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README.md
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README.md

Service mesh example

This stack demonstrates 3 simple Python HTTP server applications, and particularly, the HTTP routing between them. The point to demonstrate here, is that the services themselves don't need to worry about dealing with service discovery or any other means of finding the target applications to send requests to, and can conveniently just talk to their tightly coupled reverse proxies. The applications need to implement the business logic only.

The actual applications are quite simple:

  • calc is a monolithic calculator application we want to break up now
  • add is only responsible for the + operation
  • mul is only responsible for the * operation
  • calc accepts add and mul requests too, but it will just forward them to its local proxy
  • calc still supports the sub and div operations itself

Each of the applications is coupled with a Consul agent that joins to a central server in the stack, and a Traefik instance that accepts incoming requests from the main routing proxy which handles external requests from users. The Traefik instances connect to the apps on localhost, within the "pod", and so do they to the coupled Consul agent to read the list of available, healthy services and their configuration.

Components

There's an OpenTracing compatible Zipkin server in the stack as well, which collects the traces from each Traefik instance. Again, the applications don't even have to be aware of tracing, their coupled proxy takes care of it for them.

The stack-inline.yml is the same apps and configuration as the stack.yml is, but everything you'd normally put in a config file is inlined, so it can be started without having to clone the repository.

Usage

To deploy the stack straight from this repository:

$ curl -fsSL https://raw.githubusercontent.com/rycus86/podlike/master/examples/service-mesh/stack-inline.yml | docker stack deploy -c - mesh

You can also try the templated version, once you have the podtemplate script installed:

$ curl -fsSL https://raw.githubusercontent.com/rycus86/podlike/master/examples/service-mesh/stack-templated.yml | podtemplate deploy -c - mesh

Then try some example requests:

$ curl -s http://127.0.0.1/v1/add/12/47
59
$ curl -s http://127.0.0.1/v2/add/12/47
59
$ curl -s http://127.0.0.1/v1/mul/12/3
36
$ curl -s http://127.0.0.1/v2/mul/12/3
36
$ curl -s http://127.0.0.1/v1/sub/12/30
-18
$ curl -s http://127.0.0.1/v1/div/128/17
7.52941176471

Or launch it on the Docker Playground and check the services on the exposed host.

Traefik listens on port 80 for incoming requests as shown above, plus its dashboard is accessible on port 8080, so you can have a look at the generated frontends and backends, and also some health stats. The Consul management UI is available on port 8500, where you can see the services, their health and metadata. Finally, Zipkin listens on port 9411, where you can see how the requests are routed and processed.