GraphQL Subscriptions

[davimacedo]

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New Pull Request Checklist

• [ X ] I am not disclosing a vulnerability.
• [ X ] I am creating this PR in reference to an issue.

Issue Description

This PR add subscription support to the GraphQL API.

Related issue: https://github.com/parse-community/parse-server/issues/6617

Approach

We are basically taking a ride with the existing Live Query implementation. In order to use subscriptions, the allowed class names needs to be listed in the liveQuery configuration. A Live Query server is not needed though. We are simulating a ws adapter in order to connect directly to the live query implementation without actually creating sockets (which would not make sense).

With something like the following, the GraphQL API, Subscriptions, and Playground will be mounted and can be tested via this PR:

./bin/parse-server --appId APPLICATION_ID --masterKey MASTER_KEY --databaseURI mongodb://localhost/test --liveQuery '{"classNames": ["MyClass"]}' --mountGraphQL --mountSubscriptions --mountPlayground

It is still a work in progress. We need to improve the where input (since most of operations are not available at Live Query), and test/improve the node/originalNode output. We still need to create/fix test-cases.

But overall it is working and can be tested.

@Moumouls any feedback?

TODOs before merging

• [ ] Add test cases
• [ ] Add entry to changelog
• [ ] Add changes to documentation (guides, repository pages, in-code descriptions)
• [ ] Add security check
• [ ] Add new Parse Error codes to Parse JS SDK
• [ ] ...

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[codecov[bot]]

Codecov Report

Merging #7227 (a733d24) into master (91a0108) will decrease coverage by 0.63%. The diff coverage is 48.61%.

@@            Coverage Diff             @@
##           master    #7227      +/-   ##
==========================================
- Coverage   94.01%   93.38%   -0.64%     
==========================================
  Files         172      173       +1     
  Lines       12873    13047     +174     
==========================================
+ Hits        12103    12184      +81     
- Misses        770      863      +93     

Impacted Files	Coverage Δ
src/Controllers/index.js	96.66% <ø> (ø)
src/LiveQuery/QueryTools.js	93.19% <0.00%> (-1.49%)	:arrow_down:
src/Options/Definitions.js	100.00% <ø> (ø)
src/Options/index.js	100.00% <ø> (ø)
src/GraphQL/loaders/parseClassSubscriptions.js	16.07% <16.07%> (ø)
src/Controllers/ParseGraphQLController.js	90.32% <30.76%> (-5.52%)	:arrow_down:
src/GraphQL/ParseGraphQLSchema.js	93.30% <30.76%> (-4.15%)	:arrow_down:
src/GraphQL/ParseGraphQLServer.js	72.61% <48.78%> (-20.57%)	:arrow_down:
src/cli/parse-server.js	33.33% <50.00%> (+0.52%)	:arrow_up:
src/ParseServer.js	89.14% <75.00%> (-0.46%)	:arrow_down:
... and 5 more

---

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[mtrezza]

⚠️ Important change for merging PRs from Parse Server 5.0 onwards!

We are planning to release the first beta version of Parse Server 5.0 in October 2021.

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[Moumouls]

It seems here that we need to move from subscriptions-transport-ws (not maintained) to https://github.com/enisdenjo/graphql-ws

[Moumouls]

I don't know enough about websocket systems to give useful feedback:

My questions would be more generalized:

• Does this implementation will support multi instance (with Redis) ?
• I'm not sure to see where the subscription server will resolve the graphql query (fields/subfields etc...)

As i understand the main goal is to reuse the livequery server, we internally forward subscriptions to the Livequery server and then the LivequeryServer will "push" updates through the GraphQL subscriptionServer.

Also as you said we need to create a dedicated MyClassSubscriptionWhereInput to cover usable subscriptions.

@davimacedo