Loki Logger Backend#

The loki backend writes structured JSON log records to the standard output.

It is intended for structured log aggregation systems such as Grafana Loki.

Example output:

{
    "timestamp": "2026-07-16T20:46:01.105+00:00",
    "level": "INFO",
    "logger": "DEV-UUID",
    "message": "Counter=1",
    "asset_uuid": "DEVICE-001",
    "temperature": 42.3
}

Contextual logging#

The Loki backend automatically serializes all contextual information attached to a logger using OpenFactoryLogger.with_context.

Additional context supplied through the standard Python extra argument is also included in the JSON output.

Configuration#

The Loki backend is selected by setting the following environment variable:

OPENFACTORY_LOG_BACKEND=loki

Human-readable log files#

If the OPENFACTORY_TEXT_LOG_DIRECTORY environment variable is set, the backend additionally writes human-readable log messages to a text log file in the specified directory.

This is useful when structured JSON logs are collected by Grafana Loki while developers still want readable log files on disk.

API Reference#

class openfactory.logging.backends.loki.LokiLoggerBackend[source]#

Bases: object

Logging backend for Grafana Loki.

static configure(logger, level, prefix, text_log_directory)[source]#

Configure a logger for the Grafana Loki logging backend.

Return type:

None

Parameters:

  • logger (logging.Logger) – Logger to configure.

  • level (int) – Logging level.

  • prefix (str) – Prefix for human-readable log messages.

  • text_log_directory (str | None) – Directory where human-readable log files are written. If None, the default directory is used.