Microservice Consul Sample
However, this demo uses Hashicorp Consul for service discovery and Apache httpd as a reverse proxy to route the calls to the services and as a load balancer.
This project creates a complete micro service demo system in Docker containers. The services are implemented in Java using Spring and Spring Cloud.
It uses three microservices:
Orderto process orders. (http://localhost:8080 when started locally)
Customerto handle customer data. (http://localhost:8080)
Catalogto handle the items in the catalog. (http://localhost:8080)
Consul has a Web UI. You can access it at port 8500 of your Docker host. Also the homepage at port 8080 contains a link to the Consul UI
Also you can use Consul's DNS interface with e.g. dig:
dig @192.168.99.100 -p 8600 order.service.consul. dig @192.168.99.100 -p 8600 order.service.consul. ANY dig @192.168.99.100 -p 8600 order.service.consul. SRV
Note that the demo uses the original Consul Docker image provided by Hashicorp. However, the demo does not use a Consul cluster and only stores the data in memory i.e. it is certainly not fit for production.
All the Spring Cloud microservices (customer, catalog and order) register themselves in the Consul server. An alternative approach to register the services is Registrator. An alternative to using Apache HTTP as a load balancer would e.g. be Fabio.
Apache HTTP Load Balancer
Apache HTTP is used to provide the web page of the demo at
port 8080. It also forwards HTTP requests to the microservices whose ports
are not exposed! Apache HTTP is configured as a reverse proxy for this - and
as a load balancer i.e. if you start multiple instances of a microservices
docker-compose scale catalog=2, Apache will recognize the new instance.
To configure this Apache HTTP needs to get all registered services from Consul. Consul Template is used for this. It uses a template for the Apache HTTP configuration and fills in the IP addresses of the registered services.
The Docker container therefore runs two processes: Apache HTTP and Consul Template. Consul Template starts Apache httpd and also restarts Apache httpd when new services are registered in the Consul server.
Please refer to the subdirectory
apache to see how this works.
Prometheus is a monitoring system. The code
includes code to export metrics to Prometheus in
com.ewolff.microservice.order.prometheus. Also the docker-compose
docker-compose-prometheus.yml includes a Prometheus
instance. It will listen on port 9090 on the Docker host. That way you
can monitor the application. Run it with
docker-compose -f docker-compose-prometheus.yml up -d.
The Elastic Stack provides a set
of tools to handle log data. The projects contain a Logback
logback-spring.xml so that the services log JSON
Filebeat to ship the log from a common volume to Elasticsearch.
Elasticsearch to store and analyse the logs.
Kibana to analyse the logs. You can access it on port 5601 e.g. at http://localhost:5601. The indices are called
You can run the configuration with
docker-compose -f docker-compose-elastic.yml up -d.
Zipkin is a tool to trace calls across microservices. The project includes all necessary libraries to provide traces.
A Zipkin server to store and display the data. You can access it on port 9411 e.g. at http://localhost:9411.
Microservices are configured to provide trace information.
You can run the configuration with
docker-compose -f docker-compose-zipkin.yml up -d.
- Consul for Lookup/ Discovery
- Apache as a reverse proxy to route calls to the appropriate SCS.
- Ribbon for client-side Load Balancing. See the classes
CustomerClientin the package
com.ewolff.microservice.order.clientsin the microservice-demo-order project.
- Hystrix is used for resilience. See
com.ewolff.microservice.order.clientsin the microservice-demo-order project . Note that the
CustomerClientwon't use Hystrix. This way you can see how a crash of the Customer microservices makes the Order microservice useless.
How To Run
The demo can be run with Docker Machine and Docker
See How to run for details.
Remarks on the Code
The servers for the infrastructure components are pretty simple thanks to Spring Cloud:
- microservice-consul-demo-turbine can be used to consolidate the Hystrix metrics and has a Hystrix dashboard.
The microservices are:
- microservice-consul-demo-catalog is the application to take care of items.
- microservice-consul-demo-customer is responsible for customers.
- microservice-consul-demo-order does order processing. It uses microservice-demo-catalog and microservice-demo-customer. Ribbon is used for load balancing and Hystrix for resilience.
The microservices have a Java main application in
src/test/java to run them stand alone.
microservice-demo-order uses a stub for the other services then. Also there are tests that use consumer-driven contracts. That is why it is ensured that the services provide the correct interface. These CDC tests are used in microservice-demo-order to verify the stubs. In
microserivce-demo-catalog they are used to verify the implemented REST services.