Envoy EDS server is a working Endpoint Discovery Service implementation. It stores in memory an upstream host list and allows any upstream host to register and reregister.
Internally, envoy-eds-server starts two servers:
- a gRPC server that is invoked by Envoy to fetch the list of upstream hosts. It uses the go-control-plane library provided by the Envoy authors.
- a HTTP REST API server where a new host self-registers and deregisters when graceful shutdown happens.
Envoy makes use of gRPC client stream and is able to receive notifications once an upstream host is registered or unregistered; it does not need poll to update.
As a good practice, the upstream host should invoke the registration on the REST API server periodically, like a heartbeat. This periodic registration update allows the EDS server to become stateless, avoiding in this way the need of a dynamic configuration persistence. The in-memory store of the upstream host list is a good approach because this simplifies the eds server setup (no need to persist the settings) and ensures the configuration becomes consistent even if the EDS server is restarted.
The following environment variables must be defined:
HTTP_LISTEN_PORTchoose the listen port for the HTTP server - the one where upstream hosts are registered / unregisteredGRPC_LISTEN_PORTchoose the listen port for the gRPC server - the one consumed by Envoy.EVICTION_TIMEOUT_IN_SECchoose the time interval to elapse in order to remove the EDS resource because of not receiving a heartbeat API call from the upstream host. Defaults to 42 seconds. If set to zero then the Endpoints (EDS resources) are no more removed and are kept until the envoy-eds-server is restarted.
To start a docker container from the pre-built image, run:
docker run --name envoy-eds-server --rm -p 8089:8089 -p 8086:8086 raducrisan/envoy-eds-serveror
docker run --name envoy-eds-server --rm --env EVICTION_TIMEOUT_IN_SEC=10 -p 8089:8089 -p 8086:8086 raducrisan/envoy-eds-server