tree: 64b48cbed08e61a3df395b8307670045030bcdd7 [path history] [tgz]
  1. docker/
  2. java/
  3. resources/
  4. scala/
  6. TEST_HA

Gerrit high-availability docker setup example

The Docker Compose project in the docker directory contains a simple test environment of two Gerrit masters in HA configuration, with their git repos hosted on NFS filesystem.

How to build

The project can be built using docker-compose (make sure you set the platform attribute in the docker-compose.yaml file if you're not in an amd64 arch).

To build the Docker VMs:

  # first, remove the buildx if it exists and its not running
  $ docker buildx inspect docker-ha | grep Status
  $ docker buildx rm docker-ha
  # create the docker-ha buildx node, provide your architecture and start it up
  docker buildx create --name docker-ha --platform "linux/amd64" --driver docker-container --use \
  && docker buildx inspect --bootstrap \
  && docker-compose build

Building the Docker VMs using a non-default user id

First, update the user id in the NFS Dockerfile. This is done simply by modifying the file setting the non-default user id. Then, run the following:

  $ export GERRIT_UID=$(id -u)
  $ docker-compose build --build-arg GERRIT_UID

Above, exporting that UID is optional and will be 1000 by default. Build the gerrit images this way only if the user with id 1000 on your host is not owned by you. For example, some corporate environments use a restricted 1000 user (id). In that case, the containerized application may fail to write towards the host (through volumes). Important: The user id in gerrit must be the same as the uid in the NFS server, otherwise you will encounter file ownership problems on any filesystem operation.

That UID will be the one set for the containerized gerrit user. Latter‘s group will remain as default (1000). This is because groups known from the host need to be redefined for containers. Setting that user’s group in the container is not necessary for writing anyway, as opposed to its user id. The individual gerrit user's writing permission does suffice.

How to run

Use the ‘up’ target to startup the Docker Compose VMs.

  $ docker-compose up -d

Background on using an NFS server

We are using the erichough/nfs-server image mainly because it's easy to use & we had success with it. The work has been inspired by this blog post.

The containers start with the privileged flag set, which is a security risk but necessary to work around permission issues.

It is worth noting that we are exposing the /var/gerrit/git directory as the nfs-share. This is because more often than not it‘s the git directory that’s shared over the network. You can change this in the nfs server and gerrit docker files, and in the exports.txt file.

The NFS server is using a static IP. The Docker Compose YAML file defines a bridge network with the subnet (this is what allows us to give the NFS Server a known, static IP).

The addr= option (in the nfs-client-volume volume) is the reason we need a static IP for the server (and hence a configured subnet for the network). Note that using a name (ie. addr=nfs-server) we weren't able to get the DNS resolution to work properly.

Also in the Docker Compose file we can see that the nfs-server container uses a healthcheck, this is necessary to control when the gerrit services will start up (they need to start after the nfs server is fully up-and-running).

Finally, we are providing an exports.txt file, which again utilises the subnet we provided during the bridge network creation. This file is baked into the image sacrificing a bit of flexibility, but we feel this is a small price to pay to have everything automated.

Gerrit high-availability local setup example

  1. Init gerrit instances with high-availability plugin installed:
    1. Optionally, set http port of those instance to 8081 and 8082.
    2. Make sure ssh ports on those instances are different. (i.e. 29418 and 29419)
    3. Make sure instances share the same git repo.
    4. Create and provide shared directory to those instances.
  2. Set up high-availability plugin.
    1. main.sharedDirectory = “the created shared directory above”.
    2. peerInfo.strategy = static
    3. peerInfo “static”.url = other_instance_url (i.e http://localhost:8081 or http://localhost:8082)

How to test

Consider the instructions on how to use Gerrit core's Gatling framework, to run non-core test scenarios such as this plugin one below:

  $ sbt "gatling:testOnly"

This is a scenario that can serve as an example for how to start testing an HA Gerrit system. That scenario tries to clone a project created on gerrit 1 (port 8081) but from gerrit 2 (on 8082). The scenario therefore expects Gerrit HA to have properly synchronized the new project from 1 to 2. That project gets deleted after, here using HA Gerrit straight (through default http port 80).

Scenario scala source files and their companion json resource ones are stored under the usual src/test directories. That structure follows the scala package one from the scenario classes. The core framework expects such a directory structure for both the scala and resources (json data) files.

Alternatively, the TEST_HA script can be used to run Gatling tests which provides a minimum configuration to run the test.

How to stop

Simply type CTRL+C on the window that started the environment and all the VMs will stop. Their state will be persisted and the next run will continue with the same data.

How to clean

If you want to stop and cleanup all the previous state, use the ‘down’ target.

  $ docker-compose down