This time a simple question - does peek update statistics for cache misses / hits or do only get & getAll do this?

[javafanboy]

I am deep diving into some performance results we are seeing. In some situations we do "peek" towards our front cache (in a near cache setup) to determine how to proceed in our execution (favoring in some cases to do bulk requests of items not in the front cache over retrieving them one by one) .

I would naively have assumed that only get & getAll requests update the hit/miss statistics but one of my coworkers asked me if peek could also play in here (i.e. when peek return null is this recorded as a miss and when it returns a value as a hit?) so to be 100% sure how to interpret the results we see I wanted to confirm this....

I suppose it would be good to make this clear in the documentation of the peek method also it, at least to us, was not obvious....

[javafanboy]

To be clear I think it is unfortunate if peek does not update these counters for the front cache as it, in my view, is a fully valid alternative to using get. If using peek a miss (returning null) should of course not update any statistics on the back cache though...

[aseovic]

Sometimes the best thing to do is look at the actual implementation ;-)

https://github.com/oracle/coherence/blob/master/prj/coherence-core/src/main/java/com/tangosol/net/cache/LocalCache.java#L463

But to answer your question, no, peek doesn't update the statistics, as the comment in it explicitly states:

    public Object peek(Object oKey)
        {
        // avoid super.get() because it affects statistics
        OldCache.Entry entry = (OldCache.Entry) getEntryInternal(oKey);
        return entry == null ? null : entry.getValue();
        }

The stats are updated within getEntry method, based on the result of the getEntryInternal call, the same call peek uses:

    public SafeHashMap.Entry getEntry(Object oKey)
        {
        // check if the cache needs flushing
        tryEvict();

        Entry entry = (Entry) getEntryInternal(oKey);
        if (entry == null)
            {
            m_stats.registerMiss();
            }
        else
            {
            m_stats.registerHit();
            entry.touch();
            }

        return entry;
        }

[aseovic]

Of course, nothing prevents you from extending LocalCache and overriding peek to update statistics accordingly, if that's what you really want.

You'd just have to switch from using the standard local-scheme to your custom class-scheme for your front cache.

[aseovic]

Finally, keep in mind that peek is LocalCache-specific operation that is not exposed via CacheMap interface, so it may not be available in other local cache/backing map implementations, such as CaffeineCache (and indeed, it isn't).

Basically, it means you are tying your code to LocalCache.

[javafanboy]

Thanks for the info and good suggestion with the subclassing.