Rest API using Lambda and API Getway - amazon-web-services

Question

I start study AWS serverless using lambda and API Getway, So I was thinking to create a REST API for a sample project. I noticed that in API Getway, we only can create the http methods which can trigger lambda functions, So I'm not sure if I get this right but, do we need one lambda function for each api route? or we can handle it somehow using one lambda function.
For example, lets say my project need api for below list :
Login
Register
GetUserData
Then if I going to make this by using API Getway and Lambda, I need to have 3 Lambda functions?
Like if I want create API for those mentioned above, it should be something like this for the endpoints ?
https://API_GETWAY_DOMAIN/STAGE/LAMBDA_FUNCTION_FOR_LOGIN
https://API_GETWAY_DOMAIN/STAGE/LAMBDA_FUNCTION_FOR_REGISTER
https://API_GETWAY_DOMAIN/STAGE/LAMBDA_FUNCTION_FOR_GET_USER_DATA
And is there any way to send multi http request to one lambda function, and handle each one of them inside the lambda?

Answer 1

It is possible to have multiple API Gateway routes direct to the same Lambda function. How to set that up depends on how you're maintaining your infrastructure.
For example, if you're using CloudFormation with the Serverless Application Model (SAM), which I recommend since it's probably the most straightforward way to keep track of serverless infrastructure (and infrastructure as code = awesome), you would define your AWS::Serverless::Function with a separate API Gateway source event for each route you define in your AWS::Serverless::Api.
Something like the following:
YourApi:
Type: AWS::Serverless::Api
Properties:
...
DefinitionBody:
swagger: 2.0
...
paths:
'/Login':
post:
x-amazon-apigateway-integration:
# APIG->Lambda requests are always POST
httpMethod: post
type: aws_proxy
uri:
Fn::Sub: arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${YourLambda.Arn}/invocations
'/Register':
post:
x-amazon-apigateway-integration:
# APIG->Lambda requests are always POST
httpMethod: post
type: aws_proxy
uri:
Fn::Sub: arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${YourLambda.Arn}/invocations
'/GetUserData':
get:
x-amazon-apigateway-integration:
# APIG->Lambda requests are always POST
httpMethod: post
type: aws_proxy
uri:
Fn::Sub: arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${YourLambda.Arn}/invocations
YourLambda:
Type: AWS::Serverless::Function
Properties:
...
Events:
login:
Type: Api
Properties:
Path: '/Login'
Method: post
RestApiId: {Ref: YourApi}
register:
Type: Api
Properties:
Path: '/Register'
Method: post
RestApiId: {Ref: YourApi}
getUserData:
Type: Api
Properties:
Path: '/GetUserData'
Method: get
RestApiId: {Ref: YourApi}
Keep in mind, though, that there are pros and cons to consolidating routes into one Lambda function. This StackOverflow question/answer explores that, but I'd like to add a few more benefits to separated Lambda functions:
Clearer metrics on how often your routes are getting called - You get invocations/errors/etc. metrics in CloudWatch for each Lambda function out-of-the-box, so separating them can make it easy to see how often people are registering versus logging in, etc.
More granular alarming - You can set different latency/error/etc. thresholds for different routes, and if an alarm goes off, you know exactly which Lambda function it's for.