efrecon/disque repository overview

⁠Disque Docker Image

This is a Docker minimal image for running Disque⁠, an in-memory, distributed job queue from the same author⁠ as redis⁠. The image is based on Alpine⁠ and configuration can happen through setting environment variables starting with DISQUE_. The special environment variable DISQUE_MEET can be used to establish cluster formations.

⁠Usage

To create a disque server, run the following command:

docker run efrecon/disque:1.0-rc1

Any configuration variable that appears in the default Disque configuration⁠ can be set in two different ways:

1. By appending a command-line option which name is the same as the configuration variable, though led by a double-dash. This is as per the Disque main server behaviour.

2. By setting an environment variable according to the following rules: the environment variable will be in uppercase, all single dashes from the Disque configuration variable should be replaced by underscores and the environment variable should start with DISQUE_.

So, to set the port, you could run any of the two commands below:

docker run efrecon/disque:1.0-rc1 --port 3456
docker run --env DISQUE_PORT=3456 efrecon/disque:1.0-rc1

⁠Clustering

The environment variable DISQUE_MEET can be used to meet a number of other already running Disque server. The variable should contain a space separated list of pairs <hostname>:<port> where <port> (and the colon sign preceeding it) can be omitted and will default to 7711. While Disque require the MEET command to accept an IP address, creating the cluster using the DISQUE_MEET environment variable allows for hostnames, which facilitates the creation of distributed clusters. From this directory, and using the example compose⁠ file, you can easily create a cluster of 3 nodes using the following command (assuming that you have docker-compose installed):

docker-compose up --scale slave=2

Disque has no slave or master. In the example setup, the runtime existence of the three equivalent nodes ensures the persistence of the queues. The compose file persists queue state into a volume associated to the master service to ease cold restarts.

⁠Implementation

This image takes its roots in richnorth/disque⁠, while being based on the minimal Alpine⁠ image and taking heavy inspiration of the official⁠ redis image. The image is directly compiled from the official released source. To ensure proper compilation on Alpine, support for backtrace is manually removed from config.h⁠ in the Dockerfile⁠.

Support for environment variables led by DISQUE_ is implemented as part of the entrypoint. The implementation will copy the default configuration file from Disque, modify it per the environment variables and start with the disque server using the modified copy of the default configuration file.

The only exception to these DISQUE_ environment variables is the DISQUE_MEET. Instead, whenever it exists, a temporary helper process implemented as meet.sh⁠ will wait for the local Disque server to be running, resolve all hostnames pointed at by the content of the DISQUE_MEET environment variable and request the local Disque server to meet those remote IP addresses. The implementation will automatically wait for the remote servers to be up and running (and available at the relevant port) before trying to join.