Uncaught Error: Unimplemented type: 3 still here

[mofoyoda]

I'm getting an error similar to #861. It doesn't fire on every tile, but occasionally on particular tiles.
I'm serving data rendered with mapnik through tilelive-bridge, so pbf tiles are by the spec I guess.
Does this error fire when reading source attribute fields or geometry also?
Data-wise, I've got a single layer with valid polygon geometry and just two fields (integer and string) served from postgis.
Any clues why this happens?

[mourner]

@mofoyoda the error generally fires when it sees something it doesn't expect when decoding tiles from protocol buffers. Can you send us a sample of a particular tile that doesn't work?

[mofoyoda]

@mourner yep, I've put some tiles to a gist here

I've also tested on different browsers and found out Safari and FF throw this error more frequently than Chrome. But the error always points to Pbf.ReadFields and Pbf.skip.

[mofoyoda]

I've been digging into tilelive output to check if it's Pbf decoder error or not, and I've figured out this:
When I just serve tiles from tilelive output like:

tileSource.getTile(z, x, y, function(err, tile, headers) {
  res.set(headers);
  res.send(tile);
} 

There are no errors when decoding it, but when I serve the same tile from the filesystem:

tileSource.getTile(z, x, y, function(err, tile, headers) {
  fs.writeFile(config.tilePath + '/' + z + '/' + x + '/' + y + '.pbf', tile, {encoding: 'base64'}, function (err) {
      rtile = readFileSync(config.tilePath + '/' + z + '/' + x + '/' + y + '.pbf', {encoding: 'base64'});
      res.set(headers);
      res.send(tile);
  });
});

I get Uncaught Error: Unimplemented type: 3
How can a tile buffer be corrupted when writing it out and reading back from fs? Maybe I've messed up encoding or smth?

[jfirebaugh]

Are you serving it gzipped and with Content-Encoding: gzip (so that the browser decodes it), but saving it gzipped and not decoding it when served from filesystem?

[mofoyoda]

Thanks, @jfirebaugh I got it running now. I'm serving with Content-Encoding: gzip both from tilelive output and filesystem. When I changed readFile and res.send to just res.sendFile it started working as expected. Sorry, guys, I guess Pbf decoding works fine. I'll check out some more and confirm that here.

But I still don't get how writeFile + readFile change the content of the tile. Maybe the content should be cast to buffer after being read?

[jfirebaugh]

But I still don't get how writeFile + readFile change the content of the tile.

It doesn't. The issue was likely that you were serving gzipped files sometimes with Content-Encoding: gzip and sometimes not. mapbox-gl-js always expects non-gzipped PBFs, i.e. if they are served gzipped they need to have Content-Encoding: gzip so that the browser performs decoding.

[gmaclennan]

Hey a note on this having hit the same problem myself: the vector tile API https://tiles.mapbox.com/v4/ currently seems to ignore any 'Accept-Encoding' header and returns tiles encoded as gzip regardless.

[1254859753]

Hello, how should I use Content-Encoding: gzip?