Howto load guava with entries

Question

I need a cache of failed entries, which I am trying to build using the following statements:

    failedJobCache =
            CacheBuilder.newBuilder()
                    .maximumSize(100) // maximum 100 records can be cached
                    .expireAfterAccess(30, TimeUnit.MINUTES) // cache will expire after 30 minutes of access
                    .build(new CacheLoader<String, JobDto>() {
                        @Override
                        public JobDto load(String s) throws Exception {
                            JobDto found = failedJobCache.get(s);
                            if (found != null)
                                return found;
                            else
                                return null;
                        }
                    });

And:

// add failed entries
failedJobCache.put(jobDto.getUniqueId(), jobDto);

// respective check before running the job if its
// already in the cache and should be skipped:
JobDto existing = failedJobCache.get(jobDto.getUniqueId());
if (existing != null) {
    logger.debug("Nothing to do, job already processed!" + jobDto.getUniqueId());
    return;
}

Unfortunately I encounter:

Exception in thread "main" com.google.common.util.concurrent.UncheckedExecutionException: java.lang.IllegalStateException: Recursive load of: ...

Question How do I add only failed entries to the cache?

Answer 1

CacheLoader.load(K) is only called if there isn't "an already-loaded value for a given key" ( CacheBuilder.build(LoadingCache) ).

As such, calling LoadingCache.get(K) from CacheLoader.load(K) creates a recursive load that, if allowed to execute, would recurse too deeply causing a StackOverflowError to be thrown.

From the information provided in your example it does not appear you need a LoadingCache<K, V> but just a Cache<K, V> . Call CacheBuilder.build() without a CacheLoader<K, V> .

See CachesExplained · google/guava Wiki for more details.

Answer 2

The loading function has a recursion it seems. This happens when You are trying to load an entry in your cache and somewhere in the loader function tries to call it again.

You can debug and identify the method making such calls.