generic-connection-pool 0.2.0

Installation

You can install generic-connection-pool with pip:

$ pip install generic-connection-pool

Quickstart

The following example illustrates how to create asynchronous ssl socket pool:

import asyncio
from typing import Tuple

from generic_connection_pool.asyncio import ConnectionPool
from generic_connection_pool.contrib.socket_async import TcpStreamConnectionManager

Hostname = str
Port = int
Endpoint = Tuple[Hostname, Port]
Connection = Tuple[asyncio.StreamReader, asyncio.StreamWriter]


async def main() -> None:
    pool = ConnectionPool[Endpoint, Connection](
        TcpStreamConnectionManager(ssl=True),
        idle_timeout=30.0,
        max_lifetime=600.0,
        min_idle=3,
        max_size=20,
        total_max_size=100,
        background_collector=True,
    )

    async with pool.connection(endpoint=('www.wikipedia.org', 443), timeout=5.0) as (reader, writer):
        request = (
            'GET / HTTP/1.0\n'
            'Host: www.wikipedia.org\n'
            '\n'
            '\n'
        )
        writer.write(request.encode())
        await writer.drain()
        response = await reader.read()

        print(response.decode())

asyncio.run(main())

Configuration

Synchronous and asynchronous pools supports the following parameters:

• connection_manager: connection manager instance

• acquire_timeout: connection acquiring default timeout

• dispose_batch_size: number of connections to be disposed at once (if background collector is started the parameter is ignored)

• dispose_timeout: connection disposal timeout

• background_collector: start worker that disposes timed-out connections in background maintain provided pool state otherwise they will be disposed on each connection release

• idle_timeout: number of seconds after which a connection will be closed respecting min_idle parameter (the connection will be closed only if the connection number exceeds min_idle)

• max_lifetime: number of seconds after which a connection will be closed (min_idle parameter will be ignored)

• min_idle: minimum number of connections the pool tries to hold (for each endpoint)

• max_size: maximum number of connections (for each endpoint)

• total_max_size: maximum number of connections (for all endpoints)

Generic nature

Since the pool has generic nature is can be used for database connections as well:

import psycopg2.extensions

from generic_connection_pool.contrib.psycopg2 import DbConnectionManager
from generic_connection_pool.threding import ConnectionPool

Endpoint = str
Connection = psycopg2.extensions.connection


def main() -> None:
    dsn_params = dict(dbname='postgres', user='postgres', password='secret')

    pool = ConnectionPool[Endpoint, Connection](
        DbConnectionManager(
            dsn_params={
                'master': dict(dsn_params, host='db-master.local'),
                'replica-1': dict(dsn_params, host='db-replica-1.local'),
                'replica-2': dict(dsn_params, host='db-replica-2.local'),
            },
        ),
        acquire_timeout=2.0,
        idle_timeout=60.0,
        max_lifetime=600.0,
        min_idle=3,
        max_size=10,
        total_max_size=15,
        background_collector=True,
    )

    with pool.connection(endpoint='master') as conn:
        cur = conn.cursor()
        cur.execute("SELECT * FROM pg_stats;")
        print(cur.fetchone())

    with pool.connection(endpoint='replica-1') as conn:
        cur = conn.cursor()
        cur.execute("SELECT * FROM pg_stats;")
        print(cur.fetchone())

    pool.close()


main()

Extendability

If built-in connection managers are not suitable for your task the one can be easily created by yourself:

import socket
from ssl import SSLContext, SSLSocket
from typing import Optional, Tuple

from generic_connection_pool.threding import BaseConnectionManager, ConnectionPool

Hostname = str
Port = int
SslEndpoint = Tuple[Hostname, Port]
Connection = SSLSocket


class SslSocketConnectionManager(BaseConnectionManager[SslEndpoint, Connection]):
    """
    SSL socket connection manager.
    """

    def __init__(self, ssl: SSLContext):
        self._ssl = ssl

    def create(self, endpoint: SslEndpoint, timeout: Optional[float] = None) -> Connection:
        hostname, port = endpoint

        sock = self._ssl.wrap_socket(socket.socket(type=socket.SOCK_STREAM), server_hostname=hostname)
        sock.settimeout(timeout)
        sock.connect((hostname, port))

        return sock

    def dispose(self, endpoint: SslEndpoint, conn: Connection, timeout: Optional[float] = None) -> None:
        conn.settimeout(timeout)
        try:
            conn.shutdown(socket.SHUT_RDWR)
        except OSError:
            pass

        conn.close()


def main() -> None:
    pool = ConnectionPool[SslEndpoint, Connection](
        SslSocketConnectionManager(ssl=SSLContext()),
        idle_timeout=30.0,
        max_lifetime=600.0,
        min_idle=3,
        max_size=20,
        total_max_size=100,
        background_collector=True,
    )

    with pool.connection(endpoint=('www.wikipedia.org', 443), timeout=5.0) as sock:
        request = (
            'GET / HTTP/1.0\n'
            'Host: www.wikipedia.org\n'
            '\n'
            '\n'
        )
        sock.write(request.encode())
        response = []
        while chunk := sock.recv():
            response.append(chunk)

        print(b''.join(response).decode())

    pool.close()


main()