@bonniernews/logger

Bonnier News logger library, that makes it easier to unify logging. It is pre-configured for GCP and includes tracing capabilities for Express servers.

npm install @bonniernews/logger

Usage

Here is an example server with log tracing enabled.

import {
  fetchGcpProjectId,
  getHttpTraceHeader,
  middleware,
  logger as BNLogger
} from "@bonniernews/logger";
import express from "express";
import pino from "pino";

const logger = BNLogger();
const app = express();

app.use(middleware);

// Fetches the project ID from the GCP metadata server in the background on startup.
// This is only necessary if you don't set the `GCP_PROJECT` environment variable.
fetchGcpProjectId();

app.get("/", async (req, res) => {
  logger.info("Hello, world!");

  const response = await fetch("https://some.service.bn.nr/some/endpoint", {
    headers: { ...getHttpTraceHeader() },
  });

  ...
});

Logger Interface

Options

This library uses the Pino logger, and instances are created using the same options. In most cases this is not needed, and you can use the defaults:

• Uses info as the minimum log level
• JSON logging with severity and message fields for non-local environments - in line with GCP structured logging standards
• Pretty logging enabled for local development and test environments

Log Levels

The logger has the following levels, with their corresponding GCP severity mapping:

| Log level | GCP severity | | --------- | ------------ | | trace | DEBUG | | debug | DEBUG | | info | INFO | | warn | WARNING | | error | ERROR | | fatal | CRITICAL |

Log messages

Here are a few examples on how to use the logger:

import { logger } from "@bonniernews/logger";

const log = logger({ level: "debug" });

log.debug("This is just a message");

log.info("This is how to use %s strings: %d", "template", 123);

log.info({ any: { additional: "data" } }, "I'm attaching relevant data");

const error = new Error("Oops!");

// This will set error.message as the log message,
// and add a serialized error object under the `err` key:
log.warn(error);

// The `err` key is special, and triggers error serialization:
log.error({ err: error }, "This message takes precedence over err.message");

Tracing

If you want to decorate logs with tracing fields for incoming requests, use the library's middleware, which will use Node async hooks to store and decorate all logs using the standardized traceparent header.