d4vidsha/rpc-framework

Remote Procedure Call (RPC) framework written in C.

Remote Procedure Call (RPC) System

In this project, we will implement a remote procedure call (RPC) system using a client-server architecture.

Getting Started

client.c and server.c are the client and server programs which use the RPC system. The full API of the RPC system is defined in rpc.h, while the RPC system is implemented in rpc.c.

Quick Start

# compile the client and server programs
make

# run the server program on port 8080
./rpc-server -p 8080

# in another terminal, run the client program on ipv6 loopback address ::1 on port 8080
./rpc-client -i ::1 -p 8080

# clean up the compiled files
make clean

# format the source code
make format

Usage

Server

./rpc-server [-p port]

The server program will listen for incoming connections on the specified port. If no port is specified, then the server will listen on port 3000.

Client

./rpc-client [-i ip_address] [-p port]

The client program will connect to the specified IP address and port. If no IP address is specified, then the client will connect to the ipv6 loopback address ::1. If no port is specified, then the client will connect to port 3000.

Development

If you want to debug the RPC system, then #define DEBUG TRUE in config.h. This will print out debug messages to stdout.

Ensure you are using Valgrind frequently to check for memory leaks:

valgrind --leak-check=full --show-leak-kinds=all ./rpc-server -p 8080
valgrind --leak-check=full --show-leak-kinds=all ./rpc-client -i ::1 -p 8080

About the RPC System

Protocol Design

We will use a single rpc_message struct to represent both requests and responses.

Operations

1. Client sends rpc_message to server.
2. Server receives rpc_message.
3. Server sends a new rpc_message to client.
4. Client receives rpc_message.

Message Structure

The rpc_message struct will contain the following fields:

Field	Data Type	Description
request_id	int	The ID of the request. Useful for matching requests to responses. The current implementation does not use this but including this may be useful for future extendibility.
op	enum	The operation can be either FIND, CALL, REPLY_SUCCESS, or REPLY_FAILURE.
function_name	char *	The name of the function to be called or returned.
data	rpc_data	The data to be passed to the function or returned by the function.

This rpc_message struct will be serialised into a byte array and sent over the network. When serialising, we already ensure that there are no padding or endianness issues.

Notable Mentions

• A hash table is used to store the function pointers in the server program.
• A protocol with a request and response message structure is used to communicate between the client and server programs. The serialisation and deserialisation of the messages are done through functions in protocol.c.
• Elias Gamma Coding is used for the serialisation and deserialisation of size_t data types.

rpc-framework's Issues

Handle memory allocation errors without `assert()`, which will currently exit the program.

Limit concurrent connections to the server by using a queue.

Limit concurrent connections to the server by using a queue. Currently, all open and closed connections (the sockfds) are stored in a linked list.

Use integer inside `rpc_handle`.

Use integer inside rpc_handle as opposed to a fixed-length array of characters.