Yaffle/EventSource

EventSource causes IE11 to lock-up, freeze and act erratically with high-frequency EventSource in Angular 4

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#104 opened on Feb 8, 2018

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help wanted

Description

I'm using this EventSource polyfill in an Angular 4 application that calls an EventSource that returns new messages every 500ms. When using IE11 on Windows Server 2016, the IE window (and dev tools!) instantly lock-up and become unresponsive for a few seconds, before resuming but lagging the entire system, including Windows Task Manager. Curiously, Windows Task Manager reports no unusual CPU usage, or significantly increased memory usage.

I ran it with the IE F12 Developer Tools Profiler, which shows a lot of time is spent in Angular's zone handler and change-detection code - so something very inefficient is going on in there. I speculate this polyfill is conflicting with Angular's Zone.js patching of XMLHttpRequest.

Has anyone else observed similar behaviour?

Contributor guide

Tech stack
javascript
Domain
frontendperformance
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
unclear
Prerequisites
JavaScriptAngular basicsZone.jsIE11 debugging
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
25
Research direction
Investigate the interaction between the EventSource polyfill and Angular's Zone.js patching of XMLHttpRequest. Use IE11 F12 developer tools profiler to identify specific functions causing high time in change detection. Look into the polyfill's event source implementation in the repository to see how it handles high frequency events. Consider implementing a debounce or limiting update frequency to reduce Zone.js overhead.