Automatic Persisted Queries

[SlavaUtesinov]

This PR is a preparation for implementation of Automatic Persisted Queries (APQ) in a server project PR - graphql-dotnet/server#132. Briefly, in case of APQ, a query field can be omitted, execution of a request will be implemented by means of additional hash field (sha256Hash) which corresponds to the query which has been saved on server side in advance, The request will look this way:

{
  operationName: 'MyQuery',
  variables: null,
  extensions: {
    persistedQuery: {
      version: 1,
      sha256Hash: hashOfQuery
    }
  }
}

[codecov-commenter]

Codecov Report

Merging #3118 (3976014) into master (cd42366) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #3118      +/-   ##
==========================================
+ Coverage   84.34%   84.35%   +0.01%     
==========================================
  Files         362      362              
  Lines       15884    15896      +12     
  Branches     2579     2583       +4     
==========================================
+ Hits        13397    13409      +12     
  Misses       1871     1871              
  Partials      616      616              

Impacted Files	Coverage Δ
...phQL.NewtonsoftJson/GraphQLRequestJsonConverter.cs	81.35% <100.00%> (+0.99%)	⬆️
...phQL.SystemTextJson/GraphQLRequestJsonConverter.cs	84.31% <100.00%> (+0.98%)	⬆️
src/GraphQL/Transport/GraphQLRequest.cs	100.00% <100.00%> (ø)
src/GraphQL/Resolvers/FuncFieldResolver.cs	90.12% <0.00%> (+0.79%)	⬆️

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[sungam3r]

Protocol here - https://www.apollographql.com/docs/react/api/link/persisted-queries/#protocol (Apollo JS stuff is an implementation).

[sungam3r]

Suggested change

	/// when a client sends only SHA-256 hash of the query given that corresponding key-value pair has been persisted on a server beforehand.
	/// when a client sends only SHA-256 hash of the query in <see cref="Extensions"/> given that corresponding key-value pair has been persisted on a server beforehand.

[sungam3r]

@Shane32 Note that graphql-over-http spec implicitly says that query field is required

but I think that it is not a big deal to make it optional. We are going to use APQ in production pretty soon. It's a rather simple concept, requires ~20 lines of code (in server project) and it saves a lot of network/memory/CPU reources (being used with document caching). Also note that APQ != document caching implemented in GraphQL.MemoryCache. These are diffferent features that may be used together.

[Shane32]

FYI, the persisted query implementation can easily be done with a custom IDocumentExecuter which essentially wraps another IDocumentExecuter. Since the implementation returns a proper GraphQL response in the case that a match is not found, I'm pretty sure it does not need to interact with the server project at all. However, the server project needs to be modified to allow requests without a query specified.

[Shane32]

@sungam3r I use something similar to APQ already - but only for logging purposes. Each query is hashed and logged, allowing me to compute statistics for any query over a large period of time with very little database / storage space required. Adding APQ would be rather trivial to implement, and would enhance performance.

In v6 of GraphQL we should consider allowing IConfigureExecution to 'wrap' a document executer execution, thereby being able to implement APQ, or the MemoryCache, or appending Apollo Trace statistics without having any special code within with document executer itself. Some DI engines already allow such configuration built-in, called decorators, but MSDI does not have decorator support.