New gofast protobuf code

[cory-stripe]

Summary

Uses gogo-protobuf's gofast code generator for faster marshal and unmarshaling.

Motivation

I stumbled into a comment somewhere that gogo-protobuf was way faster than stock protobuf on account of it not using reflection and generating more code for marshaling and unmarshaling. I gave it a whirl and it turns out to be way faster.

Using the same benchmark we made for #234 we get these results with the gogo-protobuf "gogo-fast" compiler:

Unmarshaling (which we do a lot of):

benchmark               old ns/op     new ns/op     delta
BenchmarkParseSSF-8     521           173           -66.79%

benchmark               old allocs     new allocs     delta
BenchmarkParseSSF-8     3              2              -33.33%

benchmark               old bytes     new bytes     delta
BenchmarkParseSSF-8     384           176           -54.17%

So it's 66% faster, and uses 54% less ram with one fewer alloc. Wow! I did not test marshaling since I don't know that we even do that in this code anywhere.

Marshaling (important for client libs):

benchmark                 old ns/op     new ns/op     delta
BenchmarkMarshalSSF-8     294           28.9          -90.17%

benchmark                 old allocs     new allocs     delta
BenchmarkMarshalSSF-8     1              0              -100.00%

benchmark                 old bytes     new bytes     delta
BenchmarkMarshalSSF-8     208           0             -100.00%

Well, that's exciting. 90% reduction and zero allocations. I suspect it's because we're not writing it it to anything in the test. We emit it to a Writer in the code.

Needs

I'm not certain how to add the gogo-protobuf binary to the Dockerfile so that this works with go-generate. I assume a go get added won't DWIW, or will it?

Test plan

gogo-protobuf says it is goprotobuf compatible, so I am relying on existing unit tests + a normal test cycle in QA.

r? @aditya-stripe

[stripe-ci]

Gerald Rule: Copy Observability on Veneur and Unilog pull requests

cc @stripe/observability
cc @stripe/observability-stripe

[ChimeraCoder]

We do marshal, within the trace package (which other Go services that use Veneur as a client library would use). Let's add a benchmark for that?

[ChimeraCoder]

Also, you'll have to update the build process in both Travis and and Jenkins. Updating the latter will fix the build error we're getting (though we have to update the former too, or else we're not properly testing the actual code we run).

Scanning the gogo/protobuf installation instructions, adding a go get should do the right thing, assuming that's what you did locally as well.

[cory-stripe]

Ok, ready for re-r @aditya-stripe now that I'm done fucking up the build.

[ChimeraCoder]

Is there a reason for dropping the -v flag here?

[ChimeraCoder]

Maybe let's rebase this so wtf cory isn't in our git log forever? ;)

lgtm other than that!

[cory-stripe]

re-approval for rebase