modelcontextprotocol / modelcontextprotocol/java-sdk
StdioClientTransport: Inbound Scheduler and Error Scheduler threads are locked on Windows
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Descripción
Bug description
Two threads, Inbound Scheduler and Error Scheduler, remain locked forever (at java.io.FileInputStream.readBytes native call) in io.modelcontextprotocol.client.transport.StdioClientTransport after the graceful shutdown is completed using closeGracefully method.
Looks like a Windows specific issue with native I/O calls. The problem is observed when running on Windows. No problems with Linux environment.
The thread dump is attached.
dump_jdk17.txt
See "pool-2-thread-1" and "pool-5-thread-1" dumps.
Environment
Windows 11 Enterprise
mcp-core 0.17.1
Spring AI 2.0.0-SNAPSHOT
JDK Temurin 17.0.14 (also tried Amazon Corretto 21.0.5)
Linux Behavior
Works fine under Ubuntu 24.04 and JDK Temurin 21.0.10
Steps to reproduce
- Run the steps from the Spring AI Filesystem Demo example on Windows.
- The Java application process is not terminated as expected.
Expected behavior
The Java process terminates after running the Spring AI Filesystem Demo example.
Possible solution
On Windows, use daemon threads for inbound and error schedulers
private ThreadFactory daemonThreadFactory = runnable -> {
Thread t = new Thread(runnable);
t.setDaemon(true);
return t;
};
if (isWindows) {
this.inboundScheduler = Schedulers.fromExecutorService(Executors.newSingleThreadExecutor(daemonThreadFactory), "inbound");
this.errorScheduler = Schedulers.fromExecutorService(Executors.newSingleThreadExecutor(daemonThreadFactory), "error");
}
Tried this solution locally. It resolves the termination issue. But the graceful shutdown logic in io.modelcontextprotocol.client.transport.StdioClientTransport#closeGracefully should be revised as well.
Guía de contribución
Primeros pasos
- Lee el issue completo y luego la guía de contribución del proyecto.
- Comenta en el issue que vas a ocuparte — evita que dos personas hagan lo mismo.
- Haz un fork del repositorio y trabaja en una rama.
- Abre un pull request que haga referencia al número del issue.
Línea de trabajo
Comienza en io.modelcontextprotocol.client.transport.StdioClientTransport, centrándote en el Inbound Scheduler, el Error Scheduler y el método closeGracefully; después, revisa el volcado de hilos de Windows adjunto en busca de lecturas bloqueadas. Reproduce Spring AI Filesystem Demo en Windows y verifica que el apagado termine el proceso de Java sin dejar bloqueados los hilos del scheduler.
Escrito por el modelo de indexación a partir del texto del issue.
Evaluación
- Stack tecnológico
- java
- Área
- backend
- Tipo de issue
- Error
- Dificultad
- 4/5
- Tiempo estimado
- 3-5 días
- Estado de actividad
- Estancado
- Claridad
- Bastante claro
- Aptitud para principiantes
- 38/100