Working with Project Topics in Google Pub/Sub

[ Overview ] [ Operation details ] [ Sample configuration ]

Overview

The following operations allow you to work with project topics. Click an operation name to see details on how to use it.

For a sample proxy service that illustrates how to work with project topics, see Sample configuration.

Operation	Description
createTopic	Creates a new topic.
publishMessage	Publishes messages to a specified topic.

Operation details

This section provides more details on each of the operations.

Creating a topic

The createTopic operation creates a new topic with the name that you specify.

createTopic

<googlepubsub.createTopic>
    <topicName>{$ctx:topicName}</topicName>
    <projectId>{$ctx:projectId}</projectId>
</googlepubsub.createTopic>

Properties

topicName: The name that you want to give the topic that you are creating.
projectId: The unique ID of the project within which you want to create a topic.

Sample request

Following is a sample request that can be handled by the createTopic operation:

createtopic

{
  "apiUrl":"https://pubsub.googleapis.com",
  "apiVersion":"v1",
  "accessToken": "ya29.GlwABYxVvbJG2NhgX_NQhxjtF_0G9bzf0FEj_shNWgF_GXmYFpwIxjeYQF0XQXrBjjcrJukforOeyTAHoFfSQW0x-OrrZ2lj47Z6k6DAYZuUv3ZhJMl-ll4mvouAbc",
  "topicName":"topicA",
  "projectId":"rising-parser-123456"
}

Related Google Pub/Sub documentation

https://cloud.google.com/pubsub/docs/reference/rest/v1/projects.topics/create

Publishing messages

The publishMessage operation publishes a message to a specified topic.

publishMessage

<googlepubsub.publishMessage>
    <topicName>{$ctx:topicName}</topicName>
    <projectId>{$ctx:projectId}</projectId>
    <data>{$ctx:data}</data>
    <attributes>{$ctx:attributes}</attributes>
</googlepubsub.publishMessage>

Properties

topicName: The unique name of the topic to which the message is to be published.
projectId: The unique ID of the project within which the topic is created.
data: The message payload.
attributes[Optional]: Additional attributes for the message.

Sample request

Following is a sample request that can be handled by the publishMessage operation.

publishMessage

{
  "apiUrl":"https://pubsub.googleapis.com",
  "apiVersion":"v1",
  "accessToken": "ya29.GlwABYxVvbJG2NhgX_NQhxjtF_0G9bzf0FEj_shNWgF_GXmYFpwIxjeYQF0XQXrBjjcrJukforOeyTAHoFfSQW0x-OrrZ2lj47Z6k6DAYZuUv3ZhJMl-ll4mvouAbc",
  "projectId":"rising-parser-123456",
  "topicName":"topicA",
  "data":"hi",
  "attributes:{"key": "value1","key2":"values2"}
}

Related Google pub/sub documentation

https://cloud.google.com/pubsub/docs/reference/rest/v1/projects.topics/publish

Sample configuration

Following is a sample proxy service that illustrates how to connect to Google Pub/Sub with the init operation, and then use the createTopic operation. The sample request for this proxy can be found in createTopic sample request. You can use this sample as a template for using other operations in this category.

Sample Proxy

<?xml version="1.0" encoding="UTF-8"?>
<proxy xmlns="http://ws.apache.org/ns/synapse"
 name="createTopic"
 startOnLoad="true"
 statistics="disable"
 trace="disable"
 transports="http,https">
 <target>
 <inSequence>
 		<property expression="json-eval($.accessToken)" name="accessToken"/>
 		<property expression="json-eval($.apiUrl)" name="apiUrl"/>
		<property expression="json-eval($.apiVersion)" name="apiVersion"/>
 		<property name="topicName" expression="json-eval($.topicName)"/>
        <property name="projectId" expression="json-eval($.projectId)"/>
 		<googlepubsub.init>
 			<apiUrl>{$ctx:apiUrl}</apiUrl>
 			<apiVersion>{$ctx:apiVersion}</apiVersion>
			<accessToken>{$ctx:accessToken}</accessToken>
 		</googlepubsub.init>
 		<googlepubsub.createTopic>
            <topicName>{$ctx:topicName}</topicName>
            <projectId>{$ctx:projectId}</projectId>
        </googlepubsub.createTopic>
 		<respond/>
 </inSequence>
 <outSequence>
 	<log/>
 	<send/>
 </outSequence>
 </target>
</proxy>