CODEWITHSUNDEEP
jenkinsjenkins-pipelinejenkins-plugins
Samuel GIFFARD
Samuel GIFFARD

Reputation: 842

Jenkins lock by label

What I'm trying to achieve

How I'm tackling the problem

What I've done

I changed the number of executors on my machines from 1 to 2.

Solution 1: Locking the resource

In jobA's pipeline, I have:

node('windows-agent-label') {
    lock("${env.NODE_NAME}-exclusive") {
        //...
    }
}

Running the job (1st time) gives me:

[Pipeline] Start of Pipeline
[Pipeline] node
Running on build1 in J:\jenkins\workspace\jobA
[Pipeline] {
[Pipeline] lock
Trying to acquire lock on [build1-exclusive]
Resource [build1-exclusive] did not exist. Created.
Lock acquired on [build1-exclusive]

And the 2nd time (while the first one is still building):

[Pipeline] Start of Pipeline
[Pipeline] node
Running on build1 in J:\jenkins\workspace\jobA@2
[Pipeline] {
[Pipeline] lock
Trying to acquire lock on [build1-exclusive]
Found 0 available resource(s). Waiting for correct amount: 1.
[build1-exclusive] is locked, waiting...

It works! The second build is blocked until the first one releases the lock. However, the second one is already dispatched to the node and uses an executor slot. Really not nice! If I move the lock() directive outside of the node() one, I don't have the env.NODE_NAME yet, so the lock cannot work.

Apparently, there's another way...

Solution 2: Locking by requesting a label

I have a label named windows-agent-label which contains 2 nodes: build1 and build2.

In jobA's pipeline, I have:

lock(label: 'windows-agent-label', quantity: 1) {
    node('windows-agent-label') {
        //...
    }
}

Running the job gives me:

[Pipeline] Start of Pipeline
[Pipeline] lock
Trying to acquire lock on [Label: windows-agent-label, Quantity: 1]
Found 0 available resource(s). Waiting for correct amount: 1.
[Label: windows-agent-label, Quantity: 1] is locked, waiting...

Absolutely nothing is running on build1.

All of my /lockable-resources/ are FREE.

Questions

Upvotes: 5

Views: 10623

Answers (1)

Samuel GIFFARD
Samuel GIFFARD

Reputation: 842

The solution

In the lock documentation, there's a missing (undocumented) parameter: variable. When used with label, it stores into an env variable the name of the acquired lock.

Missing here: https://plugins.jenkins.io/lockable-resources

Visible there: https://issues.jenkins-ci.org/browse/JENKINS-40997

lock(label: 'windows-agent-label', quantity: 1, variable: 'LOCK_NAME') {
    node(env.LOCK_NAME - '-exclusive') {
        //...
    }
}

So, this requests a lock from all the ones that are under a certain label. They are always formed (by choice) as ${NODE_NAME}-exclusive. If I can't get a lock on resource, that means they're all used up. If I get one, that means NODE_NAME (could be build1, build2, ...) is available. So, I go to the given node.

Upvotes: 7

Related Questions