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.

• Examples
• Parameters
• Starting a Process using a Payload Archive
• Starting a Process using an Existing Project
• Starting an External Process
• Scheduling a Process
• Specifying Profiles
• File Attachments
• Forking a Process
• Forking Multiple Instances
• Synchronous Execution
• Suspending Parent Process
• Suspending for Completion
• Waiting for Completion
• Handling Cancellation and Failures
• Cancelling Processes
• Tagging Subprocesses
• Output Variables

Examples

• process_from_a_process
• starting a new subprocess from a flow using a payload archive;
• fork - starting a subprocess;
• fork_join
• starting multiple subprocesses and waiting for completion.

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

The start action starts a new subprocess using the specified payload archive. The ID of the started process is stored as the first element of ${jobs} array:

- log: "I've started a new process: ${jobs[0]}"

Starting a Process using an Existing Project

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

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

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

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.

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"

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

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

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

The IDs of the started processes are stored as ${jobs} array.

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"

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

The IDs of the started processes arestored as ${jobs} array.

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

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

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
      
  - log: "Done: ${jobs}"

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

  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 the completion of other process:

flows:
  default:
  - set:
      children: []

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

  - ${children.addAll(jobs)}

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

  - ${children.addAll(jobs)}

  - ${concord.suspendForCompletion(children)}

  - log: "process is resumed."

Waiting for Completion

To wait for a completion of a process:

flows:
  default:
  - ${concord.waitForCompletion(jobIds)}

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

The expression returns a map of process statuses:

{
  "56e3dcd8-a775-11e7-b5d6-c7787447ca6d": "FINISHED",
  "5cd83364-a775-11e7-aadd-53da44242629": "FAILED"
}

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 cancel action can be used to cancel the execution of a subprocess.

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

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

Setting sync to true forces the 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

Output values are stored as a jobOut variable:

- 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:

configuration:
  arguments:
    name: "Concord"

flows:
  default:
    - task: concord
      in:
        action: fork
        forks:
          - entryPoint: onFork
            arguments:
              msg: "Hello"
          - entryPoint: onFork
            arguments:
              msg: "Bye"
        sync: true
        suspend: true
        outVars:
          - varFromFork

    - log: "${jobOut}"

  onFork:
    - log: "Running in a fork"
    - set:
        varFromFork: "${msg}, ${name}"

In the example above, the jobOut variable has the following structure:

{
    "54e21668-d011-11e9-8369-6b27f0faf40f": {
        "varFromFork": "Hello, Concord"
    },
    "6ac8b356-d011-11e9-81f6-73dd6c99b3b2": {
        "varFromFork": "Bye, Concord"
    }
}

Because each fork can produce a variable with the same name, the values are nested into objects with the fork ID as the key.

To get output variables for already running processes use getOutVars method:

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

    # start the first fork
    - task: concord
      in:
        action: fork
        entryPoint: forkA
        sync: false
        outVars:
          - x

    # save the first fork's ID
    - ${children.addAll(jobs)}

    # start the second fork
    - task: concord
      in:
        action: fork
        entryPoint: forkB
        sync: false
        outVars:
          - y

    # save the second fork's ID
    - ${children.addAll(jobs)}

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

    # print out 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 then its output variables are empty.