public ReferencedResource<SharedSourceSession> retainSource(SourceSessionParams p) {
        return sourcesCreator.retain(sourceLock, sources, p);
    }
Class to encapsulate access to slobrok sessions.

@author Steinar Knutsen
@author Einar Rosenvinge
container-messagebus/src/main/java/com/yahoo/container/jdisc/messagebus/SessionCache.java