mpdaio/connection.py

   1 # -*- coding: utf-8 -*-
   2 # SPDX-FileCopyrightText: 2012-2024  kaliko <kaliko@azylum.org>
   3 # SPDX-License-Identifier: LGPL-3.0-or-later
   4 """https://stackoverflow.com/questions/55879847/asyncio-how-to-reuse-a-socket#%E2%80%A6
   5 """
   6
   7 import asyncio
   8 import contextlib
   9 import logging
  10
  11 from collections import OrderedDict
  12 from types import TracebackType
  13 from typing import Any, List, Optional, Tuple, Type
  14
  15 from . import HELLO_PREFIX
  16 from .exceptions import MPDProtocolError
  17
  18 try:  # Python 3.7
  19     base = contextlib.AbstractAsyncContextManager
  20 except AttributeError as err:
  21     base = object  # type: ignore
  22
  23 Server = str
  24 Port = int
  25 Host = Tuple[Server, Port]
  26 log = logging.getLogger(__name__)
  27
  28
  29 class ConnectionPool(base):
  30     def __init__(
  31         self,
  32         max_connections: int = 1000,
  33         loop: Optional[asyncio.AbstractEventLoop] = None,
  34     ):
  35         self.max_connections = max_connections
  36         self._loop = loop or asyncio.get_event_loop()
  37
  38         self._connections: OrderedDict[Host,
  39                                        List["Connection"]] = OrderedDict()
  40         self._semaphore = asyncio.Semaphore(max_connections)
  41
  42     async def connect(self, server: Server, port: Port, timeout: int) -> "Connection":
  43         host = (server, port)
  44
  45         # enforce the connection limit, releasing connections notifies
  46         # the semaphore to release here
  47         await self._semaphore.acquire()
  48
  49         connections = self._connections.setdefault(host, [])
  50         log.debug('got %s in pool', len(connections))
  51         # find an un-used connection for this host
  52         connection = next(
  53             (conn for conn in connections if not conn.in_use), None)
  54         #if connection:
  55         #    log.debug('reusing %s', connection)
  56         if connection is None:
  57             # disconnect the least-recently-used un-used connection to make space
  58             # for a new connection. There will be at least one.
  59             for conns_per_host in reversed(self._connections.values()):
  60                 for conn in conns_per_host:
  61                     if not conn.in_use:
  62                         await conn.close()
  63                         break
  64
  65             log.debug('about to connect %s', host)
  66             reader, writer = await asyncio.wait_for(
  67                     asyncio.open_connection(server, port),
  68                     timeout
  69                     )
  70             #log.debug('Connected to %s:%s', host[0], host[1])
  71             connection = Connection(self, host, reader, writer)
  72             await connection._hello()
  73             connections.append(connection)
  74
  75         connection.in_use = True
  76         # move current host to the front as most-recently used
  77         self._connections.move_to_end(host, False)
  78         log.debug('connection %s in use', connection)
  79
  80         return connection
  81
  82     async def close(self):
  83         """Close all connections"""
  84         connections = [c for cs in self._connections.values() for c in cs]
  85         self._connections = OrderedDict()
  86         log.info('Closing all connections')
  87         for connection in connections:
  88             await connection.close()
  89
  90     def _remove(self, connection):
  91         conns_for_host = self._connections.get(connection._host)
  92         if not conns_for_host:
  93             return
  94         conns_for_host[:] = [c for c in conns_for_host if c != connection]
  95
  96     def _notify_release(self):
  97         self._semaphore.release()
  98
  99     async def __aenter__(self) -> "ConnectionPool":
 100         return self
 101
 102     async def __aexit__(
 103         self,
 104         exc_type: Optional[Type[BaseException]],
 105         exc: Optional[BaseException],
 106         tb: Optional[TracebackType],
 107     ) -> None:
 108         await self.close()
 109
 110     def __del__(self) -> None:
 111         connections = [repr(c)
 112                        for cs in self._connections.values() for c in cs]
 113         if not connections:
 114             return
 115
 116         context = {
 117             "pool": self,
 118             "connections": connections,
 119             "message": "Unclosed connection pool",
 120         }
 121         self._loop.call_exception_handler(context)
 122
 123
 124 class Connection(base):
 125     def __init__(
 126         self,
 127         pool: ConnectionPool,
 128         host: Host,
 129         reader: asyncio.StreamReader,
 130         writer: asyncio.StreamWriter,
 131     ):
 132         self._host = host
 133         self._pool = pool
 134         self._reader = reader
 135         self._writer = writer
 136         self._closed = False
 137         self.in_use = False
 138
 139     def __repr__(self):
 140         host = f"{self._host[0]}:{self._host[1]}"
 141         return f"Connection<{host}>#{id(self)}"
 142
 143     @property
 144     def closed(self):
 145         return self._closed
 146
 147     def release(self) -> None:
 148         logging.debug('releasing %r', self)
 149         self.in_use = False
 150         self._pool._notify_release()
 151
 152     async def close(self) -> None:
 153         if self._closed:
 154             return
 155         logging.debug('closing %r', self)
 156         self._closed = True
 157         self._writer.close()
 158         self._pool._remove(self)
 159         try:
 160             await self._writer.wait_closed()
 161         except AttributeError:  # wait_closed is new in 3.7
 162             pass
 163
 164     async def _hello(self) -> None:
 165         """Consume HELLO_PREFIX"""
 166         self.in_use = True
 167         data = await self.readuntil(b'\n')
 168         rcv = data.decode('utf-8')
 169         if not rcv.startswith(HELLO_PREFIX):
 170             raise MPDProtocolError(f'Got invalid MPD hello: "{rcv}"')
 171         log.debug('consumed hello prefix: %r', rcv)
 172         self.version = rcv.split('\n')[0][len(HELLO_PREFIX):]
 173         log.info('protocol version: %s', self.version)
 174
 175
 176     def __getattr__(self, name: str) -> Any:
 177         """All unknown attributes are delegated to the reader and writer"""
 178         if self._closed or not self.in_use:
 179             raise ValueError("Can't use a closed or unacquired connection")
 180         if hasattr(self._reader, name):
 181             return getattr(self._reader, name)
 182         return getattr(self._writer, name)
 183
 184     async def __aenter__(self) -> "Connection":
 185         if self._closed or not self.in_use:
 186             raise ValueError("Can't use a closed or unacquired connection")
 187         return self
 188
 189     async def __aexit__(
 190         self,
 191         exc_type: Optional[Type[BaseException]],
 192         exc: Optional[BaseException],
 193         tb: Optional[TracebackType],
 194     ) -> None:
 195         self.release()
 196
 197     def __del__(self) -> None:
 198         if self._closed:
 199             return
 200         context = {"connection": self, "message": "Unclosed connection"}
 201         self._pool._loop.call_exception_handler(context)