easer internals

In order to have all the basic functions a cloud ready component should have, easer is built-upon the npac architecture, which is a lightweight Ports and Adapters Container for applications running on Node.js platform.

To act as MESSAGING Gateway, easer uses the built-in npac-webserver-adapter.

Note: There are two ways of implementing service modules with the npac-webserver-adapter:

1. Service implementations are built-into the server. in this case you need to make a standalone npac based server, using directly the npac-wsgw-adapters module, and integrate the endpoint implementations into this server. In this case the endpoint implementations have to be referred in the swagger files via the operationId properties of the endpoint descriptors.

2. The easer way: You implement a standalone service module, that listens to NATS topic (defined by the endpoint URI and method), define the API via swagger, and start the following system components: the NATS server, the service implementation module, and the easer server configured with the API descriptors.

With easer it possible to create two-way asynchronous communication between the frontend and the backing services. The frontend uses websocket and the easer forwards the messages towards NATS topics. it also works in the opposite direction, easer can subscibe to NATS topics and the received messages are forwarded towards the frontend via websocked. This feature is build upon the npac-wsgw-adapters module. There is helper tool called wsgw, that makes possible to publish to and subscribe for topics. This tool can send and recive messages through both NATS and websocket topics. See the README files of the mentioned modules and tools for details.