Improve performance of webui and sort table

[TrimmingFool]

On each list update, addTorrents caused ruTorrent to become unresponsive for a short period of time. This is very noticeable when thousands of torrents are refreshed. Primarily, this was due to calling format in setValue regardless of whether the value has changed.

There are multiple performance improvements in this PR:

• Sort table
  • Calls to setValue, add/remove/hide/unhideRow, clearRows, resize or scrollTo will not update the DOM immediately. Instead, changes are written to pendingSync and after delaying with a debounce of 50ms or a throttle of 500ms the DOM is updated.
  • setValue now considers the table cell value as dirty if the val changed instead of fmtVal. It appears, that checking the formatted value was only done to update Last Updated column in the Trackers table.
  • refreshRows now adds extra rows to the DOM in order to avoid blank (padding) regions becoming visible when scrolling.
• WebUI
  • addTorrents now uses a background task which is implemented with requestIdleCallback. Except for the first load, the task will only run during the allotted time. Due to setLazy(true) and the debounce of 50ms the sort table will only be updated once addTorrents is done. Further, updateLabels and other DOM updates are done after the task is done in an requestAnimationFrame callback.
  • updateLabel now avoids DOM updates if its data has not changed.
  • matchTegs now uses pre-initialized regular expression objects.
  • updatePeers now caches its values similar to updateTrackers.

@stickz https://github.com/Novik/ruTorrent/releases/tag/v4.1-beta.1 My pleasure! At the moment I have no further changes in store.

[stickz]

@TrimmingFool I can't merge this pull request until the next development cycle of version 4.2. There are already major changes to stable.js and webui.js in version 4.1. We won't be able to track changes and fix bugs. It could be a couple months.

I already made optimizations to ruTorrent for thousands of torrents. The situation here is not dire. These changes are drastic and need to be tested thoroughly before I can even release a beta version for them. The performance gains are small for most users.

Would you be interested in taking a look at the etags for plugin caching? They are broken and causing web browser caching issues. We can load ruTorrent in 300ms (3 times faster) for most users, if we fix this problem and re-enable the feature. This is the last element for near instantaneous loading times. I already optimized out everything else out including addTorrents.

[TrimmingFool]

I can't merge this pull request until the next development cycle of version 4.2

@stickz I also see no rush 👍

I already made optimizations to ruTorrent [...] including addTorrents

You optimized the first load time. However, this PR eliminates hanging during periodic GUI updates.

Would you be interested in taking a look at the etags for plugin caching?

I looked into it. We could get the etag matching $_SERVER['HTTP_IF_NONE_MATCH'] == $etag working with:

$etag = '"'.strtoupper(dechex(crc32($content))).'"';
// The ETag may gain encoding info. For instance: "{fingerprint}-gzip"
Utility::str_starts_with(trim($_SERVER['HTTP_IF_NONE_MATCH'], '"'), trim($etag, '"')))

Unfortunately, it seems that this is not fixed so easily.

At the point where Cached::send is called, most of the processing/loading is already done. I tested that returning 304 Not Modified at that point does not provide a speedup.
If we assume that users do not update the plugin sources (and expect the changes to show up without disabling the cache), we could try exiting getplugins.php early with 304 Not Modified by deriving the etag from a version number. However, loading all php plugins by calling require_once (or by simply not exiting early) should not be forgotten.

That being said, I am not interested in implementing this myself, though.

[stickz]

@TrimmingFool Could you give the develop branch a try to confirm your changes work correctly. There were some conflicts with the last v4.1 stable release I had to resolve. https://github.com/Novik/ruTorrent/releases/tag/v4.1