Friday, September 21, 2012

Groovy Dependencies, Grape, and Firewalls

Groovy is a powerful and fun language. One of the nice features, particularly useful for internal tools,  is the ability to deliver scripts that are self contained with the only pre-requisite being that you have groovy installed. One of the tools that enables this is the Grape dependency management mechanism. Using Grape, rather than delivering a zip file with all dependencies, or requiring that modules be installed as part of the global system installation, you can add a line like this to your script:

@Grab(group='org.springframework', module='spring', version='2.5.6')

This will grap the dependency into a local repository if it is not present already. It makes the startup time for the first run of a script a bit slower, but it also greatly simplifies the delivery of short, script-based tools.

If you are in production environment behind a firewall, you might find that that this mechanism doesn't work because you can't access the public repositories. You can address this by adding an annotation to the file to add your repository to the list

@GrabResolver(name='restlet', root='http://maven.mycompany.com/proxy')

When I first tried this, it seemed to take a very long time for the script to run, with no output.

To diagnose the problem, I needed to have the GrabResolver tell me what it was doing. Looking at the code the way to do this was to set the ivy.message.logger.level system property.

My command line to get detailed output was:

groovy -Divy.message.logger.level=4 Script.groovy

This gave me enough output to see that Grape was looking in the local repository last after timing out when trying the standard repositories. The easiest fix I found for this was create a $HOME/.groovy/GrapeConfig.xml file as described in the Grape documentation. The new local config only has one ibiblio repository element, which is the company repository manager.

<ivysettings>
  <settings defaultresolver="downloadGrapes">
  <resolvers>
    <chain name="downloadGrapes">
      <filesystem name="cachedGrapes">
        <ivy pattern="${user.home}/.groovy/grapes/[organisation]/[module]/ivy-[revision].xml">
        <artifact pattern="${user.home}/.groovy/grapes/[organisation]/[module]/[type]s/[artifact]-[revision].[ext]">
      </artifact></ivy></filesystem>
      &lt;ibiblio m2compatible="true" name="proxy-repository" root="http://maven.mycompany.com/proxy/">
    </ibiblio></chain>
  </resolvers>
</settings>
</ivysettings>


This sped things up significantly.

There may be another way to address the problem, and I welcome feedback. But since this wasn't obvious from the documentation, I thought it might be worth sharing.

Note, this is based on Groovy 2.0.2.

Saturday, September 8, 2012

Automation

I recently wrote a short article on on StickyMinds.com about automation. After it was published I came across another related post by Jim Coplien which makes the point that automation should come after you have figured out your process.

I'm not sure that Jim and I disagree in principle on anything related to when to automate, but I wanted to make one point. I think it's important to start out an process that is likely to be automated with the idea of automation in mind. If you don't, you are likely to make decisions that are both not important to getting your work done and which would make automation harder to implement.  As I've said before in the context of deployment, the sooner you consider your constraints the easier it will be to build a system that addresses your real problems.

The hard thing is identifying which "requirements" are there out of expediency (or perhaps laziness) and which are there out of need. Having an iterative approach to any kind of automation can help you with this.  Do a process, write a script to do it, then once the script works well, figure out how to get the script to work more "automatically."

Your process model should come first, before you consider tools, or even automation.  But you can benefit by building automation into the process early, and iteratively improving it.