Topic Management

Topics and Subscriptions

Management console of WSO2 Complex Event Processor allows users to create/delete topics & subtopics and to make subscriptions for topics for its embedded Local Broker.

Topic browser allows users to view all the topics available in the Local Broker in a tree view. User can perform all the operations with regarding a topic via this view.

Add Topic

Click on "Main" section of the left panel and click on "Add" menu item under "Topics" Menu.

Topic Browser

Initially this tree view does not display any of the operations available for the topic. When user clicks on the topic, it will display all the operations available for that particular topic.

Operations available for a particular topic are :

Add Subtopic
Subscribe
Details
Delete

Add Subtopic

Add subtopic feature provided user the ability to add a topic under the existing topic. When adding a new topic under an existing topic, user can provide the name of the new topic and set the permissions for publishing and subscribing for that topic.

Once a subtopic is added, it will direct to the Topic Browsing tree. If user wants to add a topic directly to the root, user can click on the 'Add' sub menu item under topics menu in the left panel.

All the subscriptions for a particular topic is done in this page. Once a user click on the subscribe link in topic browser, it will directed to this page. To do a subscription to that topic , user has to give some details as in following table.

Detail	Description
Topic	User does not need to specify the topic here , since its automatically sets up.
Subscription Mode	This is the mode of the subscription and there are three modes. The default mode for the subscription is "Topic Only". With this mode, user creates the subscription only to the topic. In that mode subscribers only receive events which are published only to that topic. Next mode of subscription is "Topic and Immediate child". In this mode subscribers of the topic receives events published not only the specified topic but also to the immediate child of that topic. Last mode of subscription is "Topic and Children". In this mode subscribers of the specified topic will receive events published to the specified topic and all its children.
Event Sink URL	This is the URL which the subscriber should provide to receive events published. When events are published to the topic, they are sent to the specified URL here.
Expiration Time	Here user can specify the expiration time of the subscription. This is not a required parameter and if user leave it alone, subscription will never be expired.

Topic Details

Following table shows all the details related with a topic can be viewed in this page.

Detail	Description
Permission Details	Permissions related with the topic can be viewed here and if the user wants to change the permissions with regarding that topic, user can change the ticks on the provided check boxes and click on update permissions button.
WS Subscription Details	All the ws subscriptions for the topic and its all children are listed here. If the user wants to unsubscribe from the topic, he can simply click on the unsubscribe link on the last column of each row.
Publish	This publish option provide the user the ability publish a sample XML message to a topic. Once there is a subscription for the topic, event sink URL will receive that published XML message once its click on the publish button after placing a xml message in the provided space.

Delete

This will delete the topic from the server. To delete a topic , subscription count for that topic and its children should be zero. Otherwise it will prompt an error message specifying that there are subscriptions for the topic or its children.