json-rpc-client-gen

A Node client stub generator for JSON-RPC Systems

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NOTE This package is in experimental phase and currently only supports TCP/IP for communication.

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This wraps the complexities of:

1. Client to server network communication.
2. Sending and parsing JSON-RPC network requests and responses.

Getting started

1. Make sure than Node is installed. The binary can run on Node v12 but v18 or higher is recommended.

   • Currently, the project only supports ES Module resolution which is fully supported by Node v12 and higher.

2. In your project, create a configuration file jsonrpcgen.config.json

   • The config file will be read from the CWD upwards.
   • See Configuration file section for options.

3. Run the binary to generate the client stub for your RPC server.

   json-rpc-client-gen
   

   or

   npx json-rpc-client-gen
   

Sample Usage

import stub from './client-stub/index.js'

stub.on('connect', async () => {
  // Event Emitter data access
  stub.on('data', (data) => {
    console.log('data received:', data)
  })
  
  // Promises data access
  console.log(await Promise.all([stub.add(1, 2), stub.subtract(5, 2)]))
})

stub.connect()

Client stub

• The client stub code generated currently only supports ESM.
• There's some support pseudo-parallelism using Promise API static methods. But currently it only uses one socket stream, hence data is sent and obtained from the same layer 4 source. Support for TCP sockets pooling will be implemented in the future.
• Methods will implicitly connect to the server if the socket is closed/destroyed, however the requests can be buffered in user memory if not yet connected. You can choose to explicitly call the connect method on the stub if you want appropriate stub lifecycle handling.

Stub error handling

Method response error

rejects with the error (see JSON-RPC specification) payload from the response.

Stub errors

Includes:

• Receiving malformed messages
• Timeouts
• Socket errors

This will be emitted with the error event so appropriate on error handler can be given so it would not be thrown. This is emitted asynchronously so as to limit the interference with important synchronous operations of the consumer and the stub.

stub.on('error', (err) => {
   ...
})

Usage error

This will be thrown such as the wrong usage of the batch method (see Batching). This provides granular error handling for synchronous errors.

Methods result access

The results of the methods exposed by the stub can be accessed via:

1. Promises

const data = await stub.add(1, 2)
const moreData = await Promise.all([stub.add(1, 2), stub.subtract(5, 3)])

console.log(data)

2. Event Emitters

stub.on('data', (result) => {
  console.log(result)
})

• Emitted result is the RAW JSON response.

Batching

• As mentioned above, consumers can do their own batching using Promise API static methods.
• The stub also exposes a batch method, an implementation of the JSON-RPC batch specification. This allows a consumer to pass RPC in object form. This would return a list of promises corresponding to the RPC at each index. See usage below.

// batching using promises
const [res1, res2] = await Promise.all([stubs.method1(param1), stub.method2(param1)])

// stub batching
const [res1, res2] = await stub.batch([
   { method: 'method1', params: { param1: 'param1' }, isNotification: true },
   { method: 'method2', params: { param1: 'param1' }, isNotification: false },
])

Promise batching vs Batch method

• Promise batching will send the requests to the server one-by-one in a concurrent manner.
• batch method will send the requests to the server in an array. This returns a list of promises.

batch method param

/**
 * params and isNotification fields are optional
 */
{
   method: 'method1', // string
   params: { param1: 'param1' }, // object of parameters for the RPC, can also be an array for positional arguments
   isNotification: true // whether the RPC is a notification
}

Configuration file

Options	Type	Default	Description	Example
source	string	-	JSON file for your function	./src/functions.esrpc.json
host	string	-	Target server hostname or IPv4/IPv6 (uses dns.lookup())	localhost
port	number	-	Target server port	25
targetDir	string	-	Directory where client stub file will be emitted	./src/client
version (optional)	1.0 or 2.0	2.0	JSON-RPC specification version	2.0
socketTimeout (optional)	number	300000 ms/5 mins	Period in ms where a socket will be idle before being destroyed	10000
connectionTimeout (optional)	number	300000 ms/5 mins	Period in ms where a TCP handshake can be successful, rejects and emits an error if timed out	10000

Functions definitions

Function signatures that your server supports are defined in a file in source parameter in the configuration file

{
   "method1": {
      "parameters": ["param1", "param2"]
   },
   "method2": {
      "parameters": ["param1", "param2"]
   }
}