Publish event to GraphQL subscription

  • Article

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 a 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

<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.

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

<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>

Next steps

For more information about working with policies, see: