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Set etag on pmtiles serve responses #137

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merged 9 commits into from
Feb 13, 2024
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msbarry
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@msbarry msbarry commented Feb 10, 2024

Set etag on tile, metadata, and tilejson responses. By default it uses the etag from the archive but you can opt into computing an etag per-resource with --tile-etag flag. The default archive etag behavior minimizes runtime overhead and is guaranteed to return a new etag when tile contents changes, but also ends up changing the etag (and purging intermediate caches) when the archive changes but an individual tile is the same between old and new archive.

This also implements If-Match and If-None-Match header handling by using go's built-in http.ServeContent utility. As a side effect this also means that pmtiles serve now supports range requests within individual tiles.

main.go Outdated
@@ -88,6 +89,7 @@ var cli struct {
CacheSize int `default:"64" help:"Size of cache in Megabytes."`
Bucket string `help:"Remote bucket"`
PublicURL string `help:"Public base URL of tile endpoint for TileJSON e.g. https://example.com/tiles/"`
TileEtag bool `help:"Generate etag for each tile instead of using archive etag"`
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The way I implemented this it also applies to metadata json and tilejson responses. Should I remove those? Or make this --resource-etag? or just leave it as-is?

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Also in my tests on a 32-core machine enabling this reduces throughput from 40k tiles per second to 36k tiles per second.

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maybe --unique-etags instead, to make it clearer the effect?

caddy/pmtiles_proxy.go Outdated Show resolved Hide resolved
@@ -294,6 +296,7 @@ func (server *Server) getTileJSON(ctx context.Context, httpHeaders map[string]st
}

httpHeaders["Content-Type"] = "application/json"
httpHeaders["Etag"] = generateEtag(tilejsonBytes)
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I think the end result is case-insensitive but the capitalization convention seems to be ETag with a capital T, any objections to changing it to that?

@bdon bdon merged commit 800168b into protomaps:main Feb 13, 2024
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2 participants