Not able to query using gremlinpython

Question

I'm using gremlinpython to access the data in Janusgraph, but it is throwing an exception whereas the data is accessible from Gremlin shell.

Here is the Python code which I'm running remotely:

from gremlin_python import statics
from gremlin_python.structure.graph import Graph
from gremlin_python.process.graph_traversal import __
from gremlin_python.process.strategies import *
from gremlin_python.driver.driver_remote_connection import DriverRemoteConnection

graph = Graph()
g = graph.traversal().withRemote(DriverRemoteConnection('ws://<IP>:8182/gremlin','g', 
username="janusgraph"))
print g.V().has('name', 'saturn').next()

This is the exception that I'm getting:

Traceback (most recent call last):
  File "test.py", line 10, in <module>
    print g.V().has('name', 'saturn').next()
  File "/root/venv/lib/python2.7/site-packages/gremlin_python/process/traversal.py", line 70, in next
    return self.__next__()
  File "/root/venv/lib/python2.7/site-packages/gremlin_python/process/traversal.py", line 43, in __next__
    self.traversal_strategies.apply_strategies(self)
  File "/root/venv/lib/python2.7/site-packages/gremlin_python/process/traversal.py", line 346, in apply_strategies
    traversal_strategy.apply(traversal)
  File "/root/venv/lib/python2.7/site-packages/gremlin_python/driver/remote_connection.py", line 143, in apply
    remote_traversal = self.remote_connection.submit(traversal.bytecode)
  File "/root/venv/lib/python2.7/site-packages/gremlin_python/driver/driver_remote_connection.py", line 54, in submit
    results = result_set.all().result()
  File "/root/venv/lib/python2.7/site-packages/concurrent/futures/_base.py", line 462, in result
    return self.__get_result()
  File "/root/venv/lib/python2.7/site-packages/concurrent/futures/_base.py", line 414, in __get_result
    raise exception_type, self._exception, self._traceback
KeyError: None

Output from the Gremlin shell:

gremlin> graph = JanusGraphFactory.open('conf/janusgraph-hbase-es.properties')
==>standardjanusgraph[hbase:[slv-01, slv-02, slv-03]]
gremlin> GraphOfTheGodsFactory.load(graph)
==>null
gremlin> g = graph.traversal()
==>graphtraversalsource[standardjanusgraph[hbase:[slv-01, slv-02, slv-03]], standard]
gremlin> saturn = g.V().has('name', 'saturn').next()
==>v[4152]
gremlin> g.V(saturn).valueMap()
==>[name:[saturn],age:[10000]]

Configuration files for Gremlin server:

gremlin-server.yaml

host: <IP>
port: 8182
scriptEvaluationTimeout: 30000
channelizer: org.apache.tinkerpop.gremlin.server.channel.WebSocketChannelizer
graphs: {
  graph: conf/gremlin-server/janusgraph-hbase-es.properties
}
plugins:
  - janusgraph.imports
scriptEngines: {
  gremlin-groovy: {
    imports: [java.lang.Math],
    staticImports: [java.lang.Math.PI],
    scripts: [scripts/empty-sample.groovy]}}
serializers:
  - { className: org.apache.tinkerpop.gremlin.driver.ser.GryoMessageSerializerV1d0, config: { ioRegistries: [org.janusgraph.graphdb.tinkerpop.JanusGraphIoRegistry] }}
  - { className: org.apache.tinkerpop.gremlin.driver.ser.GryoLiteMessageSerializerV1d0, config: {ioRegistries: [org.janusgraph.graphdb.tinkerpop.JanusGraphIoRegistry] }}
  - { className: org.apache.tinkerpop.gremlin.driver.ser.GryoMessageSerializerV1d0, config: { serializeResultToString: true }}
  - { className: org.apache.tinkerpop.gremlin.driver.ser.GraphSONMessageSerializerGremlinV1d0, config: { ioRegistries: [org.janusgraph.graphdb.tinkerpop.JanusGraphIoRegistryV1d0] }}
  - { className: org.apache.tinkerpop.gremlin.driver.ser.GraphSONMessageSerializerGremlinV2d0, config: { ioRegistries: [org.janusgraph.graphdb.tinkerpop.JanusGraphIoRegistry] }}
  - { className: org.apache.tinkerpop.gremlin.driver.ser.GraphSONMessageSerializerV1d0, config: { ioRegistries: [org.janusgraph.graphdb.tinkerpop.JanusGraphIoRegistryV1d0] }}
processors:
  - { className: org.apache.tinkerpop.gremlin.server.op.session.SessionOpProcessor, config: { sessionTimeout: 28800000 }}
  - { className: org.apache.tinkerpop.gremlin.server.op.traversal.TraversalOpProcessor, config: { cacheExpirationTime: 600000, cacheMaxSize: 1000 }}
metrics: {
  consoleReporter: {enabled: true, interval: 180000},
  csvReporter: {enabled: true, interval: 180000, fileName: /tmp/gremlin-server-metrics.csv},
  jmxReporter: {enabled: true},
  slf4jReporter: {enabled: true, interval: 180000},
  gangliaReporter: {enabled: false, interval: 180000, addressingMode: MULTICAST},
  graphiteReporter: {enabled: false, interval: 180000}}
maxInitialLineLength: 4096
maxHeaderSize: 8192
maxChunkSize: 8192
maxContentLength: 65536
maxAccumulationBufferComponents: 1024
resultIterationBatchSize: 64
writeBufferLowWaterMark: 32768
writeBufferHighWaterMark: 65536

janusgraph-hbase-es.properties

# JanusGraph configuration sample: HBase and Elasticsearch
#
# This file connects to HBase using a Zookeeper quorum
# (storage.hostname) consisting solely of localhost.  It also connects
# to Elasticsearch running on localhost over Elasticsearch's native "Transport"
# protocol.  Zookeeper, the HBase services, and Elasticsearch must already 
# be running and available before starting JanusGraph with this file.

# The primary persistence provider used by JanusGraph.  This is required. 
# It should be set one of JanusGraph's built-in shorthand names for its
# standard storage backends (shorthands: berkeleyje, cassandrathrift,
# cassandra, astyanax, embeddedcassandra, cql, hbase, inmemory) or to the
# full package and classname of a custom/third-party StoreManager
# implementation.
#
# Default:    (no default value)
# Data Type:  String
# Mutability: LOCAL

gremlin.graph=org.janusgraph.core.JanusGraphFactory

storage.backend=hbase
storage.hbase.ext.zookeeper.znode.parent=/hbase-unsecure
storage.hbase.table = janusgraph

# The hostname or comma-separated list of hostnames of storage backend
# servers.  This is only applicable to some storage backends, such as
# cassandra and hbase.
#
# Default:    127.0.0.1
# Data Type:  class java.lang.String[]
# Mutability: LOCAL
storage.hostname=slv-01,slv-02,slv-03

# Whether to enable JanusGraph's database-level cache, which is shared
# across all transactions. Enabling this option speeds up traversals by
# holding hot graph elements in memory, but also increases the likelihood
# of reading stale data.  Disabling it forces each transaction to
# independently fetch graph elements from storage before reading/writing
# them.
#
# Default:    false
# Data Type:  Boolean
# Mutability: MASKABLE
cache.db-cache = true

# How long, in milliseconds, database-level cache will keep entries after
# flushing them.  This option is only useful on distributed storage
# backends that are capable of acknowledging writes without necessarily
# making them immediately visible.
#
# Default:    50
# Data Type:  Integer
# Mutability: GLOBAL_OFFLINE
#
# Settings with mutability GLOBAL_OFFLINE are centrally managed in
# JanusGraph's storage backend.  After starting the database for the first
# time, this file's copy of this setting is ignored.  Use JanusGraph's
# Management System to read or modify this value after bootstrapping.
cache.db-cache-clean-wait = 20

# Default expiration time, in milliseconds, for entries in the
# database-level cache. Entries are evicted when they reach this age even
# if the cache has room to spare. Set to 0 to disable expiration (cache
# entries live forever or until memory pressure triggers eviction when set
# to 0).
#
# Default:    10000
# Data Type:  Long
# Mutability: GLOBAL_OFFLINE
#
# Settings with mutability GLOBAL_OFFLINE are centrally managed in
# JanusGraph's storage backend.  After starting the database for the first
# time, this file's copy of this setting is ignored.  Use JanusGraph's
# Management System to read or modify this value after bootstrapping.
cache.db-cache-time = 180000

# Size of JanusGraph's database level cache.  Values between 0 and 1 are
# interpreted as a percentage of VM heap, while larger values are
# interpreted as an absolute size in bytes.
#
# Default:    0.3
# Data Type:  Double
# Mutability: MASKABLE
cache.db-cache-size = 0.5

# The indexing backend used to extend and optimize JanusGraph's query
# functionality. This setting is optional.  JanusGraph can use multiple
# heterogeneous index backends.  Hence, this option can appear more than
# once, so long as the user-defined name between "index" and "backend" is
# unique among appearances.Similar to the storage backend, this should be
# set to one of JanusGraph's built-in shorthand names for its standard
# index backends (shorthands: lucene, elasticsearch, es, solr) or to the
# full package and classname of a custom/third-party IndexProvider
# implementation.
#
# Default:    elasticsearch
# Data Type:  String
# Mutability: GLOBAL_OFFLINE
#
# Settings with mutability GLOBAL_OFFLINE are centrally managed in
# JanusGraph's storage backend.  After starting the database for the first
# time, this file's copy of this setting is ignored.  Use JanusGraph's
# Management System to read or modify this value after bootstrapping.
index.search.backend=elasticsearch

# The hostname or comma-separated list of hostnames of index backend
# servers.  This is only applicable to some index backends, such as
# elasticsearch and solr.
#
# Default:    127.0.0.1
# Data Type:  class java.lang.String[]
# Mutability: MASKABLE
index.search.hostname=<ES IP>:9201
index.search.index-name = search

Could someone please help here? Thanks.

Answer 1

The problem is with the latest version (3.3.3) of gremlinpython. Using 3.2.6 as the version of gremlinpython will fix this issue. Check out this blog for a complete guide of connecting to Janusgraph using Python.