325 lines
9.8 KiB
Python
325 lines
9.8 KiB
Python
|
"""
|
||
|
|
Code concerned with waiting in different contexts (blocking, async, etc).
|
||
|
|
|
||
|
|
These functions are designed to consume the generators returned by the
|
||
|
|
`generators` module function and to return their final value.
|
||
|
|
|
||
|
|
"""
|
||
|
|
|
||
|
|
# Copyright (C) 2020 The Psycopg Team
|
||
|
|
|
||
|
|
|
||
|
|
import os
|
||
|
|
import select
|
||
|
|
import selectors
|
||
|
|
from typing import Dict, Optional
|
||
|
|
from asyncio import get_event_loop, wait_for, Event, TimeoutError
|
||
|
|
from selectors import DefaultSelector
|
||
|
|
|
||
|
|
from . import errors as e
|
||
|
|
from .abc import RV, PQGen, PQGenConn, WaitFunc
|
||
|
|
from ._enums import Wait as Wait, Ready as Ready # re-exported
|
||
|
|
from ._cmodule import _psycopg
|
||
|
|
|
||
|
|
WAIT_R = Wait.R
|
||
|
|
WAIT_W = Wait.W
|
||
|
|
WAIT_RW = Wait.RW
|
||
|
|
READY_R = Ready.R
|
||
|
|
READY_W = Ready.W
|
||
|
|
READY_RW = Ready.RW
|
||
|
|
|
||
|
|
|
||
|
|
def wait_selector(gen: PQGen[RV], fileno: int, timeout: Optional[float] = None) -> RV:
|
||
|
|
"""
|
||
|
|
Wait for a generator using the best strategy available.
|
||
|
|
|
||
|
|
:param gen: a generator performing database operations and yielding
|
||
|
|
`Ready` values when it would block.
|
||
|
|
:param fileno: the file descriptor to wait on.
|
||
|
|
:param timeout: timeout (in seconds) to check for other interrupt, e.g.
|
||
|
|
to allow Ctrl-C.
|
||
|
|
:type timeout: float
|
||
|
|
:return: whatever `!gen` returns on completion.
|
||
|
|
|
||
|
|
Consume `!gen`, scheduling `fileno` for completion when it is reported to
|
||
|
|
block. Once ready again send the ready state back to `!gen`.
|
||
|
|
"""
|
||
|
|
try:
|
||
|
|
s = next(gen)
|
||
|
|
with DefaultSelector() as sel:
|
||
|
|
while True:
|
||
|
|
sel.register(fileno, s)
|
||
|
|
rlist = None
|
||
|
|
while not rlist:
|
||
|
|
rlist = sel.select(timeout=timeout)
|
||
|
|
sel.unregister(fileno)
|
||
|
|
# note: this line should require a cast, but mypy doesn't complain
|
||
|
|
ready: Ready = rlist[0][1]
|
||
|
|
assert s & ready
|
||
|
|
s = gen.send(ready)
|
||
|
|
|
||
|
|
except StopIteration as ex:
|
||
|
|
rv: RV = ex.args[0] if ex.args else None
|
||
|
|
return rv
|
||
|
|
|
||
|
|
|
||
|
|
def wait_conn(gen: PQGenConn[RV], timeout: Optional[float] = None) -> RV:
|
||
|
|
"""
|
||
|
|
Wait for a connection generator using the best strategy available.
|
||
|
|
|
||
|
|
:param gen: a generator performing database operations and yielding
|
||
|
|
(fd, `Ready`) pairs when it would block.
|
||
|
|
:param timeout: timeout (in seconds) to check for other interrupt, e.g.
|
||
|
|
to allow Ctrl-C. If zero or None, wait indefinitely.
|
||
|
|
:type timeout: float
|
||
|
|
:return: whatever `!gen` returns on completion.
|
||
|
|
|
||
|
|
Behave like in `wait()`, but take the fileno to wait from the generator
|
||
|
|
itself, which might change during processing.
|
||
|
|
"""
|
||
|
|
try:
|
||
|
|
fileno, s = next(gen)
|
||
|
|
if not timeout:
|
||
|
|
timeout = None
|
||
|
|
with DefaultSelector() as sel:
|
||
|
|
while True:
|
||
|
|
sel.register(fileno, s)
|
||
|
|
rlist = sel.select(timeout=timeout)
|
||
|
|
sel.unregister(fileno)
|
||
|
|
if not rlist:
|
||
|
|
raise e.ConnectionTimeout("connection timeout expired")
|
||
|
|
ready: Ready = rlist[0][1] # type: ignore[assignment]
|
||
|
|
fileno, s = gen.send(ready)
|
||
|
|
|
||
|
|
except StopIteration as ex:
|
||
|
|
rv: RV = ex.args[0] if ex.args else None
|
||
|
|
return rv
|
||
|
|
|
||
|
|
|
||
|
|
async def wait_async(gen: PQGen[RV], fileno: int) -> RV:
|
||
|
|
"""
|
||
|
|
Coroutine waiting for a generator to complete.
|
||
|
|
|
||
|
|
:param gen: a generator performing database operations and yielding
|
||
|
|
`Ready` values when it would block.
|
||
|
|
:param fileno: the file descriptor to wait on.
|
||
|
|
:return: whatever `!gen` returns on completion.
|
||
|
|
|
||
|
|
Behave like in `wait()`, but exposing an `asyncio` interface.
|
||
|
|
"""
|
||
|
|
# Use an event to block and restart after the fd state changes.
|
||
|
|
# Not sure this is the best implementation but it's a start.
|
||
|
|
ev = Event()
|
||
|
|
loop = get_event_loop()
|
||
|
|
ready: Ready
|
||
|
|
s: Wait
|
||
|
|
|
||
|
|
def wakeup(state: Ready) -> None:
|
||
|
|
nonlocal ready
|
||
|
|
ready |= state # type: ignore[assignment]
|
||
|
|
ev.set()
|
||
|
|
|
||
|
|
try:
|
||
|
|
s = next(gen)
|
||
|
|
while True:
|
||
|
|
reader = s & WAIT_R
|
||
|
|
writer = s & WAIT_W
|
||
|
|
if not reader and not writer:
|
||
|
|
raise e.InternalError(f"bad poll status: {s}")
|
||
|
|
ev.clear()
|
||
|
|
ready = 0 # type: ignore[assignment]
|
||
|
|
if reader:
|
||
|
|
loop.add_reader(fileno, wakeup, READY_R)
|
||
|
|
if writer:
|
||
|
|
loop.add_writer(fileno, wakeup, READY_W)
|
||
|
|
try:
|
||
|
|
await ev.wait()
|
||
|
|
finally:
|
||
|
|
if reader:
|
||
|
|
loop.remove_reader(fileno)
|
||
|
|
if writer:
|
||
|
|
loop.remove_writer(fileno)
|
||
|
|
s = gen.send(ready)
|
||
|
|
|
||
|
|
except StopIteration as ex:
|
||
|
|
rv: RV = ex.args[0] if ex.args else None
|
||
|
|
return rv
|
||
|
|
|
||
|
|
|
||
|
|
async def wait_conn_async(gen: PQGenConn[RV], timeout: Optional[float] = None) -> RV:
|
||
|
|
"""
|
||
|
|
Coroutine waiting for a connection generator to complete.
|
||
|
|
|
||
|
|
:param gen: a generator performing database operations and yielding
|
||
|
|
(fd, `Ready`) pairs when it would block.
|
||
|
|
:param timeout: timeout (in seconds) to check for other interrupt, e.g.
|
||
|
|
to allow Ctrl-C. If zero or None, wait indefinitely.
|
||
|
|
:return: whatever `!gen` returns on completion.
|
||
|
|
|
||
|
|
Behave like in `wait()`, but take the fileno to wait from the generator
|
||
|
|
itself, which might change during processing.
|
||
|
|
"""
|
||
|
|
# Use an event to block and restart after the fd state changes.
|
||
|
|
# Not sure this is the best implementation but it's a start.
|
||
|
|
ev = Event()
|
||
|
|
loop = get_event_loop()
|
||
|
|
ready: Ready
|
||
|
|
s: Wait
|
||
|
|
|
||
|
|
def wakeup(state: Ready) -> None:
|
||
|
|
nonlocal ready
|
||
|
|
ready = state
|
||
|
|
ev.set()
|
||
|
|
|
||
|
|
try:
|
||
|
|
fileno, s = next(gen)
|
||
|
|
if not timeout:
|
||
|
|
timeout = None
|
||
|
|
while True:
|
||
|
|
reader = s & WAIT_R
|
||
|
|
writer = s & WAIT_W
|
||
|
|
if not reader and not writer:
|
||
|
|
raise e.InternalError(f"bad poll status: {s}")
|
||
|
|
ev.clear()
|
||
|
|
ready = 0 # type: ignore[assignment]
|
||
|
|
if reader:
|
||
|
|
loop.add_reader(fileno, wakeup, READY_R)
|
||
|
|
if writer:
|
||
|
|
loop.add_writer(fileno, wakeup, READY_W)
|
||
|
|
try:
|
||
|
|
await wait_for(ev.wait(), timeout)
|
||
|
|
finally:
|
||
|
|
if reader:
|
||
|
|
loop.remove_reader(fileno)
|
||
|
|
if writer:
|
||
|
|
loop.remove_writer(fileno)
|
||
|
|
fileno, s = gen.send(ready)
|
||
|
|
|
||
|
|
except TimeoutError:
|
||
|
|
raise e.ConnectionTimeout("connection timeout expired")
|
||
|
|
|
||
|
|
except StopIteration as ex:
|
||
|
|
rv: RV = ex.args[0] if ex.args else None
|
||
|
|
return rv
|
||
|
|
|
||
|
|
|
||
|
|
# Specialised implementation of wait functions.
|
||
|
|
|
||
|
|
|
||
|
|
def wait_select(gen: PQGen[RV], fileno: int, timeout: Optional[float] = None) -> RV:
|
||
|
|
"""
|
||
|
|
Wait for a generator using select where supported.
|
||
|
|
"""
|
||
|
|
try:
|
||
|
|
s = next(gen)
|
||
|
|
|
||
|
|
empty = ()
|
||
|
|
fnlist = (fileno,)
|
||
|
|
while True:
|
||
|
|
rl, wl, xl = select.select(
|
||
|
|
fnlist if s & WAIT_R else empty,
|
||
|
|
fnlist if s & WAIT_W else empty,
|
||
|
|
fnlist,
|
||
|
|
timeout,
|
||
|
|
)
|
||
|
|
ready = 0
|
||
|
|
if rl:
|
||
|
|
ready = READY_R
|
||
|
|
if wl:
|
||
|
|
ready |= READY_W
|
||
|
|
if not ready:
|
||
|
|
continue
|
||
|
|
# assert s & ready
|
||
|
|
s = gen.send(ready) # type: ignore
|
||
|
|
|
||
|
|
except StopIteration as ex:
|
||
|
|
rv: RV = ex.args[0] if ex.args else None
|
||
|
|
return rv
|
||
|
|
|
||
|
|
|
||
|
|
poll_evmasks: Dict[Wait, int]
|
||
|
|
|
||
|
|
if hasattr(selectors, "EpollSelector"):
|
||
|
|
poll_evmasks = {
|
||
|
|
WAIT_R: select.EPOLLONESHOT | select.EPOLLIN,
|
||
|
|
WAIT_W: select.EPOLLONESHOT | select.EPOLLOUT,
|
||
|
|
WAIT_RW: select.EPOLLONESHOT | select.EPOLLIN | select.EPOLLOUT,
|
||
|
|
}
|
||
|
|
else:
|
||
|
|
poll_evmasks = {}
|
||
|
|
|
||
|
|
|
||
|
|
def wait_epoll(gen: PQGen[RV], fileno: int, timeout: Optional[float] = None) -> RV:
|
||
|
|
"""
|
||
|
|
Wait for a generator using epoll where supported.
|
||
|
|
|
||
|
|
Parameters are like for `wait()`. If it is detected that the best selector
|
||
|
|
strategy is `epoll` then this function will be used instead of `wait`.
|
||
|
|
|
||
|
|
See also: https://linux.die.net/man/2/epoll_ctl
|
||
|
|
"""
|
||
|
|
try:
|
||
|
|
s = next(gen)
|
||
|
|
|
||
|
|
if timeout is None or timeout < 0:
|
||
|
|
timeout = 0
|
||
|
|
else:
|
||
|
|
timeout = int(timeout * 1000.0)
|
||
|
|
|
||
|
|
with select.epoll() as epoll:
|
||
|
|
evmask = poll_evmasks[s]
|
||
|
|
epoll.register(fileno, evmask)
|
||
|
|
while True:
|
||
|
|
fileevs = None
|
||
|
|
while not fileevs:
|
||
|
|
fileevs = epoll.poll(timeout)
|
||
|
|
ev = fileevs[0][1]
|
||
|
|
ready = 0
|
||
|
|
if ev & ~select.EPOLLOUT:
|
||
|
|
ready = READY_R
|
||
|
|
if ev & ~select.EPOLLIN:
|
||
|
|
ready |= READY_W
|
||
|
|
# assert s & ready
|
||
|
|
s = gen.send(ready)
|
||
|
|
evmask = poll_evmasks[s]
|
||
|
|
epoll.modify(fileno, evmask)
|
||
|
|
|
||
|
|
except StopIteration as ex:
|
||
|
|
rv: RV = ex.args[0] if ex.args else None
|
||
|
|
return rv
|
||
|
|
|
||
|
|
|
||
|
|
if _psycopg:
|
||
|
|
wait_c = _psycopg.wait_c
|
||
|
|
|
||
|
|
|
||
|
|
# Choose the best wait strategy for the platform.
|
||
|
|
#
|
||
|
|
# the selectors objects have a generic interface but come with some overhead,
|
||
|
|
# so we also offer more finely tuned implementations.
|
||
|
|
|
||
|
|
wait: WaitFunc
|
||
|
|
|
||
|
|
# Allow the user to choose a specific function for testing
|
||
|
|
if "PSYCOPG_WAIT_FUNC" in os.environ:
|
||
|
|
fname = os.environ["PSYCOPG_WAIT_FUNC"]
|
||
|
|
if not fname.startswith("wait_") or fname not in globals():
|
||
|
|
raise ImportError(
|
||
|
|
"PSYCOPG_WAIT_FUNC should be the name of an available wait function;"
|
||
|
|
f" got {fname!r}"
|
||
|
|
)
|
||
|
|
wait = globals()[fname]
|
||
|
|
|
||
|
|
elif _psycopg:
|
||
|
|
wait = wait_c
|
||
|
|
|
||
|
|
elif selectors.DefaultSelector is getattr(selectors, "SelectSelector", None):
|
||
|
|
# On Windows, SelectSelector should be the default.
|
||
|
|
wait = wait_select
|
||
|
|
|
||
|
|
elif selectors.DefaultSelector is getattr(selectors, "EpollSelector", None):
|
||
|
|
wait = wait_epoll
|
||
|
|
|
||
|
|
else:
|
||
|
|
wait = wait_selector
|