Support for VertexPrograms

[mssrini]

Background: we used earlier janusgraph+hbase and now we want to move towards foundation db on k8. So we are trying out the janusgraph-foundation db adaptor

During the tests, we figured out that our existing algorithms, similar to the link below
https://github.com/apache/tinkerpop/blob/master/gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/computer/ranking/pagerank/PageRankVertexProgram.java

is failing due to the below errors

08:47:48 ERROR org.janusgraph.diskstorage.keycolumnvalue.scan.StandardScannerExecutor - Exception trying to setup the job:
org.janusgraph.diskstorage.PermanentBackendException: Permanent failure in storage backend
        at com.experoinc.janusgraph.diskstorage.foundationdb.FoundationDBKeyValueStore.getSlice(FoundationDBKeyValueStore.java:137) ~[janusgraph-foundationdb-0.1.0.jar:na]
        at org.janusgraph.diskstorage.keycolumnvalue.keyvalue.OrderedKeyValueStoreAdapter.getKeys(OrderedKeyValueStoreAdapter.java:116) ~[janusgraph-core-0.4.1.jar:na]
        at org.janusgraph.diskstorage.keycolumnvalue.KCVSUtil.getKeys(KCVSUtil.java:70) ~[janusgraph-core-0.4.1.jar:na]
        at org.janusgraph.diskstorage.keycolumnvalue.scan.StandardScannerExecutor.addDataPuller(StandardScannerExecutor.java:92) ~[janusgraph-core-0.4.1.jar:na]
        at org.janusgraph.diskstorage.keycolumnvalue.scan.StandardScannerExecutor.run(StandardScannerExecutor.java:121) ~[janusgraph-core-0.4.1.jar:na]
        at java.lang.Thread.run(Thread.java:748) [na:1.8.0_201]
Caused by: org.janusgraph.diskstorage.PermanentBackendException: Max transaction reset count exceeded
        at com.experoinc.janusgraph.diskstorage.foundationdb.FoundationDBTx.getRange(FoundationDBTx.java:188) ~[janusgraph-foundationdb-0.1.0.jar:na]
        at com.experoinc.janusgraph.diskstorage.foundationdb.FoundationDBKeyValueStore.getSlice(FoundationDBKeyValueStore.java:129) ~[janusgraph-foundationdb-0.1.0.jar:na]
        ... 5 common frames omitted
Exception in thread "Thread-4" java.lang.NullPointerException
        at org.janusgraph.diskstorage.keycolumnvalue.scan.StandardScannerExecutor.cleanup(StandardScannerExecutor.java:224)
        at org.janusgraph.diskstorage.keycolumnvalue.scan.StandardScannerExecutor.cleanupSilent(StandardScannerExecutor.java:235)
        at org.janusgraph.diskstorage.keycolumnvalue.scan.StandardScannerExecutor.run(StandardScannerExecutor.java:125)
        at java.lang.Thread.run(Thread.java:748)

Has anyone faced similar errors before? appreciate your help. thanks.