fix for re-request expired resources causing infinite loop #4255
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setTimeout has a maximum value of 2147483647 (32bit integer) for all browsers. If set higher than that. the timeout is immediately fired. For tile cache expiry longer than 24 days, this results in an infinite tile fetch loop.
lbud
suggested changes
Feb 10, 2017
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Minor issue regarding the readability of that number but otherwise this is great, thanks @tobinbradley (and @AndyMoreland)!
src/source/source_cache.js
Outdated
| @@ -438,7 +438,7 @@ class SourceCache extends Evented { | |||
| this._timers[id] = setTimeout(() => { | |||
| this.reloadTile(id, 'expired'); | |||
| this._timers[id] = undefined; | |||
| }, tileExpires - new Date().getTime()); | |||
| }, Math.min(tileExpires - new Date().getTime(), 2147483647)); | |||
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Could you change this to Math.pow(2, 31) - 1 (for clarity)? Same below.
|
Done. Thanks! That is more clear than a random wildly-large number. |
lbud
approved these changes
Feb 10, 2017
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Credit to @AndyMoreland for figuring the problem out (see discussion on #3944).
setTimeout has a maximum value of 2147483647 (32bit integer) for all browsers. If set higher than that, the timeout is immediately fired.
For a tile with an expiry longer than ~24 days, like a tile with a
max-age=2592000Cache-Control header (30 days),tileExpires - new Date().getTime()> 2147483647, and you end up in an infinite tile fetch loop.Fortunately the browser knows the tile hasn't expired so it feeds GL JS from the browser cache and doesn't pound the tile server. But it does pound the browser pretty hard.