daily-logfile

Quick and simple cluster-aware logging into daily files.

Use Daily Logfile Logger to log events, data and/or errors into locally generated files. Each logfile is date stamped and only contains logs for that date. Log entries are time stamped to milliseconds.

By default, if application runs on cluster, each cluster node logs into separate file. If cluster identifier is set, then logs are written into single file for all cluster nodes, and log entries are stamped with worker id and process id.

Target: ES2022 [NodeJS][ESM+CJS].

Logging functions

Use functions trace, debug, info, warn, and error to write logs conditionally, depending on specified minimum log level. For example, if minimum log level is INFORMATION then trace and debug will not write into a logfile. Use functions fail and log to write logs unconditionally.

LogLevel enumeration

Logger allows logging with the following levels:

• TRACE
• DEBUG
• INFORMATION
• WARNING
• ERROR
• FAILURE

Logger configuration parameters

• dir: Logfile directory, defaults to current working directory.
• tag: Logfile tag to identify logging application, defaults to empty string.
• ext: Logfile extension, defaults to 'log'.
• utc: If true date-time values are in UTC, defaults to false.
• stack: If true writes error stack trace if available, defaults to false.
• stdout: If true additionally writes logs to stdout, defaults to false.
• level: Minimum log level, errors and failures are always logged, defaults to INFORMATION.
• cluster: Logfile cluster identifier if logs to be written into a single file for all cluster nodes. By default, each cluster node logs into separate logfile [dir|CWD]/YYYY-MM-DD[.tag].[worker-id].[ext|log], where CWD is current working directory.

If multiple instances of Logger are used, make sure that each instance has different dir/tag/ext combination, and cluster identifier.

How to use Logger

Sample code to log events and errors:

...
const logf = new Logger( { tag: 'test', utc: true } );
...
logf.info( 'log some info' );
logf.log( 'logging some data', { val: 'abc', anotherValue: 'def' }, [ 1, 2 ] );
...
logf.error( 'something went wrong', new Error( 'Test Error' ), obj );
...

Generated logfile

Sample log file 2023-07-12.test.log:

|14:18:57|
|349| log some info
|411| logging some data
{"val":"abc","anotherValue":"def"}
[1,2]
|14:18:58|
|010| something went wrong
Test Error
{"objProp1":"a"}