This commit ensures that the TIMEOUT is always checked prior to
returning data to the client, and that the elapsed command time
cannot be greater than the timeout value.
This commit changes the logic for managing the expiration of
objects in the database.
Before: There was a server-wide hashmap that stored the
collection key, id, and expiration timestamp for all objects
that had a TTL. The hashmap was occasionally probed at 20
random positions, looking for objects that have expired. Those
expired objects were immediately deleted, and if there was 5
or more objects deleted, then the probe happened again, with
no delay. If the number of objects was less than 5 then the
there was a 1/10th of a second delay before the next probe.
Now: Rather than a server-wide hashmap, each collection has
its own ordered priority queue that stores objects with TTLs.
Rather than probing, there is a background routine that
executes every 1/10th of a second, which pops the expired
objects from the collection queues, and deletes them.
The collection/queue method is a more stable approach than
the hashmap/probing method. With probing, we can run into
major cache misses for some cases where there is wide
TTL duration, such as in the hours or days. This may cause
the system to occasionally fall behind, leaving should-be
expired objects in memory. Using a queue, there is no
cache misses, all objects that should be expired will be
right away, regardless of the TTL durations.
Fixes#616
This commit addresses an issue where the sarama kafka library
leaks memory when a connection closes unless the metrics
configuration that was passed to new connection is also closed.
Fixes#613
Returns 'ok' if the server is the leader or a follower with
a 'caught up' log.
This is mainly for HTTP connections that are using an
orchestration environment like kubernetes, but will work as a
general RESP command.
For HTTP a '200 OK' for 'caught up' and
'500 Internal Server Error' otherwise.
See #608
