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‎ThirdParty/Slack/README.md‎

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# Creating Slack Notifications for CloudWatch Alarms
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## Configure WebHook in Slack
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1. Create a Slack App: <https://api.slack.com/apps/new>
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1. Search for and select **Incoming WebHooks**.
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1. Set **Activate Incoming Webhooks** to **On**.
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1. Select **Add New Webhook to Workspace**.
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1. Choose the default channel where messages will be sent and click **Authorize**.
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1. Note the webhook URL from the **Webhook URLs for Your Workspace** section. For example, `https://hooks.slack.com/services/T0HABCGK/BDEFG93SS/BeBSKJHDHmWwyv2SYV4apv1O`
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F
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```sh
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WEBHOOK_URL=https://hooks.slack.com/services/T0HABCGK/BDEFG93SS/BeBSKJHDHmWwyv2SYV4apv1O
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```
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Test the webhook:
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```sh
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curl -X POST -H 'Content-type: application/json' --data '{"text":"Hello, World!"}' $WEBHOOK_URL
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```
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## Create an SNS Topic
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```sh
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aws sns create-topic --name high-cpu-alarm
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```
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Note the `TopicArn`.
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## Create CloudWatch Alarm
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Send notification to SNS topic when CPU utilization > 40%:
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```sh
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aws cloudwatch put-metric-alarm \
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--alarm-name cpu-mon \
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--alarm-description "Alarm when CPU exceeds 40%" \
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--metric-name CPUUtilization \
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--namespace AWS/EC2 \
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--statistic Average \
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--period 60 \
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--evaluation-periods 1 \
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--threshold 40 \
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--comparison-operator GreaterThanThreshold \
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--dimensions Name=InstanceId,Value=i-12345678901234567 \
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--alarm-actions arn:aws:sns:us-east-1:123456789012:high-cpu-alarm \
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--unit Percent
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```
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## Create SSM Parameter
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```sh
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aws ssm put-parameter --cli-input-json '{"Type": "SecureString", "KeyId": "alias/aws/ssm", "Name": "SlackWebHookURL", "Value": "'"$WEBHOOK_URL"'"}'
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```
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## Create Lambda Execution Role
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Attach the following managed policies:
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- AmazonSSMFullAccess
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- AWSLambdaBasicExecutionRole
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## Create Lambda Function
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Use the SNS topic as a trigger.
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## Stress the CPU
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```sh
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# Install Extra Packages for Enterprise Linux
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sudo amazon-linux-extras install epel
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# Install stress
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sudo yum install -y stress
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# Beat it up for 5 mins
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stress --cpu 2 --timeout 300s
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```

‎ThirdParty/Slack/lambda_execution_role.json‎

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{
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"Version": "2012-10-17",
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"Statement": [{
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"Effect": "Allow",
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"Action": [
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"kms:Decrypt"
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],
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"Resource": [
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"<your KMS key ARN>"
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]
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}]
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}

‎ThirdParty/Slack/lambda_function.py‎

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import json
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from urllib.error import HTTPError, URLError
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from urllib.request import Request, urlopen
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import boto3
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ssm = boto3.client('ssm')
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def lambda_handler(event, context):
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print(json.dumps(event))
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message = json.loads(event['Records'][0]['Sns']['Message'])
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print(json.dumps(message))
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alarm_name = message['AlarmName']
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new_state = message['NewStateValue']
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reason = message['NewStateReason']
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slack_message = {
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'text': f':fire: {alarm_name} state is now {new_state}: {reason}\n'
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f'```\n{message}```'
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}
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webhook_url = ssm.get_parameter(
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Name='SlackWebHookURL', WithDecryption=True)
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req = Request(webhook_url['Parameter']['Value'],
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json.dumps(slack_message).encode('utf-8'))
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try:
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response = urlopen(req)
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response.read()
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print(f"Message posted to Slack")
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except HTTPError as e:
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print(f'Request failed: {e.code} {e.reason}')
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except URLError as e:
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print(f'Server connection failed: {e.reason}')

‎ThirdParty/Slack/sample_alarm.json‎

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{
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"AlarmName": "cpu-mon",
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"AlarmDescription": "Alarm when CPU exceeds 40%",
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"AWSAccountId": "123456789012",
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"NewStateValue": "ALARM",
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"NewStateReason": "Threshold Crossed: 1 datapoint [99.0 (18/03/19 18:06:00)] was greater than or equal to the threshold (40.0).",
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"StateChangeTime": "2019-03-18T18:11:58.507+0000",
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"Region": "US East (Ohio)",
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"OldStateValue": "OK",
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"Trigger": {
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"MetricName": "CPUUtilization",
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"Namespace": "AWS/EC2",
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"StatisticType": "Statistic",
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"Statistic": "AVERAGE",
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"Unit": null,
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"Dimensions": [{
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"value": "i-12345678901234567",
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"name": "InstanceId"
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}],
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"Period": 300,
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"EvaluationPeriods": 1,
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"ComparisonOperator": "GreaterThanOrEqualToThreshold",
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"Threshold": 40,
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"TreatMissingData": "",
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"EvaluateLowSampleCountPercentile": ""
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}
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}

‎ThirdParty/Slack/sample_sns_message.json‎

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{
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"Records": [{
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"EventSource": "aws:sns",
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"EventVersion": "1.0",
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"EventSubscriptionArn": "arn:aws:sns:us-east-2:123456789012:high-cpu-alarm:37113ff5-bc0f-47e7-93cb-a568393b1cdf",
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"Sns": {
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"Type": "Notification",
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"MessageId": "c5185dee-b948-5a60-8240-08e75ff37af7",
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"TopicArn": "arn:aws:sns:us-east-2:123456789012:high-cpu-alarm",
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"Subject": "ALARM: \"cpu-mon\" in US East (Ohio)",
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"Message": "{\"AlarmName\":\"cpu-mon\",\"AlarmDescription\":\"Alarm when CPU exceeds 40%\",\"AWSAccountId\":\"123456789012\",\"NewStateValue\":\"ALARM\",\"NewStateReason\":\"Threshold Crossed: 1 datapoint [99.66666666666667 (18/03/19 18:28:00)] was greater than or equal to the threshold (40.0).\",\"StateChangeTime\":\"2019-03-18T18:33:31.823+0000\",\"Region\":\"US East (Ohio)\",\"OldStateValue\":\"OK\",\"Trigger\":{\"MetricName\":\"CPUUtilization\",\"Namespace\":\"AWS/EC2\",\"StatisticType\":\"Statistic\",\"Statistic\":\"AVERAGE\",\"Unit\":null,\"Dimensions\":[{\"value\":\"i-0bae13e726155adc3\",\"name\":\"InstanceId\"}],\"Period\":300,\"EvaluationPeriods\":1,\"ComparisonOperator\":\"GreaterThanOrEqualToThreshold\",\"Threshold\":40.0,\"TreatMissingData\":\"\",\"EvaluateLowSampleCountPercentile\":\"\"}}",
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"Timestamp": "2019-03-18T18:33:31.872Z",
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"SignatureVersion": "1",
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"Signature": "WiZ8lP42Gu7VHwgBWW1wuXtYlP5why37F5BV/8jxhNmdJVLjwdqbP6lEmPrvz3qNnhxly5P2UPGqCkB6B6U1HCXR+9Xt4td9boMs9mf3zAkC93rJbnUEkURmuIcSqlaSZ0odPK/53VCR3mYkQUc9nkOVBVvlrIAFhx8EtUme7MHV0sju1pchkunTECv9cSmbn9TP2SNkai+KIRfzFSXA7aEsr1m/VbLrzIAynWtxRdO+hksZdkFXd8pm3R5B6ElipuiIErQbVjF9hc7ytFqxIZBP8b5Vpq8ecaoV2g87zuZ7p+bY118td95IT6f9xATMZuv1hwm4LwRn5SukWQ+EQw==",
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"SigningCertUrl": "https://sns.us-east-2.amazonaws.com/SimpleNotificationService-6aad65c2f9911b05cd53efda11f913f9.pem",
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"UnsubscribeUrl": "https://sns.us-east-2.amazonaws.com/?Action=Unsubscribe&SubscriptionArn=arn:aws:sns:us-east-2:123456789012:high-cpu-alarm:37113ff5-bc0f-47e7-93cb-a568393b1cdf",
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"MessageAttributes": {}
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}
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}]
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}

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