Tile Handling of 204/404 results

[cns-solutions-admin]

Handling of tile results 204/404 could be improved:

• 404 on tile request: currently error message that not found, continues processing, but tries to reload the tile whenever the tile is needed
• 204 on tile request: error that invalid image format (0-byte file is always invalid), processing aborted. Tries to reload again whenever needed.

It would be better, if

• 204 is handled as no-data-available (e.g. no terrain available): this fact should also be stored in the source cache to avoid reloading
• 404 on tile requests are not retried (for some time), if at least one tile for that source was already successfully loaded.

(detected by #1551)

maplibre-gl-js version:
2.3.0

browser:
browser-independent

Steps to Trigger Behavior

With a layer whose tile source does not contain all tiles

1. zoom in, watch for missing tiles (in browser network monitor)
2. zoom out, zoom in again at same spot => available tiles are not reloaded, tiles having returned 204/404 are retried again.

Link to Demonstration

E.g. https://maplibre.org/maplibre-gl-js-docs/example/3d-terrain/

Expected Behavior

No invalid-format error messages for tile results 204
204/404 results are cached for some time and not reloaded each time

Actual Behavior

Invalid-format error message for tile result 204
Tile requests returning 204/404 are retried again, whenever that tile is needed (e.g. zoom out/in again)

[HarelM]

What's the difference between this issue and #1551? Are both tracking the same problem?

[cns-solutions-admin]

This describes an improved handling of tile responses and caching.

#1551 describes a specific problem that might be solved by the improved 204-response handling of this issue.

[HarelM]

There's an open PR which is waiting for code review comments I believe:

• Better raster 204 handling #2325

I've also refactored the a lot of code around the sources and workers and there's a specific way to handle 404, feel free to add the relevant logic there:

• Async Actor #3233