A Go gRPC service that implements a bi-directional streaming method to find the maximum number.

Implement a gRPC bi-directional streaming client and server system:

• The client will stream numbers and sign each number with a private key
• The server will receive numbers, verify request signature with a matching public key
• When the signature is valid, the server will stream back maximum number it has received so far

• Created a simple gRPC bi-directional streaming client and server using protobuf
• The request object from the client sends a int64 number and signature of the signed number
• The response object from server send back a int64 number
• The client uses go routines to send & receive numbers in parallel
• A simple interface crypto/Key is created to allow different implementations of how to read public & private keys. The default implementation is crypto/FileKey , which as name suggests reads private & public keys from a filesystem
• Similarly, the crypto/PublicKey & crypto/PrivateKey interfaces allow different implementations of how to sign data and verify its signature. The default implementations crypto/RSAPublicKey & crypto/RSAPrivateKey uses sha256 and RSA X.509 PEM formatted keys to sign and verify
• config/config.go makes it easier to change the values of the most important variables either by updating the default values or using the environment vars. Please see environment variables section for more details
• The client and server integration tests build the server/server.go executable and run it va exec.Command. It is done this way to have control over the server process and kill it at the end of the tests to free the port

• Maybe use sha-512 in RSA key implementations to save bandwidth
• On the server side, maybe use chain of responsibility pattern to verify signature and determine the new maximum number
• Extract out the shared code between tests to a common package

1. make (http:https://www.gnu.org/software/make/)
2. Go 1.11+
3. protobuf tool (https://github.com/google/protobuf/releases)

1. Generate a new RSA key in $HOME/.ssh
   1. Go to $HOME/.ssh via terminal
   2. Run command openssl genrsa -out maxnumber_rsa_private.pem 2048
   3. Run command openssl rsa -in maxnumber_rsa_private.pem -pubout -out maxnumber_rsa_public.pem
   4. Run command chmod 600 maxnumber_rsa* to change file permissions
2. make install
3. make gen-rpc
4. make run-server - by default server runs on port 7000
5. make run-client

To run tests, do: make test

There are number of variables that can be configured via environment vars to override their default values (i.e., gRPC server port etc). The following variables are configurable:

• GRPC_PORT, default value is 7000
• GRPC_PRIVATE_KEY, default value is $HOME/.ssh/maxnumber_rsa_private.pem
• GRPC_PUBLIC_KEY, default value is $HOME/.ssh/maxnumber_rsa_public.pem
• GRPC_TOTAL_NUMBERS, total numbers to send; default value is 15
• GRPC_NUMBER_MULTIPLIER, random number multiplier; default value is 100