[wp-trac] [WordPress Trac] #44458: Catch WSODs and provide a means for recovery for end users

[WordPress Trac]

#44458: Catch WSODs and provide a means for recovery for end users
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 Reporter:  schlessera                           |       Owner:  flixos90
     Type:  task (blessed)                       |      Status:  closed
 Priority:  normal                               |   Milestone:  5.1
Component:  Bootstrap/Load                       |     Version:
 Severity:  normal                               |  Resolution:  fixed
 Keywords:  has-patch needs-testing servehappy   |     Focuses:  multisite
  needs-dev-note                                 |
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Changes (by flixos90):

 * status:  assigned => closed
 * resolution:   => fixed


Comment:

 In [changeset:"44524" 44524]:
 {{{
 #!CommitTicketReference repository="" revision="44524"
 Bootstrap/Load: Introduce fatal error recovery mechanism allowing users to
 still log in to their admin dashboard.

 This changeset introduces a `WP_Shutdown_Handler` class that detects fatal
 errors and which extension (plugin or theme) causes them. Such an error is
 then recorded, and an error message is displayed. Subsequently, in certain
 protected areas, for example the admin, the broken extension will be
 paused, ensuring that the website is still usable in the respective area.
 The major benefit is that this mechanism allows site owners to still log
 in to their website, to fix the problem by either disabling the extension
 or solving the bug and then resuming the extension.

 Extensions are only paused in certain designated areas. The frontend for
 example stays unaffected, as it is impossible to know what pausing the
 extension would cause to be missing, so it might be preferrable to clearly
 see that the website is temporarily not accessible instead.

 The fatal error recovery is especially important in scope of encouraging
 the switch to a maintained PHP version, as not necessarily every WordPress
 extension is compatible with all PHP versions. If problems occur now, non-
 technical site owners that do not have immediate access to the codebase
 are not locked out of their site and can at least temporarily solve the
 problem quickly.

 Websites that have custom requirements in that regard can implement their
 own shutdown handler by adding a `shutdown-handler.php` drop-in that
 returns the handler instance to use, which must be based on a class that
 inherits `WP_Shutdown_Handler`. That handler will then be used in place of
 the default one.

 Websites that would like to modify specifically the error template
 displayed in the frontend can add a `php-error.php` drop-in that works
 similarly to the existing `db-error.php` drop-in.

 Props afragen, bradleyt, flixos90, ocean90, schlessera, SergeyBiryukov,
 spacedmonkey.
 Fixes #44458.
 }}}

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Ticket URL: <https://core.trac.wordpress.org/ticket/44458#comment:56>
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