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#CS441: Homework 6 ##Using gRPC & REST requests to invoke AWS Lambda function through AWS API Gateway

##Prerequisites

• protoc should be installed
• SBT and Scala should be installed
• Internet connection required

##Steps to run

1. Open command line at root of project (i.e. at /chinmay_gangal_hw6)

2. Run sbt. This launches the sbt command line

3. Run clean. This erases previous cached output files

4. Run compile. This would generate the scala files required from proto using protobuf

5. First we need to start gRPC server, by executing command runMain GRPCServer.

6. Open another terminal, since the previous would be occupied by the listening server

7. Redo step 2

   Before we move on to running the gRPC client, we need to understand the format of input parameters for the calculator.

   We have 3 parameters: 2 operands and an operator

   Each operand is a valid number (integer & float) For operator, we have 3 choice: add, sub, mul & div which stand for addition, subtraction, multiplication & division respectively

   The input is provided in the following format: operand1,operand2,operator

   For example, to calculate 5/3, we input 5,3,div

   Observe that the order of the operands is important for subtraction and division

8. Now we execute client, with command line parameters. Type runMain GRPCClient <input-as-shown-above> command.

9. The output will contain a line ...Result: <calculation-output>.

This is the result of your input returned from AWS Lambda function, accessed through AWS API Gateway

##Development steps

• Implementing Lambda & its API
  1. Created Lambda function for calculator using AWS SAM. URL: https://7ub4yveql2.execute-api.us-east-1.amazonaws.com/public/calc
  2. Added API Gateway to Lambda method, then tested online as REST request, and then from Postman
• Implmenting gRPC in Scala 3. Installed protoc and tested gRPC for Java application using protobuf for Java on .proto file(s) 4. Implemented local gRPC client-server as a Hello World application in Scala using ScalaPB. Client & server are able to exchange basic String messages
• Integrating and testing 5. Connected this implementation with API from step 2 6. Added test cases, and config file

##Technologies used

• Scala
• SBT
• gRPC
• ScalaPB: ProtoBuf for Scala

##Author Chinmay Gangal: [email protected]