Common handler and filter patterns

Quick reference recipes for specific handler and filter types.

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Handler that wraps an existing service client

class ExistingServiceHandler(logging.Handler):
    """Wrap an existing service client."""

    def __init__(self, client):
        super().__init__()
        self.client = client  # e.g., a sentry client

    def emit(self, record):
        self.client.send_record(self.format(record), level=record.levelname)

Handler that writes JSON

class JSONHandler(logging.Handler):
    def emit(self, record):
        entry = {
            "timestamp": record.created,
            "level": record.levelname,
            "message": record.getMessage(),
            "module": record.module,
        }
        # Write JSON somewhere

Filter that uses record metadata

class MetadataAwareFilter(BaseHandlerFilter):
    def filter(self, record):
        # Filters can look at extra metadata
        if "skip_logging" in record.__dict__:
            return False
        return True

# Usage:
log.info("skip me", extra={"skip_logging": True})

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Next steps

• Look at existing handlers in handlers.py for patterns
• Look at ThrottleFilter for a complex filter example
• Check test files in tests/logging/ for usage examples
• Add your handler/filter, submit a PR!