Do not log client scrape disconnects as errors#331
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When a scraper (e.g. Prometheus) closes the connection before the /metrics response is fully written, promhttp calls the configured ErrorLog once per metric family, flooding the log with "error encoding and sending metric family: ... write: broken pipe" lines for a single benign event (a scrape timeout or the scraper restarting). Detect EPIPE/ECONNRESET in the promhttp error logger and log those at V(1) instead of the error stream. Genuine encoding/gathering errors are still logged as errors. Signed-off-by: Gaál György <gb12335@gmail.com>
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Problem
When a scraper (e.g. Prometheus) closes the
/metricsconnection before the response is fully written,promhttpinvokes the configuredErrorLogonce per metric family. A single benign event — a scrape timeout or the scraper restarting — floods the log with dozens of identical lines:This is a client-side disconnect (the agent is being scraped and the peer went away mid-response), not an agent fault, but it is reported at error level and is easily mistaken for a real failure. See #289.
Change
Detect
EPIPE/ECONNRESETin the promhttp error logger and log those atV(1)instead of the error stream. Genuine encoding/gathering errors continue to be logged as errors.