Limiting concurrency on cron jobs?

[spiffytech]

I'm trying to create a singleton cron job (TypeScript SDK). It looks like an expression is mandatory, but the cron scheduler runs tasks with a null input, so I can't figure out what CEL to use.

Here's what I'm trying:

const mytask = hatchet.task({
  name: "my-task",
  retries: 3,
  on: {
    cron: "* * * * *",
  },
  concurrency: {
    maxRuns: 1,
    limitStrategy: ConcurrencyLimitStrategy.CANCEL_NEWEST,
    expression: "input",
  },
  fn: async () => {
  }
})

Run failed -> failed to parse step expression (input): output must evaluate to a string or integer: got map

Input:

{
  "input": null,
  "overrides": null,
  "parents": {},
  "triggered_by": "manual",
  "triggers": {
    "filter_payload": null
  },
  "user_data": null
}

[grutt]

hi @spiffytech, if you goal is just "global concurrency" a string key like "'gobal'" should work.

[spiffytech]

Is this the syntax you meant?

  concurrency: {
    maxRuns: 1,
    limitStrategy: ConcurrencyLimitStrategy.CANCEL_NEWEST,
    expression: "global",
  }

failed to parse step expression (global): ERROR: <input>:1:1: undeclared reference to 'global' (in container '')
 | global
 | ^

[grutt]

Not quite, there should be a sneaky single quote in there so global is treated as string within the cel:

  concurrency: {
    maxRuns: 1,
    limitStrategy: ConcurrencyLimitStrategy.CANCEL_NEWEST,
    expression: "'global'",
  }

[spiffytech]

Working now, thanks!

[grutt]

Glad to hear it!