Parallel

Overview

The Parallel operation runs several branches at the same time and waits until all of them are done; only then does the workflow go on with the next action. Each branch is a list of actions of its own that run one after the other, just like Actions, including further If, Loop or Parallel.

A typical case: an invoice is uploaded to the SFTP server and then deleted from the inbox folder, and at the same time a mail goes to accounting. One after the other, the mail would wait for the upload; with Parallel the run takes only as long as the slowest branch.

In the visual editor, Parallel shows one column per branch with its name. Add branches in the panel on the right with Add branch, rename or remove them there; add actions with the + in a branch’s column.

Structure

{
  "Type": "Parallel",
  "Name": "Distribute",
  "Parameters": {
    "Branches": [
      {
        "Name": "Archive",
        "Actions": [
          { "Type": "FTP", "Name": "Upload", "Parameters": { … } },
          { "Type": "SMB", "Name": "CleanUp", "Parameters": { … } }
        ]
      },
      {
        "Name": "Notify",
        "Actions": [ { "Type": "SMTP", "Name": "Accounting", "Parameters": { … } } ]
      }
    ],
    "OnBranchError": "WaitForAll",
    "MaxConcurrent": 0
  }
}

Parameter	Default	Meaning
Branches	–	The branches, each with Name and Actions
Branches[].Name	Branch1, Branch2, …	The branch’s name, unique within the Parallel. Its result is reachable by it; don’t use spaces, dots or braces.
Branches[].Actions	–	The branch’s actions, run one after the other
OnBranchError	WaitForAll	What happens when a branch fails: WaitForAll lets the other branches finish, StopOthers cancels them
MaxConcurrent	0 (all)	At most this many branches at the same time; the others wait until one is done

Names

The names of all actions must be unique in the whole workflow, across branches too: two branches run at the same time and would otherwise overwrite the same result. RUNOS does not load a workflow with duplicate names in a Parallel, nor one with two branches of the same name.

Run and errors

• Inside a branch the same applies as in the Do of an If: if an action fails, the remaining actions of that branch don’t run. An action’s own error policy applies first, e.g. SkipAction (the branch goes on) or Retry.
• A failed branch makes the Parallel fail as soon as the other branches have finished (WaitForAll) or been cancelled (StopOthers). Then the error policy of the Parallel or the workflow decides what happens next, and OnError runs as for any other action.
• StopOthers starts no new action in the other branches; an action that is already running is cancelled if it supports that, otherwise it finishes first.
• A StopWorkflow action in a branch ends the run: the other branches start no new action afterwards.
• Results from another branch of the same Parallel may not be there yet during the run. Use them only in actions after the Parallel; otherwise the editor warns.
• A Loop in a branch has its own {{item}}, {{index}} and {{count}}, even while a loop runs in another branch at the same time.

Result

"Response": {
  "Branches": {
    "Archive": { "State": "Completed", "Error": null, "ElapsedMs": 2140.5, "Results": [ { … }, { … } ] },
    "Notify":  { "State": "Failed", "Error": "Accounting: …", "ElapsedMs": 310.2, "Results": [ { … } ] }
  },
  "CompletedCount": 1,
  "FailedCount": 1,
  "CancelledCount": 0
}

A branch’s State is Completed, Failed or Cancelled (cancelled by StopOthers). Results holds the result of each action of the branch. After the Parallel, a branch result is reachable as {{Distribute.Response.Branches.Archive.State}}, and the results of the actions by their names as usual, e.g. {{Upload.Response…}}.

Example

Archive and report an incoming invoice at the same time; if the upload fails, the mail is not waited for but cancelled:

{
  "Type": "Parallel",
  "Name": "Distribute",
  "Parameters": {
    "OnBranchError": "StopOthers",
    "Branches": [
      {
        "Name": "Archive",
        "Actions": [
          {
            "Type": "FTP",
            "Name": "Upload",
            "Parameters": {
              "Protocol": "SFTP",
              "Server": "{{connector.Archive.BaseUrl}}",
              "User": "{{connector.Archive.Username}}",
              "Password": "{{connector.Archive.Password}}",
              "Operation": "Upload",
              "Source": "{{FilePath}}",
              "Destination": "/invoices/"
            }
          }
        ]
      },
      {
        "Name": "Notify",
        "Actions": [
          {
            "Type": "SMTP",
            "Name": "Accounting",
            "Parameters": {
              "SmtpServer": "smtp.example.com",
              "From": "runos@example.com",
              "To": "accounting@example.com",
              "Subject": "New invoice {{FileName}}",
              "Body": "The invoice {{FileName}} has arrived."
            }
          }
        ]
      }
    ]
  }
}