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Exclusive Join not working when embedded in Fork/Join

See original GitHub issue

Exclusive Join not working when embedded in Fork/Join

Problem

Hello,

In one of our workflows we have a very specific with the following (generic) flow: Note: the task types assigned to any TASK step(s) are not bound to any specific task type, this can be either a JOIN/FORK, LAMBDA, SIMPLE, etc… task type.

FORK(T1) -> |
             TASK*(T2)                                          -> |
             DECISION(T2) -> TASK*(T3|T4) -> EXCLUSIVE JOIN(T5) -> |
                                                                    JOIN(T6)

When we embed a decision with an exclusive join inside another fork/join, the workflow will not continue processing after the exclusive join and with that never completing the parent join. This only happens when we have the parent join (T6), join on the exclusive join (T5) (which is valid, see “Working alternative”).

Failing decision metadata representation:

{
  "name" : "exclusive_join_test",
  "description" : "Exclusive Join Test",
  "version" : 1,
  "tasks" : [
    {
      "taskReferenceName" : "fork",
      "name" : "fork",
      "forkTasks" : [
        [
          {
            "name" : "lambda_nothing",
            "taskReferenceName" : "lambda_nothing",
            "inputParameters" : {
              "scriptExpression" : "return {value: \"nothing\"}"
            },
            "type" : "LAMBDA",
            "optional" : false,
            "asyncComplete" : false
          }
        ],
        [
          {
            "name" : "decision_test",
            "taskReferenceName" : "decision_test",
            "inputParameters" : {
              "case_value_param" : "${workflow.input.decision}"
            },
            "type" : "DECISION",
            "caseValueParam" : "case_value_param",
            "decisionCases" : {
              "true" : [
                {
                  "taskReferenceName" : "lambda_true",
                  "name" : "lambda_true",
                  "inputParameters" : {
                    "value" : "${workflow.input.decision}",
                    "scriptExpression" : "return {value: $.value}"
                  },
                  "optional" : false,
                  "type" : "LAMBDA",
                  "asyncComplete" : false
                }
              ]
            },
            "defaultCase" : [
              {
                "name" : "lambda_false",
                "taskReferenceName" : "lambda_false",
                "inputParameters" : {
                  "value" : "${workflow.input.decision}",
                  "scriptExpression" : "return {value: $.value}"
                },
                "type" : "LAMBDA",
                "optional" : false,
                "asyncComplete" : false
              }
            ],
            "optional" : false,
            "asyncComplete" : false
          },
          {
            "name" : "exclusive_join",
            "taskReferenceName" : "exclusive_join",
            "type" : "EXCLUSIVE_JOIN",
            "joinOn" : [
              "lambda_true",
              "lambda_false"
            ],
            "optional" : false,
            "defaultExclusiveJoinTask" : [
              "decision_test"
            ],
            "asyncComplete" : false
          }
        ]
      ],
      "type" : "FORK_JOIN"
    },
    {
      "name" : "join",
      "taskReferenceName" : "join",
      "joinOn" : [
        "lambda_nothing",
        "exclusive_join"
      ],
      "type" : "JOIN"
    }
  ],
  "inputParameters" : [
    "decision"
  ],
  "schemaVersion" : 2,
  "restartable" : true,
  "workflowStatusListenerEnabled" : false
}

Working alternative

However, when we isolate the same exclusive join outside of the fork/join, the exclusive join completes and the workflow continues as expected:

Working decision metadata representation:

{
  "name" : "exclusive_join_test",
  "description" : "Exclusive Join Test",
  "version" : 1,
  "tasks" : [
    {
      "name" : "decision_test",
      "taskReferenceName" : "decision_test",
      "inputParameters" : {
        "case_value_param" : "${workflow.input.decision}"
      },
      "type" : "DECISION",
      "caseValueParam" : "case_value_param",
      "decisionCases" : {
        "true" : [
          {
            "taskReferenceName" : "lambda_true",
            "name" : "lambda_true",
            "inputParameters" : {
              "value" : "${workflow.input.decision}",
              "scriptExpression" : "return {value: $.value}"
            },
            "optional" : false,
            "type" : "LAMBDA",
            "asyncComplete" : false
          }
        ]
      },
      "defaultCase" : [
        {
          "name" : "lambda_false",
          "taskReferenceName" : "lambda_false",
          "inputParameters" : {
            "value" : "${workflow.input.decision}",
            "scriptExpression" : "return {value: $.value}"
          },
          "type" : "LAMBDA",
          "optional" : false,
          "asyncComplete" : false
        }
      ],
      "optional" : false,
      "asyncComplete" : false
    },
    {
      "name" : "exclusive_join",
      "taskReferenceName" : "exclusive_join",
      "type" : "EXCLUSIVE_JOIN",
      "joinOn" : [
        "lambda_true",
        "lambda_false"
      ],
      "optional" : false,
      "defaultExclusiveJoinTask" : [
        "decision_test"
      ],
      "asyncComplete" : false
    }
  ],
  "inputParameters" : [
    "decision"
  ],
  "schemaVersion" : 2,
  "restartable" : true,
  "workflowStatusListenerEnabled" : false
}