GemFire Dispatcher Thread Stuck on socketWrite0 Call

Products

• VMware Tanzu Gemfire

Issue/Introduction

GemFire dispatcher thread is observed to be stuck on the native method call socketWrite0. A sample stack trace is shown below:

[warn <ThreadMonitor>] Thread has been performing the same operation for <XX seconds> and number of thread monitor iterations  
Thread Name: <Client Message Dispatcher for YYYY> state: RUNNABLE  
Thread stack for "Client Message Dispatcher for YYYY":  
java.lang.ThreadState: RUNNABLE (in native)  
at java.net.SocketOutputStream.socketWrite0(Native Method)  
at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java)  
at java.net.SocketOutputStream.write(SocketOutputStream.java)  
at org.apache.geode.internal.cache.tier.sockets.Message.flushBuffer(Message.java)  
at org.apache.geode.internal.cache.tier.sockets.Message.sendBytes(Message.java)

Environment

GemFire version 10.1.1 

Cause

This situation arises when the client-side socket buffer is full because the client is either slow to consume data or has stopped reading altogether. Consequently, the socket’s send buffer becomes saturated, causing the GemFire dispatcher thread to block on the native socketWrite0 call while attempting to write data.

Additional Context:

• Threads stuck in socketWrite0 usually indicate TCP send buffer congestion where the receiver side is not able to read the data quickly enough.
• Such threads will remain in the RUNNABLE state on native socket operations until the buffer is freed or the socket is closed.
• If this does not cause disconnections, cluster member failures, or systemic instability, it can be transient but should not be ignored entirely.
• GemFire does not provide an internal thread timeout to kill or restart such threads automatically.

Resolution

This is a known product issue fixed starting with GemFire version 10.1.2. To resolve this issue, upgrade your GemFire installation to version 10.1.2 or higher.

Recommendations:

• Monitor client consumption patterns to ensure timely reading from sockets, preventing socket buffer congestion.
• If upgrading to version 10.1.2 or newer is not immediately feasible:
• Review client-side application logs and network conditions to verify that reading from sockets is active and timely.
• Restart any durable clients that appear stuck or unresponsive to restore normal socket communication.
• Regularly update to supported GemFire versions to benefit from bug fixes and performance improvements.

For more related information, consider reviewing best practices such as limiting server subscription queue memory use.