Added AWS Lambda to CDA

Author: rishabkumar7

CDA.md

@@ -1348,6 +1348,163 @@ about the change
 
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+# AWS Lambda
+## AWS Lambda language support 
+- Node.js (JavaScript) 
+- Python 
+- Java (Java 8 compatible) 
+- C# (.NET Core) 
+- Golang 
+- C# / Powershell 
+- Ruby 
+- Custom Runtime API (community supported, example Rust)
+
+## AWS Lambda Pricing: example 
+- You can find overall pricing information here: https://aws.amazon.com/lambda/pricing/ 
+- Pay per calls : 
+    - First 1,000,000 requests are free 
+    - $0.20 per 1 million requests thereafter ($0.0000002 per request) 
+- Pay per duration: (in increment of 100ms) 
+    - 400,000 GB-seconds of compute time per month if FREE 
+    - == 400,000 seconds if function is 1GB RAM 
+    - == 3,200,000 seconds if function is 128 MB RAM 
+    - After that $1.00 for 600,000 GB-seconds
+
+## Lambda – Synchronous Invocations
+- Synchronous: CLI, SDK, API Gateway, Application Load Balancer
+- Results is returned right away
+- Error handling must happen client side (retries, exponential backoff, etc…)
+
+## Lambda - Synchronous Invocations - Services
+- User Invoked:
+    - Elastic Load Balancing (Application Load Balancer)
+    - Amazon API Gateway
+    - Amazon CloudFront (Lambda@Edge)
+    - Amazon S3 Batch
+- Service Invoked:
+    - Amazon Cognito
+    - AWS Step Functions
+- Other Services:
+    - Amazon Lex
+    - Amazon Alexa
+    - Amazon Kinesis Data Firehose
+
+## Lambda – Asynchronous Invocations
+- S3, SNS, CloudWatch Events…
+- The events are placed in an Event Queue
+- Lambda attempts to retry on errors
+    - 3 tries total
+    - 1 minute wait after 1st , then 2 minutes wait
+- Make sure the processing is idempotent (in case of retries)
+- If the function is retried, you will see duplicate logs entries in CloudWatch Logs
+- Can define a DLQ (dead-letter queue) – SNS
+or SQS – for failed processing (need correct IAM permissions)
+- Asynchronous invocations allow you to speed
+up the processing if you don’t need to wait for
+the result (ex: you need 1000 files processed)
+
+## Lambda - Asynchronous Invocations - Services
+- Amazon Simple Storage Service (S3)
+- Amazon Simple Notification Service (SNS)
+- Amazon CloudWatch Events / EventBridge
+- AWS CodeCommit (CodeCommit Trigger: new branch, new tag, new push)
+- AWS CodePipeline (invoke a Lambda function during the pipeline, Lambda must callback)
+----- other -----
+- Amazon CloudWatch Logs (log processing)
+- Amazon Simple Email Service
+- AWS CloudFormation
+- AWS Config
+- AWS IoT
+- AWS IoT Events
+
+## Lambda@Edge
+- You have deployed a CDN using CloudFront
+- What if you wanted to run a global AWS Lambda alongside?
+- Or how to implement request filtering before reaching your application?
+- For this, you can use Lambda@Edge:
+deploy Lambda functions alongside your CloudFront CDN
+    - Build more responsive applications
+    - You don’t manage servers, Lambda is deployed globally
+    - Customize the CDN content
+    - Pay only for what you use
+
+## Lambda Execution Role (IAM Role)
+- Grants the Lambda function permissions to AWS services / resources
+- Sample managed policies for Lambda:
+    - AWSLambdaBasicExecutionRole – Upload logs to CloudWatch.
+    - AWSLambdaKinesisExecutionRole – Read from Kinesis
+    - AWSLambdaDynamoDBExecutionRole – Read from DynamoDB Streams
+    - AWSLambdaSQSQueueExecutionRole – Read from SQS
+    - AWSLambdaVPCAccessExecutionRole – Deploy Lambda function in VPC
+    - AWSXRayDaemonWriteAccess – Upload trace data to X-Ray.
+- When you use an event source mapping to invoke your function, Lambda uses the execution role to read event data.
+- Best practice: create one Lambda Execution Role per function
+
+## Lambda Resource Based Policies
+- Use resource-based policies to give other accounts and AWS services permission to use your Lambda resources
+- Similar to S3 bucket policies for S3 bucket
+- An IAM principal can access Lambda:
+- if the IAM policy attached to the principal authorizes it (e.g. user access)
+- OR if the resource-based policy authorizes (e.g. service access)
+- When an AWS service like Amazon S3 calls your Lambda function, the resource-based policy gives it access.
+
+## Lambda Environment Variables
+- Environment variable = key / value pair in “String” form
+- Adjust the function behavior without updating code
+- The environment variables are available to your code
+- Lambda Service adds its own system environment variables as well
+- Helpful to store secrets (encrypted by KMS)
+- Secrets can be encrypted by the Lambda service key, or your own CMK
+
+## Lambda Functions /tmp space
+- If your Lambda function needs to download a big file to work…
+- If your Lambda function needs disk space to perform operations…
+- You can use the /tmp directory
+- Max size is 512MB
+- The directory content remains when the execution context is frozen,
+providing transient cache that can be used for multiple invocations
+(helpful to checkpoint your work)
+- For permanent persistence of object (non temporary), use S3
+
+## Lambda Function Dependencies
+- If your Lambda function depends on external libraries: for example AWS X-Ray SDK, Database Clients, etc…
+- You need to install the packages alongside your code and zip it together
+- For Node.js, use npm & “node_modules” directory
+- For Python, use pip --target options
+- For Java, include the relevant .jar files
+- Upload the zip straight to Lambda if less than 50MB, else to S3 first
+- Native libraries work: they need to be compiled on Amazon Linux
+- AWS SDK comes by default with every Lambda function
+
+## AWS Lambda Limits to Know - per region
+- Execution:
+    - Memory allocation: 128 MB – 3008 MB (64 MB increments)
+    - Maximum execution time: 900 seconds (15 minutes)
+    - Environment variables (4 KB)
+    - Disk capacity in the “function container” (in /tmp): 512 MB
+    - Concurrency executions: 1000 (can be increased)
+- Deployment:
+    - Lambda function deployment size (compressed .zip): 50 MB
+    - Size of uncompressed deployment (code + dependencies): 250 MB
+    - Can use the /tmp directory to load other files at startup
+    - Size of environment variables: 4 KB
+
+## AWS Lambda Best Practices
+- Perform heavy-duty work outside of your function handler
+- Connect to databases outside of your function handler
+- Initialize the AWS SDK outside of your function handler
+- Pull in dependencies or datasets outside of your function handler
+- Use environment variables for:
+- Database Connection Strings, S3 bucket, etc… don’t put these values in your code
+- Passwords, sensitive values… they can be encrypted using KMS
+- Minimize your deployment package size to its runtime necessities.
+- Break down the function if need be
+- Remember the AWS Lambda limits
+- Use Layers where necessary
+- Avoid using recursive code, never have a Lambda function call itself
+
+----------------------------------------------
+
 # API Gateway
 ## API Gateway -- Integrations High Level
 - Lambda Function