of features and third party modules.

If you like what you’ve seen about Gru so far and want to see it evolve further, please consider contributing to the project at Github by suggesting new features, sending patches or reporting bugs.