[PoC] Experimental Rust parser + benchmark

[fpacanowski]

Ever since Aaron Patterson published his "Ruby outperforms C" article, I was curious about how Rust based parser would fare in this comparison. To satisfy my curiosity I wrote a gem that's yet another implementation of GraphQL parser.

There are 3 parts to this PR:

• the parser gem itself
• benchmark that compares Ruby, C, and Rust parser implementations
• Dockerfile to make the result reproducible

The parser gem is a thin wrapper over graphql-parser crate. It first parses the input string to Rust structure, and then recursively traverses said structure to build ruby-graphql's AST. Note that this is a proof-of-concept, not production-ready code. Also note that's not the fastest Rust GraphQL parser out there, e.g. Stellate claims to be over 8x faster. It does offer a nice speed gain though (run on e2-standard-2 VM in Google Cloud):

Warming up --------------------------------------
      parsing - Rust   112.000  i/100ms
         parsing - C    83.000  i/100ms
      parsing - Ruby    76.000  i/100ms
Calculating -------------------------------------
      parsing - Rust      1.124k (± 1.8%) i/s -     33.712k in  30.004060s
         parsing - C    849.502  (± 1.8%) i/s -     25.481k in  30.005166s
      parsing - Ruby    766.000  (± 1.6%) i/s -     23.028k in  30.070330s

Comparison:
      parsing - Rust:     1123.9 i/s
         parsing - C:      849.5 i/s - 1.32x  slower
      parsing - Ruby:      766.0 i/s - 1.47x  slower

Whether this speed gain is worth adding another language to the project is up for debate. Parsing is rarely the bottleneck, but I imagine in a large deployment a faster parser can translate to some savings. Anyway, I've spent significant amount of time on this, so I thought I'd share the effects.

@rmosolgo FYI.

[rmosolgo]

Hi! Thanks for sharing your work here, very impressive. It looks like you've prepared this work in a separate gem at https://github.com/fpacanowski/rust_graphql_parser. Is there anything else I can help with?

[fpacanowski]

Hi! Thanks for sharing your work here, very impressive. It looks like you've prepared this work in a separate gem at https://github.com/fpacanowski/rust_graphql_parser. Is there anything else I can help with?

Yes, the code in this PR is an exact copy of the code in the other repo. I shared this PR to highlight the possibility for improving parser performance further by employing Rust and its ecosystem of parser libraries. The code I have works, but would require some amount of work to make it robust enough for serious production use. To be honest I'm no longer incentivized to work on it as I moved to a company that doesn't use GraphQL. But maybe this PR will be useful to someone :)