How to cache data via Guava Cache using available memory as parameter?

Question

It is possible remove data from cache, when available runtime memory near with overflow? The cache implementetion is below:

Cache<String, Cache<String, List<String>>> cache = CacheBuilder.newBuilder()
            .maximumWeight((int) ((Runtime.getRuntime().totalMemory() / 1024) * 0.9))
            .weigher((Weigher<String, Cache<String, List<String>>>) (key, val) -> runtimeMemory())
            .build();

public static int runtimeMemory() {
        long totalMemory = Runtime.getRuntime().totalMemory() / 1024;
        long freeMemory = Runtime.getRuntime().freeMemory() / 1024;
        return (int) (totalMemory - freeMemory);
    }

It is work or no ? Or weigher summarizes runtimeMemory() for each value?

Louis Wasserman · Accepted Answer · 2019-09-28 17:02:11Z

3

There is no good way for Guava's Cache -- or any on-heap cache implementation, honestly -- to do what you ask. Soft references may appear to work, but are much more likely to cause awful behavior -- e.g. your JVM may perform continuous, constant full garbage collections.

The best way to address this issue is really and truly to experiment and find a maximumSize parameter that works for you. Your implementation will not work, either, as it doesn't attempt to weigh one particular entry.

edited Sep 28, 2019 at 17:02

answered Sep 24, 2019 at 19:04

Louis Wasserman

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Srđan Miljević · Accepted Answer · 2019-09-24 16:19:30Z

0

If your objective is to avoid running out of memory JVM-wide, then the garbage collector is the right guy for the job. I suggest you use soft-values, like so:

Cache<String, Cache<String, List<String>>> cache = CacheBuilder.newBuilder()
        .softValues()
        .build();

This sets up a cache which wraps any value it stores in a SoftReference. Softly-referenced objects will be garbage-collected in a globally least-recently-used manner in response to memory demand and entry invalidated in the cache.

answered Sep 24, 2019 at 16:19

Srđan Miljević

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