Experiments

Examine logs#

Try the following experiments in the coding environment given below!

• Start the system and examine the logs of microservice-order-invoicing and microservice-order-shipping with docker logs -f msatom_invoicing_1 respectively docker logs -f msatom_shipping_1.
• The microservices log messages when they poll data from the Atom feed, because there are new orders.
• If you start additional instances of a microservice with docker compose up --scale, these new instances will collect orders via the Atom feed and log information about them. In doing so, only one instance writes at a time; the other ones ignore the data.
• Create orders and notice this behavior based on the log messages.
• Explore the code to find out what the log messages mean and where they are put out.

Create new microservice#

Supplement the system with an additional microservice.

• As an example, a microservice can be used that credits the customer with a bonus depending on the value of the order or that counts the orders.
• Of course, you can copy and modify one of the existing microservices.
• Implement a microservice which polls the URL http://order:8080/feed.
• In addition, the microservice should display an HTML page with some information (customer bonus or number of calls).
• Package the microservice in a Docker image and reference it in docker-compose.yml. There you can also determine the name of the Docker container.
• Create a link from the container apache to the container with the new service in docker-compose.yml and from the container with the new service to the container order.
• The microservice has to be accessible via the homepage. For this purpose, you have to create a load balancer for the new Docker container in the file 000-default.conf in the Docker container apache. Use the name of the Docker container for this. Then, add a link to the new load balancer in index.html.
• Optional: Add HTTP caching format.

Other experiments#

• Currently, it is only possible to request all orders at once in the Atom feed. You can implement paging so that only a subset of the orders is returned.

• At the moment, the system runs with Docker compose. However, it could also run on a different infrastructure. Port the system to one of these platforms:

  • On a microservices platform (chapter 12).
  • On Kubernetes. Chapter 13 discusses Kubernetes in more detail.
  • On Cloud Foundry. chapter 14 deals with Cloud Foundry.

• Instead of using the Atom format, you could also deliver your own representation of a feed.

  • For example, as a JSON document. Change the implementation in the example so that it uses its own custom data.

We’ll conclude this chapter in the next lesson.