Worker nodes aren't started when pipeline requests to run parallel parts on same node

[tm-slavik57]

Version report

Jenkins and plugins versions report:

Jenkins: 2.319
OS: Linux - 4.14.198-152.320.amzn2.x86_64
---
ace-editor:1.1
active-directory:2.25
analysis-model-api:10.6.0
ansicolor:1.0.0
ant:1.12
antisamy-markup-formatter:2.4
apache-httpcomponents-client-4-api:4.5.13-1.0
artifact-manager-s3:1.16
artifactory:3.13.2
authentication-tokens:1.4
aws-credentials:1.32
aws-global-configuration:1.7
aws-java-sdk:1.12.101-300.vc09c7be9cb57
aws-java-sdk-cloudformation:1.12.101-300.vc09c7be9cb57
aws-java-sdk-codebuild:1.12.101-300.vc09c7be9cb57
aws-java-sdk-ec2:1.12.101-300.vc09c7be9cb57
aws-java-sdk-ecr:1.12.101-300.vc09c7be9cb57
aws-java-sdk-ecs:1.12.101-300.vc09c7be9cb57
aws-java-sdk-elasticbeanstalk:1.12.101-300.vc09c7be9cb57
aws-java-sdk-iam:1.12.101-300.vc09c7be9cb57
aws-java-sdk-logs:1.12.101-300.vc09c7be9cb57
aws-java-sdk-minimal:1.12.101-300.vc09c7be9cb57
aws-java-sdk-ssm:1.12.101-300.vc09c7be9cb57
blueocean:1.24.6
blueocean-autofavorite:1.2.4
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blueocean-github-pipeline:1.24.6
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blueocean-pipeline-editor:1.24.6
blueocean-pipeline-scm-api:1.25.1
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blueocean-rest-impl:1.25.1
blueocean-web:1.25.1
bootstrap4-api:4.6.0-3
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workflow-support:3.8
ws-cleanup:0.39
xunit:3.0.4

• What Operating System are you using (both controller, and any agents involved in the problem)?

Linux

Reproduction steps

We have 5 nodes with the id of some_node, each node has 3 slots.

We have the following Jenkins pipeline (simplified):

ansiColor('xterm') {
  def tests = getTestsToRun()

  parallel tests
}

def getTestsToRun() {
  node('some_node') { 
    def tests = [:]
    for (int i = 0; i < 50; i++) {
      tests["test${i}"] = createTest("test-${i}")
    }
    return tests
  }
}

def createTest(String testString) {
  return {
    node('some_node') {
      echo "Running test ${testString} - before sleep"
      sleep(60)
      echo "Running test ${testString}) - after sleep"
    }
  }
}

Results

When we run the pipeline, the Build Queue contains all the part of test-job

Expected result: All the some_node worker nodes will be started to handle the long queue of part jobs

Actual result: Only 1 worker node is brought up to handle the test-job while other workers continue to be offline