BJ Logger

A centralized logger for Node.js applications. This package provides a simple way to log messages to CloudWatch Logs, as well as to a file. It also supports multiple transports, allowing you to log to multiple destinations.

Installation

To install the package, run the following command:

npm install bj-logger

Usage

Basic Usage

To use the package, you need to create an instance of the Logger class and pass in the service name and any transports you want to use. Here's an example:

import { Logger, ConsoleTransport, CloudWatchTransport } from 'bj-logger'

const logger = new Logger('MyService', [
    new ConsoleTransport(),
    new CloudWatchTransport({
        region: process.env.AWS_REGION,
        accessKeyId: process.env.AWS_ACCESS_KEY_ID,
        secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY,
        logGroupName: 'MyLogGroup',
        logStreamName: 'MyLogStream'
    })
])

logger.info('This is a log message')

In this example, we're creating a Logger instance with the service name "MyService". We're also passing in two transports: a ConsoleTransport and a CloudWatchTransport. The ConsoleTransport logs to the console, while the CloudWatchTransport logs to CloudWatch Logs.

Logging to a File

You can also log to a file by creating a FileTransport and passing in the path to the log file. Here's an example:

import { Logger, FileTransport } from 'bj-logger'

const logger = new Logger('MyService', [new FileTransport('log/app.log')])

logger.info('This is a log message')

In this example, we're creating a Logger instance with the service name "MyService". We're also passing in a FileTransport that logs to a file named "app.log" in the "log" directory.

Logging to Multiple Transports

You can log to multiple transports by passing in an array of transports to the Logger constructor. Here's an example:

import { Logger, ConsoleTransport, CloudWatchTransport, FileTransport } from 'bj-logger'

const logger = new Logger('MyService', [
    new ConsoleTransport(),
    new CloudWatchTransport({
        region: process.env.AWS_REGION,
        accessKeyId: process.env.AWS_ACCESS_KEY_ID,
        secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY,
        logGroupName: 'MyLogGroup',
        logStreamName: 'MyLogStream'
    }),
    new FileTransport('log/app.log')
])

logger.info('This is a log message')

In this example, we're creating a Logger instance with the service name "MyService". We're also passing in three transports: a ConsoleTransport, a CloudWatchTransport, and a FileTransport. The ConsoleTransport logs to the console, the CloudWatchTransport logs to CloudWatch Logs, and the FileTransport logs to a file named "app.log" in the "log" directory.

Logging with Structured Data

You can log structured data by passing in an object with the message, service, traceId, timestamp, and body properties to the Logger constructor. Here's an example:

import { Logger, ConsoleTransport, CloudWatchTransport, FileTransport } from 'bj-logger'

const logger = new Logger('MyService', [
    new ConsoleTransport(),
    new CloudWatchTransport({
        region: process.env.AWS_REGION,
        accessKeyId: process.env.AWS_ACCESS_KEY_ID,
        secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY,
        logGroupName: 'MyLogGroup',
        logStreamName: 'MyLogStream'
    }),
    new FileTransport('log/app.log')
])

logger.info({
    message: 'This is a log message',
    service: 'MyService',
    traceId: '12345678-1234-1234-1234-123456789012',
    timestamp: new Date().toISOString(),
    body: {
        key1: 'value1',
        key2: 'value2'
    }
})

In this example, we're creating a Logger instance with the service name "MyService". We're also passing in three transports: a ConsoleTransport, a CloudWatchTransport, and a FileTransport. The ConsoleTransport logs to the console, the CloudWatchTransport logs to CloudWatch Logs, and the FileTransport logs to a file named "app.log" in the "log" directory.

Logging with Custom Levels

You can log with custom levels by passing in a string or an object with the level property to the Logger constructor. Here's an example:

import { Logger, ConsoleTransport, CloudWatchTransport, FileTransport } from 'bj-logger'

const logger = new Logger('MyService', [
    new ConsoleTransport(),
    new CloudWatchTransport({
        region: process.env.AWS_REGION,
        accessKeyId: process.env.AWS_ACCESS_KEY_ID,
        secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY,
        logGroupName: 'MyLogGroup',
        logStreamName: 'MyLogStream'
    }),
    new FileTransport('log/app.log')
])

logger.info('This is a log message')
logger.warn('This is a warning message')
logger.error('This is an error message')

In this example, we're creating a Logger instance with the service name "MyService". We're also passing in three transports: a ConsoleTransport, a CloudWatchTransport, and a FileTransport. The ConsoleTransport logs to the console, the CloudWatchTransport logs to CloudWatch Logs, and the FileTransport logs to a file named "app.log" in the "log" directory.

The Logger instance has methods for logging at different log levels, such as info, warn, and error. Each method takes a string or an object as its argument. If you pass a string, it will be treated as the message to log. If you pass an object, it will be treated as the log entry.