think3.1+dwz的系统缓存意思写入失败，权限和磁盘空间查了都没有问题。
删除缓存可以正常运行一段时间，然后又出现这个错误。
移植到新的ubuntu系统，正常了半个月，就出现这种情况。
回复讨论(解决方案)
这分明是连接 mysql 失败
重新启动ubuntu就可以了
检查一下错误日志看看
应该是你的mysql服务 停止了，或者是被另外的程序占用了。
mysql 错误日志信息
140807 9:44:59 [Warning] Using unique option prefix myisam-recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead.140807 9:44:59 [Note] Plugin 'FEDERATED' is disabled.140807 9:44:59 InnoDB: The InnoDB memory heap is disabled140807 9:44:59 InnoDB: Mutexes and rw_locks use GCC atomic builtins140807 9:44:59 InnoDB: Compressed tables use zlib 1.2.3.4140807 9:44:59 InnoDB: Initializing buffer pool, size = 128.0M140807 9:44:59 InnoDB: Completed initialization of buffer pool140807 9:44:59 InnoDB: highest supported file format is Barracuda.140807 9:44:59 InnoDB: Waiting for the background threads to start140807 9:40:10 InnoDB: 5.5.38 started; log sequence number 2477014140807 9:40:10 [Note] Server hostname (bind-address): '127.0.0.1'; port: 3306140807 9:40:10 [Note] - '127.0.0.1' resolves to '127.0.0.1';140807 9:40:10 [Note] Server socket created on IP: '127.0.0.1'.140807 9:40:10 [Note] Event Scheduler: Loaded 0 events140807 9:40:10 [Note] /usr/sbin/mysqld: ready for connections.Version: '5.5.38-0ubuntu0.12.04.1' socket: '/var/run/mysqld/mysqld.sock' port: 3306 (Ubuntu)
应该是你的mysql服务 停止了，或者是被另外的程序占用了。
查看mysql是启动的，早上又出现这种情况，有重启了一次。
Apache错误日志
[Thu Aug 07 09:44:29 2014] [warn] child process 1331 still did not exit, sending a SIGTERM[Thu Aug 07 09:44:29 2014] [warn] child process 2069 still did not exit, sending a SIGTERM[Thu Aug 07 09:44:29 2014] [warn] child process 2070 still did not exit, sending a SIGTERM[Thu Aug 07 09:44:31 2014] [notice] caught SIGTERM, shutting down[Thu Aug 07 09:44:59 2014] [notice] Apache/2.2.22 (Ubuntu) PHP/5.3.10-1ubuntu3.13 with Suhosin-Patch configured -- resuming normal operations[Thu Aug 07 09:45:59 2014] [error] [client 116.22.142.9] File does not exist: /var/www/dx/default, referer: http://218.20.201.217/index/system2.html[Thu Aug 07 09:46:00 2014] [error] [client 116.22.142.9] File does not exist: /var/www/dx/default, referer: http://218.20.201.217/index/system2.html[Thu Aug 07 09:46:08 2014] [error] [client 116.22.142.9] PHP Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 40961 bytes) in /var/www/dx/Library/Common/common.php on line 684, referer: http://218.20.201.217/index/system2.html[Thu Aug 07 09:46:22 2014] [error] [client 116.22.142.9] File does not exist: /var/www/dx/default, referer: http://218.20.201.217/index/system2.html[Thu Aug 07 09:51:37 2014] [error] [client 116.22.142.9] PHP Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 40961 bytes) in /var/www/dx/Library/Common/common.php on line 684, referer: http://218.20.201.217/index/system2.html[Thu Aug 07 09:51:48 2014] [error] [client 116.22.142.9] File does not exist: /var/www/dx/default, referer: http://218.20.201.217/index/system2.html
难道是传说中的假死。
应该是你的mysql服务 停止了，或者是被另外的程序占用了。
查看mysql是启动的，早上又出现这种情况，有重启了一次。
mysql 重新安装，最好的解决办法
内存不够了
找到原因了，查到磁盘被 mysql-bin.00001文件删除占用的很大的空间 ，删除掉这些文件，重启mysql出现这种情况，再删除mysql-bin.index重启一下就没事了