SCS jQuery Sample

Deutsche Anleitung zum Starten des Beispiels

For Self-contained Systems multiple frontends need to be integrated. This sample shows how to do this. JavaScript Code on the frontend is used to load parts from other SCS. A hyperlink marked with class embeddablewill be replaced with the content found at that URL.

So for example <a class="embeddable" href="/catalog/2.snippet">item</a> would be replaced by whatever a GET to /catalog/2.snippetreturns. You can find the code for this in layout.html in microservice-demo/microservice-demo-order/src/main/resources/templates/layout.html .

Varnish serves as a cache and also to provide both SCS at a common URL. Note that this could also be done with a reverse proxy e.g. Apache httpd or Nginx.

This project creates a Docker setup with the complete systems based on Docker Compose and Docker Machine. The services are implemented in Java using Spring and Spring Cloud.

It uses two very simple SCS:

• Order to enter orders.
• Catalog to handle the items in the catalog.

How To Run

See How to run for details.

Remarks on the Code

The SCS are:

• microservice-demo-catalog is the application to take care of items. You can access it at /catalog. Also it is used by order to display HTML snippets with the choice of items and the text for each item in an order.
• microservice-demo-order does order processing. It outputs esi:include in its HTML files to include the HTML snippets of microservices-demo-catalog. These are interpreted my the Varnish web cache.

Varnish provides both SCS at common URLs. The default.vcl in the directory docker/varnish includes the configuration to enable this. It defines two backends - one for each SCS. HTTP requests to /catalog are mapped to the catalog SCS while the default is the order SCS. The time to live for each item in the cache is 30s i.e. after 30 seconds an entry in the cache in invalidated and the call goes to the backend. The grace is 15m: Even if the entry in the cache is invalid it will be served for 15 more minutes of the backend is not accessible. So if the backend crashes the cache can still provide some resilience.

The microservices have an Java main application in src/test/java to run them stand alone with some test data.

Architecture Disclaimer

This is a technology demo. The coupling between the two components in this case is very tight - the integration is providing rather small components that are embedded in specific pages. In a real world architecture this should not be the case. Please refer to http://scs-architecture.org/ to better understand the architecture this should support.