Starts a worker pool with a dispatcher and N worker threads.

A worker pool paired with its queue name (derived from the registry).

allWorkers =
  [ namedWorkerPool emailConfig      -- "email_jobs"
  , namedWorkerPool imageConfig      -- "image_jobs"
  ]

main = runWorkerPools (Proxy @MyRegistry) allWorkers (\_ -> pure ())

Create a named worker pool, deriving the name from the type-level registry.

Run worker pools with shared shutdown state. Filters to queues listed in ARBITER_ENABLED_QUEUES (all if unset). The setup action receives the shared TVar for installing signal handlers.

Run only the worker pools whose names appear in the enabled list.

Get enabled queues from an environment variable.

If the environment variable is set and non-empty, parses it as a comma-separated list of queue names. Each name is validated against the registry - invalid names cause an error. If not set or empty, returns all queue names from the registry.

Example:

-- With ENABLED_QUEUES="email_jobs,notifications"
queues <- getEnabledQueues ENABLED_QUEUES (Proxy @MyRegistry)
-- Returns: ["email_jobs", "notifications"]

-- With ENABLED_QUEUES unset or empty
queues <- getEnabledQueues ENABLED_QUEUES (Proxy @MyRegistry)
-- Returns: all queues from registry

-- With ENABLED_QUEUES="email_jobs,invalid_queue"
-- Throws error: "Unknown queue names: invalid_queue"

Handler result types. () is fire-and-forget; any (ToJSON a, FromJSON a) is stored in the results table when the job has a parent and decoded when read by a rollup finalizer.

A cron schedule definition.

Use cronJob to construct (eagerly parses the cron expression). For a non-UTC timezone, use cronJobInTimezone (also validates the tz name).

How overlapping cron ticks are deduplicated.

Bound on replay of missed ticks. Applies at startup and mid-flight.

Smart constructor for CronJob. Parses the cron expression eagerly.

Returns Left with an error message if the cron expression is invalid.

cronJob "nightly-report" "0 3 * * *" SkipOverlap
  (\_kind _tick -> defaultJob (GenerateReport "nightly"))

The builder receives a TickKind (Live for the current minute, Replay for any catch-up tick) and the tick time.

To enable backfill, set it via record update:

let Right cj = cronJob "nightly-report" "0 3 * * *" AllowOverlap
      (\kind tick -> (defaultJob (GenerateReport tick))
         { priority = case kind of Replay -> 10; Live -> 0 })
in cj { backfill = Backfill 86400 }  -- replay up to 24 hours

Note: cron expressions are evaluated in UTC. "0 3 * * *" fires at 03:00 UTC regardless of the server's local timezone.

Upsert default expression and overlap for each CronJob into the cron_schedules table. Preserves any user overrides and enabled state.

Convert an OverlapPolicy to its text representation.

Parse an OverlapPolicy from text.