setData() is blocking

[mcwhittemore]

I'm currently doing some perf work on gl-draw and found that the call to setData for a geojson source takes ~6milli on average when calling it with an object. I haven't checked what happens when you call it with a url.

Because this api can take a url, I assumed it was an async function that did its hard work on its own time. Should setData be async? If so, I can dive in and find out why its not. If not, I can work around this in gl-draw, I just wanted to check.

Also, the length of time this function takes from a synchronous point of view is all over the place even if the geojson object is more or less the same size.

[jfirebaugh]

It is async, in that it transfers data to a web worker for processing. But passing a lot of data to a web worker is inherently expensive, which is why we recommend using a URL.

This has been discussed previously, see #1391, #1504, #1762, #1505, etc.

[tikhonbelousko]

@jfirebaugh can I use url which will be sending GeoBuf? Or mapbox only expects GeoJSON? Can I gzip it at least?

[mourner]

@dazzz gzipped GeoJSON works fine (with the right headers). We may add support for geobuf in future though, as a side effect of #1504.