cromio 0.0.6

Cromio Server

Cromio

Cross-platform JSON-RPC framework for microservice communication.

Cromio provides both a server and a client in multiple languages, so services written in different stacks can talk to each other using the same wire protocol. Currently supported:

• Node.js — published as cromio on npm
• Python — published as cromio on PyPI

Both implementations support:

• RPC and streaming triggers
• gzip-compressed JSON payloads
• Zod/Pydantic schema validation
• Built-in extensions: logger, Prometheus metrics, rate limiter, OpenTelemetry tracing
• Load balancing, retries, and timeouts on the client
• Mutual TLS (mTLS) between client and server

Installation

Python

pip install cromio
# or
pip install cromio[http2]   # if you need HTTP/2 support

Node.js

npm install cromio
# or
yarn add cromio

Quick Start

Python Server

from cromio import Server
from pydantic import BaseModel

class GreetSchema(BaseModel):
    name: str

server = Server(host="0.0.0.0", port=3000)

@server.on_trigger("greet", schema=GreetSchema)
def greet_handler(context):
    return {"message": f"Hello, {context['body']['name']}!"}

server.start()(lambda url: print(f"Server listening on {url}"))

Python Client

from cromio import Client

client = Client(
    servers=[{"url": "http://localhost:3000"}],
    credentials={"secret_key": "my-secret"},
)

response = client.trigger("greet", {"name": "World"})
print(response["data"])  # {"message": "Hello, World!"}

Node.js Server

import { Server, Types } from "cromio";
import { z } from "zod";

const GreetSchema = z.object({
  name: z.string(),
});

const server = new Server({
  port: 3000,
  host: "0.0.0.0",
});

server.schema(GreetSchema).onTrigger("greet", async (payload: Types.Server.OnTriggerType<z.infer<typeof GreetSchema>>) => {
  return { message: `Hello, ${payload.body.name}!` };
});

server.start((url) => {
  console.log(`Server listening on ${url}`);
});

Node.js Client

import { Client } from "cromio";

const client = new Client({
  servers: [{ url: "http://localhost:3000" }],
  credentials: { secretKey: "my-secret" },
});

const response = await client.trigger("greet", { name: "World" });
console.log(response.data); // { message: "Hello, World!" }

Mutual TLS (mTLS)

Both Python and Node.js clients/servers support mTLS by passing certificate buffers or file paths.

Python client with mTLS:

from cromio import Client

client = Client(
    servers=[{
        "url": "https://localhost:3443",
        "tls": {
            "ca": open("certs/ca.pem", "rb").read(),
            "cert": open("certs/client-cert.pem", "rb").read(),
            "key": open("certs/client-key.pem", "rb").read(),
        },
    }],
    credentials={"secret_key": "my-secret"},
)

Node.js server with mTLS:

import { Server } from "cromio";
import fs from "fs";

const server = new Server({
  port: 3443,
  tls: {
    key: fs.readFileSync("certs/server-key.pem"),
    cert: fs.readFileSync("certs/server-cert.pem"),
    ca: fs.readFileSync("certs/ca.pem"),
    requestCert: true,
    rejectUnauthorized: true,
  },
});

Documentation

Document	Description
01-overview.md	Project overview, goals, and status
02-architecture.md	System architecture and key concepts
03-nodejs.md	Node.js package (Server, Client, Extensions)
04-python.md	Python package (Server, Client, Extensions)
05-protocol.md	Wire protocol specification
06-extensions.md	Extension system and built-in extensions
07-getting-started.md	Quick start guides
08-production-checklist.md	Production readiness checklist (P0/P1/P2)

Project Structure

apps/
├── nodejs/   # Node.js package (published as "cromio" on npm)
├── python/   # Python package (published as "cromio" on PyPI)
└── test/     # Integration tests for Node.js and Python

License

MIT