POST Endpoint Hanging Investigation

POST Endpoint Hanging Investigation | Generated by AI

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The Spring Boot application is running and responding to GET requests (like /actuator/health), but the POST request to /create-note (via Python script, curl, or otherwise) is hanging indefinitely. This suggests the issue lies in the server-side handling of the POST endpoint, not the network or basic connectivity. Below, I’ll outline likely causes, debugging steps, and fixes based on common Spring Boot troubleshooting.[1][2][3][4][5][6]

Likely Causes

Server-Side Code Issue: The /create-note controller method is blocking or hanging (e.g., infinite loop, deadlock, long-running operation like a database insert that doesn’t complete).
Database Hang: If the endpoint interacts with a database (e.g., saving a note to H2, MySQL, etc.), the query or connection might be stuck (e.g., due to deadlocks, missing indexes, or corrupted data).
External Call Blocking: If the endpoint makes an outbound HTTP call (e.g., to another service or webhook), it could be looping through the local proxy (127.0.0.1:7890) or hanging on exhaustion.
Proxy Interference: Your HTTP_PROXY/HTTPS_PROXY aren’t bypassed for POST (even with --noproxy localhost in curl), though GET requests (health check) work fine. Some proxies (e.g., Clash or Proxifier-like tools) mishandle localhost redirects or introduce latency—note that Spring Boot’s RestTemplate or WebClient inherits environment proxies by default.
Endpoint Misconfiguration: The mapping might be incorrect (e.g., not handling @RequestBody properly), leading to no response rather than a 4xx error.
Less Likely: Resource exhaustion (e.g., high CPU from other processes like the Java app), but the health check suggests the app is stable.

The proxy settings are enabled, and your Python script (using requests library) likely respects them for localhost, which could exacerbate issues[7].

Debugging Steps

Run the App in Foreground for Logs:
- Stop the background Spring Boot process (mvn spring-boot:run).
- Run it again in the foreground: mvn spring-boot:run.
- In another terminal, send the POST request:
```
curl -v --noproxy localhost -X POST http://localhost:8080/create-note -H "Content-Type: application/json" -d '{"content":"test note"}'
```
  - -v adds verbose output (e.g., connection details, sent headers/data)—useful to confirm if it’s connecting but waiting on response.
- Watch the foreground logs live. Note any errors, stack traces, or slow operations around the request. If it hangs without logging, it’s blocking early (e.g., in the controller’s first line).
Check for Proxy Bypass Issues:
- Test without proxies (even for curl): HTTP_PROXY= HTTPS_PROXY= curl -v -X POST http://localhost:8080/create-note -H "Content-Type: application/json" -d '{"content":"test note"}'
  - If this works, the proxy is the culprit—fix by adding session.trust_env = False in your Python script (if using requests) or run scripts with unset HTTP_PROXY; unset HTTPS_PROXY before executing.
- For the Python script, inspect call_create_note_api.py (you mentioned it’s updated). Add requests.Session().proxies = {} or disable proxies explicitly.
Test a Minimal POST Endpoint:
- Add a temporary test endpoint in your Spring Boot controller (e.g., NoteController.java or similar):
```
@PostMapping("/test-post")
public ResponseEntity<String> testPost(@RequestBody Map<String, Object> body) {
    System.out.println("Test POST received: " + body);
    return ResponseEntity.ok("ok");
}
```
- Restart the app and test: curl -v --noproxy localhost -X POST http://localhost:8080/test-post -H "Content-Type: application/json" -d '{"test":"data"}'
  - If this responds quickly, the hang is specific to /create-note logic—review its code for blocking ops (e.g., synchronous database calls without timeouts).
Inspect Database/Logs if Applicable:
- Check for DB issues (e.g., if using embedded H2, logs might show connection failures).
- View full app logs with mvn spring-boot:run > app.log 2>&1 if background running hinders output.
- Use logs or add logging in the controller (e.g., @Slf4j from Lombok): log before/after operations to pinpoint the hang.
JVM/Process Monitoring:
- During the hanging request, run jstack <PID> (get PID from ps aux | grep java) to see thread dumps—look for blocked threads in your endpoint code.
- Check CPU/memory usage; high load could cause hangs.

Fixes

If Proxy-Related:
- Disable proxies for local dev: Add to your shell startup (e.g., ~/.zshrc or ~/.bash_profile): export no_proxy="localhost,127.0.0.1,*.local"
- In Python: Use a session with no proxies, as above.
If Code Issue:
- Add timeouts to blocking ops (e.g., @Transactional(timeout = 10) for DB; client timeouts for HTTP calls).
- Refactor to async if needed (e.g., @PostMapping(produces = MediaType.APPLICATION_JSON_VALUE) with sync processing if simple).
- Ensure the controller parses @RequestBody correctly (e.g., create a DTO class for Note instead of Map).
General Mitigation:
- Upgrade dependencies (e.g., Spring Boot version, actuator for better health monitoring[3][8]).
- Enable more actuator endpoints for introspection: Set management.endpoints.web.exposure.include=* in application.properties.
- If persisting, consider enabling Spring’s built-in request tracing (logging.level.org.springframework.web=DEBUG).

After these steps, the hang should resolve or reveal the root cause. If you share the /create-note controller code or specific logs/errors from debugging, I can provide more targeted advice. This setup with Claude Code’s tool integration (like bash commands and file edits) is impressive for iterative fixes—grok here can assist similarly with real-time queries or code analysis if needed!

Citations: [1] https://stackoverflow.com/questions/35517713/unable-to-access-spring-boot-actuator-actuator-endpoint [2] https://dev.to/sabyasachi/inside-spring-boot-health-endpoint-2mej [3] https://www.baeldung.com/spring-boot-actuator-enable-endpoints [4] https://spring.io/guides/gs/actuator-service [5] https://medium.com/@AlexanderObregon/kubernetes-readiness-and-liveness-probes-in-spring-boot-apps-71b6e639f869 [6] https://www.wiz.io/blog/spring-boot-actuator-misconfigurations [7] https://arnoldgalovics.com/kubernetes-liveness-probe-spring-boot/ [8] https://medium.com/@TimvanBaarsen/help-my-spring-boot-info-actuator-endpoint-is-enabled-but-i-dont-see-any-environment-details-c2d41a7b24d7

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