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Subscriptions

A task subscription is the expression of a task's intent to receive certain events, filtering by topic. A subscription consists of an event topic, optionally combined with a time offset, which creates a delay.
A task may have any number of subscriptions.

Delays

... are accomplished using subscription offsets, as described below. This heading is here for folks searching for a way to delay their tasks. ;)

Offsets

A subscription offset defines the amount of time a task should wait or delay (!!) before responding to the incoming event. It's the easiest way to add a delay to a task's subscription to a specific topic. (For finer control over event timing, try using the run_at option of the Event action.)
Subscription offsets are appended to the subscription topic, and are of the form "+1.hour". Offsets may be given using minutes, hours, days, weeks, months, or years. There is no limit to how large the subscription offset may be.
A subscription with an offset looks like "shopify/customers/create+1.hour".
To learn more about scheduling work with Mechanic, see Scheduling.
The Shopify variables available to tasks always contain data drawn from the event itself. If a task has a offset event subscription, this data may be outdated by the time the task runs.
To reload the data in a Shopify variable, use something like this:
{% unless event.preview %}
{% assign customer = customer.reload %}
{% endunless %}
Remember, Mechanic does not permit access to the Shopify API during event preview. Using this unless statement ensures that reloading only happens during a live event.

Using Liquid

A task's subscriptions are parsed for Liquid, at the time the task is saved. Combined with task options, this is an opportunity to generate subscriptions based on user configuration, adding or removing subscriptions based on the user's choice, or adjusting subscription offset based on a user-entered value.
One subscription is permitted per line. Blank lines and leading/trailing whitespace are permitted.

Examples

Conditional subscription
shopify/orders/create
​
{% if options.send_email_when_order_cancelled__boolean %}
shopify/orders/cancelled
{% endif %}
Dynamic offset
shopify/orders/paid+{{ options.days_to_wait_before_followup__number_required }}.days
Optional offset
shopify/customers/create{% if options.wait_one_hour__boolean %}+1.hour{% endif %}