重新创建数据库容器时，Debezium 源任务无法重新连接到 postgresql 数据库

Question

我们有一个 kubernetes 集群，其中 Debezium 作为来自 Postgresql 的源任务运行并写入 kafka。 Debezium、postgres 和 kafka 都在不同的 pod 中运行。 当 postgres pod 被删除并且 kubernetes 重新创建 pod 时，debezium pod 无法重新连接。 来自 debezium pod 的日志：

    2018-07-17 08:31:38,311 ERROR  ||  WorkerSourceTask{id=inventory-connector-0} Task is being killed and will not recover until manually restarted   [org.apache.kafka.connect.runtime.WorkerTask]
    2018-07-17 08:31:38,311 INFO   ||  [Producer clientId=producer-4] Closing the Kafka producer with timeoutMillis = 30000 ms.   [org.apache.kafka.clients.producer.KafkaProducer]

Debezium 会继续尝试每隔一段时间刷新未完成的消息，但会出现以下异常：

    2018-07-17 08:32:38,167 ERROR  ||  WorkerSourceTask{id=inventory-connector-0} Exception thrown while calling task.commit()   [org.apache.kafka.connect.runtime.WorkerSourceTask]
    org.apache.kafka.connect.errors.ConnectException: org.postgresql.util.PSQLException: Database connection failed when writing to copy
    at io.debezium.connector.postgresql.RecordsStreamProducer.commit(RecordsStreamProducer.java:151)
    at io.debezium.connector.postgresql.PostgresConnectorTask.commit(PostgresConnectorTask.java:138)
    at org.apache.kafka.connect.runtime.WorkerSourceTask.commitSourceTask(WorkerSourceTask.java:437)
    at org.apache.kafka.connect.runtime.WorkerSourceTask.commitOffsets(WorkerSourceTask.java:378)
    at org.apache.kafka.connect.runtime.SourceTaskOffsetCommitter.commit(SourceTaskOffsetCommitter.java:108)
    at org.apache.kafka.connect.runtime.SourceTaskOffsetCommitter.access$000(SourceTaskOffsetCommitter.java:45)
    at org.apache.kafka.connect.runtime.SourceTaskOffsetCommitter$1.run(SourceTaskOffsetCommitter.java:82)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
    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: org.postgresql.util.PSQLException: Database connection failed when writing to copy
    at org.postgresql.core.v3.QueryExecutorImpl.flushCopy(QueryExecutorImpl.java:942)
    at org.postgresql.core.v3.CopyDualImpl.flushCopy(CopyDualImpl.java:23)
    at org.postgresql.core.v3.replication.V3PGReplicationStream.updateStatusInternal(V3PGReplicationStream.java:176)
    at org.postgresql.core.v3.replication.V3PGReplicationStream.forceUpdateStatus(V3PGReplicationStream.java:99)
    at io.debezium.connector.postgresql.connection.PostgresReplicationConnection$1.doFlushLsn(PostgresReplicationConnection.java:246)
    at io.debezium.connector.postgresql.connection.PostgresReplicationConnection$1.flushLsn(PostgresReplicationConnection.java:239)
    at io.debezium.connector.postgresql.RecordsStreamProducer.commit(RecordsStreamProducer.java:146)
    ... 13 more
    Caused by: java.net.SocketException: Broken pipe (Write failed)
    at java.net.SocketOutputStream.socketWrite0(Native Method)
    at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:111)
    at java.net.SocketOutputStream.write(SocketOutputStream.java:155)
    at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:82)
    at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:140)
    at org.postgresql.core.PGStream.flush(PGStream.java:553)
    at org.postgresql.core.v3.QueryExecutorImpl.flushCopy(QueryExecutorImpl.java:939)
    ... 19 more

有没有办法让 debezium 在可用时重新建立与 postgres 的连接？ 还是我缺少一些配置？

• Debezium 0.8 版
• kubernetes 版本 1.10.3
• postgres 9.6 版

Answer 1

看起来这是一个常见问题，并且在 debezium 和 kafka 中都有开放的功能请求

https://issues.jboss.org/browse/DBZ-248

https://issues.apache.org/jira/browse/KAFKA-5352

虽然这些是开放的，但看起来这是预期的行为

作为一种解决方法，我已将此活性探针添加到部署中

    livenessProbe:
        exec:
          command:
          - sh
          - -ec
          - ipaddress=$(ip addr | grep 'state UP' -A2 | tail -n1 | awk '{print $2}' | cut -f1  -d'/'); reply=$(curl -s $ipaddress:8083/connectors/inventory-connector/status | grep -o RUNNING | wc -l); if [ $reply -lt 2 ]; then exit 1; fi;
        initialDelaySeconds: 30
        periodSeconds: 5

第一个子句获取容器IP地址：

    ipaddress=$(ip addr | grep 'state UP' -A2 | tail -n1 | awk '{print $2}' | cut -f1 -d'/');

第二个子句发出请求并计算响应 json 中“RUNNING”的实例数：

    reply=$(curl -s $ipaddress:8083/connectors/inventory-connector/status | grep -o RUNNING | wc -l);

如果 'RUNNING' 出现的次数少于两次，则第三个子句返回退出代码 1

    if [ $reply -lt 2 ]; then exit 1; fi

它似乎正在进行初始测试 - 即重新启动 postgres DB 会触发 debezium 容器的重新启动。我猜想像这样的脚本（虽然可能是'robustified'）可以包含在图像中以方便探测。