Envoy Invalid Access Log Format

What is Envoy Invalid Access Log Format

Understanding Envoy Proxy

Envoy is an open-source edge and service proxy designed for cloud-native applications. It is often used as a communication bus and universal data plane for large microservice architectures. Envoy's primary purpose is to manage network traffic, providing features like load balancing, service discovery, and observability.

Identifying the Symptom: Invalid Access Log Format

When configuring Envoy, you might encounter an error related to the access log format. This issue typically manifests as a failure to start the Envoy service or an error message in the logs indicating an invalid format specification.

Common Error Messages

"Invalid access log format string" "Failed to parse access log format"

Understanding the Issue

The "Invalid Access Log Format" error occurs when the format specified for logging access requests does not conform to the expected syntax. Envoy uses a specific format for access logs, which allows for detailed customization of log output. However, any deviation from the expected syntax can lead to this error.

Why It Happens

This issue often arises due to typographical errors, incorrect placeholders, or unsupported format specifiers in the access log configuration.

Steps to Fix the Invalid Access Log Format

To resolve this issue, follow these steps:

1. Review the Access Log Configuration

Open your Envoy configuration file and locate the access log section. It typically looks like this:

{ "access_log": [ { "name": "envoy.file_access_log", "config": { "path": "/var/log/envoy/access.log", "format": "" } } ]}

Ensure that the <FORMAT_STRING> is correctly specified.

2. Validate the Format String

Refer to the Envoy Access Log Documentation to verify the correct syntax for format strings. Common placeholders include:

%START_TIME%: The start time of the request. %REQ(:METHOD)%: The HTTP method of the request. %RESP(X-ENVOY-UPSTREAM-SERVICE-TIME)%: The upstream service time.

3. Correct the Format String

Based on your review, correct any errors in the format string. Ensure that all placeholders are correctly spelled and supported by Envoy.

4. Test the Configuration

After making changes, test your Envoy configuration using the following command:

envoy --mode validate -c /path/to/envoy.yaml

This command checks the configuration for errors without starting the service.

Conclusion

By carefully reviewing and correcting the access log format, you can resolve the "Invalid Access Log Format" issue in Envoy. Always refer to the latest Envoy Documentation for updates and best practices.