Multi-Instance Loggers

Each new Wiz(config) is a fully independent logger — separate level, masked keys, transports, scope, and correlation ID. Instances share no global state.

Basic scoped instances

import { Wiz } from "@gouranga_samrat/log-wiz";

const dbLogger   = new Wiz({ scope: "database", level: "debug" });
const httpLogger = new Wiz({ scope: "http",     level: "info"  });
const authLogger = new Wiz({ scope: "auth",     level: "trace" });

dbLogger.debug("Connection pool ready", { meta: { poolSize: 10 } });
// -> █ DBG  ... [database] Connection pool ready

httpLogger.info("GET /healthz -> 200", { meta: { latencyMs: 2 } });
// -> █ INF  ... [http] GET /healthz -> 200

authLogger.warn("Failed login attempt", { meta: { ip: "1.2.3.4", attempts: 3 } });
// -> █ WRN  ... [auth] Failed login attempt

Correlation IDs across instances

Attach a per-request ID to link related entries across all loggers:

import { Wiz } from "@gouranga_samrat/log-wiz";

const db   = new Wiz({ scope: "db" });
const http = new Wiz({ scope: "http" });

// Express middleware
app.use((req, res, next) => {
  const requestId = req.headers["x-request-id"] as string ?? crypto.randomUUID();
  req.requestId = requestId;
  next();
});

// In your route handler — pass correlationId per call
app.post("/users", async (req, res) => {
  const cid = req.requestId;

  http.info("Incoming request", { correlationId: cid, meta: { path: req.path } });
  db.debug("Running INSERT", { correlationId: cid, meta: { table: "users" } });
  http.info("Response sent", { correlationId: cid, meta: { status: 201 } });
});

All three entries share the same correlationId, making them trivially filterable in any log aggregator.

Instance-level correlation ID

For workers, jobs, or connection handlers where every log always shares the same ID:

const workerLogger = new Wiz({
  scope: "queue-worker",
  correlationId: `worker-${process.pid}`,
  level: "info",
});

// Every entry from this instance carries correlationId automatically
workerLogger.info("Job started", { meta: { jobId: "j-123" } });
workerLogger.info("Job complete", { meta: { duration: "142ms" } });

Different file directories per instance

const appLogger = new Wiz({
  scope: "app",
  file: { dir: "./logs/app", maxFiles: 7 },
});

const accessLogger = new Wiz({
  scope: "access",
  format: "json",
  file: { dir: "./logs/access", maxFiles: 30 },
});

Module-level pattern

Export a logger instance per module — the Node.js module cache ensures it’s a singleton within that module:

import { Wiz } from "@gouranga_samrat/log-wiz";

export const logger = new Wiz({
  scope: "payment",
  level: process.env.NODE_ENV === "production" ? "info" : "debug",
  file: { dir: "./logs", maxFiles: 7 },
});

// src/services/payment.ts — usage
import { logger } from "./logger";

export async function chargeCard(amount: number) {
  logger.info("Charging card", { meta: { amount } });
}