Learn to implement microservices across a range of common tech stacks.

Scalability & System Design for Developers

In this module, we’ll look at some fundamental concepts for implementing microservices. Within each concept, learn about the different technologies used to implement it. The technologies include front-end integration with Edge Side Includes (ESI), asynchronous microservices with Kafka and REST feeds, synchronous microservices with the Netflix stack, and Consul, Docker, Kubernetes, Cloud Foundry. Each technology is described and then demonstrated with real code.

Microservice Architecture: Practical Implementation

# Experiments

Here are some experiments you can do with all that you've learned in this chapter.

Supplement the system with an additional microservice.

# Try it yourself!
Try all the experiments in the environment below.

version: '3'
services:
  common:
    image: educative1/mapi_scsesi_common
  order:
    image: educative1/mapi_scsesi_order 
    ports:
     - "8090:8080"
  varnish:
    image: educative1/mapi_scsesi_varnish
    links:
     - common
     - order
    ports:
     - "8080:8080"

atom-kafka-scs-netflix-up

React

Dart

GoJS React

Typescript React

Vue.js

  * A microservice that simply displays a static HTML page can serve as an example.

  * The new microservice should integrate header, navigation bar, and
    footer of the common microservice via ESI tags.
  * Package the microservice as a Docker image and reference it in
     `docker-compose.yml`. There you can also determine the name of the Docker container.
  * The microservice has to be accessible via Varnish.  To achieve that, you have to integrate a new backend with the name of the
    Docker container in `default.vcl` and adapt the routing in
    `vcl_recv()`.
  * Now you should be able to access the new microservice at <http:localhost:8080/name> if the Docker containers run on the
    local computer and the new service is configured in Varnish’s routing
    with `name`. The ESI tags should have been replaced by
    HTML code.

* The Go application returns only a dynamic HTML fragment -- the
 navigation bar with the current time. Instead of the Go application,
 a web server can also deliver static pages. For example, replace the
 Go application with an Apache httpd server that delivers the HTML
 fragments and the Bootstrap library. The time does not necessarily
 have to be displayed in the navigation bar, so a static HTML fragment
 is all that is needed.

* Change the caching so that the pages are immediately invalidated
 when new orders are received. You can, for example, use matching HTTP
 headers as explained in a
 [chapter](http://book.varnish-software.com/4.0/chapters/HTTP.html) of
 the Varnish book. An alternative is to remove objects directly from
 the cache.  The Varnish book also contains a
 [chapter](http://book.varnish-software.com/4.0/chapters/Cache_Invalidation.html)
 on this option.

* Replace the Varnish cache in the example with [Squid](http://www.squid-cache.org/), 
which also implements ESI.

* Replace ESI with SSI and replace the Varnish cache with an Apache httpd or nginx.

* What happens if the web servers fail? Simulate the failure with
 `docker-compose up --scale common=0` or `docker-compose up --scale
 order=0`. Which parts of the web page still work? Is it still
 possible to place orders, for example?


In this lesson, we'll look at some experiments that you can try out with SSI using ESI.