Fix websocket timer throttle blocking writes #670
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darrachequesne
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Jun 22, 2021
An immediate setTimeout was used to unblock the WebSocket write. Unfortunately, this setTimeout can be throttled by browsers when the tab is backgrounded. This can lead to missed pong responses to server pings, which eventually leads to disconnection. Related: #649
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Note: the
engine.io.jsfile is the generated output ofmake engine.io.js, and should not be manually modified.The kind of change this PR does introduce
Current behaviour
An immediate setTimeout is used to unblock the WebSocket write. Unfortunately, this setTimeout can be throttled by browsers when the tab is backgrounded. This can lead to missed pong responses to server pings which leads to disconnects.
New behaviour
Move the unblocking code block into a then handler of an immediate Promise.resolve. The then handler does not suffer from Timer throttling and will ensure the code gets executed asynchronously without unintended delay.
Other information (e.g. related issues)
#649 (comment)