43 lines
1.5 KiB
Markdown
43 lines
1.5 KiB
Markdown
|
---
|
||
|
|
tags: [AWS, SNS, SQS]
|
||
|
|
created: Monday, November 25, 2024
|
||
|
|
---
|
||
|
|
|
||
|
|
# AWS SNS
|
||
|
|
|
||
|
|
The Simple Notification Service is another form of messaging service in AWS,
|
||
|
|
similar to [SQS](AWS_SQS.md). The key difference is that SNS pushes messages out
|
||
|
|
to subscribers whereas SQS stores the messages until they are processed.
|
||
|
|
|
||
|
|
Before a message can be sent, and SNS topic must exist. One service such as a
|
||
|
|
lambda will _publish_ to this topic. Another service, will _subscribe_ to the
|
||
|
|
topic and be alerted when a message is sent to it.
|
||
|
|
|
||
|
|
With SNS, one message can be sent to multiple subscribers simultaneously. In
|
||
|
|
addition there is message filtering at the subscription level so subscribers can
|
||
|
|
choose to receive only the messages they are interested in.
|
||
|
|
|
||
|
|
Many other AWS services can act as SNS subscribers. Some common examples:
|
||
|
|
|
||
|
|
- SQS queues
|
||
|
|
- Lambda functions (trigger on receipt of a message)
|
||
|
|
- HTTP endpoints
|
||
|
|
- Email/SMS/Push notifications to mobile apps
|
||
|
|
|
||
|
|
## Combining with SQS
|
||
|
|
|
||
|
|
Utilising SNS with SQS is a common pattern in serverless applications.
|
||
|
|
|
||
|
|
We use SNS to decouple publishers from subscribers and then use SQS to handle
|
||
|
|
the different subscriber tasks. This is known as the "Fanout-Queue" pattern.
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
For example, an order is placed which results in a publication event to an SNS
|
||
|
|
topic.
|
||
|
|
|
||
|
|
Multiple systems subscribe to this topic, e.g. an inventory system, a shipping
|
||
|
|
system and an analytics system.
|
||
|
|
|
||
|
|
Each system has its own queue for processing the message.
|