outlabs-taskq

Postgres-native durable task queue for Python services.

Status: alpha — 0.1.0a40 uses SQL contract 0.6.12 and Protocol revision 1.0.18. Additive SQL contracts 0.6.9–0.6.12 and migrations 0045–0048 add an installation-bound terminal host-effect row lock and database-role queue admission owner. The 0.6.12 correction closes replay and standalone-scheduler admission paths, stores role identity by OID, removes owner checks from the queue-row lock path, and adds audited adoption and rotation for paused, quiesced queues. See ADR-038 and ADR-039. The resource-oriented, non-interactive CLI is a complete operator and coding-agent surface over direct PostgreSQL and HTTP.

SQL functions in schema taskq are the contract. The Python package provides the installer, typed client, worker runtime, and an optional FastAPI facade. outlabs-auth is an optional adapter, not a hard dependency. Queue storage may be co-resident with the host database or dedicated; the HTTP facade may use OutLabsAuth, a host-supplied/remote authorizer, or simple packaged credentials, while trusted direct-SQL deployments use PostgreSQL capability roles.

Docs

Start here:

Install

Install the exact published prerelease selected by the consumer lockfile:

pip install outlabs-taskq==0.1.0a38

Credential handling

Keep DSNs and HTTP credentials out of shell history and process arguments. Supply them through the process environment using a secret manager, container secret, or service supervisor, then omit the DSN from commands. A context stores only the environment-variable name:

# TASKQ_STAGING_DSN is the short-lived owner/migration DSN supplied by the deployment environment.
taskq --context staging db plan -o json
taskq --context staging db verify

# A context file is optional when the caller supplies target identity explicitly.
taskq --dsn-env TASKQ_STAGING_DSN \
  --expected-environment staging --actor operator:release-agent \
  db verify -o json

taskq db plan, taskq db migrate, and taskq db verify require a superuser or a managed database-owner role with access to the private migration ledger and exact catalog. Migration also requires CREATEROLE. On PostgreSQL 16/18, the installer bootstraps taskq_owner and retains owner membership on that migration role so later owner-only binding and upgrades work. This must be a dedicated owner/migration credential: never give it to an API, worker, or scheduler. Runtime logins receive only the required TaskQ capability roles.

Migration 0019 deliberately stops at an unbound target before scheduler activation. Inspect and bind the safe fingerprint, then resume migration:

PLAN=$(taskq --context staging db plan -o json)
# Review PLAN and extract data.plan_digest.
taskq --context staging --yes db migrate --plan-digest "$PLAN_DIGEST"
taskq --context staging target show -o json
taskq --context staging --yes target bind staging \
  --expected-installation-id "$TASKQ_INSTALLATION_ID" \
  --expected-binding-version 0
taskq --context staging db plan -o json
taskq --context staging --yes db migrate --plan-digest "$PLAN_DIGEST"
taskq --context staging db verify

Run the framework-neutral scheduler with static target expectations. The bounded mode is first-class for platform timers and scale-to-zero databases:

taskq --context staging scheduler run
taskq --context staging scheduler once -o json
taskq --context staging scheduler doctor -o json

taskq --context staging schedule manifest plan examples/schedules.minimal.yaml -o json
taskq --context staging schedule manifest apply examples/schedules.minimal.yaml \
  --plan-digest "$PLAN_DIGEST"

Activating or resuming an interval schedule is from now: the first scheduler pass initializes its recurrence and the first job becomes due after one full interval. Activation does not enqueue an immediate job. Size attended pilot windows accordingly, or use an explicit one-shot job when an immediate canary is required.

The scheduler is a clock, not a task executor. Run one supervised scheduler per database/environment, but place workers according to the application's existing operating model. A single host-native worker can use a combined registry and subscribe to multiple queues; TaskQ does not require one container per worker, queue, task, or schedule. Prefer existing local worker hosts unless a particular task has a documented cloud availability, latency, or network requirement.

Concurrency model

TaskQ does not serialize independent jobs. A job without a concurrency_key may run alongside any other claim, up to the explicit WorkerOptions.concurrency and any configured queue flow cap. Worker concurrency defaults to one as a safe deployment setting; applications that have parallel-safe handlers must size it deliberately.

Use a concurrency_key only to name a real shared resource such as a browser session, licensed renderer, or rate-limited provider. Jobs with different keys do not block each other. A named key with no registered limit is conservatively capped at one; raise that cross-worker cap with set_concurrency_limit when the resource safely supports more than one user. Do not stamp unrelated stages with one host-wide key: process lanes and task-name claim filters provide isolation, while resource keys provide cross-worker mutual exclusion.

Priority controls which eligible job is claimed first; it does not create parallel capacity and cannot bypass worker, queue, flow-key, or concurrency-key limits. Keep ordering policy and resource capacity as separate decisions.

Every recurring source manifest must set catchup: fire_once or catchup: fire_all explicitly. Do not rely on the current skip default: the released SQL contract intentionally accepts only zero occurrences for that policy, so continuous polling advances without enqueueing. A corrected skip_missed semantic requires a new SQL migration and compatibility audit; it is not being patched only in Python.

Worker services may still use their runtime settings. Operator CLI commands require an explicit context or complete connection flags; they never infer a current context or endpoint. HTTP contexts store a bearer-token environment-variable name, never a literal token or arbitrary header value. OutLabs IAM provisioning reads TASKQ_AUTH_DSN.

Use https:// for traffic that leaves a protected private network. The mounted facade intentionally publishes its public wire contract at /taskq/openapi.json; deployments that do not want that route reachable should gate it at the host application or reverse proxy.

Package layout

src/taskq/
  sql/           # migrations 0001-0021, runner/verifier, manifest, SQL transport
  scheduler.py   # standalone runtime, bounded mode, doctor, YAML plan/apply
  protocol.py    # closed command/outcome/error single-source (Tier-0 parity-tested)
  continuations.py # pure policy compiler, negotiation, and derived identities
  registry.py    # typed Task[In, Out] registry
  client.py      # TaskQ facade: transactional typed enqueue
  transport.py   # TaskqTransport protocol
  worker.py      # supervisor + fair poll/presence/shutdown service
  settings.py    # secret-safe worker environment/CLI configuration
  testing.py     # fake client, enqueue assertions, direct work, inline and drain helpers
  cli/            # Click registry, contexts, transports, safety, output, errors
  http/          # optional clients, mounted facade, composable runtime/lifespan

Consumer testing

Fast unit tests can replace one facade without starting a worker or database:

from taskq.testing import FakeTaskQClient

with tq.replace_client(FakeTaskQClient()) as fake:
    await application_call()
    fake.assert_enqueued("mail.send", where={"payload.recipient": "me@example.test"})

Inline mode executes registered handlers immediately; bounded drain tests queued behavior without sleeps:

from taskq.testing import drain, inline_mode

async with inline_mode(tq) as recorder:
    await application_call()
    assert recorder.settled("mail.send")[0].is_complete

report = await drain(tq, queue="mail", max_jobs=100)
assert report.completed == 1

These are consumer-test conveniences, not production modes. The fake intentionally does not model PostgreSQL fencing, privileges, budgets, or transaction isolation. Use a scratch PostgreSQL transaction with work, require_enqueued, or drain(..., connection=connection) when those contracts matter; every helper preserves caller transaction ownership and makes runaway caps fail loudly.

Atomic native follow-ups

A handler declares its finite child graph in the registry and returns typed children with its successful result. The parent settlement and every child insert commit together; the worker never receives a generic producer client.

from taskq import Complete, Followup, FollowupTarget, Task, TaskRegistry

child = Task(
    name="listing.enrich",
    queue="enrichment",
    input_model=EnrichInput,
    output_model=EnrichOutput,
    handler=enrich,
)

async def discover(payload: DiscoverInput) -> Complete:
    return Complete(
        result={"accepted": True},
        followups=(
            Followup(
                step="enrich",
                job_type=child.name,
                queue=child.queue,
                payload={"listing_id": payload.listing_id},
            ),
        ),
    )

parent = Task(
    name="listing.discover",
    queue="discovery",
    input_model=DiscoverInput,
    output_model=DiscoverOutput,
    followup_targets=(FollowupTarget(queue=child.queue, job_type=child.name),),
    handler=discover,
)

registry = TaskRegistry((parent, child))

Worker construction rejects missing or queue-mismatched target declarations. HTTP completion authorizes the parent queue before decoding the body, then authorizes every distinct child queue before SQL; direct SQL retains the trusted runner-role boundary.

Development gates

Protect main with pull requests, require branches to be current, and require the CI gates that run on pull requests: lint, dependency-audit, both import-isolation and unit Python lanes, built-artifacts, both PostgreSQL sql-contract lanes, both fresh-cluster-security lanes, races, stage3-audit, migrations, bench-smoke, and both PostgreSQL load-smoke lanes. The scheduled/dispatchable million-row-plans job keeps structural plans honest without charging every pull request. Do not bypass a failed required check except through the repository's explicit break-glass process.

License

MIT — see LICENSE.