loki-logger-handler

loki_logger_handler

A logging handler that sends log messages to (Grafana) Loki in JSON format.

Features

• Logs pushed in JSON format by default
• Custom labels definition
• Allows defining loguru and logger extra keys as labels
• Logger extra keys added automatically as keys into pushed JSON
• Publish in batch of Streams
• Publish logs compressed

Args

• url (str): The URL of the Loki server.
• labels (dict): A dictionary of labels to attach to each log message.
• label_keys (dict, optional): A dictionary of keys to extract from each log message and use as labels. Defaults to None.
• additional_headers (dict, optional): Additional headers for the Loki request. Defaults to None.
• timeout (int, optional): Timeout interval in seconds to wait before flushing the buffer. Defaults to 10 seconds.
• compressed (bool, optional): Whether to compress the log messages before sending them to Loki. Defaults to True.
• loguru (bool, optional): Whether to use LoguruFormatter. Defaults to False.
• default_formatter (logging.Formatter, optional): Formatter for the log records. If not provided,LoggerFormatter or LoguruFormatter will be used.
• enable_self_errors (bool, optional): Set to True to show Hanlder errors on console. Defaults to False

Loki 3.0

• enable_structured_loki_metadata (bool, optional): Whether to include structured loki_metadata in the logs. Defaults to False. Only supported for Loki 3.0 and above
• loki_metadata (dict, optional): Default loki_metadata values. Defaults to None. Only supported for Loki 3.0 and above
• loki_metadata_keys (arrray, optional): Specific log record keys to extract as loki_metadata. Only supported for Loki 3.0 and above

Formatters

• LoggerFormatter: Formatter for default python logging implementation
• LoguruFormatter: Formatter for Loguru python library

How to use

Logger

from loki_logger_handler.loki_logger_handler import LokiLoggerHandler,
import logging
import os 

# Set up logging
logger = logging.getLogger("custom_logger")
logger.setLevel(logging.DEBUG)

# Create an instance of the custom handler
custom_handler = LokiLoggerHandler(
    url=os.environ["LOKI_URL"],
    labels={"application": "Test", "environment": "Develop"},
    label_keys={},
    timeout=10,
)
# Create an instance of the custom handler

logger.addHandler(custom_handler)
logger.debug("Debug message", extra={'custom_field': 'custom_value'})

Loguru

from loki_logger_handler.loki_logger_handler import LokiLoggerHandler
from loki_logger_handler.formatters.loguru_formatter import LoguruFormatter
from loguru import logger
import os 

os.environ["LOKI_URL"]="https://USER:[e-mail]/loki/api/v1/push"

custom_handler = LokiLoggerHandler(
    url=os.environ["LOKI_URL"],
    labels={"application": "Test", "environment": "Develop"},
    label_keys={},
    timeout=10,
    default_formatter=LoguruFormatter(),
)
logger.configure(handlers=[{"sink": custom_handler, "serialize": True}])

logger.info(
    "Response code {code} HTTP/1.1 GET {url}", code=200, url="https://loki_handler.io"
)

Loki messages samples

Without extra

{
  "message": "Starting service",
  "timestamp": 1681638266.542849,
  "process": 48906,
  "thread": 140704422327936,
  "function": "run",
  "module": "test",
  "name": "__main__"
}

With extra

{
  "message": "Response code  200 HTTP/1.1 GET https://loki_handler.io",
  "timestamp": 1681638225.877143,
  "process": 48870,
  "thread": 140704422327936,
  "function": "run",
  "module": "test",
  "name": "__main__",
  "code": 200,
  "url": "https://loki_handler.io"
}

Exceptions

{
  "message": "name 'plan' is not defined",
  "timestamp": 1681638284.358464,
  "process": 48906,
  "thread": 140704422327936,
  "function": "run",
  "module": "test",
  "name": "__main__",
  "file": "test.py",
  "path": "/test.py",
  "line": 39
}

Loki Query Sample

Loki query sample :

{environment="Develop"} |= `` | json

Filter by level:

{environment="Develop", level="INFO"} |= `` | json

Filter by extra:

{environment="Develop", level="INFO"} |= `` | json | code=`200`

Loki Structured Metadata

Loki structured metadata to include additional context in your logs. This can be useful for filtering and querying logs in Loki.

We can add metadata in 3 ways:

1. Defile static loki_metadata that will be injected into all logs lines
2. Use logger extra options adding metadata inside loki_metadata key
3. Use logger loki_metadata_keys to move logs keys to loki metadata.

Example global metadata

from loki_logger_handler.loki_logger_handler import LokiLoggerHandler
import logging
import os

# Set up logging
logger = logging.getLogger("custom_logger")
logger.setLevel(logging.DEBUG)

# Create an instance of the custom handler with structured metadata
custom_handler = LokiLoggerHandler(
  url=os.environ["LOKI_URL"],
  labels={"application": "Test", "environment": "Develop"},
  label_keys={},
  timeout=10,
  enable_structured_loki_metadata=True,
  loki_metadata={"service": "user-service", "version": "1.0.0"}
)

logger.addHandler(custom_handler)

In this example, the loki_metadata dictionary includes metadata that will be attached to every log message. The enable_structured_loki_metadata flag ensures that this metadata is included in the logs.

Example log metadata

from loki_logger_handler.loki_logger_handler import LokiLoggerHandler
import logging
import os

# Set up logging
logger = logging.getLogger("custom_logger")
logger.setLevel(logging.DEBUG)

# Create an instance of the custom handler with structured metadata
custom_handler = LokiLoggerHandler(
  url=os.environ["LOKI_URL"],
  labels={"application": "Test", "environment": "Develop"},
  label_keys={},
  timeout=10,
  enable_structured_loki_metadata=True,
  loki_metadata={"service": "user-service", "version": "1.0.0"}
)

logger.addHandler(custom_handler)

logger.info("User acction", extra={"loki_metadata": {"user_id": 12345, "operation": "update", "status": "success"}})

from loki_logger_handler.loki_logger_handler import LokiLoggerHandler
import logging
import os

# Set up logging
logger = logging.getLogger("custom_logger")
logger.setLevel(logging.DEBUG)

# Create an instance of the custom handler with structured metadata
custom_handler = LokiLoggerHandler(
  url=os.environ["LOKI_URL"],
  labels={"application": "Test", "environment": "Develop"},
  label_keys={},
  timeout=10,
  enable_structured_loki_metadata=True,
  loki_metadata={"service": "user-service", "version": "1.0.0"},
  loki_metadata_keys=["trace_id"]
)

logger.addHandler(custom_handler)

logger.info("User acction", extra={"loki_metadata": {"user_id": 12345, "operation": "update", "status": "success"}, "trace_id": "000-000000-0000"})

Querying Logs with Structured Metadata

You can query logs in Loki using the structured metadata.

This query will return all logs where the service metadata is set to user-service.

{application="Test"} |= `` | service="user-service"

This query will return all logs where the user_id metadata is set to 12345.

{application="Test"} |= `` | user_id="12345"

This query will return all logs where the trace_id metadata is set to 000-000000-0000.

{application="Test"} |= `` | trace_id="000-000000-0000"

Development Environment: Dev Container

This project uses a Dev Container to provide a consistent and reproducible development environment. A Dev Container ensures all team members have the same tools, dependencies, and configurations, avoiding "works on my machine" issues.

---

Why Use a Dev Container?

• Consistency: Ensures everyone works in the same environment, regardless of the host OS.
• Isolation: Keeps project dependencies separate from your system.
• Portability: Easily onboard new developers by setting up the environment with a single command.
• Pre-configured Tools: Includes all required tools and dependencies for the project.

---

Getting Started with the Dev Container

To start working with the Dev Container, follow these steps:

Prerequisites

1. Install Docker Desktop (required for running containers).
2. Install Visual Studio Code (VS Code).
3. Install the Dev Containers extension in VS Code:
   • Go to Extensions (Ctrl+Shift+X / Cmd+Shift+X) and search for Dev Containers.
   • Install the extension by Microsoft.

Setup Instructions

1. Clone the repository
2. Open in VS Code
3. Open the Command Palette (Ctrl+Shift+P / Cmd+Shift+P) and select: Dev Containers: Reopen in Container

• VS Code will:
  • Pull the Dev Container image.
  • Install all dependencies and tools specified.

Resources

The loki_logger_handler Dev Container provides the following resources:

• Grafana: Accessible externally at http://localhost:3000.
• Loki: Accessible internally at http://loki:3100/loki/api/v1/push. You can use this URL in your code as the publish endpoint for logs. Logs can be viewed and queried via the Grafana interface.

os.environ["LOKI_URL"]=http://loki:3100/loki/api/v1/push

License

The MIT License