This is a tracking task for various miscellaneous tasks relating to MediaWiki PHP set-up code. It will be resolved when the sub tasks added during Spring 2018, are resolved.

Goals:

• Reduce maintenance overhead by addressing Technical-Debt.
• Make the code easier to contribute to by simplifying it and improving its documentation.
• Improve startup performance, especially for stateless requests (api.php, load.php) and read-only routes.

Sub tasks:

• Understand current initialisation logic.
• Understand current initialisation requirements.
• Understand current initialisation performance. – T233886#5532734
• Improve and simplify initialisation performance in a way that continues to satisfy current requirements.

Current code (Feb 2018)

From: /w/{entrypoint}.php:

• include PHPVersionCheck
  • PHPVersionCheck::checkRequiredPHPVersion()
  • PHPVersionCheck::checkVendorExistence()
  • PHPVersionCheck::checkExtensionExistence()
• include WebStart
  1. WebStart: assert php-env mbstring.func_overload
  2. WebStart: emit header X-Content-Type-Options: nosniff
  3. WebStart: global set $wgRequestTime
  4. WebStart: global unset $IP
  5. WebStart: define MEDIAWIKI
  6. WebStart: global set $IP
  7. WebStart: include Setup
     1. Setup: global set $wgProfiler
     2. Setup: include StartProfiler (conditional)
     3. Setup: include AutoLoader
     4. Setup: include Defines
     5. Setup: include DefaultSettings
     6. Setup: include GlobalFunctions
     7. Setup: include vendor/autoload (conditional)
     8. Setup: assert vendor
     9. Setup: php-env add HeaderCallback
     10. Setup: include LocalSettings
  8. WebStart: include OutputHandler (conditional)
  9. WebStart: register ob_start wfOutputHandler (conditional)
     1. OutputHandler: handle ValidateAllHtml (conditional)
     2. OutputHandler: handle compression (conditional)
     3. OutputHandler: emit header Content-Length (conditional)
  10. WebStart: include Setup [continued]
      1. Setup: process Profiler (implicit)
      2. Setup: process ExtensionRegistry
      3. Setup: php-env ensure mb_internal_encoding( .. )
      4. Setup: php-env ensure LC_ALL=..
      5. Setup: process mw-config phase1/2 (DefaultSettings, LocalSettings, shortcuts, derivatives, deprecations, normalising)
      6. Setup: process MWDebug
      7. Setup: process MediaWikiServices
      8. Setup: define MW_SERVICE_BOOTSTRAP_COMPLETE
      9. Setup: php-env add MWExceptionHandler
      10. Setup: include UtfNormalUtil
      11. Setup: Setup: assert validity of $wgArticlePath
      12. Setup: process mw-config phase2/2 (more defaults, shortcuts, normalising)
      13. Setup: php-env ensure wfMemoryLimit
      14. Setup: process singletons phase1/3 (wgMemc, messageMemc, parserMemc)
      15. Setup: process hooks for SetupAfterCache
      16. Setup: process singletons phase2/3 (wgContLang, wgAuth)
      17. Setup: php-env add MediaWiki\Session
      18. Setup: process singletons phase3/3 (wgUser, wgLang, wgOut, wgParser, wgTitle)
      19. Setup: process hooks for wgExtensionFunctions
      20. Setup: process Pingback

Issues

1: WebStart: assert php-env mbstring.func_overload

Unsure why this is in WebStart instead of Setup. Is it fine to apply this to CLI?

• Patch: https://gerrit.wikimedia.org/r/427272 / 5c94aed0c3ab1

3: WebStart: global set $wgRequestTime

Deprecated since MediaWiki 1.25.

• Remove usage: https://gerrit.wikimedia.org/r/304465 / 06ba5ca383
• Actual removal: https://gerrit.wikimedia.org/r/427274 / 6fe856c4bd79

4: WebStart: global unset $IP

This sanity unset() seems redundant. It's unconditionally re-assigned two lines down. Can it be removed?

• Patch: https://gerrit.wikimedia.org/r/427267 / 3aa0b0567f

7A: Setup: global set $wgProfiler
7B: Setup: include StartProfiler (conditional)

Seems like this could be folded into DefaultSettings.php, with the StartProfiler include moved down a few lines. Should be safe given we don't reference it after DefaultSettings and LocalSettings load.

• Patch: https://gerrit.wikimedia.org/r/420268 / 5209adff6cf

8: WebStart: include OutputHandler (conditional)

This (conditionally) includes a file that creates additional global functions. Should be safe to merge with GlobalFunctions and just load always. Alternatively, given this is after the autoloader, perhaps better as a class. That way also has the benefit of 1) keeping the private functions really private and 2) still only loading the file when needed.

• Patch: https://gerrit.wikimedia.org/r/420223 / 665e9b7bf2

9A: OutputHandler: handle ValidateAllHtml (conditional)

See also T191670.

• Patch: https://gerrit.wikimedia.org/r/425093 / 0da97e7a03

10A: Setup: process Profiler

• Patch: https://gerrit.wikimedia.org/r/532264 / 5f623ebc1004

10J: Setup: include UtfNormalUtil

• Patch: https://gerrit.wikimedia.org/r/435207 / 88ea69f2f7.

10K: Setup: assert validity of $wgArticlePath

• Patch: https://gerrit.wikimedia.org/r/538350 / 480b7341f835.

10L: Setup: process mw-config phase2 (more defaults, shortcuts, normalising)

Unsure why this is separate from the earlier "mw-config process" section.

• Patch: TODO

10N: Setup: process singletons phase1/3 (wgMemc, messageMemc, parserMemc)

• Removed $parserMemc in https://gerrit.wikimedia.org/r/436528 / a930bf7d7.
• Follow-up for $wgMemc and $messageMemc: T160813, T243175

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General ideas and themes (Original task description):

• Reduce number of manually included files.
• Reduce amount of commonly executed code:
  • Re-evaluate the way we normalise global configuration variables in Setup.php. We currently do it unconditionally because we want convenient access to them without needing to re-normalise at each call site. However, we are actively reducing use of global variables, typically using them (or the Config proxy) only in ServiceWiring.php and/or the constructor of a service class. Such class seems like a better place to perform normalisation than Setup.php. Benefits of doing so:
    1. Still written and run from one place (just in the relevant class instead of Setup.php)
    2. No longer unconditional on all requests.
    3. Testable - the code for supporting older configuration formats can be covered with unit tests.
    4. Maintained in context of the associated feature.
  • Continue deprecating (some) global functions in favour auto-loaded class methods.
  • Maybe start deprecating some constants in favour of auto-loaded class constants.

Related follow-up work:

• T228895: 3% of load.php spent creating DBLoadBalancerFactory in WebStart.php
• T187154: Performance regression from Apcu/ExtensionRegistry::loadFromQueue on PHP7
• T245940: Hard-deprecate and remove $wgContLang
• T160813: Deprecate and remove $wgMemc in MediaWiki Core and bundled extensions
• T243175: Deprecate and remove $messageMemc