100 Days of DevOps — Day 2 -Introduction to Simple Notification Service(SNS)

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YouTube link: https://www.youtube.com/user/laprashant/videos

Welcome to Day 2 of 100 Days of DevOps, Let extend the journey of DevOps Monitoring and Alerting https://medium.com/@devopslearning/100-days-of-devops-day-1-introduction-to-cloudwatch-metrics-b04be36307a8 with alerting concept Simple Notification Service(SNS).

Problem Statement

• To send out a notification via Email, SMS.. when an event occurs.

Solution

This can be achieved via in one of the three ways

• AWS Console
• AWS CLI
• Terraform

NOTE: This is not the complete list and there are more ways to achieve the same

What is SNS?

As per official documentation

AWS SNS is a web service that coordinates and manages the delivery or sending of messages to subscribing endpoints or clients.

We already saw this in action with CloudWatch(high CPU utilization or System/Instance Status Check) when the certain event occurs and SNS is used to send a notification. CloudWatch in combination with SNS creates a full monitoring solution with notifies the administrator in case of any environment issue(high CPU, Downtime…).

Reference

What is Amazon Simple Notification Service? - Amazon Simple Notification Service

SNS has three major components

Publisher

• The entity that triggers the sending of a message(eg: CloudWatch Alarm, Any application or S3 events)

Topic

• Object to which you publish your message(≤256KB)
• Subscriber subscribe to the topic to receive the message
• Soft limit of 10 million subscribers

Subscriber

An endpoint to a message is sent. Message are simultaneously pushed to the subscriber

• As you can see it follows the publish-subscribe(pub-sub) messaging paradigm with notification being delivered to the client using a push mechanism that eliminates the need to periodically check or poll for new information and updates.
• To prevent the message from being lost, all messages published to Amazon SNS are stored redundantly across multiple Availability Zones.

Enough of theory, let see SNS in action

Using the AWS Console

Step 1: Create a topic

• In the Amazon SNS console, choose Create topic.

• Create a topic

Step2: Subscribe to a Topic

• Choose to Create a subscription.
• The Create Subscription dialog box appears.

• Go to your email and confirm subscription

Step3: Publish to the topic

• Choose the Publish to the topic button.
• The Publish a Message page appears.

Using AWS CLI

• Create a Topic

$ aws sns create-topic --name "my-demo-sns-topic"
{
"TopicArn": "arn:aws:sns:us-west-2:1234556667:my-demo-sns-topic"
}

• Subscribe to a Topic

$ aws sns subscribe --topic-arn arn:aws:sns:us-west-2:123456667:my-demo-sns-topic --protocol email --notification-endpoint test@gmail.com
{
"SubscriptionArn": "pending confirmation"
}

• Publish to a Topic

$ aws sns publish --topic-arn arn:aws:sns:us-west-2:1234567:my-demo-sns-topic --message "hello from sns"
{
"MessageId": "d651b7d5-2d66-58c8-abe4-e30822a3aa3e"
}

• To list all the subscriptions

$ aws sns list-subscriptions
{
"Subscriptions": [
{
"Owner": "1234567889",
"Endpoint": "test@gmail.com",
"Protocol": "email",
"TopicArn": "arn:aws:sns:us-west-2:1234567788:HighCPUUtilization",
"SubscriptionArn": "arn:aws:sns:us-west-2:1234567788:HighCPUUtilization:a28e2be8-40cd-4f8b-83d9-33b2c858749d"
},

• Unsubscribe from a Topic

aws sns unsubscribe --subscription-arn arn:aws:sns:us-west-2:1234567899:my-demo-sns-topic:f28124be-850b-4a2e-8d3e-a3dc4f7cca1a

• Delete a topic

$ aws sns delete-topic --topic-arn arn:aws:sns:us-west-2:1234567788:my-demo-sns-topic

• List a topic

$ aws sns list-topics
{
"Topics": [
{
"TopicArn": "arn:aws:sns:us-west-2:123333345555:mydemosnstopic"
}
]
}

100daysofdevops/100daysofdevops

Using Terraform

# main.tf
resource "aws_sns_topic" "alarm" {
  name = "alarms-topic"

  delivery_policy = <<EOF
{
  "http": {
    "defaultHealthyRetryPolicy": {
      "minDelayTarget": 20,
      "maxDelayTarget": 20,
      "numRetries": 3,
      "numMaxDelayRetries": 0,
      "numNoDelayRetries": 0,
      "numMinDelayRetries": 0,
      "backoffFunction": "linear"
    },
    "disableSubscriptionOverrides": false,
    "defaultThrottlePolicy": {
      "maxReceivesPerSecond": 1
    }
  }
}
EOF

  provisioner "local-exec" {
    command = "aws sns subscribe --topic-arn ${self.arn} --protocol email --notification-endpoint ${var.alarms_email}"
  }
}
# variables.tf
variable "alarms_email" {
  default = "laprashant@gmail.com"
}
# outputs.tf
output "sns_topic" {
  value = "${aws_sns_topic.alarm.arn}"
}

GitHub link

100daysofdevops/100daysofdevops

Looking forward from you guys to join this journey and spend a minimum an hour every day for the next 100 days on DevOps work and post your progress using any of the below medium.

• Twitter: @100daysofdevops OR @lakhera2015
• Facebook: https://www.facebook.com/groups/795382630808645/
• Medium: https://medium.com/@devopslearning
• Slack: https://devops-myworld.slack.com/messages/CF41EFG49/
• GitHub Link:https://github.com/100daysofdevops

Reference

100 Days of DevOps — Day 0