tomcat意外停止，大神帮忙看下日志?报错

上午9点23分，网站访问不了，这是tomcat的日志：

Aug 3, 2015 12:06:18 AM org.apache.coyote.http11.AbstractHttp11Processor process
INFO: Error parsing HTTP request header
 Note: further occurrences of HTTP header parsing errors will be logged at DEBUG level.
Aug 3, 2015 1:43:32 AM org.apache.coyote.http11.AbstractHttp11Processor process
INFO: Error parsing HTTP request header
 Note: further occurrences of HTTP header parsing errors will be logged at DEBUG level.
Aug 3, 2015 3:24:12 AM org.apache.coyote.http11.AbstractHttp11Processor process
INFO: Error parsing HTTP request header
 Note: further occurrences of HTTP header parsing errors will be logged at DEBUG level.
Aug 3, 2015 5:15:39 AM org.apache.coyote.http11.AbstractHttp11Processor process
INFO: Error parsing HTTP request header
 Note: further occurrences of HTTP header parsing errors will be logged at DEBUG level.
Aug 3, 2015 9:00:03 AM org.apache.coyote.http11.AbstractHttp11Processor process
INFO: Error parsing HTTP request header
 Note: further occurrences of HTTP header parsing errors will be logged at DEBUG level.
Aug 3, 2015 9:33:15 AM org.apache.coyote.AbstractProtocol pause
INFO: Pausing ProtocolHandler ["http-bio-80"]
Aug 3, 2015 9:33:16 AM org.apache.coyote.AbstractProtocol pause
INFO: Pausing ProtocolHandler ["ajp-bio-8009"]
Aug 3, 2015 9:33:18 AM org.apache.catalina.core.StandardService stopInternal
INFO: Stopping service Catalina
Aug 3, 2015 9:33:18 AM org.apache.catalina.core.StandardWrapper unload
INFO: Waiting for 198 instance(s) to be deallocated for Servlet [default]
Aug 3, 2015 9:33:19 AM org.apache.catalina.core.StandardWrapper unload
INFO: Waiting for 198 instance(s) to be deallocated for Servlet [default]
Aug 3, 2015 9:33:20 AM org.apache.catalina.core.StandardWrapper unload
INFO: Waiting for 198 instance(s) to be deallocated for Servlet [default]
Aug 3, 2015 9:33:20 AM org.apache.catalina.loader.WebappClassLoader clearReferencesJdbc
SEVERE: The web application [] registered the JDBC driver [com.mysql.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
Aug 3, 2015 9:33:20 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [] is still processing a request that has yet to finish. This is very likely to create a memory leak. You can control the time allowed for requests to finish by using the unloadDelay attribute of the standard Context implementation.
Aug 3, 2015 9:33:20 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [] is still processing a request that has yet to finish. This is very likely to create a memory leak. You can control the time allowed for requests to finish by using the unloadDelay attribute of the standard Context implementation.
Aug 3, 2015 9:33:20 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [] is still processing a request that has yet to finish. This is very likely to create a memory leak. You can control the time allowed for requests to finish by using the unloadDelay attribute of the standard Context implementation.
Aug 3, 2015 9:33:20 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [] is still processing a request that has yet to finish. This is very likely to create a memory leak. You can control the time allowed for requests to finish by using the unloadDelay attribute of the standard Context implementation.
Aug 3, 2015 9:33:20 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [] is still processing a request that has yet to finish. This is very likely to create a memory leak. You can control the time allowed for requests to finish by using the unloadDelay attribute of the standard Context implementation.
Aug 3, 2015 9:33:20 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [] is still processing a request that has yet to finish. This is very likely to create a memory leak. You can control the time allowed for requests to finish by using the unloadDelay attribute of the standard Context implementation.

:java.net.connectexception: connection timed out

重启服务器恢复正常

这是什么原因？