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Publish event to GraphQL subscription

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APPLIES TO: All API Management tiers

The publish-event policy publishes an event to one or more subscriptions specified in a GraphQL API schema. Configure the policy in a GraphQL resolver for a related field in the schema for another operation type such as a mutation. At runtime, the event is published to connected GraphQL clients. Learn more about GraphQL APIs in API Management.

Note

Set the policy's elements and child elements in the order provided in the policy statement. Learn more about how to set or edit API Management policies.

Policy statement

XML 
<http-data-source>
<!-- http-data-source is an example resolver policy -->
    <http-request>
    [...]
    </http-request>
    <http-response>
        [...]
        <publish-event>
            <targets>
                <graphql-subscription id="subscription field" />
            </targets>
        </publish-event>
    </http-response>
</http-data-source>

Elements

Name Description Required
targets One or more subscriptions in the GraphQL schema, specified in target subelements, to which the event is published. Yes

Usage

Usage notes

  • This policy is invoked only when a related GraphQL query or mutation is executed.
  • Resolver should not be defined for the corresponding subscription. Defining a publish-event policy on a source query or mutation is sufficient to trigger subscription events.

Example

The following example policy definition is configured in a resolver for the createUser mutation. It publishes an event to the onUserCreated subscription.

Example schema

type User {
  id: Int!
  name: String!
}


type Mutation {
    createUser(id: Int!, name: String!): User
}

type Subscription {
    onUserCreated: User!
}

Example policy

XML 
<http-data-source>
    <http-request>
        <set-method>POST</set-method>
        <set-url>https://contoso.com/api/user</set-url>
        <set-body template="liquid">{ "id" : {{body.arguments.id}}, "name" : "{{body.arguments.name}}"}</set-body>
    </http-request>
    <http-response>
        <publish-event>
            <targets>
                <graphql-subscription id="onUserCreated" />
            </targets>
        </publish-event>
    </http-response>
</http-data-source>

Related content

For more information about working with policies, see: