Litestar Granian

litestar-granian

litestar-granian 0.16.0 replaces Litestar's run command with a Granian-backed command and integrates Granian loggers with Litestar logging. It requires Granian 2.7.9 or later (the current lock uses 2.8.1).

Code Style Rules

• Keep handlers async when they perform I/O.
• Configure the server at the command line or programmatically via granian.Granian.
• GranianPlugin takes only an optional static mode keyword argument ("off" or "auto").
• Use the litestar run option names documented here. Do not substitute similarly named options from older Granian or Uvicorn releases.

Quick Reference

Register the plugin

from litestar import Litestar, get
from litestar_granian import GranianPlugin


@get("/health")
async def health() -> dict[str, str]:
    """Return health check response."""
    return {"status": "ok"}


app = Litestar(
    route_handlers=[health],
    plugins=[GranianPlugin()],
)

litestar --app app:app run

GranianPlugin registers the Granian-backed run command. During app initialization, it adds missing _granian and granian.access logger entries and a compatible formatter without replacing user-defined entries. It also handles the standard-library logging configuration wrapped by Litestar's StructlogPlugin.

Defaults in 0.16.0 / Granian 2.8.1

Valid Production Controls

litestar --app app:app run \
    --host 0.0.0.0 \
    --port 8000 \
    --workers 4 \
    --runtime-mode auto \
    --runtime-threads 1 \
    --backpressure 1024 \
    --granian-access-log \
    --respawn-failed-workers \
    --workers-lifetime 4h \
    --workers-max-rss 512 \
    --metrics \
    --metrics-address 127.0.0.1 \
    --metrics-port 9090

Use these option families:

Supervision and Litestar CLI Parity

litestar run has one execution model: the Litestar parent enters server lifespans once and supervises a fresh Granian child process group.

• POSIX: Starts Granian in a new session (start_new_session=True) and forwards signals (SIGINT, SIGTERM, SIGHUP) to the process group (os.killpg).
• Windows: Uses a new process group (CREATE_NEW_PROCESS_GROUP) and CTRL_BREAK_EVENT for graceful shutdown, escalating to list-based taskkill only if needed.
• Graceful Shutdown & Deadlines: The first termination signal is forwarded once and starts a deadline of --workers-kill-timeout plus five seconds (the CLI default is 5 seconds). A second signal or an expired deadline kills the process group.
• Server Lifespans: Litestar's server lifespans stay active until Granian exits and are unwound cleanly after child termination.
• Sidecar Variables: Server-lifespan sidecars receive the resolved LITESTAR_APP, LITESTAR_HOST, and LITESTAR_PORT, which is how frontend dev-server sidecars (e.g. Vite) learn the real server bind.
• Socket Activation: Inherited file descriptors (-F / --fd / --file-descriptor) are supported on POSIX systems (e.g. systemd socket activation).

Native Static Discovery

GranianPlugin(static=...) is the plugin's only constructor option:

app = Litestar(route_handlers=[health], plugins=[GranianPlugin(static="auto")])

• "off" (the default) keeps Litestar's static routing.
• "auto" lets Granian serve exactly one compatible static provider natively when its configuration is safe, and falls back to Litestar otherwise.
• Explicit --static-path-* CLI mounts always take precedence over either mode. Any other value raises ValueError at construction.

Metrics and Observability

Metrics are off by default and are controlled only by --metrics / --no-metrics. --metrics exposes Granian server and worker metrics only at http://<metrics-address>:<metrics-port>/metrics. When no Litestar Prometheus middleware is detected, the command warns that application-level request metrics are not being exported — register Litestar's PrometheusPlugin alongside it when request metrics are desired.

Programmatic / Embedded Runtime

Granian can also be executed programmatically directly from Python:

from pathlib import Path
from granian import Granian
from granian.constants import HTTPModes, Interfaces, RuntimeModes


def run_embedded() -> None:
    """Execute Granian embedded server."""
    server = Granian(
        target="app.server:app",
        address="0.0.0.0",
        port=8000,
        interface=Interfaces.ASGI,
        workers=2,
        runtime_mode=RuntimeModes.auto,
        http=HTTPModes.auto,
        ssl_cert=Path("/etc/ssl/certs/app.crt"),
        ssl_key=Path("/etc/ssl/private/app.key"),
    )
    server.serve()

Workflow

Step 1: Match the project's deployment stack

Use GranianPlugin when the project already uses litestar-granian or needs its Granian-specific CLI, HTTP/2, runtime, worker-lifecycle, metrics, or static mount controls.

Keep the project's existing ASGI server when its deployment platform, process manager, observability, or operational runbooks depend on that server. Do not replace an established server solely because Granian is available.

Use the bare granian CLI only when deployment tooling intentionally invokes Granian directly. Its CLI is a separate surface; consult the matching Granian release instead of copying litestar run options.

Step 2: Install and register

pip install "litestar-granian==0.16.0"

Add GranianPlugin() to Litestar(plugins=[...]), then run the application through litestar --app <module>:<app> run.

Step 3: Configure logging

0.16.0 always uses supervised execution and matches Granian's formatter to Litestar's automatically. There is no mode to choose:

litestar --app app:app run

--in-subprocess / --no-subprocess and --use-litestar-logger / --no-litestar-logger are accepted for backwards compatibility, but they are ignored and print a deprecation warning. Remove them from deployment scripts.

Pass an explicit JSON --log-config only when overriding the automatic formatter matching completely.

Step 4: Configure the deployment and capacity

Measure the application before changing workers, runtime threads, or backpressure. Preserve the auto runtime defaults unless load tests justify a specific runtime mode.

litestar --app app:app run \
    --host 0.0.0.0 \
    --port 8000 \
    --workers 4 \
    --backpressure 1024 \
    --granian-access-log

Terminate TLS at the platform proxy when that is the project's established boundary. For Granian-managed TLS, pass both the certificate and key:

litestar --app app:app run \
    --ssl-certificate /etc/ssl/certs/app.crt \
    --ssl-keyfile /etc/ssl/private/app.key \
    --ssl-protocol-min tls1.3

Step 5: Verify the effective command

litestar --app app:app run --help

Confirm the required options appear, start the service, exercise health and WebSocket endpoints, and load-test production capacity settings.

Guardrails

• Use the runtime-specific thread controls. The 0.16.0 command exposes --runtime-threads, --runtime-blocking-threads, --blocking-threads, and --runtime-mode.
• Use the namespaced access-log controls. The 0.16.0 command exposes --granian-access-log and --granian-access-log-fmt.
• Do not treat the plugin CLI as the bare Granian CLI. The option names overlap but are not identical (e.g. --granian-access-log vs --access-log).
• Do not claim that registering the plugin changes every deployment. GranianPlugin replaces Litestar's run command; an external ASGI command still controls its own server lifecycle.
• Do not force Granian into an established deployment stack. Match the server to the project's platform and operational requirements.
• Do not enable HTTP/2-only mode for a WebSocket endpoint. The 0.16.0 launcher disables WebSockets when --http 2 is selected.
• Do not rely on an implicit static route. Pair every repeatable --static-path-route with a --static-path-mount.
• Do not pass the deprecated compatibility flags. --in-subprocess / --no-subprocess and --use-litestar-logger / --no-litestar-logger are ignored in 0.16.0 and emit warnings.
• Do not expect --metrics to export request metrics. It exposes Granian server and worker metrics only; register Litestar's PrometheusPlugin for application-level request metrics.
• Do not perform blocking I/O in an async handler. Use an async client or explicitly offload blocking work according to the application's concurrency model; Granian's blocking-thread setting does not make arbitrary ASGI code non-blocking.
• Do not attempt --reload or --workers-max-rss on free-threaded Python. Free-threaded Python builds (GIL disabled) reject these flags with UsageError.
• Do not expect HTTP/3 support. Granian 2.8.1 supports HTTP/1.1 and HTTP/2; terminate HTTP/3 at an external proxy.

Validation Checkpoint

• The project intentionally selected Granian over its existing ASGI server.
• GranianPlugin() is registered when deployment uses litestar run.
• Every documented option appears in litestar run --help.
• Deployment scripts no longer pass deprecated --in-subprocess or --use-litestar-logger compatibility flags.
• Logging relies on automatic formatter matching or an intentional --log-config override.
• HTTP/2-only mode is not used for required WebSocket endpoints.
• Static routes and mounts have equal counts and are paired in order.
• --metrics is paired with Litestar's PrometheusPlugin when application request metrics are required.
• Worker, thread, and capacity changes are backed by load-test results.
• TLS terminates at the documented platform or Granian boundary.
• Free-threaded Python deployments omit --reload and --workers-max-rss.

Example

Task: Run an existing Litestar application with Granian, enable access logs, configure worker recycling, and expose Granian metrics to a local collector.

from litestar import Litestar, get
from litestar_granian import GranianPlugin


@get("/health")
async def health() -> dict[str, str]:
    """Return application health check status."""
    return {"status": "ok"}


app = Litestar(
    route_handlers=[health],
    plugins=[GranianPlugin(static="auto")],
)

litestar --app app:app run \
    --host 0.0.0.0 \
    --port 8000 \
    --workers 4 \
    --runtime-mode auto \
    --runtime-threads 1 \
    --granian-access-log \
    --respawn-failed-workers \
    --workers-lifetime 4h \
    --workers-max-rss 512 \
    --metrics \
    --metrics-address 127.0.0.1 \
    --metrics-port 9090

--metrics exposes Granian server and worker metrics at http://127.0.0.1:9090/metrics. Register Litestar's PrometheusPlugin alongside it to also export application-level request metrics.

References Index

• CLI Reference — Exhaustive parameter matrix for litestar run with litestar-granian and standalone granian.
• Runtime & Tuning Guide — Concurrency models, thread pools, HTTP/1 & HTTP/2 flow control, memory limits, and platform constraints.
• Embedded Runtime & Lifecycle — Programmatic granian.Granian execution, supervisor architecture, signals, lifespans, and static provider discovery.
• litestar — Application initialization and plugin registration.
• litestar-deployment — Deployment target, proxy, container, and process-manager selection.
• litestar-plugins — Litestar plugin protocols and initialization behavior.

Official References

• litestar-granian v0.16.0 source
• v0.16.0 CLI implementation
• v0.16.0 plugin implementation
• v0.16.0 changelog
• litestar-granian 0.16.0 on PyPI
• granian v2.8.1 repository
• granian documentation

Shared Styleguide Baseline

• General Principles
• Python
• Litestar