WIP - Replace esc with "embed" for packaging UI assets

[yurishkuro]

Part of #2749, closes #3229

• infra changes to use go:embed in the build to pack UI assets
• use embed.FS as a source for HTTP server for static assets
• an adapter that implements http.FileSystem that can read gzip-compressed files from embed.FS (similar to https://github.com/vearutop/statigz, but we want to avoid 3rd party dependency)

[yurishkuro]

As I was afraid, the binary size goes up a lot (+13Mb) without doing some explicit compression:

# with esc
-rwxr-xr-x      43M Feb 25 23:15 ./cmd/all-in-one/all-in-one-darwin-amd64*
# with embed
-rwxr-xr-x      56M Feb 25 23:21 ./cmd/all-in-one/all-in-one-darwin-amd64*

[codecov]

Codecov Report

Merging #2850 (1eecfee) into master (639333a) will decrease coverage by 0.48%.
The diff coverage is n/a.

❗ Current head 1eecfee differs from pull request most recent head 9af3744. Consider uploading reports for the commit 9af3744 to get more accurate results

@@            Coverage Diff             @@
##           master    #2850      +/-   ##
==========================================
- Coverage   96.47%   95.99%   -0.49%     
==========================================
  Files         260      242      -18     
  Lines       15215    14789     -426     
==========================================
- Hits        14679    14196     -483     
- Misses        453      513      +60     
+ Partials       83       80       -3     

Impacted Files	Coverage Δ
cmd/anonymizer/app/anonymizer/anonymizer.go	64.10% <0.00%> (-19.66%)	⬇️
...ugin/sampling/strategystore/adaptive/aggregator.go	53.44% <0.00%> (-9.27%)	⬇️
cmd/flags/flags.go	46.29% <0.00%> (-1.92%)	⬇️
cmd/query/app/grpc_handler.go	98.53% <0.00%> (-0.16%)	⬇️
model/span.go	100.00% <0.00%> (ø)
cmd/env/command.go	100.00% <0.00%> (ø)
cmd/flags/admin.go	82.81% <0.00%> (ø)
cmd/query/app/server.go	95.58% <0.00%> (ø)
cmd/query/app/static_handler.go	95.80% <0.00%> (ø)
plugin/storage/badger/factory.go	95.80% <0.00%> (ø)
... and 56 more

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[yurishkuro]

If all files are gzipped, then the size is comparable with esc (even a tiny bit smaller)

-rwxr-xr-x      42M Feb 25 23:40 ./cmd/all-in-one/all-in-one-darwin-amd64*

[yurishkuro]

Found a brand new library by @vearutop that serves gzipped files https://github.com/vearutop/statigz. Not sure if we want to use it. It might conflict with our usage of gorilla.CompressHandler, although we could change it so that it doesn't apply to static assets.

[yurishkuro]

@albertteoh fyi

[vearutop]

Combining statigz with gorilla.CompressHandler would work, but in a sub optimal way.

The problem is that gorilla.CompressHandler removes Accept-Encoding header before passing request to next handler.
https://github.com/gorilla/handlers/blob/v1.5.1/compress.go#L119

r.Header.Del(acceptEncoding)

In such case statigz would think user agent is not capable to receive compressed response and will decompress it on the fly, then this decompressed response will be compressed again by gorilla.CompressHandler.

Pull request has been modified.

Pull request has been modified.

[jpkrohling]

What's the status of this PR?

[yurishkuro]

It needs to be done, but I didn't have time. Currently it blows up the size of the binaries unless we introduce a new lib dependency.

[jpkrohling]

It needs to be done, but I didn't have time. Currently it blows up the size of the binaries unless we introduce a new lib dependency.

Do you think an Outreachy candidate would be able to tackle this if a good description is provided in an issue?

[yurishkuro]

yes, it's a fairly straightforward piece.

[yurishkuro]

incorporated into #3399