Chintan Shah's Blog: Salesforce Streaming API Summary

Was just working on streaming API and just putting thoughts together with different variations of streaming API :

Push Topic
Generic Topic
Platform Event

Even though underneath the cover, they all use same technology stack, they provide very different features.

	Push Topic	Generic Topic	Platform Events
Overview	Push topic is used for SOQL based subscription	Generic Topic is used to subscribe and publish arbitrary events	Platform Events is used for structured publish and subscribe There is a lot more native support for both publish and subscribe Full control over structure (payload) of the event
Replay : When client disconnect and reconnect again, they can replay from last 24 hours with id where they left from special ids : -1 from the beginning, -2 : all new events	Supported (version 36.0 +)	Supported (version 36.0 +)	Supported (version 36.0 +)
Create (Setup)	1) Using Apex Insert Statements or 2) workbench - it defaults all the param except SOQL query	Using Streaming Channel Tab or 2) Workbench	Create __e object
Support for Trigger Subscription	No	No	Yes
How to Publish	upon SOQL	Using Rest API	EventBus.publish; API : Post like sobject /services/data/v41.0/sobjects/Low_Ink__e/ Process Builder Flow
How to Subscribe	workbench (36.0) (later are causing problems) using Java (cometd lib) Using Javascript (cometd lib)	workbench using Java (cometd lib) Using Javascript (cometd lib)	using Java (cometd) Using Javascript (cometd) Using Visualforce (cometd) Process Flow Flow Trigger Workbench
Channel Name This is useful when we subscribe using cometd library	/topic/<> e.g. /topic/AccountUpdatePushTopic	/u/<> e.g. /u/GenericUpdateTopic	/event/<> e.g. /event/UpdateObjectEvent__e

Push Topic

Push Topic Setup

Workbench

we can setup a push topic using workbench, but it doesn't allow granular control over topic configuration.

APEX

NotifyForFields can be Referenced (part of query - default), Where (in where condition), All (all changes)
Once topic is inserted, we can use PushTopic object to make any update

 PushTopic pushTopic = new PushTopic();  
 pushTopic.Name = 'AccountUpdatePushTopic';  
 pushTopic.Query = 'SELECT Id, Name, AccountNumber from Account';  
 pushTopic.ApiVersion = 40.0;  
 pushTopic.NotifyForOperationCreate = true;  
 pushTopic.NotifyForOperationUpdate = true;  
 pushTopic.NotifyForOperationUndelete = true;  
 pushTopic.NotifyForOperationDelete = true;  
 pushTopic.NotifyForFields = 'Referenced';  
 insert pushTopic;

Push Topic Publish

There is no API support for publish. Any change in the data based on condition (e.g. Notify Operation and fields configured) would fire the event on the topic.

Push Topic Subscribe

Workbench

This is quick way to test and also record the channel, as we will need it later for cometd library

Java/JavaScript
covered later

Generic Topic

Generic Topic Setup

We must setup generic toipc using salesforce UI
There is no apex or workbench support to create generic topic

Generic Topic Publish

Rest API (Workbench)

URL : /services/data/v/sobjects/StreamingChannel//push

We can find streaming channel id using query (SELECT Name, ID FROM StreamingChannel)

e.g. /services/data/v40.0/sobjects/StreamingChannel/0M61I000000TN1FSAW/push

payload :

{

"pushEvents": [

{

"payload": "Broadcast message to all subscribers",

"userIds": []

}

]

}

Generic Topic Subscribe

WorkBench

Java/JavaScript:
Covered Later

Platform Events

Platform Event Setup

Essentially created two attributes (ObjectName__c and RecordId__c) so that we can publish the event having those attributes

Platform Event Publish

Apex

Publish event call doesn't fail, hence we have to go through the results
Also publish call doesn't participate in transaction, meaning if transaction has to fail, event will still publish

 List events = new List();  
 UpdateObjectEvent__e event = new UpdateObjectEvent__e(objectName__c='Account', recordId__c='1234');  
 events.add( event );  
 List results = EventBus.publish(events);  
 if( results != null && results.size() > 0 ) {  
   for (Database.SaveResult sr : results) {  
     if (sr.isSuccess()) {  
       System.debug('Successfully published event. ' + results.size() );  
     } else {  
       for(Database.Error err : sr.getErrors()) {  
         System.debug('Error returned: ' + err.getStatusCode() + ' - ' + err.getMessage());  
       }  
     }  
   }  
 } else {  
   System.debug(' Noting is published. ');  
 }

Rest API

Endpoint : /services/data/v40.0/sobjects/UpdateObjectEvent__e/
Payload : { "RecordId__c" : "123455634343", "ObjectName__c" : "Account" }

Soap API
Similar to rest api, it is just call to insert into sObject

Process Builder
not covered, but straightforward

Visual Flow
not covered, but straightforward

Platform Event Subscribe

Trigger

only after insert is supported

 trigger UpdateObjectEventTrigger on UpdateObjectEvent__e (after insert) {  
   System.debug(' UpdateObjectEventTrigger ' );  
     
   for (UpdateObjectEvent__e event : Trigger.New) {  
     System.debug(' : ' + event.RecordId__c + ' ' + event.ObjectName__c );  
   }  
     
 }

Process Builder
not covered, but straightforward

Visual Flow
not covered, but straightforward

Java/JavaScript

Covered later

Platform Event Debug

debug statements in trigger doesn't show up in debug logs, we need to enable them using below

Generic Java Subscriber Client

We need to download and build the EMP connector from salesforce

download : https://github.com/forcedotcom/EMP-Connector
unzip, and run "mvn clean install"
Use emp-connector-0.0.1-SNAPSHOT-phat.jar in the new project that we are going to create
Create a new project (java 1.8) and use below code.
Please note that channel name can be changed as per which topic we are subscribing

 package com.spring.client;  
   
 import com.salesforce.emp.connector.BayeuxParameters;  
 import com.salesforce.emp.connector.EmpConnector;  
 import com.salesforce.emp.connector.TopicSubscription;  
   
 import java.util.Map;  
 import java.util.concurrent.TimeUnit;  
 import java.util.function.Consumer;  
   
 import static com.salesforce.emp.connector.LoginHelper.login;  
   
 public class StreamingClient {  
   
   public static void main(String args[]) throws Exception {  
     long replayFrom = EmpConnector.REPLAY_FROM_EARLIEST;  
     BayeuxParameters params = login("streaming@springsoa.com", "Welcome1");  
     EmpConnector connector = new EmpConnector(params);  
     Consumer<Map<String, Object>> consumer = event -> System.out.println(String.format("Received:\n%s", event));  
     connector.start().get(5, TimeUnit.SECONDS);  
     TopicSubscription subscription = connector.subscribe("/event/UpdateObjectEvent__e", replayFrom, consumer ).get(5, TimeUnit.SECONDS);  
     System.out.println(String.format("Subscribed: %s", subscription));  
     //subscription.cancel();  
     //connector.stop();  
   }  
 }

Generic Javascript Subscriber Client

We can use cometD library to listen to the event, I had to write customer wrapper (cometdCustom.js) to greatly simply the visualforce page. We can also use this in independent HTML page,as long as we can get oauth session id.