feat(GraphQL):This PR adds subscriptions to custom DQL. #7385

JatinDev543 · 2021-02-02T13:13:19Z

Fixes GRAPHQL-993
As of now, we only allow subscriptions on GraphQL queries. As we can use DQL through @custom in graphql, many users requested to use subscriptions on custom DQL.

We have the @withSubscription directive, that we use on GraphQL types to generate subscriptions on queries for that type.
We are now extending this directive to DQL queries in custom queries. Users can specify @withSubscription directive on individual DQL queries in type Query and those queries will be added in type subscription.

For example, we have two custom DQL queries below queryTweetsSortedByAuthorFollowers and queryUserTweetCounts . queryUserTweetCounts have @withSubscription directive, and it will be added to subscription type and users will be able to subscribe to this query.

type Query {
  queryTweetsSortedByAuthorFollowers(search: String!): [Tweets] @custom(dql: """
	query q($search: string) {
		var(func: type(Tweets)) @filter(anyoftext(Tweets.text, $search)) {
			Tweets.author {
				followers as User.followers
			}
			authorFollowerCount as sum(val(followers))
		}
		queryTweetsSortedByAuthorFollowers(func: uid(authorFollowerCount), orderdesc: val(authorFollowerCount)) {
			id: uid
			text: Tweets.text
			author: Tweets.author {
			    screen_name: User.screen_name
			    followers: User.followers
			}
			timestamp: Tweets.timestamp
		}
	}
	""")

  queryUserTweetCounts: [UserTweetCount]  `@withSubscription` @custom(dql: """
	query {
		queryUserTweetCounts(func: type(User)) {
			screen_name: User.screen_name
			tweetCount: count(User.tweets)
		}
	}
	""")
}

This change is

pawanrawal

Reviewed 7 of 54 files at r1.
Reviewable status: 7 of 54 files reviewed, 5 unresolved discussions (waiting on @danielmai and @jatindevdg)

graphql/e2e/schema/generatedSchema.graphql, line 183 at r1 (raw file):

directive @dgraph(type: String, pred: String) on OBJECT | INTERFACE | FIELD_DEFINITION
directive @id on FIELD_DEFINITION
directive @withSubscription on OBJECT | INTERFACE | FIELD_DEFINITION

We should have a validation that this is only allowed on fields within Query and not fields within types.

graphql/e2e/subscription/subscription_test.go, line 75 at r1 (raw file):

# Dgraph.Authorization {"VerificationKey":"secret","Header":"Authorization","Namespace":"https://dgraph.io","Algo":"HS256"}
`
	schCustomDQL = `type Tweets {

have type tweets on the next line

graphql/schema/gqlschema.go, line 850 at r1 (raw file):

			for _, q := range defn.Fields {
				customDir := q.Directives.ForName(customDirective)
				subsDir := q.Directives.ForName(subscriptionDirective)

what happens if there is a withSubscription and its not a DQL query, is that an error?

graphql/schema/gqlschema.go, line 852 at r1 (raw file):

				subsDir := q.Directives.ForName(subscriptionDirective)
				if customDir != nil {
					if !(customDir.Arguments.ForName("dql") == nil || subsDir == nil) {

(if subsDir != nil && dql != nil) is more readable

graphql/schema/testdata/schemagen/input/custom-dql-query-with-subscription.graphql, line 18 at r1 (raw file):

type Query {
    queryTweetsSortedByAuthorFollowers(search: String!): [Tweets] @custom(dql: """

not useful for this test, please remove as this is probably already tested in another file

…QL-993

JatinDev543

Reviewable status: 3 of 56 files reviewed, 5 unresolved discussions (waiting on @danielmai and @pawanrawal)

graphql/e2e/schema/generatedSchema.graphql, line 183 at r1 (raw file):