Issue #6919 was caused by an incorrect assumption: I *assumed* that we see
the tracing session record, we can be sure that the event records for this
session had already been written. In this patch we add a paragraph to
the tracing documentation - docs/tracing.md, which explains that this
assumption is in fact incorrect:
1. On a multi-node setup, replicas may continue to write tracing events
after the coordinator "finished" (moved to background) the request
and wrote the session record.
2. Even on a single-node setup, the writes of the session record and the
individual events are asynchronous, and can happen in an unexpected
order (which is what happened in issue #6919).
Refs #6919.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20200727102438.1194314-1-nyh@scylladb.com>
