/usr/share/pyshared/pylibmc/pools.py is in python-pylibmc 1.2.3-1.
This file is owned by root:root, with mode 0o644.
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from __future__ import with_statement
from contextlib import contextmanager
from Queue import Queue
class ClientPool(Queue):
"""Client pooling helper.
This is mostly useful in threaded environments, because a client isn't
thread-safe at all. Instead, what you want to do is have each thread use
its own client, but you don't want to reconnect these all the time.
The solution is a pool, and this class is a helper for that.
>>> from pylibmc.test import make_test_client
>>> mc = make_test_client()
>>> pool = ClientPool()
>>> pool.fill(mc, 4)
>>> with pool.reserve() as mc:
... mc.set("hi", "ho")
... mc.delete("hi")
...
True
True
"""
def __init__(self, mc=None, n_slots=None):
Queue.__init__(self, n_slots)
if mc is not None:
self.fill(mc, n_slots)
@contextmanager
def reserve(self, block=False):
"""Context manager for reserving a client from the pool.
If *block* is given and the pool is exhausted, the pool waits for
another thread to fill it before returning.
"""
mc = self.get(block)
try:
yield mc
finally:
self.put(mc)
def fill(self, mc, n_slots):
"""Fill *n_slots* of the pool with clones of *mc*."""
for i in xrange(n_slots):
self.put(mc.clone())
class ThreadMappedPool(dict):
"""Much like the *ClientPool*, helps you with pooling.
In a threaded environment, you'd most likely want to have a client per
thread. And there'd be no harm in one thread keeping the same client at all
times. So, why not map threads to clients? That's what this class does.
If a client is reserved, this class checks for a key based on the current
thread, and if none exists, clones the master client and inserts that key.
Of course this requires that you let the pool know when a thread is done
with its reserved instance, so therefore ``relinquish`` must be called
before thread exit.
>>> from pylibmc.test import make_test_client
>>> mc = make_test_client()
>>> pool = ThreadMappedPool(mc)
>>> with pool.reserve() as mc:
... mc.set("hi", "ho")
... mc.delete("hi")
...
True
True
"""
def __new__(cls, master):
return super(ThreadMappedPool, cls).__new__(cls)
def __init__(self, master):
self.master = master
@property
def current_key(self):
return thread.get_ident()
@contextmanager
def reserve(self):
"""Reserve a client.
Creates a new client based on the master client if none exists for the
current thread.
"""
key = self.current_key
mc = self.pop(key, None)
if mc is None:
mc = self.master.clone()
try:
yield mc
finally:
self[key] = mc
def relinquish(self):
"""Relinquish any reserved client for the current context.
Call this method before exiting a thread if it might potentially use
this pool.
"""
return self.pop(self.current_key, None)
# This makes sure ThreadMappedPool doesn't exist with non-thread Pythons.
try:
import thread
except ImportError:
ThreadMappedPool = None
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