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DEV: Topic tracking state improvements (#12958)

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Original PR which had to be reverted **https://github.com/discourse/discourse/pull/12555**. See the description there for what this PR is achieving, plus below.

The issue with the original PR is addressed in https://github.com/discourse/discourse/pull/12958/commits/92ef54f4020111ffacb0f2a27da5d5c2855f9d5d

If you went to the `x unread` link for a tag Chrome would freeze up and possibly crash, or eventually unfreeze after nearly 10 mins. Other routes for unread/new were similarly slow. From profiling the issue was the `sync` function of `topic-tracking-state.js`, which calls down to `isNew` which in turn calls `moment`, a change I had made in the PR above. The time it takes locally with ~1400 topics in the tracking state is 2.3 seconds.

To solve this issue, I have moved these calculations for "created in new period" and "unread not too old" into the tracking state serializer.

When I was looking at the profiler I also noticed this issue which was just compounding the problem. Every time we modify topic tracking state we recalculate the sidebar tracking/everything/tag counts. However this calls `forEachTracked` and `countTags` which can be quite expensive as they go through the whole tracking state (and were also calling the removed moment functions).

I added some logs and this was being called 30 times when navigating to a new /unread route because  `sync` is being called from `build-topic-route` (one for each topic loaded due to pagination). So I just added a debounce here and it makes things even faster.

Finally, I changed topic tracking state to use a Map so our counts of the state keys is faster (Maps have .size whereas objects you have to do Object.keys(obj) which is O(n).)
This commit is contained in:
Martin Brennan 2021-05-31 09:22:28 +10:00 • committed by GitHub
parent 1374ec45c5
commit 002c676344
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14 changed files with 1442 additions and 481 deletions
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4
app/controllers/application_controller.rb
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@ -608,7 +608,9 @@ class ApplicationController < ActionController::Base
def preload_current_user_data
store_preloaded("currentUser", MultiJson.dump(CurrentUserSerializer.new(current_user, scope: guardian, root: false)))
report = TopicTrackingState.report(current_user)
serializer = ActiveModel::ArraySerializer.new(report, each_serializer: TopicTrackingStateSerializer)
serializer = ActiveModel::ArraySerializer.new(
report, each_serializer: TopicTrackingStateSerializer, scope: guardian
)
store_preloaded("topicTrackingStates", MultiJson.dump(serializer))
end