I'm trying out the new storage.backend=CQL with cassandra from the master branch (0.2.0) and I'm consistently hitting this error after a few hours of CRUD operations, which could previously be handled (0.1.0) with no problems using the storage.backend=cassandra driver.

Is this a known issue that will be addressed in the final 0.2.0 release? Any recommendations on configuration options to adjust the pool or connection sizes?

org.janusgraph.core.JanusGraphException: Could not execute operation due to backend exception

at org.janusgraph.diskstorage.util.BackendOperation.execute(BackendOperation.java:57)

at org.janusgraph.diskstorage.keycolumnvalue.cache.CacheTransaction.persist(CacheTransaction.java:95)

at org.janusgraph.diskstorage.keycolumnvalue.cache.CacheTransaction.flushInternal(CacheTransaction.java:137)

at org.janusgraph.diskstorage.keycolumnvalue.cache.CacheTransaction.commit(CacheTransaction.java:200)

at org.janusgraph.diskstorage.BackendTransaction.commitStorage(BackendTransaction.java:133)

at org.janusgraph.graphdb.database.StandardJanusGraph.commit(StandardJanusGraph.java:729)

at org.janusgraph.graphdb.transaction.StandardJanusGraphTx.commit(StandardJanusGraphTx.java:1374)

at org.janusgraph.graphdb.tinkerpop.JanusGraphBlueprintsGraph$GraphTransaction.doCommit(JanusGraphBlueprintsGraph.java:272)

at org.apache.tinkerpop.gremlin.structure.util.AbstractTransaction.commit(AbstractTransaction.java:105)

... 13 more

Caused by: org.janusgraph.diskstorage.TemporaryBackendException: Could not successfully complete backend operation due to repeated temporary exceptions after PT1M40S

at org.janusgraph.diskstorage.util.BackendOperation.executeDirect(BackendOperation.java:101)

at org.janusgraph.diskstorage.util.BackendOperation.execute(BackendOperation.java:55)

... 21 more

Caused by: org.janusgraph.diskstorage.TemporaryBackendException: Temporary failure in storage backend

at org.janusgraph.diskstorage.cql.CQLKeyColumnValueStore.lambda$null$2(CQLKeyColumnValueStore.java:123)

at org.janusgraph.diskstorage.cql.CQLKeyColumnValueStore$$Lambda$184.00000000BC05D670.apply(Unknown Source)

at io.vavr.API$Match$Case0.apply(API.java:3174)

at io.vavr.API$Match.of(API.java:3137)

at org.janusgraph.diskstorage.cql.CQLKeyColumnValueStore.lambda$static$3(CQLKeyColumnValueStore.java:120)

at org.janusgraph.diskstorage.cql.CQLKeyColumnValueStore$$Lambda$65.00000000C02B77E0.apply(Unknown Source)

at org.janusgraph.diskstorage.cql.CQLStoreManager.mutateManyUnlogged(CQLStoreManager.java:415)

at org.janusgraph.diskstorage.cql.CQLStoreManager.mutateMany(CQLStoreManager.java:346)

at org.janusgraph.diskstorage.locking.consistentkey.ExpectedValueCheckingStoreManager.mutateMany(ExpectedValueCheckingStoreManager.java:79)

at org.janusgraph.diskstorage.keycolumnvalue.cache.CacheTransaction$1.call(CacheTransaction.java:98)

at org.janusgraph.diskstorage.keycolumnvalue.cache.CacheTransaction$1.call(CacheTransaction.java:95)

at org.janusgraph.diskstorage.util.BackendOperation.executeDirect(BackendOperation.java:69)

... 22 more

Caused by: java.util.concurrent.ExecutionException: com.datastax.driver.core.exceptions.NoHostAvailableException: All host(s) tried for query failed (tried: /x.x.x.x:9042 (com.datastax.driver.core.exceptions.BusyPoolException: [/x.x.x.x] Pool is busy (no available connection and the queue has reached its max size 256)))

at com.google.common.util.concurrent.AbstractFuture$Sync.getValue(AbstractFuture.java:299)

at com.google.common.util.concurrent.AbstractFuture$Sync.get(AbstractFuture.java:286)

at com.google.common.util.concurrent.AbstractFuture.get(AbstractFuture.java:116)

at io.vavr.concurrent.Future$$Lambda$71.00000000C00F2990.apply(Unknown Source)

at io.vavr.control.Try.of(Try.java:62)

at io.vavr.concurrent.FutureImpl.lambda$run$2(FutureImpl.java:199)

at io.vavr.concurrent.FutureImpl$$Lambda$72.00000000C00F3670.run(Unknown Source)

at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:522)

... 4 more

Caused by: com.datastax.driver.core.exceptions.NoHostAvailableException: All host(s) tried for query failed (tried: /x.x.x.x:9042 (com.datastax.driver.core.exceptions.BusyPoolException: [/x.x.x.x] Pool is busy (no available connection and the queue has reached its max size 256)))

at com.datastax.driver.core.RequestHandler.reportNoMoreHosts(RequestHandler.java:211)

at com.datastax.driver.core.RequestHandler.access$1000(RequestHandler.java:46)

at com.datastax.driver.core.RequestHandler$SpeculativeExecution.findNextHostAndQuery(RequestHandler.java:275)

at com.datastax.driver.core.RequestHandler$SpeculativeExecution$1.onFailure(RequestHandler.java:338)

at com.google.common.util.concurrent.Futures$6.run(Futures.java:1310)

at com.google.common.util.concurrent.MoreExecutors$DirectExecutor.execute(MoreExecutors.java:457)

at com.google.common.util.concurrent.Futures$ImmediateFuture.addListener(Futures.java:106)

at com.google.common.util.concurrent.Futures.addCallback(Futures.java:1322)

at com.google.common.util.concurrent.Futures.addCallback(Futures.java:1258)

at com.datastax.driver.core.RequestHandler$SpeculativeExecution.query(RequestHandler.java:297)

at com.datastax.driver.core.RequestHandler$SpeculativeExecution.findNextHostAndQuery(RequestHandler.java:272)

at com.datastax.driver.core.RequestHandler.startNewExecution(RequestHandler.java:115)

at com.datastax.driver.core.RequestHandler.sendRequest(RequestHandler.java:95)

at com.datastax.driver.core.SessionManager.executeAsync(SessionManager.java:132)

at org.janusgraph.diskstorage.cql.CQLStoreManager.lambda$null$24(CQLStoreManager.java:406)

at org.janusgraph.diskstorage.cql.CQLStoreManager$$Lambda$106.00000000C0938C00.apply(Unknown Source)

at io.vavr.collection.Iterator$35.getNext(Iterator.java:1632)

at io.vavr.collection.AbstractIterator.next(AbstractIterator.java:34)

at io.vavr.collection.Iterator$34.getNext(Iterator.java:1510)

at io.vavr.collection.AbstractIterator.next(AbstractIterator.java:34)

at io.vavr.collection.Iterator$34.getNext(Iterator.java:1510)

at io.vavr.collection.AbstractIterator.next(AbstractIterator.java:34)

at io.vavr.collection.Traversable.foldLeft(Traversable.java:471)

at io.vavr.concurrent.Future.sequence(Future.java:549)

at org.janusgraph.diskstorage.cql.CQLStoreManager.mutateManyUnlogged(CQLStoreManager.java:388)

at org.janusgraph.diskstorage.cql.CQLStoreManager.mutateMany(CQLStoreManager.java:346)

at org.janusgraph.diskstorage.locking.consistentkey.ExpectedValueCheckingStoreManager.mutateMany(ExpectedValueCheckingStoreManager.java:79)

at org.janusgraph.diskstorage.keycolumnvalue.cache.CacheTransaction$1.call(CacheTransaction.java:98)

at org.janusgraph.diskstorage.keycolumnvalue.cache.CacheTransaction$1.call(CacheTransaction.java:95)

at org.janusgraph.diskstorage.util.BackendOperation.executeDirect(BackendOperation.java:69)

at org.janusgraph.diskstorage.util.BackendOperation.execute(BackendOperation.java:55)

at org.janusgraph.diskstorage.keycolumnvalue.cache.CacheTransaction.persist(CacheTransaction.java:95)

at org.janusgraph.diskstorage.keycolumnvalue.cache.CacheTransaction.flushInternal(CacheTransaction.java:137)

at org.janusgraph.diskstorage.keycolumnvalue.cache.CacheTransaction.commit(CacheTransaction.java:200)

at org.janusgraph.diskstorage.BackendTransaction.commitStorage(BackendTransaction.java:133)

at org.janusgraph.graphdb.database.StandardJanusGraph.commit(StandardJanusGraph.java:729)

at org.janusgraph.graphdb.transaction.StandardJanusGraphTx.commit(StandardJanusGraphTx.java:1374)

at org.janusgraph.graphdb.tinkerpop.JanusGraphBlueprintsGraph$GraphTransaction.doCommit(JanusGraphBlueprintsGraph.java:272)

at org.apache.tinkerpop.gremlin.structure.util.AbstractTransaction.commit(AbstractTransaction.java:105)

... 13 more