What is considered a live trace?

[braunsonm]

I haven't been able to find any docs on how this works internally in Tempo. We have a large number of apps that are very busy and we recently run up against the 10k default limit for active traces.
Since traces can be added to with additional spans at anytime, what is an active trace? Is it a timer before flushed to disk? This also drives the metric tempo_ingester_live_traces

[mapno]

Hi! A live trace is a trace that hasn't received a new batch of spans in more than ingester.trace_idle_period seconds (default 10s). After that, the trace is flushed to disk and appended to the WAL.

If after that time, Tempo receives a new batch, a new live trace will be created in memory.

[braunsonm]

Perfect thank you! I assume if a new batch is received for an existing trace after that, it is merged with the existing trace on disk? (You said a new live trace is created)

[mapno]

That's correct. Not immediately, but eventually both batches will get merged into one. Still, during that time, searches for that trace will find all batches.