@azure/logger

What is @azure/logger?

@azure/logger is a logging utility provided by Microsoft Azure that allows developers to create and manage logs for their applications. It is designed to be lightweight and easy to use, making it suitable for both small and large-scale applications. The package provides various functionalities to control the logging level, format, and output destination.

What are @azure/logger's main functionalities?

Basic Logging

This feature allows you to create a logger instance and log messages at different levels such as info, warning, and error.

const { createClientLogger } = require('@azure/logger');
const logger = createClientLogger('my-namespace');
logger.info('This is an info message');
logger.warning('This is a warning message');
logger.error('This is an error message');

Setting Log Level

This feature allows you to set the log level, so only messages at that level or higher will be logged. In this example, only warning and error messages will be logged.

const { setLogLevel } = require('@azure/logger');
setLogLevel('warning');
const { createClientLogger } = require('@azure/logger');
const logger = createClientLogger('my-namespace');
logger.info('This info message will not be logged');
logger.warning('This warning message will be logged');

Custom Loggers

This feature allows you to create custom loggers with different namespaces, which can help in organizing and filtering logs based on different parts of your application.

const { createClientLogger } = require('@azure/logger');
const customLogger = createClientLogger('custom-namespace');
customLogger.info('This is a custom info message');

Other packages similar to @azure/logger

winston

Winston is a versatile logging library for Node.js that supports multiple transports (e.g., console, file, HTTP) and log levels. It is highly configurable and can be extended with custom transports and formats. Compared to @azure/logger, Winston offers more flexibility and a broader range of features, but it may be more complex to set up.

bunyan

Bunyan is a simple and fast JSON logging library for Node.js. It is designed to produce logs in a structured JSON format, making it easy to parse and analyze. Bunyan also supports log levels and multiple output streams. Compared to @azure/logger, Bunyan focuses on JSON logging and may be more suitable for applications that require structured log data.

pino

Pino is a fast and low-overhead logging library for Node.js. It is designed for high-performance logging and produces logs in a JSON format. Pino supports log levels and can be integrated with various transports and log management systems. Compared to @azure/logger, Pino is optimized for performance and may be a better choice for applications with high logging throughput.

README

Azure Logger client library for JavaScript

The @azure/logger package can be used to enable logging in the Azure SDKs for JavaScript.

Logging can be enabled for the Azure SDK in the following ways:

• Setting the AZURE_LOG_LEVEL environment variable
• Calling setLogLevel imported from "@azure/logger"
• Calling enable() on specific loggers
• Using the DEBUG environment variable.

Note that AZURE_LOG_LEVEL, if set, takes precedence over DEBUG. Only use DEBUG without specifying AZURE_LOG_LEVEL or calling setLogLevel.

Getting started

Installation

Install this library using npm as follows

npm install @azure/logger

Key Concepts

The @azure/logger package supports the following log levels specified in order of most verbose to least verbose:

• verbose
• info
• warning
• error

When setting a log level, either programmatically or via the AZURE_LOG_LEVEL environment variable, any logs that are written using a log level equal to or less than the one you choose will be emitted.

For example, setting the log level to warning will cause all logs that have the log level warning or error to be emitted.

NOTE: When logging requests and responses, we sanitize these objects to make sure things like Authorization headers that contain secrets are not logged.

Request and response bodies are never logged. Headers are redacted by default, unless present in the following list or explicitly allowed by the client SDK:

• "x-ms-client-request-id",
• "x-ms-return-client-request-id",
• "x-ms-useragent",
• "x-ms-correlation-request-id",
• "x-ms-request-id",
• "client-request-id",
• "ms-cv",
• "return-client-request-id",
• "traceparent",
• "Access-Control-Allow-Credentials",
• "Access-Control-Allow-Headers",
• "Access-Control-Allow-Methods",
• "Access-Control-Allow-Origin",
• "Access-Control-Expose-Headers",
• "Access-Control-Max-Age",
• "Access-Control-Request-Headers",
• "Access-Control-Request-Method",
• "Origin",
• "Accept",
• "Accept-Encoding",
• "Cache-Control",
• "Connection",
• "Content-Length",
• "Content-Type",
• "Date",
• "ETag",
• "Expires",
• "If-Match",
• "If-Modified-Since",
• "If-None-Match",
• "If-Unmodified-Since",
• "Last-Modified",
• "Pragma",
• "Request-Id",
• "Retry-After",
• "Server",
• "Transfer-Encoding",
• "User-Agent",
• "WWW-Authenticate",

Examples

Example 1 - basic usage

const { EventHubClient } = require('@azure/event-hubs');

const logger = require('@azure/logger');
logger.setLogLevel('info');

// operations will now emit info, warning, and error logs
const client = new EventHubClient(/* params */);
client.getPartitionIds()
  .then(ids => { /* do work */ })
  .catch(e => { /* do work */ });
});

Example 2 - redirect log output

const { AzureLogger, setLogLevel } = require("@azure/logger");

setLogLevel("verbose");

// override logging to output to console.log (default location is stderr)
AzureLogger.log = (...args) => {
  console.log(...args);
};

Using AzureLogger, it is possible to redirect the logging output from the Azure SDKs by overriding the AzureLogger.log method. This may be useful if you want to redirect logs to a location other than stderr.

Next steps

You can build and run the tests locally by executing rushx test. Explore the test folder to see advanced usage and behavior of the public classes.

Troubleshooting

If you run into issues while using this library, please feel free to file an issue.

Contributing

If you'd like to contribute to this library, please read the contributing guide to learn more about how to build and test the code.