createLambdaFuncs.md

Create lamda functions

AWS Lambda

• A serverless, event-driven compute service
• Able to run code for virtually any type of application or backend service without provisioning or managing servers.
• In this application lambda will be triggered using API Gateway

Terminonlogy and Concepts

• Serverless function: Piece of code that will be executed by a compute service, on demand.
• Lambda trigger: The type of event that will make a Lambda (serverless) function run.

Required functions

There will be two lambda functions created:

• postFeedback to post to the database
• getFeedback to get a random feedback item from database

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Implementation - Creating functions

Step 01:

• Give the function a name, in this case postFeedback
• Use runtime of python 3.9 or above
• Architecture x86

Step 02:

• Under persmissions, click on change default execution role
• This gives the lambda function basic access to dynamoDB
• Select create a new role from AWS policy templates
• Give the role a name
• For the policy search for and select simple microservice permissions
• Click create function

Using simple micoservice permissions is not best practice; custom services should operate on the policy of least priviledge, giving as few permissions as possible to reduce overhead and maximize privacy and security.

Step 03:

• Paste in the python code from postFeedback found here ../lambda/

Step 04:

• Repeat step 1, but use the name getFeedback
• Under change default execution role, select use existing
• Select the same one created in step 2
• Repeat step 3, getFeedback found here ../lambda/

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Implementation - Testing

Step 05:

• To begin testing this code open the postFeedback function
• Comment out input = event['input']
• Uncomment input = 'hello from lambda'
• File -> save
• Remember to change this back after we post the function

Step 06:

• Click on test provide and event name, then save

Step 07:

• Click on the test tab
• Click on the orange test button
• Execution result should be successful
• This only tests the the code is CAN run, it does not post to the database

Step 08:

• To run a test that posts to the database, we need to deploy it
• Go back to the code tab, and click deploy
• You must deploy each time changes are made to the code

Step 09:

• Go back to the test tab and run test again
• This time the details in execution result will be different
• Open a new tab and go back to dynamoDB
• To view the items in the table, click on the table name
• Then the orange button at the top right explore table items
• Clicking the refresh button will fetch newly added items

Step 10:

• Uncomment input = event['input']
• Comment out input = 'hello from lambda'
• This reverses the change in step 5

Step 11:

• To test getFeedback, make sure the code is deployed
• Repeat step 6
• Click on the test tab
• Click on the orange test button
• Execution result should be successful
• The item just posted to the database should be returned

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Next -> Create REST API