Function parse_crontab 

pub fn parse_crontab(crontab: &str) -> Result<Vec<Crontab>, CrontabParseError>

Parse a crontab definition into a Vec of crontab

Tasks are by default read from a crontab file next to the tasks folder (but this is configurable in library mode). Please note that our syntax is not 100% compatible with cron’s, and our task payload differs. We only handle timestamps in UTC. The following diagram details the parts of a Graphile Worker crontab schedule:

┌───────────── UTC minute (0 - 59)
│ ┌───────────── UTC hour (0 - 23)
│ │ ┌───────────── UTC day of the month (1 - 31)
│ │ │ ┌───────────── UTC month (1 - 12)
│ │ │ │ ┌───────────── UTC day of the week (0 - 6) (Sunday to Saturday)
│ │ │ │ │ ┌───────────── task (identifier) to schedule
│ │ │ │ │ │    ┌────────── optional scheduling options
│ │ │ │ │ │    │     ┌────── optional payload to merge
│ │ │ │ │ │    │     │
│ │ │ │ │ │    │     │
* * * * * task ?opts {payload}

Comment lines start with a #.

For the first 5 fields we support an explicit numeric value, * to represent all valid values, */n (where n is a positive integer) to represent all valid values divisible by n, range syntax such as 1-5, and any combination of these separated by commas.

The task identifier should match the following regexp /^[_a-zA-Z][_a-zA-Z0-9:_-]*$/ (namely it should start with an alphabetic character and it should only contain alphanumeric characters, colon, underscore and hyphen). It should be the name of one of your Graphile Worker tasks.

The opts must always be prefixed with a ? if provided and details configuration for the task such as what should be done in the event that the previous event was not scheduled (e.g. because the Worker wasn’t running). Options are specified using HTTP query string syntax (with & separator).

Currently we support the following opts:

• id=UID where UID is a unique alphanumeric case-sensitive identifier starting with a letter - specify an identifier for this crontab entry; by default this will use the task identifier, but if you want more than one schedule for the same task (e.g. with different payload, or different times) then you will need to supply a unique identifier explicitly.
• fill=t where t is a “time phrase” (see below) - backfill any entries from the last time period t, for example if the worker was not running when they were due to be executed (by default, no backfilling).
• max=n where n is a small positive integer - override the max_attempts of the job.
• queue=name where name is an alphanumeric queue name - add the job to a named queue so it executes serially.
• priority=n where n is a relatively small integer - override the priority of the job.

NOTE: changing the identifier (e.g. via id) can result in duplicate executions, so we recommend that you explicitly set it and never change it.

NOTE: using fill will not backfill new tasks, only tasks that were previously known.

NOTE: the higher you set the fill parameter, the longer the worker startup time will be; when used you should set it to be slightly larger than the longest period of downtime you expect for your worker.

Time phrases are comprised of a sequence of number-letter combinations, where the number represents a quantity and the letter represents a time period, e.g. 5d for five days, or 3h for three hours; e.g. 4w3d2h1m represents 4 weeks, 3 days, 2 hours and 1 minute (i.e. a period of 44761 minutes). The following time periods are supported:

• s - one second (1000 milliseconds)
• m - one minute (60 seconds)
• h - one hour (60 minutes)
• d - one day (24 hours)
• w - one week (7 days)

The payload is a JSON5 object; it must start with a {, must not contain newlines or carriage returns (\n or \r), and must not contain trailing whitespace. It will be merged into the default crontab payload properties.

Each crontab job will have a JSON object payload containing the key _cron with the value being an object with the following entries:

• ts - ISO8601 timestamp representing when this job was due to execute
• backfilled - true if the task was “backfilled” (i.e. it wasn’t scheduled on time), false otherwise