How to execute gremlin query with mogwai - groovy

Question

Im trying to query a titan db 0.5.4 via mogwai, but when I run the following script i get the error: rexpro.exceptions.RexProScriptException: transaction is not open
and I found the same question here
P.S there is no tag for mogwai
script:
#!/usr/bin/env python3
from mogwai.connection import execute_query, setup
con = setup('127.0.0.1', graph_name="bio4j", username="re", password="re")
results = execute_query("2 * a",params={"a":2}, connection= con)
print(results)
results = execute_query("bio4j.E",params={}, connection= con)
print(results)
log:
$ ./bin/rexster.sh --start
0 [main] INFO com.tinkerpop.rexster.Application - .:Welcome to Rexster:.
93 [main] INFO com.tinkerpop.rexster.server.RexsterProperties - Using [/Users/Phoenix/Dropbox/Graph4Bio/Titan/rexhome/config/rexster.xml] as configuration source.
102 [main] INFO com.tinkerpop.rexster.Application - Rexster is watching [/Users/Phoenix/Dropbox/Graph4Bio/Titan/rexhome/config/rexster.xml] for change.
730 [main] INFO com.thinkaurelius.titan.graphdb.configuration.GraphDatabaseConfiguration - Generated unique-instance-id=0a69045d1736-AngryMac-local1
804 [main] INFO com.thinkaurelius.titan.diskstorage.Backend - Initiated backend operations thread pool of size 8
905 [main] INFO com.thinkaurelius.titan.diskstorage.log.kcvs.KCVSLog - Loaded unidentified ReadMarker start time Timepoint[1455128079919000 μs] into com.thinkaurelius.titan.diskstorage.log.kcvs.KCVSLog$MessagePuller#302c971f
908 [main] INFO com.tinkerpop.rexster.RexsterApplicationGraph - Graph [bio4j] - configured with allowable namespace [tp:gremlin]
932 [main] INFO com.tinkerpop.rexster.config.GraphConfigurationContainer - Graph bio4j - titangraph[berkeleyje:/Users/Phoenix/Dropbox/Graph4Bio/Bio4j/bio4j] loaded
939 [main] INFO com.tinkerpop.rexster.server.metrics.HttpReporterConfig - Configured HTTP Metric Reporter.
941 [main] INFO com.tinkerpop.rexster.server.metrics.ConsoleReporterConfig - Configured Console Metric Reporter.
2058 [main] INFO com.tinkerpop.rexster.server.HttpRexsterServer - HTTP/REST thread pool configuration: kernal[4 / 4] worker[8 / 8]
2060 [main] INFO com.tinkerpop.rexster.server.HttpRexsterServer - Using org.glassfish.grizzly.strategies.LeaderFollowerNIOStrategy IOStrategy for HTTP/REST.
2160 [main] INFO com.tinkerpop.rexster.server.HttpRexsterServer - Rexster Server running on: [http://localhost:8182]
2160 [main] INFO com.tinkerpop.rexster.server.RexProRexsterServer - Using org.glassfish.grizzly.strategies.LeaderFollowerNIOStrategy IOStrategy for RexPro.
2160 [main] INFO com.tinkerpop.rexster.server.RexProRexsterServer - RexPro thread pool configuration: kernal[4 / 4] worker[8 / 8]
2162 [main] INFO com.tinkerpop.rexster.server.RexProRexsterServer - Rexster configured with [DefaultSecurity].
2163 [main] INFO com.tinkerpop.rexster.server.RexProRexsterServer - RexPro Server bound to [0.0.0.0:8184]
2177 [main] INFO com.tinkerpop.rexster.server.ShutdownManager - Bound shutdown socket to /127.0.0.1:8183. Starting listener thread for shutdown requests.
152568 [Grizzly(2) SelectorRunner] INFO com.tinkerpop.rexster.protocol.EngineController - ScriptEngineManager has factory for: ECMAScript
152568 [Grizzly(2) SelectorRunner] INFO com.tinkerpop.rexster.protocol.EngineController - ScriptEngineManager has factory for: gremlin-groovy
152568 [Grizzly(2) SelectorRunner] INFO com.tinkerpop.rexster.protocol.EngineController - Registered ScriptEngine for: gremlin-groovy
152569 [Grizzly(2) SelectorRunner] INFO com.tinkerpop.rexster.protocol.EngineHolder - Initializing gremlin-groovy engine with additional imports.
153259 [Grizzly(2) SelectorRunner] INFO com.tinkerpop.rexster.protocol.EngineHolder - ScriptEngine initializing with a custom script
154074 [Grizzly(2) SelectorRunner] INFO com.tinkerpop.rexster.protocol.EngineController - ScriptEngineManager has factory for: Groovy
154076 [Grizzly(2) SelectorRunner] INFO com.tinkerpop.rexster.protocol.session.RexProSessions - RexPro Session created: a2b416ce-75ea-4ecb-9835-b287162c90cb
154354 [Grizzly(4)] INFO com.tinkerpop.rexster.protocol.session.RexProSessions - Try to destroy RexPro Session: a2b416ce-75ea-4ecb-9835-b287162c90cb
154355 [Grizzly(4)] INFO com.tinkerpop.rexster.protocol.session.RexProSessions - RexPro Session destroyed or doesn't otherwise exist: a2b416ce-75ea-4ecb-9835-b287162c90cb
154356 [Grizzly(5)] INFO com.tinkerpop.rexster.protocol.session.RexProSessions - RexPro Session created: 5b8a669f-615d-4f84-9d1e-2d10624347f0
154525 [Grizzly(7)] WARN com.tinkerpop.rexster.protocol.server.ScriptServer - Could not process script [bio4j.E] for language [groovy] on session [[B#6634722f] and request [[B#68f38099]
154527 [Grizzly(8)] INFO com.tinkerpop.rexster.protocol.session.RexProSessions - Try to destroy RexPro Session: 5b8a669f-615d-4f84-9d1e-2d10624347f0
154527 [Grizzly(8)] INFO com.tinkerpop.rexster.protocol.session.RexProSessions - RexPro Session destroyed or doesn't otherwise exist: 5b8a669f-615d-4f84-9d1e-2d10624347f0
154529 [Grizzly(1)] INFO com.tinkerpop.rexster.protocol.session.RexProSessions - Try to destroy RexPro Session: 00000000-0000-0000-0000-000000000000
154529 [Grizzly(1)] INFO com.tinkerpop.rexster.protocol.session.RexProSessions - RexPro Session destroyed or doesn't otherwise exist: 00000000-0000-0000-0000-000000000000

Answer 1

Maintainer of mogwai here.
What version of mogwai are you using? in 0.7.7 there is no return value for setup method and the connection object should not be passed around. In fact when you call setup it creates a connection pool (a synchronous rexpro connection pool since there was no concurrency option specified). So in general, just call setup once for the life of your app and you can use execute query without any references.
Also this message in particular stands out:
154525 [Grizzly(7)] WARN com.tinkerpop.rexster.protocol.server.ScriptServer - Could not process script [bio4j.E] for language [groovy] on session [[B#6634722f] and request [[B#68f38099]
Is your graph configured with a graph name of "bio4j"? The default titan graph name is "graph" and the default graph object name mogwai uses is "g". If you have a graph name of "bio4j" you wouldn't reference this directly, you'd use the graph object name associated to the transaction. You can think of a graph-name as a database name in a SQL database, and the graph object being the transactional reference to said database. This is configured in the xml configuration file when starting titan. Particularly:
<graphs>
<graph>
<graph-name>graph</graph-name>
....
</graph>
</graphs>
So assuming you changed that from "graph" to "bio4j" and left the default graph_obj_name in the setup function as "g", then your query should read "g.E".