Thread-safe in-memory cache

Question

I need a simple thread-safe in-memory cache in my Scala application.

I need a data structure which support this operation from scala.collection.mutable.MapLike:

def getOrElseUpdate(key: A, op: => B)

and I want this operation to be atomic. Is this operation atomic in scala.collection.concurrent.TrieMap? Or should I use some other data structure?

I use Scala 2.10, but will probably upgrade to 2.11 soon.

I don't want to use scala.collection.mutable.SynchronizedMap, since it is deprecated in Scala 2.11.

Answer 1

TrieMap is appropriate for such a case

A concurrent hash-trie or TrieMap is a concurrent thread-safe lock-free implementation of a hash array mapped trie.

And getOrElseupdate in TrieMap is thread-safe to use. So yes you should use it. As per this, triemap is actually awesome when the insertion rate is really high. Though the difference can be hardly observed.

Answer 2

Alas, TrieMap does not override getOrElseUpdate, which makes this method not thread safe.

SI-7943 TrieMap method getOrElseUpdate is not thread-safe