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Home > docs > plugins v2 > Concord Task

Concord Task

The concord task allows users to start and manage new processes from within running processes.

The task is provided automatically for all flows, no external dependencies necessary.

Parameters

All parameter sorted alphabetically. Usage documentation can be found in the following sections:

  • action - string, name of the action (start, startExternal, fork, kill);
  • activeProfiles - list of string values, profiles to activate;
  • apiKey - string, Concord API key to use. If not specified the task uses the current process’ session key;
  • arguments - input arguments of the starting processes;
  • disableOnCancel - boolean, disable onCancel flow in forked processes;
  • disableOnFailure - boolean, disable onFailure flow in forked processes;
  • entryPoint - string, name of the starting process’ flow;
  • ignoreFailures - boolean, ignore failed processes;
  • instanceId - UUID, ID of the process to kill;
  • org - string, name of the process’ organization, optional, defaults to the organization of the calling process;
  • outVars - list of string values, out variables to capture;
  • payload - path to a ZIP archive or a directory, the process’ payload;
  • requirements - object, allows specifying the process’ requirements;
  • project - string, name of the process’ project;
  • repo - string, name of the project’s repository to use;
  • repoBranchOrTag - string, overrides the configured branch or tag name of the project’s repository;
  • repoCommitId - string, overrides the configured GIT commit ID of the project’s repository;
  • startAt - ISO 8601 date/time value, the process’ start time;
  • suspend - boolean, if true and sync is enabled the process suspends waiting for the child process to complete (only for actions start and fork);
  • sync - boolean, wait for completion if true, defaults to false;
  • debug - boolean, if true the plugin logs additional debug information, defaults to false;
  • tags - list of string values, the process’ tags;
  • attachments - list of file attachments;

Starting a Process using a Payload Archive

flows:
  default:
  - task: concord
    in:
      action: start
      payload: payload.zip
    out: jobOut

The start action starts a new subprocess using the specified payload archive. The ID of the started process is stored in the id attribute:

- if: ${jobOut.ok}
  then:
    - log: "I've started a new process: ${jobOut.id}"
  else:
    - log: "Error with child process: ${jobOut.error}"

Starting a Process using an Existing Project

flows:
  default:
  - task: concord
    in:
      action: start
      org: myOrg
      project: myProject
      payload: payload.zip
    out: jobOut

The start expression with a project parameter and a payload in the form of a zip archive or the name of a folder in your project repository, starts a new subprocess in the context of the specified project.

Alternatively, if the project has a repository configured, the process can be started by configuring the repository:

flows:
  default:
  - task: concord
    in:
      action: start
      project: myProject
      repo: myRepo
    out: jobOut

The process is started using the resources provided by the specified archive, project and repository.

Starting an External Process

To start a process on an external Concord instance use the startExternal action:

flows:
  default:
  - task: concord
    in:
      baseUrl: "http://another.concord.example.com:8001"
      apiKey: "myApiKey"
      action: startExternal
      project: myProject
      repo: myRepo
    out: jobOut

Connection parameters can be overridden using the following keys:

  • baseUrl - Concord REST API endpoint. Defaults to the current server’s API endpoint address;
  • apiKey - user’s REST API key.

Note: The suspend: true option is not supported with the startExternal action.

Scheduling a Process

To schedule a process to a specific date and time, use the startAt parameter:

flows:
  default:
  - task: concord
    in:
      action: start
      ...
      startAt: "2018-03-16T23:59:59-05:00"
    out: jobOut

The startAt parameter accepts an ISO-8601 string, java.util.Date or java.util.Calendar values. It is important to include a timezone as the server may use a different default timezone value.

Specifying Profiles

To specify which profiles are used to start the process, use the activeProfiles parameter:

flows:
  default:
  - task: concord
    in:
      action: start
      ...
      activeProfiles:
      - firstProfile
      - secondProfile
    out: jobOut

The parameter accepts either a YAML array or a comma-separated string value.

File Attachments

To start a process with file attachments, use the attachments parameter. An attachment can be a single path to a file, or a map which specifies a source and destination filename for the file. If the attachment is a single path, the file is placed in the root directory of the new process with the same name.

flows:
  default:
  - task: concord
    in:
      ...
      attachments:
      - ${workDir}/someDir/myFile.txt
      - src: anotherFile.json
        dest: someFile.json
    out: jobOut

This is equivalent to the curl command:

curl ... -F myFile.txt=@${workDir}/someDir/myFile.txt -F someFile.json=@anotherFile.json ...

Forking a Process

Forking a process creates a copy of the current process. All variables and files defined at the start of the parent process are copied to the child process as well:

flows:
  default:
  - task: concord
    in:
      action: fork
      entryPoint: sayHello
    out: jobOut

  - log: "Forked child process: ${jobOut.ids[0]}"

  sayHello:
  - log: "Hello from a subprocess!"

The ID of the started process is stored in the ids array attribute of the returned result.

Note: Due to the current limitations, files created after the start of a process cannot be copied to child processes.

Forking Multiple Instances

It is possible to create multiple forks of a process with a different sets of parameters:

flows:
  default:
  - task: concord
    in:
      action: fork
      forks:
      - entryPoint: pickAColor
        arguments:
          color: "red"
      - entryPoint: pickAColor
        arguments:
          color: "green"
      - entryPoint: pickAColor
        instances: 2
        arguments:
          color: "blue"
    out: jobOut

The instances parameter allows spawning of more than one copy of a process.

The IDs of the started processes are stored in the ids array in the result.

- log: "Forked child processes: ${jobOut.ids}"

Synchronous Execution

By default, all subprocesses are started asynchronously. To start a process and wait for it to complete, use sync parameter:

flows:
  default:
  - tasks: concord
    in:
      action: start
      payload: payload.zip
      sync: true
    out: jobOut

If a subprocess fails, the task throws an exception. To ignore failed processes use ignoreFailures: true parameter:

flows:
  default:
  - tasks: concord
    in:
      action: start
      payload: payload.zip
      sync: true
      ignoreFailures: true
    out: jobOut

Suspending Parent Process

There’s an option to suspend the parent process while it waits for the child process completion:

flows:
  default:
  - task: concord
    in:
      action: start
      org: myOrg
      project: myProject
      repo: myRepo
      sync: true
      suspend: true
    out: jobOut

  - log: "Done: ${jobOut.id}"

This can be very useful to reduce the amount of Concord agents needed. With suspend: true, the parent process does not consume any resources including agent workers, while waiting for the child process.

suspend can be used with the fork action as well:

flows:
  default:
  - task: concord
    in:
      action: fork
      forks:
        - entryPoint: sayHello
        - entryPoint: sayHello
        - entryPoint: sayHello
      sync: true
      suspend: true
    out: jobOut

  sayHello:
    - log: "Hello from a subprocess!"

Currently, suspend can only be used with the start and fork actions.

Note: Due to the current limitations, files created after the start of the parent process are not preserved. Effectively, the suspend works in the same way as the forms.

Suspending for Completion

You can use the follow approach to suspend a process until the completion of the other process:

flows:
  default:
  - set:
      children: []

  - task: concord
    in:
      action: start
      payload: payload
    out: jobOut

  - ${children.add(jobOut.id)}

  - task: concord
    in:
      action: start
      payload: payload
    out: jobOut

  - ${children.add(jobOut.id)}

  - ${concord.suspendForCompletion(children)}

  - log: "process is resumed."

Waiting for Completion

To wait for a completion of a process:

flows:
  default:
  # wait for one id
  - ${concord.waitForCompletion(id)}

  # or multiple
  - ${concord.waitForCompletion(ids)}

The ids value is a list (as in java.util.List) of process IDs.

The expression returns a map of process entries. To see all returned fields, check with the Process API:

{
  "56e3dcd8-a775-11e7-b5d6-c7787447ca6d": {
    "status": "FINISHED"
  },
  "5cd83364-a775-11e7-aadd-53da44242629": {
    "status": "FAILED",
    "meta": {
      "out": {
        "lastError": {
          "message": "Something went wrong."
        }
      }
    }
  }
}

Handling Cancellation and Failures

Just like regular processes, subprocesses can have onCancel and onFailure flows.

However, as process forks share their flows, it may be useful to disable onCancel or onFailure flows in subprocesses:

flows:
  default:
  - task: concord
    in:
      action: fork
      disableOnCancel: true
      disableOnFailure: true
      entryPoint: sayHello

  sayHello:
  - log: "Hello!"
  - throw: "Simulating a failure..."
  
  # invoked only for the parent process
  onCancel:
  - log: "Handling a cancellation..."
  
  # invoked only for the parent process
  onFailure:
  - log: "Handling a failure..."

Cancelling Processes

The kill action can be used to terminate the execution of a process.

flows:
  default:
  - task: concord
    in:
      action: kill
      instanceId: ${someId}
      sync: true

The instanceId parameter can be a single value or a list of process IDs.

Setting sync to true forces the task to wait until the specified processes are stopped.

Tagging Subprocesses

The tags parameters can be used to tag new subprocess with one or multiple labels.

flows:
  default:
  - task: concord
    in:
      action: start
      payload: payload.zip
      tags: ["someTag", "anotherOne"]

The parameter accepts either a YAML array or a comma-separated string value.

Tags are useful for filtering (sub)processes:

flows:
  default:
  # spawn multiple tagged processes
  
  onCancel:
  - task: concord
    in:
      action: kill
      instanceId: "${concord.listSubprocesses(parentInstanceId, 'someTag')}"

Output Variables

Variables of a child process can be accessed via the outVars configuration. The functionality requires the sync parameter to be set to true.

flows:
  default:
    - task: concord
      in:
        action: start
        project: myProject
        repo: myRepo
        sync: true
        # list of variable names
        outVars:
        - someVar1
        - someVar2
      out: jobOut

    - log: "We got ${jobOut.someVar1} and ${jobOut.someVar2}"

When starting multiple forks their output variables are collected into a nested object with fork IDs as keys:

flows:
  default:
    # empty list to store fork IDs
    - set:
        children: []

    # start the first fork and save the result as "firstResult"
    - task: concord
      in:
        action: fork
        entryPoint: forkA
        sync: false
        outVars:
          - x
      out: firstResult

    # save the first fork's ID
    - ${children.add(firstResult.id)}

    # start the second fork and save the result as "secondResult"
    - task: concord
      in:
        action: fork
        entryPoint: forkB
        sync: false
        outVars:
          - y
      out: secondResult

    # save the second fork's ID
    - ${children.add(secondResult.id)}

    # grab out vars of the forks
    - expr: ${concord.getOutVars(children)} # accepts a list of process IDs
      out: forkOutVars

    # print the out-vars grouped by fork
    - log: "${forkOutVars}"

  forkA:
    - set:
        x: 1

  forkB:
    - set:
        y: 2

Note: the getOutVars method waits for the specified processes to finish. If one of the specified processes fails, its output is going to be empty.

In runtime v2 all variables are “local” – limited to the scope they were defined in. The outVars mechanism grabs only the top-level variables, i.e. variables available in the entryPoint scope:

flows:
  # caller
  default:
    - task: concord
      in:
        action: fork
        sync: true
        entryPoint: onFork
        outVars:
          - foo
          - bar
      out: forkResult

    - log: "${concord.getOutVars(forkResult.id)}"

  # callee
  onFork:
    - set:
        foo: "abc" # ok, top-level variable

    - call: anotherFlow # not ok, "bar" stays local to "anotherFlow"

    - call: anotherFlow # ok, "bar" pushed into the current scope, becomes a top-level variable
      out:
        - bar

  anotherFlow:
    - set:
        bar: "xyz"

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