elastic_cron/README.md

Luzifer / elastic_cron

This project is a quick and dirty replacement for running a cron daemon inside docker containers while logging into an elasticsearch instance.

The code is basically a fork of the rsyslog_cron repo modified to log into elasticsearch.

Advantages

• It logs the output of the jobs into an elasticsearch instance
• Crons can be started on seconds, not only on minutes like a conventional cron
• Due to the logs cron jobs can get debugged
• On success and failure a HTTP ping to Healthchecks or Cronitor can be executed

Usage

1. Put the binary into your container
2. Generate a YAML file containing the cron definition
3. Watch your crons get executed in your log stream

Config format

---

elasticsearch:
  index: 'elastic_cron-%{+YYYY.MM.dd}'
  servers:
    - http://localhost:9200
  auth: [username, password]

jobs:
  - name: date
    schedule: "0 * * * * *"
    cmd: "/bin/date"
    args:
      - "+%+"
    ping_success: "https://..."
    ping_failure: "https://..."

...

• elasticsearch
  • index - Name of the index to write messages to (understands same date specifier as ES beats)
  • servers - List of elasticsearch instances of the same cluster to log to
  • auth - List consisting of two elements: username and password
• schedule - consists of 6 instead of the normal 5 fields:

field         allowed values
-----         --------------
second        0-59
minute        0-59
hour          0-23
day of month  1-31
month         1-12 (or names, see below)
day of week   0-7 (0 or 7 is Sun, or use names)

Standard format for crontab entries is supported. (See man 5 crontab)