[wp-trac] [WordPress Trac] #40441: High server resource usage and timeouts during image uploads

[WordPress Trac]

#40441: High server resource usage and timeouts during image uploads
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 Reporter:  enshrined    |       Owner:
     Type:  enhancement  |      Status:  new
 Priority:  normal       |   Milestone:  Awaiting Review
Component:  Media        |     Version:
 Severity:  normal       |  Resolution:
 Keywords:               |     Focuses:
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Comment (by blobfolio):

 A common bottleneck comes from source files that are inappropriately
 large, which subsequently require extra processing power and memory for
 every downsize pass.

 One workaround would be to generate a more reasonable pseudo-source if the
 original is excessive (e.g. 2000px cap if the source is > 5000px) and use
 that for any thumbnails of equal or lesser size. This will have some
 quality loss due to recompression so would need to be user-controlled,
 probably defaulting to DON'T. But it would definitely help with timeout
 issues on budget shared hosting.

 There is also optimization potential within the `class-wp-image*` files
 themselves: they could maintain a static copy of the last source image
 resource to have been generated rather than destroying all traces of it at
 the end of the run. `protected static $_last = array( $filepath =>
 $resource );` Since this is so often called in a loop using the same file
 over and over again, it would allow the class to refer to the cached
 source rather than starting from scratch at each iteration. In cases where
 an application initiates the image editor against multiple sources (like a
 bulk thumbnail regeneration plugin), the usual cleanup can be run at the
 ''beginning'' of each new cycle to free up memory held for the last one
 (rather than the end of every cycle).

 While this does mean there will be an uncleared resource at the end of the
 process, it should still translate to a decent performance win,
 particularly in cases where the source files are gratuitously large.

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Ticket URL: <https://core.trac.wordpress.org/ticket/40441#comment:1>
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