Logging

Warpweft follows the library convention: it emits through named loggers and never configures logging. There is no basicConfig, no handler, no level set by default - that is the application's job. A NullHandler is attached to the warpweft logger so records drop silently until you opt in.

Logging is deliberately sparse and complements telemetry rather than duplicating it: per-call detail lives in OpenTelemetry spans/metrics (see telemetry.md); logs cover coarse lifecycle and diagnostic events (container start/stop, a component degrading at startup, a circuit breaker opening/closing, a call degrading to a stub).

Logger names

Loggers follow the module path under the warpweft hierarchy, e.g. warpweft.core.composition.container, warpweft.core.pipeline.builtin.circuit_breaker. Tune any branch independently.

Turning it on

Standard logging:

import logging

logging.getLogger("warpweft").setLevel(logging.INFO)
logging.basicConfig()  # your handler/format

# or per subsystem
logging.getLogger("warpweft.core.pipeline.builtin.circuit_breaker").setLevel(logging.WARNING)

Records propagate to whatever handlers your application attaches to the root (or to warpweft) - the library plugs into your setup automatically, with no coupling.

Turning it off

Off is the default (NullHandler, no level). To silence it even when the root is configured:

logging.getLogger("warpweft").setLevel(logging.CRITICAL + 1)
# or
logging.getLogger("warpweft").disabled = True

Correlation id in logs (opt-in)

Attach CorrelationIdFilter to your handler to surface the ambient correlation id (set by the runtime per request, or via use_correlation_id) in your format string:

from warpweft.core.logging import CorrelationIdFilter

handler = logging.StreamHandler()
handler.addFilter(CorrelationIdFilter())  # adds record.correlation_id
handler.setFormatter(logging.Formatter("%(correlation_id)s %(name)s: %(message)s"))
logging.getLogger("warpweft").addHandler(handler)

Warpweft does not install the filter for you - it is a plain logging.Filter.

Don't log secrets

The same caution as elsewhere: never log resolved settings verbatim - they may contain API keys or DSNs. Use pydantic.SecretStr for secret fields.