我们正在使用 JBoss 版本 7.0.2，其中托管了 6 个以上的 war 文件。在生产环境中，它工作正常，但有时在尝试连接数据库时会抛出异常“通信链路故障”。当异常持续出现时，CPU 负载会自动增加。
数据库- MYSQL，操作系统- UBUNTU。下面发布的是服务器日志、c3p0 配置和 JBoss 配置。
什么时候会抛出这个异常，在什么情况下？
C3p0:-
<entry key="hibernate.max_fetch_depth" value="3"> </entry>
<entry key="hibernate.hbm2ddl.auto" value="validate"></entry>
<entry key="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"></entry>
<entry key="hibernate.connection.url" value="${hibernate.connection.url}"></entry>
<entry key="hibernate.connection.username" value="${hibernate.connection.username}"></entry>
<entry key="hibernate.connection.password" value="${hibernate.connection.password}"></entry>
<entry key="hibernate.show_sql" value="true"></entry>
<entry key="hibernate.transaction.manager_lookup_class" value="org.hibernate.transaction.BTMTransactionManagerLookup"></entry>
<entry key="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"></entry>
<entry key="hibernate.connection.provider_class" value="org.hibernate.connection.C3P0ConnectionProvider"></entry>
<entry key="hibernate.c3p0.max_size" value="200"></entry>
<entry key="hibernate.c3p0.min_size" value="10"></entry>
<entry key="hibernate.c3p0.acquire_increment" value="100"></entry>
<entry key="hibernate.c3p0.idle_test_period" value="120"></entry>
<entry key="hibernate.c3p0.max_statements" value="2000"></entry>
<entry key="hibernate.c3p0.timeout" value="60"></entry>
<entry key="hibernate.c3p0.validate" value="true"></entry>
<entry key="hibernate.c3p0.unreturnedConnectionTimeout" value="600"></entry>
<entry key="hibernate.c3p0.debugUnreturnedConnectionStackTraces" value="true"></entry>
jBoss 配置：-
<connection-url>
jdbc:mysql://xxxx:3306/xxxx
</connection-url>
<driver>
com.mysql
</driver>
<transaction-isolation>
TRANSACTION_READ_COMMITTED
</transaction-isolation>
<pool>
<min-pool-size>
10
</min-pool-size>
<max-pool-size>
100
</max-pool-size>
<prefill>
false
</prefill>
<use-strict-min>
false
</use-strict-min>
<flush-strategy>
FailingConnectionOnly
</flush-strategy>
</pool>
<security>
<user-name>
xxxxx
</user-name>
<password>
xxxxx
</password>
</security>
<validation>
<check-valid-connection-sql>
select 1
</check-valid-connection-sql>
<validate-on-match>
true
</validate-on-match>
<background-validation>
false
</background-validation>
<use-fast-fail>
false
</use-fast-fail>
</validation>
<timeout>
<blocking-timeout-millis>
5000
</blocking-timeout-millis>
<idle-timeout-minutes>
60000
</idle-timeout-minutes>
<set-tx-query-timeout/>
</timeout>
<statement>
<prepared-statement-cache-size>
0
</prepared-statement-cache-size>
</statement>
服务器日志：-
21:14:02,016 WARNING [org.hibernate.util.JDBCExceptionReporter] (http-xxxx-1.1.1.1-8080-101) **SQL Error: 0, SQLState: 08S01**
21:14:02,017 SEVERE [org.hibernate.util.JDBCExceptionReporter] (http-xxxx-1.1.1.1-8080-101) **Communications link failure**
The last packet successfully received from the server was 63,109 milliseconds ago. The last packet sent successfully to the server was 63,108 milliseconds ago.
21:14:02,017 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) org.springframework.dao.DataAccessResourceFailureException: could not execute query; nested exception is org.hibernate.exception.JDBCConnectionException: could not execute query
21:14:02,018 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.springframework.orm.hibernate3.SessionFactoryUtils.convertHibernateAccessException(SessionFactoryUtils.java:631)
21:14:02,018 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.springframework.orm.hibernate3.HibernateAccessor.convertHibernateAccessException(HibernateAccessor.java:412)
21:14:02,018 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.springframework.orm.hibernate3.HibernateTemplate.doExecute(HibernateTemplate.java:411)
21:14:02,018 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.springframework.orm.hibernate3.HibernateTemplate.executeWithNativeSession(HibernateTemplate.java:374)
21:14:02,019 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.springframework.orm.hibernate3.HibernateTemplate.findByCriteria(HibernateTemplate.java:1046)
21:14:02,039 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:248)
21:14:02,039 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:198)
21:14:02,039 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
21:14:02,039 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:280)
21:14:02,040 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:248)
21:14:02,040 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:275)
21:14:02,040 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:161)
21:14:02,041 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.jboss.as.web.security.SecurityContextAssociationValve.invoke(SecurityContextAssociationValve.java:139)
21:14:02,041 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.jboss.as.web.NamingValve.invoke(NamingValve.java:57)
21:14:02,041 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.jboss.as.web.NamingValve.invoke(NamingValve.java:57)
21:14:02,041 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:154)
21:14:02,041 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
21:14:02,042 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
21:14:02,042 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:362)
21:14:02,042 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:877)
21:14:02,043 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:667)
21:14:02,055 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:952)
21:14:02,055 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at java.lang.Thread.run(Thread.java:745)
21:14:02,055 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) Caused by: org.hibernate.exception.JDBCConnectionException: could not execute query
21:14:02,056 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:99)
21:14:02,056 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
21:14:02,056 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.hibernate.loader.Loader.doList(Loader.java:2545)
21:14:02,056 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2276)
21:14:02,057 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.hibernate.loader.Loader.list(Loader.java:2271)
21:14:02,057 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:119)
21:14:02,057 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1716)
21:14:02,057 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:347)
21:14:02,057 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.springframework.orm.hibernate3.HibernateTemplate$36.doInHibernate(HibernateTemplate.java:1056)
21:14:02,058 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.springframework.orm.hibernate3.HibernateTemplate$36.doInHibernate(HibernateTemplate.java:1)
21:14:02,058 ERROR [stderr] (http-xxxx-1.1.1.1-8080-101) at org.springframework.orm.hibernate3.HibernateTemplate.doExecute(HibernateTemplate.java:406)