[wp-trac] [WordPress Trac] #34330: Locks API for atomic data manipulation

[WordPress Trac]

#34330: Locks API for atomic data manipulation
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 Reporter:  lpghatguy        |      Owner:
     Type:  feature request  |     Status:  new
 Priority:  normal           |  Milestone:  Awaiting Review
Component:  Database         |    Version:  trunk
 Severity:  normal           |   Keywords:
  Focuses:                   |
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 I originally opened a ticket at #34304 for locking methods specifically
 for post metadata. @rmccue made a note that a full-scale locking API might
 be more useful than a locking API specifically for post or userdata.

 I won't fully iterate over why locking is beneficial, but in short, it
 prevents data races that can have bad results.

 So now I'm here to propose a locking API for all sorts of things:
 - Posts
 - Users
 - Post/User Meta
 - Options

 Initiailly, I proposed an API using methods like
 `get_and_update_post_meta`, taking in the normal parameters for
 `get_post_meta` and the like, but also taking a callback method. During
 the callback, the data would be locked and only accessible from the
 callback itself.

 I provided a prototype implementation using MySQL's `GET_LOCK` and similar
 methods; it is attached here. To scale to the full system, it would
 require lock checking code in all queries reading any data, which might be
 a large undertaking. I haven't researched the potential performance
 implications of this, or how it would be applied to more complicated data.

 Some questions I'd like to look into:
 - What would a full-scope locking API look like?
 - Is this feature useful for a regular WordPress site?
 - Is this a problem other users have encountered?
 - Does this solution scale?

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Ticket URL: <https://core.trac.wordpress.org/ticket/34330>
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