rangeRead future throws interruptException on get

language = Java 8

result = transaction.getRange(new Range(startKey, endKey), limit).asList().get();

I am using foundation db as janusgraph adapter. While performing RangeReads I want to get the whole result as list. asList() method of AsyncIterable returns a CompletableFuture on which I do get to fetch the result. Most of the times this works, But in production, get() fails for around 1 percent of request with InterruptedExcpetion. If i retry n times, I get the correct result.

I have a few questions

  • Why is Interrupted Exception is being thrown on doing get() on completableFuture
  • How can I minimize the occurrence of interrupt exception.
  • can foundationDb throw interruptException on its getRange

Can you provide the complete exception stack trace to give more hints on what could be going on?

I am using https://github.com/experoinc/janusgraph-foundationdb as adapter for janusgraph.
this stacktrace is for multiRange which in itself calls getRange method.

failed to get multi range for queries [[Ljava.lang.Object;@6e2a12c6]
java.lang.InterruptedException
at java.util.concurrent.CompletableFuture.reportGet(CompletableFuture.java:347)
at java.util.concurrent.CompletableFuture.get(CompletableFuture.java:1908)
at com.experoinc.janusgraph.diskstorage.foundationdb.FoundationDBTx.getMultiRange(FoundationDBTx.java:241)
at com.experoinc.janusgraph.diskstorage.foundationdb.FoundationDBKeyValueStore.getSlices(FoundationDBKeyValueStore.java:191)
at org.janusgraph.diskstorage.keycolumnvalue.keyvalue.OrderedKeyValueStoreAdapter.getSlice(OrderedKeyValueStoreAdapter.java:78)
at org.janusgraph.diskstorage.keycolumnvalue.KCVSProxy.getSlice(KCVSProxy.java:81)
at org.janusgraph.diskstorage.BackendTransaction$2.call(BackendTransaction.java:287)
at org.janusgraph.diskstorage.BackendTransaction$2.call(BackendTransaction.java:284)
at org.janusgraph.diskstorage.util.BackendOperation.executeDirect(BackendOperation.java:68)
at org.janusgraph.diskstorage.util.BackendOperation.execute(BackendOperation.java:54)
at org.janusgraph.diskstorage.BackendTransaction.executeRead(BackendTransaction.java:469)
at org.janusgraph.diskstorage.BackendTransaction.edgeStoreMultiQuery(BackendTransaction.java:284)
at org.janusgraph.graphdb.database.StandardJanusGraph.edgeMultiQuery(StandardJanusGraph.java:450)
at org.janusgraph.graphdb.transaction.StandardJanusGraphTx.lambda$executeMultiQuery$5(StandardJanusGraphTx.java:1108)
at org.janusgraph.graphdb.query.profile.QueryProfiler.profile(QueryProfiler.java:99)
at org.janusgraph.graphdb.query.profile.QueryProfiler.profile(QueryProfiler.java:91)
at org.janusgraph.graphdb.transaction.StandardJanusGraphTx.executeMultiQuery(StandardJanusGraphTx.java:1108)
at org.janusgraph.graphdb.query.vertex.MultiVertexCentricQueryBuilder.execute(MultiVertexCentricQueryBuilder.java:113)
at org.janusgraph.graphdb.query.vertex.MultiVertexCentricQueryBuilder.edges(MultiVertexCentricQueryBuilder.java:133)
at org.janusgraph.graphdb.tinkerpop.optimize.JanusGraphVertexStep.initializeMultiQuery(JanusGraphVertexStep.java:138)
at org.janusgraph.graphdb.tinkerpop.optimize.JanusGraphVertexStep.initialize(JanusGraphVertexStep.java:116)
at org.janusgraph.graphdb.tinkerpop.optimize.JanusGraphVertexStep.processNextStart(JanusGraphVertexStep.java:181)
at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.hasNext(AbstractStep.java:143)
at org.apache.tinkerpop.gremlin.process.traversal.step.util.ExpandableStepIterator.next(ExpandableStepIterator.java:50)
at org.apache.tinkerpop.gremlin.process.traversal.step.filter.FilterStep.processNextStart(FilterStep.java:37)
at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.hasNext(AbstractStep.java:143)
at org.apache.tinkerpop.gremlin.process.traversal.step.util.ExpandableStepIterator.next(ExpandableStepIterator.java:50)
at org.apache.tinkerpop.gremlin.process.traversal.step.map.MapStep.processNextStart(MapStep.java:36)
at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.hasNext(AbstractStep.java:143)
at org.apache.tinkerpop.gremlin.process.traversal.step.util.ExpandableStepIterator.hasNext(ExpandableStepIterator.java:42)
at org.janusgraph.graphdb.tinkerpop.optimize.JanusGraphPropertiesStep.initialize(JanusGraphPropertiesStep.java:89)
at org.janusgraph.graphdb.tinkerpop.optimize.JanusGraphPropertiesStep.processNextStart(JanusGraphPropertiesStep.java:124)
at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.hasNext(AbstractStep.java:143)
at org.apache.tinkerpop.gremlin.process.traversal.util.DefaultTraversal.hasNext(DefaultTraversal.java:192)
at org.apache.tinkerpop.gremlin.server.util.TraverserIterator.fillBulker(TraverserIterator.java:69)
at org.apache.tinkerpop.gremlin.server.util.TraverserIterator.hasNext(TraverserIterator.java:56)
at org.apache.tinkerpop.gremlin.server.op.traversal.TraversalOpProcessor.handleIterator(TraversalOpProcessor.java:483)
at org.apache.tinkerpop.gremlin.server.op.traversal.TraversalOpProcessor.lambda$iterateBytecodeTraversal$4(TraversalOpProcessor.java:382)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)

adding code for getMulti

public synchronized  Map<KVQuery, List<KeyValue>> getMultiRange(final List<Object[]> queries)
        throws PermanentBackendException {
    Map<KVQuery, List<KeyValue>> resultMap = new ConcurrentHashMap<>();
    final List<Object[]> retries = new CopyOnWriteArrayList<>(queries);
    final List<CompletableFuture> futures = new LinkedList<>();
    for (int i = 0; i < (maxRuns * 5); i++) {
        for(Object[] obj : retries) {
            final KVQuery query = (KVQuery) obj[0];
            final byte[] start = (byte[]) obj[1];
            final byte[] end = (byte[]) obj[2];

            final int startTxId = txCtr.get();
            try {
                futures.add(tx.getRange(start, end, query.getLimit()).asList()
                        .whenComplete((res, th) -> {
                            if (th == null) {
                                retries.remove(query);
                                if (res == null) {
                                    res = Collections.emptyList();
                                }
                                resultMap.put(query, res);
                            } else {
                                if (startTxId == txCtr.get())
                                    this.restart();
                            }
                        }));
            } catch (IllegalStateException fdbe) {
                // retry on IllegalStateException thrown when tx state changes prior to getRange call
            }
        }
    }
    for (final CompletableFuture future : futures) {
        try {
            future.get();
        } catch (ExecutionException ee) {
            // some tasks will fail due to tx time limits being exceeded
        } catch (IllegalStateException is) {
            // illegal state can arise from tx being closed while tx is inflight
        } catch (Exception e) {
            log.error("failed to get multi range for queries {}", queries, e);
            throw new PermanentBackendException(e);
        }
    }

    return resultMap;
}

I was using .get() on completableFuture which throws InterruptExceptions which come with task of finding which thread interrupted completablefuture work. Instead with .join() all exceptions are RunTime Exceptions which are verbose to my use case.