Guava Cache - InvalidCacheLoadException on refresh

I have created a cache using CacheBuilder.
I have used ExpireAfterWrite and RefreshAfterWrite. I have overrided cacheloader load and reload function. Practically in reload I am calling load by creating ListenableFutureTask and submitting it to ExecutorService.
Below is stack trace I am getting -

WARNING: Exception thrown during refresh
[junit] com.google.common.cache.CacheLoader$InvalidCacheLoadException:
CacheLoader returned null for key abc.
[junit] at com.google.common.cache.LocalCache$Segment.getAndRecordStats(Unknown
Source)
[junit] at com.google.common.cache.LocalCache$Segment$1.run(Unknown Source)
[junit] at com.google.common.util.concurrent.MoreExecutors$DirectExecutor.execute(Unknown
Source)
[junit] at com.google.common.util.concurrent.ImmediateFuture.addListener(Unknown
Source)
[junit] at com.google.common.cache.LocalCache$Segment.loadAsync(Unknown Source)
[junit] at com.google.common.cache.LocalCache$Segment.refresh(Unknown Source)
[junit] at com.google.common.cache.LocalCache$Segment.scheduleRefresh(Unknown
Source)
[junit] at com.google.common.cache.LocalCache$Segment.get(Unknown Source)
[junit] at com.google.common.cache.LocalCache.get(Unknown Source)
[junit] at com.google.common.cache.LocalCache.getOrLoad(Unknown Source)

I don't know why its not able to refresh, also It doesn't get to cacheloader.load also. It return null before. I am pretty sure I am not returning null in load function.

Sample code -

public class SampleCacheLoader extends CacheLoader<String, Customer> {

private final DatabaseClient databaseClient;

private static final ExecutorService ex = Executors.newSingleThreadScheduledExecutor();

@Inject
public SampleCacheLoader(final DatabaseClient databaseClient) {
this.databaseClient = databaseClient;
}

@Override
public Customer load(final String customerId) throws Exception {
Customer customer = databaseClient.getCustomer(customerId);
if (customer == null) {
throw new Exception("Customer is null");
}
return customer;
}

@Override
public ListenableFuture<Customer> reload(final String customerId,
final Customer prevCustomer)
throws Exception {
ListenableFutureTask<Customer> task = ListenableFutureTask
.create(new Callable<Customer>() {

@Override
public Customer call() {
try {
// try to get a new value
load(customerId);

} catch (Throwable e) {
// or return the old one in the event of failure
return prevCustomer;
}
}
});

// run in the background so that concurrent get() requests still return values.
ex.execute(task);
return task;
}
}

public class SampleCache {

public LoadingCache<String, Customer> sampleCache;

@Inject
public SampleCache(final SampleCacheLoader sampleCacheLoader,
final int cacheMaxSize,
final int cacheExpireTime,
final int cacheRefreshTime,
final int concurrencryLevel,
final Ticker ticker) {
this.cache = CacheBuilder.newBuilder()
.maximumSize(cacheMaxSize)
.expireAfterWrite(cacheExpireTime, TimeUnit.MINUTES)
.refreshAfterWrite(cacheRefreshTime, TimeUnit.MINUTES)
.concurrencyLevel(concurrencryLevel)
.ticker(ticker)
.build(sampleCacheLoader);
}

public Optional<Customer> get(final String customerId) {
try {
Customer customer = cache.get(customerId);
return Optional.of(customer);
} catch (ExecutionException e) {
log.warn(String.format("failed to get customer from cache (customerId=%s)", customerId));
log.warn(e.getMessage());
}

return Optional.empty();
}

/**
* Size of customer cache.
* @return size of customer cache.
*/
public long size() {
return cache.size();
}

}

public class Customer {

private String name;
}

public class SampleCacheTest extends TestCase {

SampleCache SampleCache;

SampleCacheLoader SampleCacheLoader;

// FakeTicker to test cache expiry.
FakeTicker ft;

// Max size of cache
final int CACHE_MAX_SIZE = 1000;

// CACHE_EXPIRE_TIME is in minutes.
final int CACHE_EXPIRE_TIME = 1000;

// CACHE_REFRESH_TIME is in minutes.
final int CACHE_REFRESH_TIME = 3;

// CACHE_CONCURRENCY_LEVEL.
final int CACHE_CONCURRENCY_LEVEL = 10;

// Resource arn
final Static String CUSTOMER_ID =
"abc";

@Before
public void setUp() throws Exception {
// FaceTicker provided by google source code.
ft = new FakeTicker();
SampleCacheLoader sampleCacheLoader = new sampleCacheLoader(new DatabaseClient());
SampleCache = new SampleCache(sampleCacheLoader,
CACHE_MAX_SIZE,
CACHE_EXPIRE_TIME,
CACHE_REFRESH_TIME,
CACHE_CONCURRENCY_LEVEL,
ft);
}

@Test
public void testCacheRefreshTime() throws Exception {

Optional<Customer> customer1 = SampleCache.get(CUSTOMER_ID);
assertTrue(customer1.isPresent());
assertNotNull(customer1.get());

// Advancing time by 1 minutes and retrieve it from cache
// So that it won't expire. Gets the old entry.
advanceTimeForCache(1);

Optional<Customer> customer2 = SampleCache.get(CUSTOMER_ID);
assertTrue(customer2.isPresent());
assertNotNull(customer2.get());

// After this any get call for CUSTOMER_ID
// should initiate the refresh and Load.
// new value from db.
advanceTimeForCache(4);

// This is the place where I get CacheInvalidateStateException
Optional<Customer> customer3 = SampleCache.get(CUSTOMER_ID);


}
}


Please, provide your project and test config
– Pospolita Nikita
Jun 29 at 6:50

Cache = new Cache(simpleCacheLoader, CACHE_MAX_SIZE, // 1000 CACHE_EXPIRE_TIME, // 10 CACHE_REFRESH_TIME, // 2 CACHE_CONCURRENCY_LEVEL, 4 new FakeTicker);
– user3671657
Jun 29 at 6:54

simpleCacheLoader "returned null for key abc".
– Xaerxess
Jun 29 at 7:21

simpleCacheLoader

provide test code, provide method call and method full code, format your code, update post. I can't help you if I don't see anything
– Pospolita Nikita
Jun 29 at 7:27

@PospolitaNikita I will update it later. And will tag you again.
– user3671657
Jun 29 at 7:28

1 Answer
1

So it was @ mock at SimpleCacheLoader in test file which was not doing anything on refresh as I didn't stub the method. I should have used @ spy in this case. I got it fixed. Thanks for help everyone.

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