Cron

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This module implements a time-based job scheduler. Every job will execute a request to the hive with a predefined ingrid message payload.

docker pull registry.goingrid.io/services/cron:v0.1.0

Table of contents

Service properties

The cron service accepts no properties.

Controls

The standard control Ingrid-Mode=execution is automatically added to each job.

Service capabilities

Schedule jobs

Logging every minute (config.json)

{
  "jobs": [
    {
      "name": "logging",
      "schedule": "@every 1m",
      "ingrid_msg": {
        "Class": "log",
        "Operation": "slap",
        "Data": {
          "actor": [ "cron" ],
          "severity": [ "info" ],
          "message": [ "This is a scheduled message. See you in a minute." ]
        }
      }
    }
  ]
}

Docker configuration

cron:
  image: registry.goingrid.io/trigger/cron:v0.1.0
  deploy:
    restart_policy:
      condition: on-failure
    placement:
      constraints:
        - node.role == manager
  environment:
    NAME: "cron"
    SERVERHOST: "hive"
    SERVERAUTH: "file:///run/secrets/ing-hive-key"
    OUTPUTCHANNEL: "main"
    CONFIG: "hive://config.json"
  depends_on:
    - hive
  secrets:
    - ing-hive-key
  networks:
    - ing-entry
    - ing-middle

Service configuration

Parameter Default Description
Config "config.json" Config file used for scheduling jobs (see additional configuration file)

Additionally the cron service includes all properties of the service configuration and the output configuration.

Additional configuration file

The configuration file consists of a list of jobs. The name identifies the job name, schedule defines the scheduled time (see below for format possibilities) and ingrid_msg defines the request that will be sent.

{
  "jobs": [
    {
      "name": "Job name",
      "schedule": "@every 1m",
      "ingrid_msg": {
        "Class": "example",
        "Operation": "example",
        "Data": {
          "example": [ "example" ]
        }
      }
    }
  ]
}

CRON Expression Format

A cron expression represents a set of times, using 5 space-separated fields.

Field name Mandatory? Allowed values Allowed special characters
Minutes Yes 0-59 * / , -
Hours Yes 0-23 * / , -
Day of month Yes 1-31 * / , - ?
Month Yes 1-12 or JAN-DEC * / , -
Day of week Yes 0-6 or SUN-SAT * / , - ?

Month and Day-of-week field values are case insensitive. “SUN”, “Sun”, and “sun” are equally accepted.

The specific interpretation of the format is based on the Cron Wikipedia page: https://en.wikipedia.org/wiki/Cron

Special Characters

Asterisk ( * )

The asterisk indicates that the cron expression will match for all values of the field; e.g., using an asterisk in the 5th field (month) would indicate every month.

Slash ( / )

Slashes are used to describe increments of ranges. For example 3-59/15 in the 1st field (minutes) would indicate the 3rd minute of the hour and every 15 minutes thereafter. The form “*\/…” is equivalent to the form “first-last/…”, that is, an increment over the largest possible range of the field. The form “N/…” is accepted as meaning “N-MAX/…”, that is, starting at N, use the increment until the end of that specific range. It does not wrap around.

Comma ( , )

Commas are used to separate items of a list. For example, using “MON,WED,FRI” in the 5th field (day of week) would mean Mondays, Wednesdays and Fridays.

Hyphen ( - )

Hyphens are used to define ranges. For example, 9-17 would indicate every hour between 9am and 5pm inclusive.

Question mark ( ? )

Question mark may be used instead of ‘*’ for leaving either day-of-month or day-of-week blank.

Predefined schedules

You may use one of several pre-defined schedules in place of a cron expression.

Entry Description Equivalent To
@yearly (or @annually) Run once a year, midnight, Jan. 1st 0 0 1 1 *
@monthly Run once a month, midnight, first of month 0 0 1 * *
@weekly Run once a week, midnight between Sat/Sun 0 0 * * 0
@daily (or @midnight) Run once a day, midnight 0 0 * * *
@hourly Run once an hour, beginning of hour 0 * * * *