pylibmc:'断言" ptr-> query_id == query_id +1'函数“"memcached_get_by_key""失败 [英] pylibmc: 'Assertion "ptr->query_id == query_id +1" failed for function "memcached_get_by_key"'

问题描述

我有一个python网络应用程序，该应用程序使用 pylibmc模块连接到内存缓存服务器.如果我每秒对请求进行一次或更慢的测试，则一切正常.但是，如果我每秒发送多个请求，则我的应用程序崩溃，并且我在日志中看到以下内容:

I have a python web app that uses the pylibmc module to connect to a memcached server. If I test my app with requests once per second or slower, everything works fine. If I send more than one request per second, however, my app crashes and I see the following in my logs:

函数"memcached_get_by_key"的断言"ptr-> query_id == query_id +1"失败，可能是程序员错误，query_id未增加."，位于libmemcached/get.cc:107

Assertion "ptr->query_id == query_id +1" failed for function "memcached_get_by_key" likely for "Programmer error, the query_id was not incremented.", at libmemcached/get.cc:107

函数"memcached_get_by_key"的断言"ptr-> query_id == query_id +1"失败，可能是程序员错误，query_id未增加."，位于libmemcached/get.cc:89

Assertion "ptr->query_id == query_id +1" failed for function "memcached_get_by_key" likely for "Programmer error, the query_id was not incremented.", at libmemcached/get.cc:89

任何想法出了什么问题或如何解决?

Any idea what's going wrong or how to fix it?

我的代码如下:

self.mc = pylibmc.Client(
    servers=[os.environ.get(MEMCACHE_SERVER_VAR)],
    username=os.environ.get(MEMCACHE_USER_VAR),
    password=os.environ.get(MEMCACHE_PASS_VAR),
    binary=True
    )

#...

if (self.mc != None):
    self.mc.set(key, stored_data)

#...

page = self.mc.get(key)

推荐答案

这是线程问题. pylibmc客户端不是线程安全的.您应该将代码转换为使用 ThreadMappedPool对象以确保您为每个线程保持单独的连接.像这样:

This is a threading issue. pylibmc clients are not thread-safe. You should convert your code to use a ThreadMappedPool object to ensure you keep a separate connection for each thread. Something like this:

mc = pylibmc.Client(
    servers=[os.environ.get(MEMCACHE_SERVER_VAR)],
    username=os.environ.get(MEMCACHE_USER_VAR),
    password=os.environ.get(MEMCACHE_PASS_VAR),
    binary=True
    )
self.pool = pylibmc.ThreadMappedPool(mc)

#...

if (self.pool != None):
    with self.pool.reserve() as mc:
        mc.set(key, stored_data)

#...

if (self.pool != None):
    with self.pool.reserve() as mc:
        page = mc.get(key)

请确保在线程完成后(可能在析构函数中)调用self.pool.relinquish()！

Make sure to call self.pool.relinquish() when the thread is finished, possibly in the destructor!

(在我的情况下，发生这种情况是因为我使用 cherrypy 作为我的网络服务器，而cherrypy分别产生了10个默认情况下可以处理请求的线程.)

(In my case this happened because I was using cherrypy as my web server, and cherrypy spawns 10 separate threads to serve requests by default.)

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