Integralist/RPC: Remote Procedure Call.md

## RPC: Remote Procedure Call.md

      
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              RPC: Remote Procedure Call.md
            
          
    RPC is a way of connecting two separate services via a raw TCP socket

Note: SOAP, Thrift, REST APIs, message queues such as RabbitMQ, and key value stores such as Etcd are examples of other tools and protocols

Basic outline

The fundamental principle is, you define an RPC service:

Write a function
Add some RPC configuration
Register our function as a RPC service
Start the service and have it listen for messages on a specific port

From here we have a client service that calls the RPC service:

Write code which calls RPC function
Call the function via a specific ip/port
The 'message' is passed over as valid JSON

JSON-RPC

The client JSON could look like:

method: name of method/service
params: Array of arguments to be passed
id: usually an integer; makes it easier for client to know which request it got a response to (if the RPC calls are done asynchroneously)

{"method": "Arith.Multiply", "params": [{"A": 2, "B": 3}], "id": 1}
The RPC server JSON response could look like:

result: contains return value of method called (null if error ocurred)
error: if error occurred, indicates error code or error message, otherwise null
id: the id of the request it is responding to

{"result": 6, "error": null, "id": 1}