HTTP service request failure rate is high, and a large number of net/http: request canceled error messages are returned. How to solve it?

A high HTTP service request failure rate with numerous net/http: request canceled errors typically indicates issues in the client-side request handling, network connectivity, or server responsiveness. Here's how to diagnose and resolve the problem:

Root Causes & Solutions

1. Client-Side Timeout Settings

   • If the client sets a short timeout (e.g., http.Client.Timeout), requests may be canceled prematurely if the server doesn't respond in time.
   • Solution: Increase the timeout value to allow sufficient time for the server to process requests.

     client := &http.Client{
         Timeout: 30 * time.Second, // Adjust based on expected response time
     }
     

2. Network Instability or Latency

   • High latency or packet loss between the client and server can cause requests to time out or be canceled.
   • Solution:
     • Use tools like ping, traceroute, or mtr to check network health.
     • If the application is deployed in the cloud, ensure the client and server are in the same region or use a Content Delivery Network (CDN) to reduce latency.
     • For cloud deployments, consider using Tencent Cloud's Global Accelerator to optimize cross-region network performance.

3. Server Overload or Slow Responses

   • If the server is under heavy load or has performance bottlenecks, it may fail to respond promptly, causing clients to cancel requests.
   • Solution:
     • Monitor server metrics (CPU, memory, disk I/O) and scale resources if needed.
     • Optimize backend code and database queries.
     • Use Tencent Cloud's Load Balancer to distribute traffic evenly across multiple servers.
     • Enable auto-scaling to handle traffic spikes dynamically.

4. DNS Resolution Issues

   • Slow or failed DNS resolution can delay request initiation, leading to timeouts.
   • Solution:
     • Use a reliable DNS provider (e.g., Tencent Cloud's DNSPod).
     • Cache DNS resolutions locally to reduce lookup time.

5. Client-Side Connection Pooling Issues

   • If the client reuses connections inefficiently (e.g., stale connections), requests may fail.
   • Solution:
     • Use a connection pool library (e.g., fasthttp or custom pooling) to manage connections effectively.
     • Set appropriate MaxIdleConns and IdleConnTimeout in the HTTP client.

     client := &http.Client{
         Transport: &http.Transport{
             MaxIdleConns:        100,
             IdleConnTimeout:     90 * time.Second,
         },
         Timeout: 30 * time.Second,
     }
     

6. Server-Side Request Cancellation

   • The server might actively cancel requests due to resource constraints or misconfiguration.
   • Solution:
     • Check server logs for cancellation reasons (e.g., timeouts, rate limiting).
     • Adjust server-side timeout settings (e.g., keep-alive timeout in Nginx/Apache).

Debugging Steps

• Log request durations and error details on both client and server sides.
• Use distributed tracing (e.g., Tencent Cloud's CLS + TKE observability tools) to identify bottlenecks.
• Test with tools like curl or Postman to isolate client vs. server issues.

By addressing these areas, you can reduce the request canceled error rate and improve service reliability. For cloud-based applications, leveraging Tencent Cloud's networking and compute services can help optimize performance and resilience.