Add task queue section (#1417)

* Add task queue section

* Add links

* Explain celery beat setup

* Apply review changes

docs/developer/checkout/lifecycle.mdx

@@ -41,6 +41,11 @@ To avoid overloading the database, unfinished and unpaid checkouts are automatic
 - anonymous checkouts (neither user nor email is set) with lines after 30 days,
 - user checkouts (either user or email is set) with lines after 90 days.
 
+:::note
+The checkout deletion task is triggered by [celery beat scheduler](developer/running-saleor/task-queue.mdx#periodic-tasks).
+This feature will not work without task queue configuration. 
+:::
+
 ## Releasing Funds for Abandoned Checkouts
 
 Payments for items left in the cart by customers who did not complete the purchase will be refunded to the customer's account.
@@ -58,6 +63,11 @@ The release action is triggered only once. If a subscription for a release event
 
 To fetch paid checkouts, use the below query:
 
+:::note
+The releasing funds for abandoned checkouts task is triggered by [celery beat scheduler](developer/running-saleor/task-queue.mdx#periodic-tasks).
+This feature will not work without task queue configuration. 
+:::
+
 ```graphql {4}
 {
   checkouts(first: 10, filter: { authorizeStatus: [PARTIAL, FULL] }) {

docs/developer/checkout/order-expiration.mdx

@@ -68,6 +68,11 @@ In the above example, orders will expire after 360 minutes (6 hours), and after
 Once an unpaid order is created (via [`checkoutComplete`](api-reference/checkout/mutations/checkout-complete.mdx) or [`orderCreateFromCheckout`](api-reference/orders/mutations/order-create-from-checkout.mdx)), it remains in `UNCONFIRMED` status. If the customer does not complete the payment within `expireOrdersAfter` minutes after that, the status will change to `EXPIRED` and stock allocation will be released.
 After `deleteExpiredOrdersAfter` days orders in `EXPIRED` status will be deleted and disappear from the order list.
 
+:::note
+The order expiration and order deletion tasks are triggered by [celery beat scheduler](developer/running-saleor/task-queue.mdx#periodic-tasks).
+This feature will not work without task queue configuration. 
+:::
+
 ## How to disable order expiration
 
 To disable order expiration, set `expireOrdersAfter` to 0.

docs/developer/community/contributing.mdx

@@ -301,6 +301,11 @@ Also, do not forget about the docstring, especially in a complicated function.
 So far, we have mainly used the `GinIndex` and `ilike` operators for searching, but currently, we are testing a new solution with the use of `SearchVector` and `SearchRank`.
 You can find it in this PR [#9344](https://github.com/saleor/saleor/pull/9344).
 
+:::note
+The search vector update task is triggered by [celery beat scheduler](developer/running-saleor/task-queue.mdx#periodic-tasks).
+This feature will not work without task queue configuration. 
+:::
+
 ### API
 
 - Use `id` for mutation inputs instead of `model_name_id`.

docs/developer/discounts/promotions.mdx

@@ -41,8 +41,8 @@ When multiple promotions apply to one product, only the discount from the promot
 The discounts from rules within the single promotion are not summed up.
 
 :::note
-The catalogue discounts from promotions are calculated in the background. So the discounted
-price will not be instantly visible after promotion creation.
+The catalogue discounts from promotions are calculated in the background, triggered by [celery beat scheduler](developer/running-saleor/task-queue.mdx#periodic-tasks).
+So the discounted price will not be instantly visible after promotion creation (default interval is set to 30 seconds). 
 :::
 
 ### Examples of the use cases

docs/developer/running-saleor/task-queue.mdx

@@ -0,0 +1,57 @@
+---
+title: Task Queue
+sidebar_label: Task Queue
+---
+
+Some of the Saleor’s functionality depends on a task queue system to manage asynchronous and periodic tasks. We recommend using Celery with Redis as the message broker.
+For more information, please visit [official Celery documentation](https://docs.celeryq.dev/en/stable/index.html). 
+
+
+## Periodic tasks
+
+Celery Beat is a scheduler that triggers background tasks at regular intervals. 
+Some of the Saleor's features can't be used without proper task scheduler setup. In order to start Celery Beat server:
+
+1. Specify `CELERY_BROKER_URL` environmental variable which points to task broker (we recommend using Redis as a broker database):
+
+```shell
+set CELERY_BROKER_URL="<broker url>"
+```
+An example of the Redis broker url, running on localhost and port 6379, looks like: `redis://localhost:6379/0`.
+
+2. Run Celery worker: 
+
+```shell
+celery --app saleor.celeryconf:app worker -E --loglevel=info
+```
+
+3. As a separate process run Celery Beat: 
+
+```shell
+celery --app saleor.celeryconf:app beat --scheduler saleor.schedulers.schedulers.DatabaseScheduler 
+```
+
+Below is a list of Saleor features fired up by celery beat with default schedules:
+
+#### Tasks run in intervals:
+- Deactivate preorder for variants; 1 hour
+- Delete empty allocations; 1 hour
+- Delete expired reservations; 1 day
+- Delete outdated event data; 1 day
+- [Expire orders](developer/checkout/order-expiration.mdx); 5 minutes
+- [Recalculate price for catalog promotions](developer/discounts/promotions.mdx#catalogue-promotions); 30 seconds
+- [Release funds for abandoned checkouts](developer/checkout/lifecycle.mdx#releasing-funds-for-abandoned-checkouts); 10 minutes
+- Remove apps marked as removed; 3 hours
+- [Update search vectors](developer/community/contributing.mdx#searching); 20 seconds
+
+#### Tasks run at specific time:
+- Deactivate expired gift cards; at 0:00 AM
+- [Delete expired checkouts](developer/checkout/lifecycle.mdx#checkout-expiration-and-deletion); at 0:00 AM
+- [Delete expired orders](developer/checkout/order-expiration.mdx); at 2:00 AM base on 
+- Delete old exports files; once per day at 1:00 AM
+- Update stocks quantity allocated; once per day at 0:00 AM
+- [Promotion toggle](developer/discounts/promotions.mdx); based on promotion's start date and end date
+
+:::important
+It is important to understand that without proper task scheduler setup, the actions above will not be triggered.
+:::

sidebars/self-hosting.js

@@ -13,6 +13,7 @@ export const selfHosting = [
 
   "developer/running-saleor/debugging-emails",
   "developer/running-saleor/exposing-instance",
+  "developer/running-saleor/task-queue",
 
   title("Deploying"),
 

vercel.json

@@ -524,6 +524,10 @@
       "source": "/docs(/3.x|/next)?/category/development",
       "destination": "/developer/running-saleor/debugging-emails"
     },
+    {
+      "source": "/docs(/3.x|/next)?/category/development",
+      "destination": "/developer/running-saleor/task-queue"
+    },
     {
       "source": "/docs(/3.x|/next)?/category/saleor-app-store",
       "destination": "/developer/app-store/overview"