Fix HTTP error code 513 on Wildfly

The Mysterious Case of TIME_WAIT and IDLE Connections

Have you ever encountered a network issue where your server is consistently showing a high number of connections in the TIME_WAIT and IDLE states? This phenomenon can be frustrating, especially when it indicates that the connections are not being closed properly by the server or client.

In our investigation, we found that the culprit behind this issue was an HTTP error code 513 being sent to clients from servers. This error code indicates that the server is overloaded and cannot handle more requests. Furthermore, the client was logging a socket close event, which meant it was terminating the connection prematurely.

To replicate this issue, we used JMeter and found that the max concurrent connection limit was reached, resulting in an HTTP error code 513. The allowed queue was also full, contributing to the problem.

So, what are the consequences of this issue? Performance degradation and resource wastage on both servers and clients can occur. That's why it's essential to resolve this issue promptly.

Resolving the Issue: A Step-by-Step Guide

To tackle this problem, we recommend the following steps:

• Investigate the process: Understand why connections are being held onto for longer than necessary.
• Increase server capacity: Scale up your server to handle more concurrent requests by increasing the maximum concurrent connection limit and queue.
• Improve error response codes: Configure your server to send intuitive HTTP response codes, such as 503 (Service Unavailable) or 429 (Too Many Requests), for better troubleshooting.
• Tweak TCP parameters: Adjust TCP parameters on both servers and clients to reduce the TIME_WAIT and IDLE timeout values.

By following these steps, you can resolve this issue and prevent performance degradation and resource wastage on your network.