Thread Stuck Reasons

A stuck thread means there is a thread that is blocking for some conditions and it cannot be returned to the original thread pool (execute queue). The modern design of many application servers utilizes the concept about thread pool to maximize the whole performance. When an execute thread is blocking for something, it will mean it cannot be quickly released and repeatedly reused one after another.In most of production situations, the root cause of these stuck threads is also the root cause of the system performance degradation.

- Network connecting timeout/Read timeout
- Long SQL query execution time
- Resource contention
- Connection leak
- User threads blooming
- Excessive Full GC pause time in the application code using System.gc() RMI daemon threads or memory leaks
- Internal transaction process by a slow resource manager.
- A huge value object RMI serialization/de-serialization in the network or ‘call by value’ semantic in applications.
- Unnecessary synchronized modifier in the code.
- Remote invocation hang or a slow response of remote call of another server.
- A huge write to a very slow client.
- A loop condition in the application code even server code.
- Threads with high CPU usage exhaust the whole CPU power.
- A premature version of JVM during bytecode optimization or garbage collection.