Streaming API - PushTopic

1. What Salesforce Streaming API?

The Salesforce Streaming API is a simple way to push relevant data to your users in real-time, instead of having to refresh the screen to get new information.

This allows a user to get information without having to perform any action to retrieve it, essentially pushing new data to the screen.

2. Event-Driven (Pub/Sub) VS Point-Point Architecture Best Fit?

Event-Driven [Push Technology]	Point-Point [Pull Technology]
At some point enterprise system grows much and more complex and where decoupling of service is needed.There event driven architecture is the best fit.	When your infrastructure only has a few components, point to point integration can seem like a lightweight way to connect everything together.

3. What are the Streaming API events?

Event	Details
PushTopic	PushTopic events track field changes in Salesforce records and are tied to Salesforce records.
Generic	Generic events contain arbitrary payloads.

4. Explain Streaming API PushTopic event?

You can use Streaming API to keep your external source in sync with your 

Salesforce data with PushTopic events and Change Data Capture events.

Streaming API lets you process business logic in an external system in 

response to data changes in Salesforce.

Ex: Notify a fulfillment center whenever an opportunity is updated.

PushTopic Supported Objects :

Supports all Custom Objects & Below mentioned Standard Objects

Campaign	ContractLineItem	Case
Lead	Entitlement	ServiceAppointment
Account	Quote	ServiceContract
Contact	QuoteLineItem	WorkOrder
Opportunity	-	WorkOrderLineItem
Task	-	LiveChatTranscript

PushTopic Important Points :

1.The SELECT  statement's field list must include Id

2.Only 1 object per query is allowed

3.Aggregate queries or Semi-Joins aren't supported

4.Subscribers receives all stored events after the events specified by its replayId value and new events.

5.Limit the stream of events to only those events that match a subscription filter,Only PushTopic has this feature ,Same is not available in Generic /Platform Events.

Refer1

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6.Clients & Timeouts  - As a supported in the Bayeux protocol

•   Socket timeout : 110 Seconds
•   Reconnect timeout : 40 Seconds

PushTopic Governor Limits: Refer

PushTopic Implementation Example :

1.Apex :

PushTopic pushTopic = new PushTopic(); pushTopic.Name = 'ContAddUpdate'; pushTopic.Query = 'SELECT Id,Name,AccountId,MailingCity,MailingStreet'+           'FROM Contact Where AccountId = 016F000032XRPhQAO'; pushTopic.ApiVersion = 43.0; pushTopic.NotifyForOperationCreate = true; pushTopic.NotifyForOperationUpdate = true; pushTopic.NotifyForOperationUndelete = true; pushTopic.NotifyForOperationDelete = true; pushTopic.NotifyForFields = 'Referenced'; insert pushTopic;

2.WorkBench: Publish & Subscribe - Change Data Capture on records

How to delete PushTopic :

There are 2 options,Either deactivate /delete 

Deactivate :

PushTopic pt = new PushTopic(Id='0IFD0000000008jOAA', IsActive = false); update(pt);

Delete : Apex

List<PushTopic> pts = [SELECT Id FROM PushTopic WHERE Name = 'Channel']; Database.delete(pts);

Delete : Workbench

Select queries -> Streaming Push Topics -> select your push topic --> Details --> Delete