Envoy is an open-source edge and service proxy designed for cloud-native applications. It is often used as a sidecar proxy in microservices architectures to handle service-to-service communication, load balancing, and observability. Envoy's flexibility and configurability make it a popular choice for managing network traffic in complex environments.
One common issue encountered with Envoy is when it is not listening on the expected port. This can manifest as an inability to connect to services through Envoy, resulting in failed requests or timeouts. The symptom is typically observed when attempting to access a service through Envoy and receiving no response.
When Envoy is not listening on the expected port, you might not see explicit error messages in the logs, but rather a lack of connectivity. Checking the Envoy logs for any warnings or errors related to listener configuration can provide clues.
The root cause of Envoy not listening on a port is often due to configuration errors. Envoy's configuration is defined in YAML files, and a misconfiguration can prevent it from binding to the desired port. Additionally, if the port is already in use by another process, Envoy will fail to start the listener.
Errors in the listener configuration section of the Envoy YAML file can lead to this issue. It's crucial to ensure that the listener is correctly defined with the appropriate address and port.
To resolve the issue of Envoy not listening on the expected port, follow these steps:
Check the Envoy configuration file (typically a YAML file) to ensure that the listener is correctly defined. Look for the listeners section and verify the address and port_value:
listeners:
- name: listener_0
address:
socket_address:
address: 0.0.0.0
port_value: 8080
Ensure that the port_value matches the expected port.
Ensure that the port is not already in use by another process. You can use the following command to check for processes using the port:
lsof -i :8080
If another process is using the port, either stop that process or configure Envoy to use a different port.
After verifying the configuration and ensuring no port conflicts, restart the Envoy service to apply the changes:
systemctl restart envoy
Or, if running Envoy manually:
envoy -c /path/to/envoy.yaml
For more detailed information on configuring Envoy, refer to the Envoy Listener Configuration documentation. Additionally, the Envoy Getting Started Guide provides a comprehensive overview of setting up and running Envoy.
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