What is Envoy Envoy Not Forwarding Headers

Resolving Header Forwarding Issues in Envoy

Introduction to Envoy

Envoy is a high-performance open-source edge and service proxy designed for cloud-native applications. It is used to manage network traffic and provides features such as load balancing, service discovery, and observability. Envoy is often deployed as a sidecar in service mesh architectures, enabling seamless communication between microservices.

Identifying the Symptom

One common issue users encounter is Envoy not forwarding headers as expected. This can manifest as missing headers in requests or responses, leading to unexpected behavior in applications relying on specific headers for functionality.

Common Observations

Missing authentication tokens in forwarded requests.Absence of custom headers required for application logic.Unexpected behavior in downstream services due to missing headers.

Understanding the Issue

The root cause of headers not being forwarded is often a misconfiguration in the Envoy configuration file. Envoy requires explicit configuration to forward specific headers, and any oversight can lead to headers being dropped.

Configuration Details

Envoy uses a configuration file, typically in YAML or JSON format, to define its behavior. The http_connection_manager filter is responsible for managing HTTP connections and includes settings for header forwarding.

Steps to Fix the Issue

Step 1: Review Envoy Configuration

Begin by examining the Envoy configuration file. Look for the http_connection_manager filter configuration. Ensure that the request_headers_to_add and response_headers_to_add sections are correctly defined.

http_filters: - name: envoy.filters.network.http_connection_manager config: request_headers_to_add: - header: key: "X-Custom-Header" value: "custom-value"

Step 2: Add Required Headers

If specific headers are missing, add them to the configuration. Use the request_headers_to_add and response_headers_to_add sections to specify headers that should be forwarded.

Step 3: Validate Configuration

After making changes, validate the configuration using Envoy's built-in validation tool. Run the following command to ensure there are no syntax errors:

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

Step 4: Restart Envoy

Once the configuration is validated, restart the Envoy service to apply the changes. This can typically be done using system service management tools like systemctl or docker commands, depending on your deployment method.

Further Reading

For more detailed information on Envoy configuration, refer to the Envoy Documentation. Additionally, explore the HTTP Filters Overview for a deeper understanding of how Envoy manages HTTP traffic.