Struct rocks::listener::EventListener

pub struct EventListener;

EventListener class contains a set of call-back functions that will be called when specific RocksDB event happens such as flush. It can be used as a building block for developing custom features such as stats-collector or external compaction algorithm.

Note that call-back functions should not run for an extended period of time before the function returns, otherwise RocksDB may be blocked. For example, it is not suggested to do DB::CompactFiles() (as it may run for a long while) or issue many of DB::Put() (as Put may be blocked in certain cases) in the same thread in the EventListener callback. However, doing DB::CompactFiles() and DB::Put() in another thread is considered safe.

[Threading] All EventListener callback will be called using the actual thread that involves in that specific event. For example, it is the RocksDB background flush thread that does the actual flush to call EventListener::OnFlushCompleted().

[Locking] All EventListener callbacks are designed to be called without the current thread holding any DB mutex. This is to prevent potential deadlock and performance issue when using EventListener callback in a complex way. However, all EventListener call-back functions should not run for an extended period of time before the function returns, otherwise RocksDB may be blocked. For example, it is not suggested to do DB::CompactFiles() (as it may run for a long while) or issue many of DB::Put() (as Put may be blocked in certain cases) in the same thread in the EventListener callback. However, doing DB::CompactFiles() and DB::Put() in a thread other than the EventListener callback thread is considered safe.