General logging levels helps monitoring and analysing logs. Application can be configured so that it logs depending on severity (logging level). By default, winston use the npm logging levels
Rarely used in application but very useful for detailed logging.
Use generally when debugging and developing.
General information on regular operations.
Example:
Note {ID: 0000-999-0000} is created successfully.Use for audit purpose but depends on application
Information that is worth looking into.
Example: Bad request when adding notes. Useful to check there was error but again depends on application.
Fatal and unexpected error for a request.
Example: 500 Error when adding notes. Note: There is no known issue that causes the request to fail
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Debugging Debugging of application is easy if more useful debugging information is provided to the logging system.
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Monitoring Tools that sends alerts Depending on severity or every log can be pushed to monitoring and alerting system. Bunyan supports custom streams.
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Analysis Logs can be pushed to third party service to get detail analysis. Bunyan logs are JSON string which can be bulk pushed to NoSQL database (mongodb) for manual analysis.
Winston logging support multiple transports, meaning that different logs can be handled in different ways. More
Following example logs information to different places depending on log level.
DEBUG is printed on standard output (console). INFO into a file, and the ERROR into a separate a file.
Example:
const logger = winston.createLogger({
level: 'debug', // The minimal severity that will be logged in this logger
format: winston.format.json(),
defaultMeta: { service: 'user-service' },
transports: [
//
// - Write to all logs with level `info` and below to `combined.log`
// - Write all logs error (and below) to `error.log`.
//
new winston.transports.File({ filename: 'info.log', level: 'info' }),
new winston.transports.File({ filename: 'error.log',level: 'error' })
new winston.transports.Console({ level: 'debug', format: winston.format.simple() })
]
});