Cisco Dynamic Reverse Proxy AWS Cloud Watch Instance Monitoring Guide

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Cisco
Dynamic Reverse Proxy
Saving Minutes to Save Millions. A Guide.

Will Rooney
Cecil Hutchings
Matthew King

William.rooney@ucdenver.edu
Cecil.hutchings@ucdenver.edu
Matthew.king@ucdenver.edu

Table of Contents
I.

Summary ................................................................................................................ 2

II.

Configuring AWS S3 & CloudTrail ....................................................................... 2

III.

Tutorial: Invoke Lambda on a State change or
API call of an Amazon EC2 Instance Using
CloudWatch Events ............................................................................................... 2
Step 1: Create an AWS Lambda Function
Step 2: Create a Rule
Step 3: Test the Rule

IV.

Appendix................................................................................................................ 7
Links

Summary
The Cisco reverse proxy is secure static web server that serves web applications to Cisco developers.
Automation techniques are used to transform the static reverse proxy into a dynamic reverse proxy.
Each web application is hosted on Amazon Web Services (the cloud). Applications are
frequently added and removed to save money on cloud resource costs; applications may not be
often used and therefore do not need to be hosted on the cloud at all times. The existing static
reverse proxy does not update to reflect this. A Cisco developer typically spends a few minutes
manually updating the existing proxy every day. Over time this adds up to hours of skilled labor lost
to a trivial task. This problem is resolved by automating the tasks a developer must take to update
the proxy every time an application is created or deleted.
The Cisco Dynamic Reverse Proxy prototype utilizes Amazon Web Services (AWS) and the
python programming language to automate these tasks. The prototype monitors for instances (web
applications), as they are added and removed the prototype logs the results to cloud storage. The
final product will update the dynamic reverse proxy in fractions of a second.
Transforming a static proxy into a dynamic proxy automates a task that takes five minutes of
skilled labor. The resulting operation takes fractions of a second billed at the cost of cloud resources.
Over time automation techniques like this save millions of dollars.

Configuring AWS S3 & CloudTrail
This guide assumes general familiarity with AWS S3 and CloudTrail. For more information see:
http://docs.aws.amazon.com/awscloudtrail/latest/userguide/cloudtrail-getting-started.html

Tutorial: Invoke Lambda on a State change or API
call of an Amazon EC2 Instance Using CloudWatch
Events
The following tutorial was taken from Amazons “Log EC2 Instance State” tutorial with slight
modifications.
http://docs.aws.amazon.com/AmazonCloudWatch/latest/events/LogEC2InstanceState.html
You can create a AWS Lambda function that logs API calls for an Amazon EC2 instance. You
can choose to create a rule that runs the function whenever there is a runInstances or
terminateInstances API call. In this tutorial, you log the launch/termination of any new instance
using lambda.

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Step 1: Create an AWS Lambda Function
Create a Lambda function to log the API call events. You specify this function when you create
your rule.
To create a Lambda function
1. Open the AWS Lambda console at https://console.aws.amazon.com/lambda/.
2. If you are new to Lambda, you see a welcome page; choose Get Started Now; otherwise,
choose Create a Lambda function.
3. On the Select blueprint page, type hello for the filter, and then choose the hello-world
blueprint.
4. On the Configure triggers page, choose Next.
5. On the Configure function page, do the following:
1. Type a name and description for the Lambda function. (For example, name the
function "LogEC2InstanceAPICall".)
2. Edit the sample code for the Lambda function. For example (Python 3.6):
import boto3
import time
import json
ec2 = boto3.resource('ec2')
def lambda_handler(event, context):
"""
Handle EC2 Run and Terminate Instance API Calls.
Log Event data to S3 and POST event data to a reverse proxy.
"""
#print("Received event: " + json.dumps(event, indent=2))
# Create a timestamp to ensure unique filename for log written to S3
timestamp = time.strftime("%Y%m%d-%H%M%S")
# upload the event data to S3
bucket = 'my-bucket'
fileName = timestamp
# Event Dict
eventOutput = {}
eventOutput['Events'] = event
try:
if event['detail-type'] == 'AWS API Call via CloudTrail':
# API Call to RunInstances or TerminateInstances
eventName = event['detail']['eventName']
if eventName == 'RunInstances':
# RunInstances API Call
elif eventName == 'TerminateInstances':
# TerminateInstances API Call
else:
raise Exception('Invalid event: ' + eventName)
else:
raise Exception('Invalid detail-type: '+event['detail-type'])
except Exception as e:
# Error Parsing Event - Log Error details
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print(e)
errorDetails = {'Exception': str(e), 'EventInput': event}
eventOutput['Events'].append({"Error": errorDetails})
# Log eventOutput to S3
path = '/tmp/' + fileName
with open(path, 'w') as f: json.dump(eventOutput, f, indent=2)
s3.meta.client.upload_file(path, bucket, fileName)

*A further detailed example is included with this guide:
“cmw_instance_cloudwatch_lambda.py”
3. For Role, choose Choose an existing role and then choose your basic execution
role from Existing role. Otherwise, create a new basic execution role.
4. Choose Next.
6. On the Review page, choose Create function.

Step 2: Create a Rule
Create a rule to run your Lambda function whenever you launch/terminate an Amazon EC2
instance.
To create a CloudWatch Events rule
1. Open the CloudWatch console at https://console.aws.amazon.com/cloudwatch/.
2. In the navigation pane, choose Events, Create rule.
3. For Event source, do the following:
1. Choose Event Pattern.
2. Choose Build event pattern to match events by service.
3. Choose EC2 and then choose AWS API Call via CloudTrail.
4. Choose Specific operations(s) and then add two operations:
1. RunInstances
2. TerminateInstances

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4.
5.
6.
7.
8.

For Targets, choose Add target and then choose Lambda function.
For Function, select the Lambda function that you created.
Choose Configure details.
For Rule definition, type a name and description for the rule.
Choose Create rule.

Step 3: Test the Rule
To test your rule, launch an Amazon EC2 instance. After waiting a few minutes for the instance
to launch and initialize, you can verify that your Lambda function was invoked.
To test your rule by launching an instance
1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.
2. Launch an instance. For more information, see Launch Your Instance in the Amazon EC2
User Guide for Linux Instances.
3. Open the CloudWatch console at https://console.aws.amazon.com/cloudwatch/.
4. In the navigation pane, choose Events, Rules, select the name of the rule that you
created, and choose Show metrics for the rule.
5. To view the output from your Lambda function, do the following:
1. In the navigation pane, choose Logs.
2. Choose the name of the log group for your Lambda function
(/aws/lambda/function-name).
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3. Choose the name of log stream to view the data provided by the function for the
instance that you launched.
6. (Optional) When you are finished, you can open the Amazon EC2 console and stop or
terminate the instance that you launched. For more information, see Terminate Your
Instance in the Amazon EC2 User Guide for Linux Instances.

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Appendix
Links
•

https://d0.awsstatic.com/whitepapers/compliance/AWS_Security_at_Scale_Logging_in_AWS_Whitepaper.p
df

•

http://docs.aws.amazon.com/lambda/latest/dg/with-cloudtrail-example-prepare.html

•

http://docs.aws.amazon.com/awscloudtrail/latest/userguide/cloudtrail-create-a-trail-using-the-console-firsttime.html#advanced-settings-for-your-trail

•

http://docs.aws.amazon.com/awscloudtrail/latest/userguide/cloudtrail-create-and-update-a-trail.html

•

http://docs.aws.amazon.com/awscloudtrail/latest/userguide/cloudtrail-create-and-update-a-trail.html

•

http://docs.aws.amazon.com/awscloudtrail/latest/userguide/use-the-cloudtrail-processing-library.html

•

https://boto3.readthedocs.io/en/latest/reference/services/cloudwatch.html

•

https://aws.amazon.com/cloudwatch/pricing/

•

http://docs.aws.amazon.com/awscloudtrail/latest/userguide/cloudtrail-event-reference-record-contents.html

•

http://docs.aws.amazon.com/awscloudtrail/latest/userguide/cloudwatch-alarms-forcloudtrail.html#cloudwatch-alarms-for-cloudtrail-ec2-instance-changes

•

http://docs.aws.amazon.com/AmazonCloudWatch/latest/events/LogEC2InstanceState.html

•

https://boto3.readthedocs.io/en/latest/reference/services/ec2.html#instance

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