Basic terms
- Downstream (downstream): Envoy connected to the downstream host, and receives a transmission request response, i.e., the host sends the request.
- Upstream (upstream): an upstream connection and receives requests from the host Envoy and returns a response, i.e., the receiving host requests.
- Listener (listener): listener is named addresses (e.g., port, unix domain socket, etc.), a downstream client can connect these listeners. Envoy expose one or more listeners connected to the downstream host.
- The Cluster (cluster): refer to the same cluster is a set of logical connections Envoy upstream host. Envoy by service discovery to find members of the cluster. You can be selected by active health checks to determine the health status of the cluster member. Envoy by load balancing policy decision to which the request is routed to the cluster members.
client ---> nginx (upstream) ---> back-end services
Correspondence envoy:
downstream (downstream) ---> envoy -----> upstream (upstream)