Run consumers, crons, and streams

Background work runs as WebAssembly handlers that boatramp invokes for you instead of per HTTP request: consumers process messages off a topic, and crons invoke a route on a schedule. You declare each one in the routing section of project.cfg, pointing it at a handler, and boatramp runs it for the live deployment. For the component build and site policy, see Deploy a handler.

Declare a consumer

A consumer is invoked once per message on its topic. Give it a retry budget: a message that fails is retried up to max_attempts times, then dead-lettered.

routing: (
    consumers: [
        ( topic: "emails", component: "mailer.wasm",
          imports: ["sql", "wasi:messaging"],
          max_attempts: 5 ),
    ],
),

Declare a cron

A cron invokes an existing route on a schedule, using a standard five-field cron expression. The route runs as if a request arrived for it:

routing: (
    crons: [
        ( schedule: "0 * * * *", route: "/api/rollup" ),
    ],
),

Sync to activate the new routing. Each component is validated at sync:

boatramp sync ./dist --site my-site

validated mailer.wasm — consumer topic "emails"
activated my-site -> a1b2c3d4

Operate the dead-letter queue

When a message exhausts max_attempts, boatramp dead-letters it and retains the payload until you clear it. Once you have fixed the cause, requeue the dead-lettered messages onto the live topic:

boatramp dlq redrive emails --site my-site

redrive: 12 dead-lettered message(s) on topic "emails"

If the messages are unrecoverable, drop them and reclaim the space instead:

boatramp dlq purge emails --site my-site

purge: 12 dead-lettered message(s) on topic "emails"

To scope either command to a background alias rather than the live site, add --alias {site}/{alias}.

Watch lag and dead-letters

Check consumer backlog and dead-letter counts with boatramp stats:

boatramp stats --site my-site

site my-site
  queue/emails   invocations 512   errors 1   lag 0   dead-letters 0

A growing lag means consumers are falling behind the incoming rate; a nonzero dead-letter count is messages waiting for you to redrive or purge. For tailing guest output and the full metric surface, see Observe a running server.