WebSocket support in API Gateway

The API Gateway includes a basic WebSocket proxy which enables the Gateway to access applications that use the WebSocket protocol together with a web UI and REST API.

The service can define what WebSocket services are exposed using Eureka metadata.

Example:

eureka:
    instance:
        metadata-map:
            apiml:
                routes:
                    ws_v1:
                        gatewayUrl: "ws/v1"
                        serviceUrl: /${serviceId}/ws

These metadata make it possible for requests from wss://gatewayHost:port/ws/v1/serviceId/path to map to ws://serviceHost:port/discoverableclient/ws/path, where:

• serviceId
  is the service ID of the service

• path
  is the remaining path segment in the URL.

Security and Authentication

The API Gateway usually uses TLS with the wss protocol. Services that use TLS enable the API Gateway to use wss to access these services. Services that do not use TLS require the API Gateway to use the ws protocol without TLS. The API Gateway also supports basic authentication via WebSocket.

Subprotocols

In addition to plain WebSocket support, API Mediation Layer also supports WebSocket subprotocols. Currently, only STOMP v1.2 and STOMP v1.1 are supported and tested.

Note: It is possible to update the list of currently supported WebSocket subprotocols. Update the API Gateway configuration using the environment variable SERVER_WEBSOCKET_SUPPORTEDPROTOCOLS with the value of comma-separated subprotocol names. Support for additional subprotocols is not guaranteed as these subprotocols are not being tested.

Example:

SERVER_WEBSOCKET_SUPPORTEDPROTOCOLS=v12.stomp,v11.stomp,wamp,soap

High availability

In the high availability scenario, the API Gateway makes it possible to open a new Websocket session by utilizing the load balancing mechanism. Communication between the client and the server is handled by the API Gateway by propagating the session to a live instance.

Diagnostics

The list of active routed WebSocket sessions is available at the Actuator endpoint websockets. On localhost, it is available at https://localhost:10010/application/websockets.

Limitations

Different HTTP status code errors may result. The WebSocket session starts before the session between the Gateway and the service starts. When a failure occurs when connecting to a service, the WebSocket session terminates with a WebSocket close code and a description of the failure rather than an HTTP error code.