Help Center/ MapReduce Service/ Troubleshooting/ Using Flink/ Error netty.exception.LocalTransportException Is Reported During Flink Job Runtime
Updated on 2025-08-21 GMT+08:00

Error netty.exception.LocalTransportException Is Reported During Flink Job Runtime

Symptom

The error message "netty.exception.LocalTransportException" is displayed during Flink job runtime.

Possible Causes

Network jitter or packet loss occurs. The following tasks time out during the netty communications between upstream and downstream operators. During communications, Flink jobs communicate with each other through the socket at the JDK bottom layer, and only the OS bottom-layer interface is invoked for socket read and write. In this way, IO EXCEPTION or LocalTransPortException is thrown after timeout.

Generally, the root cause is network faults, including:

  • Network jitter or packet loss
  • Insufficient network bandwidth
  • Abnormal network between data nodes

In addition, the open source community also provides some scenarios where this error is triggered.

Solution

If the problem does not occur frequently, for example, once half a year or once a year, you do not need to be worried. If the problem occurs frequently, you are advised to check the network and switch logs. Enable automatic restart. For example, set restart-strategy to failure-rate in the flink-conf.xml file.