workflow-plugin Serialisation issues when iterating over a list of strings

[Robin Tegg]

Hi all,

I've been trying out the workflow plugin after watching the pimp-your-continuous-delivery-pipeline-with-jenkins-workflow-wjax-14 demo. And in one of the slides (24), there is an example of a for loop that looks to iterate over a list of hostnames. I've assumed that hostnames is a list

def hostnames = ["192.168.0.1", "192.168.0.2"]

for( def hostname: hostnames ) {

    sh "ssh ${hostname} ..."

  }

I'm wondering if anyone can help with my usage of arrays/lists. I'm getting the following errors when I try the above:

java.io.NotSerializableException: java.util.AbstractList$Itr

Now I understand from the docs (https://github.com/jenkinsci/workflow-plugin/blob/master/TUTORIAL.md#serialization-of-local-variables) that some variables can't be serialized before a "sh" step might happen, but as I'm new to groovy I'm struggling to understand how the above might be achieved. I've tried in a method and inline as suggested.

The workaround I have at the moment is

def hostnames = ["192.168.0.1", "192.168.0.2"]

for( int i = 0; i < hostnames.size(); i++) {

  sh "ssh ${hostnames.get(i)} ..."

}

Any pointers would be much appreciated

Thanks

Robin

[Brian Ray]

Hi Robin,

The simplest Groovy idiom for iterating over a collection is

hostnames.each { host ->
  do something interesting with host ...
}

Does this work?

Brian

[Brian Ray]

Another stab in the dark. The double quotes mean the individual hostnames are GStrings instead of Strings. Maybe starting this way:

def hostnames = ['192.168.0.1', '192.168.0.2']

[Daniel Beck]

'each' is currently broken in Workflow CPS scripts.

https://issues.jenkins-ci.org/browse/JENKINS-26481

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[Robin Tegg]

Brian,

Thanks for you help.

Not sure why this wasn't working for me yesterday, it might have been a scoping issue??

I can confirm that if I use the following inside a node{} block:

def bees = ["192.168.0.1", "192.168.0.2"]
  for( def b: bees ) {
    echo "${b}"
  }

then I get the expected output

[Robin Tegg]

Daniel,

Thanks for the .each pointer, that's saved me some head scratching

Robin

[Jesse Glick]

On Monday, February 9, 2015 at 8:48:11 AM UTC-5, Robin Tegg wrote:

java.io.NotSerializableException: java.util.AbstractList$Itr

Indeed this class in the JRE, which is used for JDK 5-style for-loops, is not serializable and so this idiom cannot be used from a flow build (which must survive Jenkins restarts). Whether we can hack around that or not, I am not sure. In the meantime, use C-style loops with an index.