learn-co-curriculum / java-mod-10-orchestrating-using-compose

Orchestrating Using Docker Compose

Learning Goals

• Understanding multi application setup in Docker Compose

Instructions

For all our use cases of containers up until now, we've been manually administering individual containers using the Docker CLI. This works for simple cases, like demonstration and one-off systems, but isn't really viable for anything more complex. When you think about scaling containers, a lot of potential problems probably come to mind about how to move from the single-container/single-node setup, to scaling across entire datacenters and regions. This is where Container Orchestration comes into play. We will have a brief overview of Kubernetes as the major Orchestration player in a later lesson, but in here we are covering Docker Compose for the purposes of local development. Docker Compose still does fit as a valid tool for developmental clustering/orchestration, and single-node Docker environments.

First Hands-On with Docker Compose

First, take a look at the below two links, and run through these for a quick Docker Compose primer. This should take you through the bare minimum to understand a simple Compose use case.

• Docker Compose
• Using Docker Compose

If you ever find yourself needing to use Docker Compose more extensively, there is a vast amount of definitive sources available in the Docker documentation you should read though. The specification for the Docker Compose file alone is an ~90 minute read.

Multi-Layer Application in Docker Compose

Now that you have a better understanding of how Docker Compose maps to how we've been utilizing Docker environments prior, go ahead and migrate our previous Postgres cluster environment into Docker Compose. There is a starter docker-compose.yml file included in this lab repository to get a jump start from, and a complete working solution in the solution branch.

Once done, your environment should be composed of the following:

• One application container
• One master Postgres container
• Two replica Postgres containers
• One PgPool container

Testing

The following commands will run the tests to validate that this environment was setup correctly. A screenshot of the successful tests can be uploaded as a submission.

Note: Docker network and container names are managed by Docker Compose. You may need to change these values if you run Docker Compose in a different directory than expected.

docker run --network java-mod-10-orchestrating-using-compose_default -it --rm -v /var/run/docker.sock:/var/run/docker.sock -v $(pwd)/test:/test inspec-lab exec docker.rb

Profile:   tests from docker.rb (tests from docker.rb)
Version:   (not specified)
Target:    local://
Target ID: 

  ✔  Application Container: Application service named "spring-boot-compose" running correctly
     ✔  #<Inspec::Resources::DockerContainerFilter:0x0000563282738858> with names =~ /spring-boot-compose/ image == "rest-service-complete:0.0.1-SNAPSHOT" ports =~ /0.0.0.0:8080/ status is expected to match [/Up/]
     ✔  HTTP GET on http://spring-boot-compose:8080/ status is expected to eq 404
  ✔  Postgres Master Running: Postgres Master service named "postgres-compose-master-1" is running
     ✔  #<Inspec::Resources::DockerImageFilter:0x0000563281096050> with repository == "bitnami/postgresql-repmgr" tag == "14.4.0-debian-11-r9" is expected to exist
     ✔  #<Inspec::Resources::DockerContainerFilter:0x00005632805ac360> with names =~ /postgres-compose-master-1/ image == "bitnami/postgresql-repmgr:14.4.0-debian-11-r9" status is expected to match [/Up/]
     ✔  PostgreSQL query: SELECT datname FROM pg_database; output is expected to include "db_test"
  ✔  Postgres Replica 1 Running: Postgres Replica 1 service named "postgres-compose-replica-1" is running
     ✔  #<Inspec::Resources::DockerContainerFilter:0x000056328275e558> with names =~ /postgres-compose-replica-1/ image == "bitnami/postgresql-repmgr:14.4.0-debian-11-r9" status is expected to match [/Up/]
     ✔  PostgreSQL query: SELECT datname FROM pg_database; output is expected to include "db_test"
  ✔  Postgres Replica 2 Running: Postgres Replica 2 service named "postgres-compose-replica-2" is running
     ✔  #<Inspec::Resources::DockerContainerFilter:0x000056328285d530> with names =~ /postgres-compose-replica-2/ image == "bitnami/postgresql-repmgr:14.4.0-debian-11-r9" status is expected to match [/Up/]
     ✔  PostgreSQL query: SELECT datname FROM pg_database; output is expected to include "db_test"
  ✔  PgPoolII Running: PgPoolII service named "pgpool-compose" is running
     ✔  #<Inspec::Resources::DockerImageFilter:0x00005632829ff438> with repository == "bitnami/pgpool" tag == "4.3.2-debian-11-r16" is expected to exist
     ✔  #<Inspec::Resources::DockerContainerFilter:0x0000563281091be0> with names =~ /pgpool-compose/ image == "bitnami/pgpool:4.3.2-debian-11-r16" status is expected to match [/Up/]
     ✔  PostgreSQL query: SELECT datname FROM pg_database; output is expected to include "db_test"
  ✔  PgPoolII Nodes Connected: PgPoolII Backend Nodes Online
     ✔  PostgreSQL query: SHOW POOL_NODES; output is expected to match "postgres-compose-master-1" and match "postgres-compose-replica-1" and match "postgres-compose-replica-2"


Profile Summary: 6 successful controls, 0 control failures, 0 controls skipped
Test Summary: 13 successful, 0 failures, 0 skipped

docker run --network java-mod-10-orchestrating-using-compose_default -it --rm -v /var/run/docker.sock:/var/run/docker.sock -v $(pwd)/test:/test inspec-lab exec postgres.rb -t docker://java-mod-10-orchestrating-using-compose_postgres-compose-master-1_1

Profile:   tests from postgres.rb (tests from postgres.rb)
Version:   (not specified)
Target:    docker://695fb0406f730d0d51c6874c9adbb8a53b72837dce9de1e681f773b6a0754ff9
Target ID: da39a3ee-5e6b-5b0d-b255-bfef95601890

  ✔  RepMgr Nodes Connected: RepMgr Backend Nodes Online
     ✔  Command: `/opt/bitnami/scripts/postgresql-repmgr/entrypoint.sh repmgr -f /opt/bitnami/repmgr/conf/repmgr.conf cluster show` stdout is expected to match "postgres-compose-master-1" and match "postgres-compose-replica-1" and match "postgres-compose-replica-2"


Profile Summary: 1 successful control, 0 control failures, 0 controls skipped
Test Summary: 1 successful, 0 failures, 0 skipped

Advanced lab

If you still have time after completing the above, go ahead and scale out the application layer to a few containers. Use Traefik to load balance the web traffic. Web Load Balancing is its own complex topic, but this guide should be straightforward enough to provide a good demonstration.

• Traefik for Docker Compose