What causes “java.io.IOException: stream was reset: CANCEL” with okhttp and spdy?

Understanding “java.io.IOException: stream was reset: CANCEL” with OkHttp and SPDY

The error “java.io.IOException: stream was reset: CANCEL” is often encountered when using OkHttp with SPDY protocol. It signifies an abrupt termination of the network stream, causing your request to fail. This article will delve into the common causes and provide solutions to resolve this frustrating issue.

Root Causes of the Error

1. SPDY Server Misconfiguration

• Server-Side Errors: The server may be improperly configured for SPDY, leading to inconsistent stream handling or unexpected behavior.
• Resource Limits: The server might impose strict resource limits, such as maximum concurrent streams or request timeouts, causing it to abruptly reset streams if exceeded.

2. Network Issues

• Intermittent Connectivity: Network instability or temporary outages can cause packet loss and disrupt the SPDY stream, leading to the “stream was reset: CANCEL” error.
• Firewall Interference: Network firewalls or proxies might interfere with the SPDY handshake or data exchange, causing stream termination.

3. Client-Side Code Problems

• Incorrect OkHttp Configuration: Improperly configured OkHttp settings, such as timeouts or connection limits, can lead to premature stream closure.
• Invalid Request: The server might reject requests due to invalid headers, incorrect request bodies, or other protocol errors.

Troubleshooting and Solutions

1. Server-Side Verification

• Check Server Configuration: Ensure the SPDY protocol is correctly enabled and configured on the server. Refer to the server’s documentation for specific instructions.
• Review Server Logs: Examine the server logs for any error messages related to SPDY or stream management that might indicate the cause of the reset.
• Increase Server Limits: If applicable, consider increasing resource limits, such as maximum concurrent streams or request timeouts, on the server to accommodate your application’s needs.

2. Network Diagnostics

• Check Network Connectivity: Test the network connection to the server for stability and packet loss using tools like ping or traceroute.
• Verify Firewall Settings: Ensure the firewall is not blocking SPDY traffic. Allow access for the required ports and protocols.
• Inspect Network Traces: Analyze network traces using tools like Wireshark to identify any issues during the SPDY handshake or data exchange.

3. OkHttp Configuration

• Set Timeouts: Configure appropriate timeouts for connection, read, and write operations to prevent hangs and stream resets due to delays. Refer to the OkHttp documentation for specific methods.
• Adjust Connection Pool: Configure the OkHttp connection pool size to manage the number of concurrent connections and prevent overloading the server.
• Retry Mechanisms: Implement retry strategies for failed requests to handle transient network errors and server-side issues.

4. Request Validation

• Validate Headers: Carefully review request headers and ensure they conform to the SPDY protocol specifications.
• Inspect Request Body: Verify the request body is formatted correctly and meets the server’s expectations.

Example Code Snippet

import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
import java.io.IOException;

public class OkHttpExample {
  public static void main(String[] args) throws IOException {
    OkHttpClient client = new OkHttpClient.Builder()
        .connectTimeout(10, java.util.concurrent.TimeUnit.SECONDS)
        .readTimeout(30, java.util.concurrent.TimeUnit.SECONDS)
        .build();
    Request request = new Request.Builder()
        .url("https://example.com/api/resource")
        .build();
    Response response = client.newCall(request).execute();
    System.out.println(response.body().string());
  }
}

Conclusion

Resolving “java.io.IOException: stream was reset: CANCEL” requires a systematic approach of eliminating potential causes. This article provided guidance on troubleshooting this error through examining server configuration, network issues, client-side code, and request validation. By carefully analyzing and implementing the suggested solutions, you can enhance the reliability and performance of your OkHttp and SPDY integrations.