Module

_drain

Shared drain-503 wire format and write helpers.

Single source of truth for the HTTP 503 response that every worker mode emits to new connections while the server is draining (SIGTERM / SIGHUP). Keeping the bytes in one place means the asyncWorker, the blocking SyncWorker and the AcceptDistributoranswer byte-identically:

HTTP/1.1 503 Service Unavailable
Connection: close
Retry-After: 1
Content-Type: text/plain; charset=utf-8
Content-Length: 23

Server shutting down...

The body is short and actionable;Retry-Aftertells well-behaved clients (and load balancers) to come back, whileConnection: close guarantees the socket is torn down after the single response.

8Functions

Functions

_draining_health_method 2 bytes | None ▼
Return GET/HEAD when *request_head* targets the configured health path.
def _draining_health_method(request_head: bytes, health_check_path: str | None) -> bytes | None
Parameters
Name Type Description
request_head bytes
health_check_path str | None
Returns
bytes | None
_draining_health_response 3 bytes ▼
Serialize the configured readiness response for the drain boundary.
def _draining_health_response(method: bytes, *, worker_id: int, active_connections: int) -> bytes
Parameters
Name Type Description
method bytes
worker_id int
active_connections int
Returns
bytes
_read_request_head_sync 3 bytes ▼
Read one bounded HTTP/1 header block from a draining socket.
def _read_request_head_sync(conn: socket.socket, config: ServerConfig, *, timeout: float | None) -> bytes
Parameters
Name Type Description
conn socket.socket
config ServerConfig
timeout float | None
Returns
bytes
_read_request_head_async 3 bytes ▼
Read one bounded HTTP/1 header block from a draining stream.
async
async def _read_request_head_async(reader: asyncio.StreamReader, config: ServerConfig, *, timeout: float | None) -> bytes
Parameters
Name Type Description
reader asyncio.StreamReader
config ServerConfig
timeout float | None
Returns
bytes
write_drain_503_sync 1 None ▼
Send the drain 503 on a blocking socket; the caller still owns the close. Tole…
def write_drain_503_sync(conn: socket.socket) -> None

Send the drain 503 on a blocking socket; the caller still owns the close.

Tolerates a client that has already gone away — a dropped connection during shutdown is expected, not exceptional.

Parameters
Name Type Description
conn socket.socket
write_drain_response_sync 5 None ▼
Inspect one bounded request and write the matching drain response.
def write_drain_response_sync(conn: socket.socket, config: ServerConfig, *, worker_id: int, active_connections: int, timeout: float | None = None) -> None
Parameters
Name Type Description
conn socket.socket
config ServerConfig
worker_id int
active_connections int
timeout float | None Default:None
write_drain_503_async 2 None ▼
Send the drain 503 on an asyncio writer and close it. Tolerates a client that …
async
async def write_drain_503_async(writer: asyncio.StreamWriter, *, timeout: float = 30.0) -> None

Send the drain 503 on an asyncio writer and close it.

Tolerates a client that has already gone away — a dropped connection during shutdown is expected, not exceptional.

Parameters
Name Type Description
writer asyncio.StreamWriter
timeout float Default:30.0
write_drain_response_async 6 None ▼
Inspect one bounded request, write its drain response, and close.
async
async def write_drain_response_async(reader: asyncio.StreamReader, writer: asyncio.StreamWriter, config: ServerConfig, *, worker_id: int, active_connections: int, timeout: float | None = None) -> None
Parameters
Name Type Description
reader asyncio.StreamReader
writer asyncio.StreamWriter
config ServerConfig
worker_id int
active_connections int
timeout float | None Default:None