level-mutex
npm install level-mutex
What is this?
level-mutex
is an abstract "lock" around a levelup
store. What it does is cycle between reads and writes, allowing all writes to return in order while queuing all reads, then running all reads and returning in order, then writing all the pending writes again. level-mutex
uses node.js' single threaded nature to your advantage so that you can maintain a higher order locking structure to insure various types of read-on-write consistency semantics.
This is currently used in couchup to ensure users cannot update a document without providing the latest revision.
While you do scope level-mutex
to a single levelup store there is nothing stopping you from having many mutexes around the same store provided you're using each to manage a separate higher order consistency guarantee. For instance, couchup
uses a mutex per database and an indefinite number of databases might exist in a single levelup store.
var levelup = mutex = ; var store = mymutex = pending = ; { mymutex} // flush all pending keys when writes have been flushed.mymutex
methods
- get
- put
- del
- peekLast
- peekFirst
- afterWrite
events
- reads
- writes
- flushed