How a payload reaches the Datadog Agent.

The aggregator knows only this behaviour, so an application can reuse an existing HTTP pool instead of the default. DdDataStreams.Transport.Req is the default and is compiled only when the optional Req dependency is available.

An implementation posts the body to the agent's /v0.1/pipeline_stats endpoint and reports the HTTP status, or the reason the request did not complete. The agent adds the API key itself, so no authentication header is passed.

post/3 must return promptly: the aggregator waits for it while handling casts and flushes, so a transport that never returns blocks aggregation and lets the mailbox grow. A transport is expected to enforce its own connect, receive and request timeouts.