Publish event to GraphQL subscription

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.

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

• Policy sections: http-response element in http-data-source resolver
• Policy scopes: GraphQL resolver only
• Gateways: dedicated, consumption

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>

Related policies

• GraphQL resolver policies

Next steps

For more information about working with policies, see:

• Tutorial: Transform and protect your API
• Policy reference for a full list of policy statements and their settings
• Policy expressions
• Set or edit policies
• Policy samples