WSO2 EI Docker容器连接Amazon RDS PostgreSQL间歇性UnknownHostException求助

在WSO2 EI 6.4.0 Docker容器中使用Amazon RDS（PostgreSQL）进行数据库操作时，大部分场景正常，但间歇性抛出java.net.UnknownHostException，无法解析RDS主机yyyy.xxx.us-west-1.rds.amazonaws.com。

完整异常堆栈 #

[2024-03-25 04:30:08,007] [-1234] [] [pool-28-thread-16661] ERROR {org.apache.synapse.mediators.db.DBLookupMediator} -  SQL Exception occurred while executing statement : select column1,column2 from schema.tabel_name where task_name=? against DataSource : jdbc/DSETL
org.postgresql.util.PSQLException: The connection attempt failed.
    at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:354)
    at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:54)
    at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:263)
    at org.postgresql.Driver.makeConnection(Driver.java:444)
    at org.postgresql.Driver.connect(Driver.java:297)
    at org.apache.tomcat.jdbc.pool.PooledConnection.connectUsingDriver(PooledConnection.java:278)
    at org.apache.tomcat.jdbc.pool.PooledConnection.connect(PooledConnection.java:182)
    at org.apache.tomcat.jdbc.pool.ConnectionPool.createConnection(ConnectionPool.java:730)
    at org.apache.tomcat.jdbc.pool.ConnectionPool.borrowConnection(ConnectionPool.java:664)
    at org.apache.tomcat.jdbc.pool.ConnectionPool.getConnection(ConnectionPool.java:200)
    at org.apache.tomcat.jdbc.pool.DataSourceProxy.getConnection(DataSourceProxy.java:128)
    at org.apache.synapse.mediators.db.DBLookupMediator.processStatement(DBLookupMediator.java:58)
    at org.apache.synapse.mediators.db.AbstractDBMediator.mediate(AbstractDBMediator.java:233)
    at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:108)
    at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:70)
    at org.apache.synapse.config.xml.AnonymousListMediator.mediate(AnonymousListMediator.java:37)
    at org.apache.synapse.config.xml.SwitchCase.mediate(SwitchCase.java:69)
    at org.apache.synapse.mediators.filters.SwitchMediator.mediate(SwitchMediator.java:134)
    at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:108)
    at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:70)
    at org.apache.synapse.mediators.filters.FilterMediator.mediate(FilterMediator.java:169)
    at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:108)
    at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:70)
    at org.apache.synapse.mediators.template.TemplateMediator.mediate(TemplateMediator.java:104)
    at org.apache.synapse.mediators.template.InvokeMediator.mediate(InvokeMediator.java:148)
    at org.apache.synapse.mediators.template.InvokeMediator.mediate(InvokeMediator.java:84)
    at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:108)
    at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:70)
    at org.apache.synapse.mediators.base.SequenceMediator.mediate(SequenceMediator.java:158)
    at org.apache.synapse.core.axis2.ProxyServiceMessageReceiver.receive(ProxyServiceMessageReceiver.java:224)
    at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:180)
    at org.apache.synapse.startup.tasks.MessageInjector.execute(MessageInjector.java:321)
    at org.wso2.carbon.mediation.ntask.NTaskAdapter.execute(NTaskAdapter.java:98)
    at org.wso2.carbon.ntask.core.impl.TaskQuartzJobAdapter.execute(TaskQuartzJobAdapter.java:67)
    at org.quartz.core.JobRunShell.run(JobRunShell.java:213)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)
Caused by: java.net.UnknownHostException: yyyy.xxx.us-west-1.rds.amazonaws.com
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:184)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
    at java.net.Socket.connect(Socket.java:589)
    at org.postgresql.core.PGStream.createSocket(PGStream.java:243)
    at org.postgresql.core.PGStream.<init>(PGStream.java:98)
    at org.postgresql.core.v3.ConnectionFactoryImpl.tryConnect(ConnectionFactoryImpl.java:132)
    at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:258)
    ... 39 more

已尝试的修复步骤 #

• 将PostgreSQL驱动版本从42.2.0升级至42.7.0
• 在CAR项目的pom.xml中添加以下依赖并重新部署：

  <dependency>
  <groupId>org.postgresql</groupId>
  <artifactId>postgresql</artifactId>
  <version>42.7.0</version>
  </dependency>
  

问题仍间歇性出现，以下是可行的解决思路：

解决思路 #

1. 排查DNS解析稳定性 #

• 在Docker容器内部间歇性执行nslookup yyyy.xxx.us-west-1.rds.amazonaws.com或dig yyyy.xxx.us-west-1.rds.amazonaws.com，确认DNS解析是否存在失败情况
• 修改Docker容器/etc/resolv.conf，更换为更可靠的DNS服务器（如AWS内部DNS、8.8.8.8）
• 调整JVM参数缩短DNS缓存时间：添加-Dnetworkaddress.cache.ttl=60，避免缓存过期的DNS记录

2. 优化数据库连接池配置 #

针对数据源jdbc/DSETL调整以下参数：

• 配置validationQuery=SELECT 1，开启testOnBorrow=true，确保每次获取连接时验证有效性
• 调整timeBetweenEvictionRunsMillis和minEvictableIdleTimeMillis，定期清理空闲无效连接
• 设置maxWait参数，避免线程无限等待连接

3. 验证网络连通性 #

• 检查Docker容器所在VPC与RDS实例的网络规则，确认无间歇性防火墙/安全组变更
• 查看AWS RDS监控指标（CPU、连接数、网络流量），排查实例是否存在临时性能瓶颈
• 在容器内持续执行ping yyyy.xxx.us-west-1.rds.amazonaws.com或telnet yyyy.xxx.us-west-1.rds.amazonaws.com 5432，记录丢包或超时情况

4. 确认驱动加载优先级 #

• 检查WSO2 EI容器<EI_HOME>/repository/components/lib目录，确保仅存在postgresql-42.7.0.jar，无旧版本驱动
• 验证CAR包部署后，驱动是否正确覆盖容器内的旧文件

5. 启用详细日志排查 #

• 在WSO2 EI的log4j.properties中开启PostgreSQL驱动DEBUG日志，或DNS解析相关日志，定位失败触发条件
• 关联异常发生时间与AWS云监控事件，排查是否存在关联触发因素

内容的提问来源于stack exchange，提问作者Justin