[wp-trac] [WordPress Trac] #23269: .maintenance location issue on symlinked install

[WordPress Trac]

#23269: .maintenance location issue on symlinked install
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 Reporter:  WPsites          |       Owner:
     Type:  enhancement      |      Status:  new
 Priority:  normal           |   Milestone:  Awaiting Review
Component:  Upgrade/Install  |     Version:  3.5
 Severity:  normal           |  Resolution:
 Keywords:  dev-feedback     |     Focuses:
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Comment (by dd32):

 `ABSPATH` really seems like the safest option to me.. but in a symlinked
 install, as noted, it's not ideal.

 `WP_CONTENT_DIR` could be shared with another install, `WP_PLUGINS_DIR`
 could be shared, and it could even have a shared themes directory. As much
 as one might expect that to be rarer than `ABSPATH` being shared, I
 suspect it might actually happen more often than expected and may cause
 unintended side effects for some people.

 Multisite also has issues with the `.maintenance` file as it can take down
 the entire instance while upgrading a theme active on only one site.

 The other option, is that we store a maintenance file alongside the `wp-
 config.php` file, as that should be unique per site,  or so you would
 think, but it's also possible to have a single wp-config.php file shared
 amongst multiple WordPress installs (in subdirectories).

 So by this point, you're probably seeing what I'm thinking here, every
 option has a downside to it.

 Another option is that we keep it in `ABSPATH`, but instead of just
 writing `$upgrading = time()` to the file (which I think is what we do) we
 also write a site-identifying string to it, for example, `$site = DB_HOST
 . DB_NAME . $table_prefix;` which we can then check on pageloads that find
 the file existing. I'm not sure this is a sure-way of doing it either, but
 it would also open the door to fixing the Multisite issue where we'd just
 define what's upgrading (`core`, `plugin:akismet/akismet.php`, `theme
 :site-specific-theme`).

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Ticket URL: <https://core.trac.wordpress.org/ticket/23269#comment:3>
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