loggark

Utilitarian Logging Library

Logger output format

Logger now emits a single JSON object per log line by default (JSON Lines). This format is easier to consume with journalctl pipelines (jq, grep, field selection).

• Default: format: 'json'
• Backward compatibility: format: 'plain'
• Context flattening in JSON mode: flat: true (default)

Example:

import { Logger } from '@knowark/loggarkjs'

const logger = new Logger({ namespace: 'api' })
logger.info('User login', { userId: 'u-123' })

Outputs:

{"timestamp":"2025-02-15T00:00:00.000Z","level":"info","namespace":"api","message":"User login","userId":"u-123"}

Additional object parameters are merged into the base log object. If keys collide, later merged values overwrite earlier keys.

If you prefer context keys at top level (for simpler jq filters), enable flattening:

const logger = new Logger({
  namespace: 'api',
  context: { correlationId: 'ABCD1234', interactor: 'Informer' },
  flat: true
})

logger.info('User login')

{"timestamp":"2025-02-15T00:00:00.000Z","level":"info","namespace":"api","correlationId":"ABCD1234","interactor":"Informer","message":"User login"}

To keep nested context under context, disable flattening:

const logger = new Logger({
  context: { correlationId: 'ABCD1234' },
  flat: false
})

Journald integration

Set the boolean globalThis.JOURNALD flag to true and Logger will open /run/systemd/journal/socket for you. Every JSON record is translated into Journald fields (PRIORITY, MESSAGE, LEVEL, optional SYSLOG_IDENTIFIER, and uppercased context payloads), so you can pipe logger.info() calls directly into journalctl for centralized viewing.

globalThis.JOURNALD = true
const logger = new Logger({ namespace: 'api' })

logger.info('User login', { userId: 'u-123', extra: undefined })

Undefined values are dropped, null turns into the string 'null', and functions/symbols are rendered so Journald receives a predictable payload. The socket connection is cached per process, so later Logger instances reuse the same transport without extra setup.