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OOM command not allowed when used memory > ‘maxmemory’ 报错排查

grep “OOM command not allowed when used memory > ‘maxmemory'” * -r
src/redis.c: “-OOM command not allowed when used memory > ‘maxmemory’.\r\n”));

查看src/redis.c

    shared.oomerr = createObject(REDIS_STRING,sdsnew(
    "-OOM command not allowed when used memory > 'maxmemory'.\r\n"));

    。。。

/* Handle the maxmemory directive.
*
* First we try to free some memory if possible (if there are volatile
* keys in the dataset). If there are not the only thing we can do
* is returning an error. */
if (server.maxmemory) {
 int retval = freeMemoryIfNeeded();
 if ((c->cmd->flags & REDIS_CMD_DENYOOM) && retval == REDIS_ERR) {
     flagTransaction(c);
    addReply(c, shared.oomerr);
    return REDIS_OK;
}
}

从代码确认报这个错，大概是内存达到最大限时不能释放出来内存报的错。

做一个简单的验证：

配置一个10M大小的Redis，利用一个python程序往里面写数据，很快得到报错：

#python t_redis.py 
Traceback (most recent call last):
  File "t_redis.py", line 21, in <module>
 start()
File "t_redis.py", line 15, in start
  s = r.set(key, v1)
File "/usr/lib/python2.6/site-packages/redis/client.py", line 647, in set
return self.execute_command('SET', name, value)
File "/usr/lib/python2.6/site-packages/redis/client.py", line 330, in execute_command
**options
File "/usr/lib/python2.6/site-packages/redis/client.py", line 312, in _execute_command
return self.parse_response(command_name, **options)
File "/usr/lib/python2.6/site-packages/redis/client.py", line 390, in parse_response
    response = self._parse_response(command_name, catch_errors)
File "/usr/lib/python2.6/site-packages/redis/client.py", line 349, in _parse_response
 raise ResponseError(response)
redis.exceptions.ResponseError: OOM command not allowed when used memory > 'maxmemory'.

结论：

1. Redis运行中监控内存的使用情况.
2. 如果只做缓存使用，需要配置上lru策略，如

    maxmemory-policy allkeys-lru
    maxmemory-samples 5
   

   如果做持久化存储说明，内存也不够用了。需要考虑增加内存。

3. 故障现场要看一下Redis的info输出，看看内存配是否达到了上限。