High CPU usage while typing

[laevandus]

🔗 Issue Links

Resolves PBE-5497

🎯 Goal

Reduce CPU usage caused by recreating CurrentChatUserController when sending typing events

📝 Summary

• Add ChatClient.UserSession for reusing objects from connect to logout
• User the shared CurrentChatUserController for reading privacy settings

🛠 Implementation

We check if we should send typing events using an internal property in the ChatChannelController which created a new instance of the CurrentChatUserController. This is called often when typing to a channel. This led to high CPU usage because controller is created and the local database is read on every character change. If the current user has, for example, a lot of muted channels, then recreating CurrentChatUser gets really expensive.

internal var shouldSendTypingEvents: Bool {
  let currentUserPrivacySettings = client.currentUserController().currentUser?.privacySettings
  …
}      

🎨 Showcase

iPhone 12 Pro Max (low power mode was on)
An account with 10 muted channels (important). I used Chewbacca.

1. Open a channel
2. Type 10 characters
3. Investigate main thread usage, especially shouldSendTypingEvents

Before	After
666 ms	56 ms
------	-----

shouldSendTypingEvents does not spend ~66 ms per character change just for checking this property. Instead, there is a single ~56 ms cost once (or almost none if the shared controller had been already created. Currently it is created on demand.)

🧪 Manual Testing Notes

• Try typing events and make sure these appear as expected.
• Log in and log out, trigger more typing events

☑️ Contributor Checklist

• I have signed the Stream CLA (required)
• This change should be manually QAed
• Changelog is updated with client-facing changes
• Changelog is updated with new localization keys
• New code is covered by unit tests
• Comparison screenshots added for visual changes
• Affected documentation updated (docusaurus, tutorial, CMS)

[Stream-SDK-Bot]

SDK Size

title	develop	branch	diff	status
StreamChat	6.73MB	6.73MB	0.0MB	🟢
StreamChatUI	4.41MB	4.41MB	0.0MB	🟢

[Stream-SDK-Bot]

SDK Performance

target	metric	benchmark	branch	performance	status
MessageList	Hitches total duration	10 ms	8.34 ms	16.6% 🔼	🟢
	Duration	2.6 s	2.54 s	2.31% 🔼	🟢
	Hitch time ratio	4 ms per s	3.27 ms per s	18.25% 🔼	🟢
	Frame rate	75 fps	78.48 fps	4.64% 🔼	🟢
	Number of hitches	1	0.8	20.0% 🔼	🟢
ChannelList	Hitches total duration	12.5 ms	26.7 ms	-113.6% 🔽	🔴
	Duration	2.6 s	2.55 s	1.92% 🔼	🟢
	Hitch time ratio	5 ms per s	10.46 ms per s	-109.2% 🔽	🔴
	Frame rate	72 fps	74.2 fps	3.06% 🔼	🟢
	Number of hitches	1.2	2.2	-83.33% 🔽	🔴

[martinmitrevski]

LGTM ✅

[nuno-vieira]

LGTM! ✅

[Stream-SDK-Bot]

SDK Size

title	develop	branch	diff	status
StreamChat	6.76MB	6.76MB	+0KB	🟢
StreamChatUI	4.41MB	4.41MB	0KB	🟢

[sonarcloud]

Quality Gate passed

Issues
151 New issues
0 Accepted issues

Measures
0 Security Hotspots
84.4% Coverage on New Code
0.1% Duplication on New Code

See analysis details on SonarCloud