Qron is a simple scheduler for message queues.

Download the latest release binary.

Or use go tool:

# this will install the qron binary to your $GOPATH/bin
$ go get github.com/mak73kur/qron/cmd/qron

Run qron:

$ ./qron /path/to/config.yml

Example config:

loader:
    type: inline
    tab: |
        * * * * * [every minute]

writer:
    type: log

There are two main sections:

• loader which tells qron where should it look for a job schedule called qrontab.
• writer that decides where to qron will publish messages.

Specific properties depend on the chosen loader and writer types.

Thanks to spf13/viper, config file supports different formats: json, toml, yaml.

If path argument is empty, qron by default will try /etc/qron.yml.

Each line is a new job.

Parameters should be separated by a single whitespace character.

First five are schedule parameters, sixth is a message body.

Message body can have whitespace or any other character, except newline.

┌───────────── min (0-59)
│ ┌────────────── hour (0-23)
│ │ ┌─────────────── day of month (1-31)
│ │ │ ┌──────────────── month (1-12)
│ │ │ │ ┌───────────────── day of week (0-6) (0 to 6 are Sunday to Saturday)
│ │ │ │ │
│ │ │ │ │
* * * * * message_body

Allowed parameter expressions:

• asterisk(*) — anything passes.
• comma(,) — 0 5,17 * * 1 — executes at 5AM and 5PM each Monday.
• slash(/) — 0 */6 * * * — shortcut for 0,6,12,18.

Qron will skip any lines that are empty or start with the comment characters (# or //).

Tab can be loaded from one of the following sources.

Store the tab directly in the same config.

loader:
    type: inline
    tab: |
        * * * * * every minute
        */2 * * * * every two minutes

The file will be read once on program start. Sending SIGHUP will trigger file reread without a restart (this is also true for redis loader).

loader:
    type: file
    path: /tmp/qrontab

Tab is stored as a single string value in Redis DB.

Separate program thread will call GET <key> every minute to update the tab on any changes.

Note: if the value gets cleared for some reason - qron will assume the tab is empty and will continue to run with nothing to publish.

loader:
    type: redis
    url: localhost:6379
    db: 0
    key: qrontab

Every minute qron checks whether a job matches the current time. If it does — qron writer will publish the job message.

For debug purposes. Writes message directly to the program output.

writer.type: log

AMQP writes messages to RabbitMQ or any other protocol implementation.

writer:
    type: amqp
    url: amqp://localhost:5672
    exchange: ""
    routing_key: qron

• verbose mode
• proper godoc
• tests for the base package
• custom msg properties e.g. ttl