The original Redis driver stored each tracing event under its own key,
as result both list and get operations required a full scan of the database.
With this patch traces are stored as Redis lists under a key equal
to trace id. So list operation iterates only over unique trace ids
and get operation retrieves the content of a specified list. Note that
list operation still needs to retrieve at least 1 event from the trace
in order to get a timestamp.
Performance test is executed with 1000 traces each consisting 1000 events:
* existing driver:
* write: 48 sec
* list: 41 sec
* get: 3.6 sec
* optimized driver:
* write: 44 sec
* list: 4.1 sec
* get: 0.01 sec
Change-Id: I09a122f91e3d26531965fe53d6df7c66f502de4c
147effea78