NoSuchElementException raised by CQLKeyColumnValueStore

[li-boxuan]

We experienced the following exception a few times in our production environment (using v0.4, but I compared the source code with v0.5 and verified there was no difference):

Caused by: java.util.NoSuchElementException: No value present

        at io.vavr.control.Option$None.get(Option.java:482)

        at org.janusgraph.diskstorage.cql.CQLKeyColumnValueStore.getSlice(CQLKeyColumnValueStore.java:290)

        at org.janusgraph.diskstorage.util.MetricInstrumentedStore.lambda$getSlice$0(MetricInstrumentedStore.java:104)

        at org.janusgraph.diskstorage.util.MetricInstrumentedStore.runWithMetrics(MetricInstrumentedStore.java:204)

        at org.janusgraph.diskstorage.util.MetricInstrumentedStore.getSlice(MetricInstrumentedStore.java:103)

        at org.janusgraph.diskstorage.keycolumnvalue.KCVSProxy.getSlice(KCVSProxy.java:76)

        at org.janusgraph.diskstorage.keycolumnvalue.KCVSProxy.getSlice(KCVSProxy.java:76)

        at org.janusgraph.diskstorage.BackendTransaction$1.call(BackendTransaction.java:271)

        at org.janusgraph.diskstorage.BackendTransaction$1.call(BackendTransaction.java:268)

        at org.janusgraph.diskstorage.util.BackendOperation.executeDirect(BackendOperation.java:68)

        ... 31 more

The exception comes from the return statement of this method:

janusgraph/janusgraph-cql/src/main/java/org/janusgraph/diskstorage/cql/CQLKeyColumnValueStore.java

Lines 279 to 292 in 9fb5726

	@Override
	public EntryList getSlice(final KeySliceQuery query, final StoreTransaction txh) throws BackendException {
	final Future<EntryList> result = Future.fromJavaFuture(
	this.executorService,
	this.session.executeAsync(this.getSlice.bind()
	.setBytes(KEY_BINDING, query.getKey().asByteBuffer())
	.setBytes(SLICE_START_BINDING, query.getSliceStart().asByteBuffer())
	.setBytes(SLICE_END_BINDING, query.getSliceEnd().asByteBuffer())
	.setInt(LIMIT_BINDING, query.getLimit())
	.setConsistencyLevel(getTransaction(txh).getReadConsistencyLevel())))
	.map(resultSet -> fromResultSet(resultSet, this.getter));
	interruptibleWait(result);
	return result.getValue().get().getOrElseThrow(EXCEPTION_MAPPER);
	}

Apparently, result.getValue() returns a None and then None.get() throws NoSuchElementException.

According to javadoc of vavr-0.9.0 Future::getValue, it returns None if the Future is not yet completed or was cancelled.

FWIW, the implementation of interruptibleWait is as follows:

janusgraph/janusgraph-cql/src/main/java/org/janusgraph/diskstorage/cql/CQLKeyColumnValueStore.java

Lines 307 to 316 in 9fb5726

	private void interruptibleWait(final Future<?> result) throws PermanentBackendException {
	try {
	result.await();
	} catch (Exception e) {
	if (e instanceof InterruptedException) {
	Thread.currentThread().interrupt();
	}
	throw new PermanentBackendException(e);
	}
	}

Has anyone seen similar issue before?

[storyteller28th]

you should show your gremlin's codes

[storyteller28th]

when you search property's value,you can use 'isPresent()',it can avoid 'NoSuchElement' exception.