Ideas to implement dynamic parallel build using jenkins pipeline plugin - jenkins

Question

I have a requirement to run a set of tasks for a build in parallel, The tasks for the build are dynamic it may change. I need some help in the implementation of that below are the details of it.
I tasks details for a build will be generated dynamically in an xml which will have information of which tasks has to be executed in parallel/serial
example:
say there is a build A.
Which had below task and the order of execution , first task 1 has to be executed next task2 and task3 will be executed in parallel and next is task 4
task1
task2,task3
task4
These details will be in an xml dynamically generated , how can i parse that xml and schedule task accordingly using pipeline plugin. I need some idea to start of with.

Answer 1

You can use Groovy to read the file from the workspace (readFile) and then generate the map containing the different closures, similar to the following:
parallel(
task2: {
node {
unstash('my-workspace')
sh('...')
}
},
task3: {
node {
unstash('my-workspace')
sh('...')
}
}
}
In order to generate such data structure, you simply iterate over the task data read using XML parsing in Groovy over the file contents you read previously.
By occasion, I gave a talk about pipelines yesterday and included very similar example (presentation, slide 34ff.). In contrast, I read the list of "tasks" from another command output. The complete code can be found here (I avoid pasting all of this here and instead refer to this off-site resource).
The kind of magic bit is the following:
def parallelConverge(ArrayList<String> instanceNames) {
def parallelNodes = [:]
for (int i = 0; i < instanceNames.size(); i++) {
def instanceName = instanceNames.get(i)
parallelNodes[instanceName] = this.getNodeForInstance(instanceName)
}
parallel parallelNodes
}
def Closure getNodeForInstance(String instanceName) {
return {
// this node (one per instance) is later executed in parallel
node {
// restore workspace
unstash('my-workspace')
sh('kitchen test --destroy always ' + instanceName)
}
}
}