Live entities show the current state; a sink keeps the samples that produced it. Choose a sink when you need historical investigation, exports, or replay. Observer does not require a database: the destination is chosen by your application.

Sinks are per-client via createClientSink; built-ins are JSONL and in-memory. They persist the final injection-merged sample. During accept, injectAttachment/Event/Issue/MetaData/ExtensionStat affects the active sample immediately; between accepts it queues; close flushes pending data before sink teardown. A sink failure is logged, not a substitute for application persistence guarantees.

Logging#

Supply a logger in Client Monitor configuration for browser logs. On the server, use setObserverLogger and the common logger API. Route these logs to your existing application logger.

Observer logger source.