log4njs
v3.2.0
Published
A very simple log utility for nodejs & typescript
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log4njs
log4njs is a very simple log utility for nodejs & typescript.
Installation
npm i log4njs --save
Migration to 3.0.0
See CHANGELOG for breaking changes.
Default usage
import { getLogger } from 'log4njs';
const log = getLogger();
$ log.info('Hello world', { foo: 'bar' });
> '[INFO] Hello world' { foo: 'bar' }
API
Settings
- level: enum
LogLevel
. The log level of the logger instance. Defaults toINFO (300)
. - prefix: String. An optional string that is prefixed to all log messages. Note that no spacing is not automatically added and must be included in the prefix string if required. Defaults to
''
. - timestamp: Boolean. Indicate if the log messages should include the current timestamp (YYYY-MM-DDTHH:mm:ss:mmmZ). Defaults to
false
. - callerInfo: Boolean. Best effort attempt to include caller filename & line number in the log entries. Defaults to
false
.- Note: callerInfo has a fairly big performance impact and is not suitable for regular production use.
- hideLogLevel: Boolean. Will not output the log level as part of the message if set to true. Default to
false
.
Example
import { getLogger, LogLevel } from 'log4njs';
const log = getLogger({ level: LogLevel.DEBUG, prefix: 'MyPrefix::', timstamp: true });
Using environment variables:
- level:
LOG_LEVEL=ERROR
- prefix:
LOG_PREFIX=MyPrefix::
- timestamp:
LOG_TIMESTAMP=true
- callerInfo:
LOG_CALLERINFO=true
- hideLogLevel:
LOG_HIDE_LOG_LEVEL=true
Modify settings runtime
Settings can be modified after the logger has been created:
const log = getLogger({ timstamp: true });
log.info('Foo');
log.getSettings().timestamp = false;
log.info('Bar');
log.getSettings().timestamp = true;
log.info('Baz');
> [INFO] 2024-01-14T13:35:08.683Z Foo
> [INFO] Bar
> [INFO] 2024-01-14T13:35:40.637Z Baz
Suppress logs
In unit tests, for example, you may want to suppress all log statements:
$ LOG_LEVEL=suppress npm test
Audit Logging
There are two Audit log level, introduced in 2.1.0.: AUDIT
& AUDIT_ALERT
.
They can only be turned off by suppressing all logs.
Audit logging is typically sensitive and important but monitored separate from error logs which is why these two new log levels were introduced.
Log levels
Each log level corresponds to a valid configuration value.
$ log.trace(message[, attachment]);
> [TRACE] ...
$ log.debug(message[, attachment]);
> [DEBUG] ...
$ log.info(message[, attachment]);
> [INFO] ...
$ log.warning(message[, attachment]);
> [WARNING] ...
$ log.error(message[, attachment]);
> [ERROR] ...
$ log.critical(message[, attachment]);
> [CRITICAL] ...
$ log.audit(message[, attachment]);
> [AUDIT] ...
$ log.auditAlert(message[, attachment]);
> [AUDIT_ALERT] ...
Masking data
To ensure that certain values are not printed to the log you can mask data. Note: It is important to clear the masks after you are done, or it may cause a memory leak over time. Note: Masks are case-sensitive. The exact string provided will be masked, nothing else.
let data = { id: 12, secret: 'abc123' };
try {
log.addMask(data.secret);
log.info('My masked log', data);
> '[INFO] My masked log' { id: 12, secret: '***' }
} finally {
log.clearMasks();
log.info('My masked log', data);
> '[INFO] My masked log' { id: 12, secret: 'abc123' }
}
You can optionally set a custom placeholder
let data = { id: 12, secret: 'abc123' };
log.addMask(data.secret, 'placeholder');
log.info('My masked log', data);
> '[INFO] My masked log' { id: 12, secret: 'placeholder' }
Benchmarks
There are a couple of sample scripts provided to highlight the performance impact of various configurations. All benchmarks run 10000 iterations.
Before running the benchmarks, run:
cd resources/benchmarks
npm i
Default usage
Default logging with or without a simple attachment:
Sample, with attachment:
node default-use.js true
> default benchmark: true: 141.929ms
Sample, without attachment:
node default-use.js
> default benchmark: false: 133.035ms
isDebugEnabled
Debug logging is usually disabled in production. Log4njs provides the option to do a pre-check when debug logging to increase performance when debug logging is turned off. Note that this does take a slight performance hit when debug logging is turned on.
Sample, with check enabled:
node check-debug.js true
> isDebugEnabled benchmark: true: 0.604ms
Sample, with check disabled:
node check-debug.js
> isDebugEnabled benchmark: false: 0.91ms
callerInfo
The callerInfo setting will attempt to extract the filename & line number of the caller. This provides useful information when it is difficult to pinpoint the source of a specific logger call but takes a fairly big performance hit.
Sample, with callerInfo enabled:
node resources/benchmarks/caller-info.js true
> CallerInfo benchmark: true: 627.254ms
Sample, with callerInfo disabled (equivalent to default use with no attachment):
node resources/benchmarks/caller-info.js
CallerInfo benchmark: false: 140.666ms