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README.md

Comdb2 on Docker

Prerequsites

  1. Install Docker Engine
  2. For using make docker-cluster Install Docker Compose
  3. Read these docs to see what everything is used for

This utility was built and tested using the following versions of Docker Engine and Compose:

Docker Engine

  • version 17.06.0-ce

Docker Compose

  • version 1.14.0

Dockerfiles

This folder contains several Dockerfiles which serve different functions in running Comdb2 on Docker.

File Description
Dockerfile.standalone Contains dependencies needed to run the database and the built source installed
Dockerfile.dev Replaces the entrypoint in Dockerfile.standalone with one that spins up a database
Dockerfile.build Contains all build dependencies to build source and output into ./build folder for use by dependent images
Dockerfile.jdbc.build JDBC Driver builder

Dependency Between Images

Dockerfile.build => Dockerfile.standalone => Dockerfile.dev
=> Dockerfile.cluster

Using make

Docker image builds and spining up a Comdb2 cluster through Docker Compose can be done through make. The following commands can be executed from the root directory of the Comdb2 project.

Command Usage
make docker-standalone Builds the comdb2-standalone:<version> Docker image
make docker-dev Builds the comdb2-dev:<version> Docker image
make docker-cluster Creates and runs a Comdb2 cluster using docker-compose after initial configuration. See docker-cluster instructions
make docker-build Creates a build container and builds the source into the contrib/docker/build/ folder
make docker-clean Removes the contrib/docker/build/ folder created in the docker-build process and runs docker-compose down to shut down and remove any running compose clusters

Using make docker-cluster

The make docker-cluster command is a way to run an example Comdb2 cluster. As configured in docker-compose.yml, this command will create a 5 node Comdb2 cluster and an "application" container called dev. There are a few setup steps to configure the host environment.

  1. Run make docker-cluster. This will create the volume-linked folders on your host machine in contrib/docker/volumes. It is expected that this will fail to start because no databases have been created yet.

  2. Create a Comdb2 Database called testdb in the node1 folder created in contrib/docker/volumes/. Steps to create a database can be found here. If you would like to modify the name of the database, also change the name in the cluster-entrypoint.sh file and rename the testdb.cfg to <dbname>.cfg.

  3. Open the LRL file (ex. testdb.lrl) in the folder. Change the dir /some/path to dir /db. Also add the following line to the end of the file cluster nodes node1 node2 node3 node4 node5.

  4. Copy all the database files that have just been created in the node1 folder into all the other nodeX folders.

  5. Run make docker-cluster and the cluster should start running. Running docker ps should show nodes 1 through 5 up and running.

To open a shell on the dev container (would be replaced by your application in actual use), run docker exec -it dev /bin/bash to open a bash shell. Once connected, run cdb2sql testdb dev to run the cdb2sql client.

To open a shell in one of the nodes in the cluster, run docker exec -it nodeX /bin/bash to open a bash shell on that node.

If your cluster is not working, try navigating to contrib/docker/ and run docker-compose up which will try to spin up the nodes in the foreground and will show any errors the cluster nodes may be experiencing.

Misc. Files

There are several additional files that are used to support Docker operations.

File Description
docker-compose.yml This is an example Docker Compose file for running a Comdb2 cluster
cluster-entrypoint.sh Entrypoint script for the example cluster
docker-dev-entrypoint.sh Entrypoint script for comdb2-dev:<version> image
runforever Shell script that runs forever. Used to keep containiers alive after startup
testdb.cfg Config file for cdb2sql when running in the example cluster