Flightdeck Zookeeper

Flightdeck Zookeeper is a minimalist Zookeeper container for Drupal sites on Kubernetes and Docker. You can use it both for local development and production.

Features:

• ConfigMap-friendly YAML configuration
• Supports ensemble mode

Tags and versions

There are several tags available for this container, each with different Zookeeper and Drupal module support:

Tags	Zookeeper Version
latest	3.7
x.y.z	3.7

Configuration

Instead of a large number of environment variables, this container relies on a file to perform all runtime configuration, flightdeck-zookeeper.yml. Inside the file, create following:

---
flightdeck_zookeeper: {}

All configuration is done as items under the flightdeck_zookeeper variable. See the following sections for details as to particular configurations.

You can provide this file in one of three ways to the container:

• Mount the configuration file at path /config/zookeeper/flightdeck-zookeeper.yml inside the container using a bind mount, configmap, or secret.
• Mount the config file anywhere in the container, and set the FLIGHTDECK_CONFIG_FILE environment variable to the path of the file.
• Encode the contents of flightdeck-zookeeper.yml as base64 and assign the result to the FLIGHTDECK_CONFIG environment variable.

Basic settings

---
flightdeck_zookeeper:
  tickTime: "1000"
  dataDir: "/data"
  clientPort: "2181"

Where:

• tickTime is the basic time unit in milliseconds used by ZooKeeper. Optional, defaults to 1000.
• dataDir is the directory to store Zookeeper files. Optional, defaults to /data.
• clientPort is the port on which to listen for client connections. Optional, defaults to 2181.

Zookeeper ensemble

Often, you will want to run multiple Zookeeper instances as an ensemble, or a redundant cluster of instances. There are several settings needed to configure an ensemble for this container:

---
flightdeck_zookeeper:
  initLimit: "120"
  syncLimit: "120"
  myId: "1"
  myIdFromHostname: false
  servers:
    - hostname: "zookeeper-0"
      quorumPort: 2888
      leaderPort: 3888
    - hostname: "zookeeper-1"
    - hostname: "zookeeper-2"

Where:

• initLimit is the amount of time in ticks (see tickTime) for a Zookeeper ensemble to reach a quorum. Optional, defaults to 120.
• syncLimit is the amount of time in ticks (see tickTime) a Zookeeper follower instance can be out of sync from the Zookeeper leader instance. Optional, defaults to 120.
• myId is the server ID number greater than 0. Required unless myIdFromHostname is true.
• myIdFromHostname instructs the container to attempt to extract the value of myid from the container hostname. Optional, defaults to true.
• servers is a list of items specifying the Zookeeper host, the quorumPort (default 2888), and the leaderPort (default 3888).

The myIdFromHostname setting is particularly useful when deploying this container as a Statefulset in Kubernetes, as hostnames end in -n where n is a zero indexed replica number. Whatever number extracted from the hostname is incremented by one (0 -> 1) so as to meet Zookeeper myid requirements.

Autopurging files

Zookeeper retains snapshots of the dataDir. You can control this behavior under the autopurge key:

---
flightdeck_zookeeper:
  autopurge:
    state: true
    snapRetainCount: 3
    purgeInterval: 24

Where:

• state is if snapshot autopurging is enabled. Optional, defaults to true.
• snapRetainCount is the number of snapshots to retain. Optional, defaults to 3.
• purgeInterval is the time in hours to purge previous snapshots. Optional, defaults to 24.

Using with Docker Compose

Create the flightdeck-zookeeper.yml file relative to your docker-compose.yml. Define the Zookeeper service mounting the file as a volume:

version: '3'
services:
  Zookeeper:
    image: ten7/flight-deck-Zookeeper
    volumes:
      - ./flightdeck-zookeeper.yml:/config/Zookeeper/flightdeck-zookeeper.yml
    ports:
      - "8003:8983"

Part of Flightdeck

This container is part of the Flightdeck library of containers for Drupal local development and production workloads on Docker, Swarm, and Kubernetes.

Flightdeck is used and supported by TEN7.

Debugging

If you need to get verbose output from the entrypoint, set flightdeck_debug to true or yes in the config file.

---
flightdeck_debug: yes

This container uses Ansible to perform start-up tasks. To get even more verbose output from the start up scripts, set the ANSIBLE_VERBOSITY environment variable to 4.

If the container will not start due to a failure of the entrypoint, set the FLIGHTDECK_SKIP_ENTRYPOINT environment variable to true or 1, then restart the container.

License

Flightdeck is licensed under GPLv3. See LICENSE for the complete language.