Expose the Sentry settings that cost RPS (sentry_logs_level, breadcrumb level, auto_session_tracking) #186

Benchmarking the stack turned up two Sentry settings that cost measurable RPS and are only reachable today by hand-building sentry_integrations or by stuffing sentry_additional_params.

1. SentryLogsHandler formats every log record for nothing

LoggingIntegration defaults to sentry_logs_level=INFO, which installs SentryLogsHandler. Its emit() calls self.format(record) before checking has_logs_enabled(client.options). lite-bootstrap never sets enable_logs, so for every lite-bootstrap service that handler formats every INFO+ record and then throws the result away.

This is amplified by LoggingInstrument: structlog is wired through structlog.stdlib.BoundLogger, so every structlog call goes through the patched logging.Logger.callHandlers and hits both Sentry handlers.

Measured on an endpoint emitting three structlog records per request (in-process, Apple M2, CPython 3.14.7, sentry-sdk 2.67.1):

The first delta is free - nothing is lost while Sentry Logs is disabled. The second costs you log breadcrumbs on error events, which is a real trade-off.

I have filed the format-before-check as an upstream bug against sentry-python (getsentry/sentry-python#7402). Even if it lands, passing sentry_logs_level=None while lite-bootstrap does not support Sentry Logs is the correct configuration.

2. auto_session_tracking is not exposed

SentryConfig does not surface it, so it defaults to True and every request starts and ends a Session (a uuid4, a lock acquisition, an aggregate update). Measured at ~7 µs/request. Services that do not use Sentry release health pay it silently.

Proposal

• Default sentry_integrations to include LoggingIntegration(sentry_logs_level=None) when the user has not supplied their own logging integration. Behaviour-preserving.
• Add sentry_auto_session_tracking: bool = True to SentryConfig, passed through to sentry_sdk.init. Default unchanged, knob documented.
• Optionally sentry_logging_breadcrumb_level: int | None = logging.INFO for the breadcrumb handler, since that is the larger of the two costs for chatty services.

Context

For the whole picture: on a trivial endpoint through uvicorn, enabling Sentry at lite-bootstrap defaults costs 39% of throughput (7952 → 4850 RPS), and essentially all of it is the Starlette/FastAPI ASGI integration, not the knobs people normally reach for. attach_stacktrace, max_breadcrumbs and dropping the default integrations all measured as no-ops on the request path. Details in the sibling docs issue.