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@title Managing the Worker Queue
@group fieldmanual

Advanced guide to managing the background worker task queue.

Overview
========

Phabricator uses daemonized worker processes to execute some tasks (like
importing repositories and sending mail) in the background.

In most cases, this queue will automatically execute tasks in an appropriate
order. However, in some cases you may want to exercise greater control over
which tasks execute, when, and at what priority.

Reference: Priority Levels
==========================

Tasks queued by Phabricator use these default priority levels:

| Priority | Name | Tasks |
|---|---|---|
| 1000 | `ALERTS` | Time-sensitive notifications and email. |
| 2000 | `DEFAULT` | Normal publishing and processing. |
| 2500 | `COMMIT` | Import of commits in existing repositories. |
| 3000 | `BULK` | Edits applied via "Bulk Edit" interface. |
| 3500 | `INDEX` | Search engine index updates. |
| 4000 | `IMPORT` | Import of commits in new repositories. |

Tasks with smaller priority numbers execute before tasks with larger priority
numbers (for example, a task with priority 1000 will execute before a task
with priority 2000).

Any positive integer is a valid priority level, and if you adjust the priority
of tasks with `bin/worker priority` you may select any level even if
Phabricator would never naturally queue tasks at that level. For example, you
may adjust tasks to priority `5678`, which will make them execute after all
other types of natural tasks.

Although tasks usually execute in priority order, task execution order is not
strictly a function of priority, and task priority does not guarantee execution
order.

Large Repository Imports
========================

The most common case where you may want to make an adjustment to the default
behavior of the worker queue is when importing a very large repository like
the Linux kernel.

Although Phabricator will automatically process imports of new repositories at
a lower priority level than all other non-import tasks, you may still run into
issues like these:

- You may also want to import one or more //other// new repositories, and
    would prefer they import at a higher priority.
  - You may find overall repository performance is impacted by the large
    repository import.

You can manually change the priority of tasks with `bin/worker priority`. For
example, if your copy of the Linux repository is `R123` and you'd like it to
import at a lower priority than all other tasks (including other imports of
new repositories), you can run a command like this:

```
phabricator/ $ ./bin/worker priority --priority 5000 --container R123
```

This means: set all tasks associated with container `R123` (in this example,
the Linux repository) to priority 5000 (which is lower than any natural
priority).

You can delay tasks until later with `bin/worker delay`, which allows you to
schedule tasks to execute at night or over the weekend. For example, to
pause an import for 6 hours, run a command like this:

```
phabricator/ $ ./bin/worker delay --until "6 hours" --container R123
```

The selected tasks will not execute until 6 hours from the time this command
is issued. You can also provide an explicit date, or "now" to let tasks begin
execution immediately.

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