Further improvements in runtime metadata loading

[mjeffryes]

Two changes to further reduce metadata load times for large providers:

1. Use segmentio/encoding/json in zero-copy mode
2. Generate a trimmed, runtime-only copy of metadata

In particular, removing extra whitespace contributed the most improvement suggesting that we may be able to obtain further savings just by shortening or eliminating frequently repeated strings.

This change is equivalent to the first codegen option described in pulumi/pulumi-aws#2799 (comment) (and combining the two yields no further improvement).

Generation of the runtime-only metadata is controlled via a flag in the ProviderInfo to allow providers to opt in individually.

Benchmarks from AWS:

Before changes

BenchmarkProviderGen
BenchmarkProviderGen-12             	       6	 189483917 ns/op	331080480 B/op	 2222893 allocs/op
BenchmarkProviderNoGen
BenchmarkProviderNoGen-12           	       7	 160893363 ns/op	287969720 B/op	 1850232 allocs/op

With zero-copy deserializer

BenchmarkProviderGen
BenchmarkProviderGen-12             	       6	 179858674 ns/op	331078597 B/op	 2222880 allocs/op
BenchmarkProviderNoGen
BenchmarkProviderNoGen-12           	       7	 155430929 ns/op	287963872 B/op	 1850211 allocs/op

With zero-copy deserializer and trimmed runtime only metadata

BenchmarkRuntimeProviderGen
BenchmarkRuntimeProviderGen-12      	       8	 132763682 ns/op	331080280 B/op	 2222892 allocs/op
BenchmarkRuntimeProviderNoGen
BenchmarkRuntimeProviderNoGen-12    	      10	 108300512 ns/op	287966743 B/op	 1850214 allocs/op

[codecov]

Codecov Report

Attention: 11 lines in your changes are missing coverage. Please review.

Comparison is base (6e919a0) 57.94% compared to head (6a98a47) 57.97%.

Files	Patch %	Lines
unstable/metadata/metadata.go	84.21%	5 Missing and 1 partial ⚠️
pkg/tfgen/generate.go	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1524      +/-   ##
==========================================
+ Coverage   57.94%   57.97%   +0.03%     
==========================================
  Files         286      286              
  Lines       39670    39687      +17     
==========================================
+ Hits        22988    23010      +22     
+ Misses      15342    15336       -6     
- Partials     1340     1341       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[iwahbe]

This looks like a good incremental step in load performance. LGTM

[iwahbe]

Is there any reason why a provider would not want this flag enabled?

Put another way, if we were 100% confident that this would work as intended, would we enable it for all of our providers?

[mjeffryes]

There's not a lot of value for smaller providers, the data in the runtime config is strictly redundant with bridge-metadata.json (while being harder to read/edite) and it requires changing up the init a bit to use the runtime file for the runtime binary. So for now, I don't think it's worthwhile to try to enable this everywhere, lots of little frictions for minimal benefit on most providers.

We might revisit this as part of a larger effort to distinguish gentime/runtime though.

[iwahbe]

That makes sense to me.