readonly traversal exception in program, but works from gremlin remote console

[Lee Mitchell]

I would greatly appreciate guidance/ideas/thoughts anybody can share on how I might resolve this error message from my program's websocket connection to a gremlin server that is scripted to provide a readonly traversal.

response message:

org.apache.tinkerpop.gremlin.process.traversal.step.map.GraphStep cannot be cast to org.apache.tinkerpop.gremlin.process.traversal.step.ByModulating

The query 

g.E().valueMap(true).toList()

works fine from a gremlin console remote connection, but not my program.

Many Thanks, Lee

------ tldr; more details below ------

I have a database(neo4j) that I have started gremlin server(3.2.0-incubating) to manage, instructing it to provide a readonly traversal (g)

globals << [g : graph.traversal(GraphTraversalSource.build().with(ReadOnlyStrategy.instance()))]

via this script

// An example of an initialization script that can be configured to run in Gremlin Server.

// Functions defined here will go into global cache and will not be removed from there

// unless there is a reset of the ScriptEngine.

def addItUp(x, y) { x + y }

// an init script that returns a Map allows explicit setting of global bindings.

def globals = [:]

// defines a sample LifeCycleHook that prints some output to the Gremlin Server console.

// note that the name of the key in the "global" map is unimportant.

globals << [hook : [

  onStartUp: { ctx ->

    ctx.logger.info("Executed once at startup of Gremlin Server.")

  },

  onShutDown: { ctx ->

    ctx.logger.info("Executed once at shutdown of Gremlin Server.")

  }

] as LifeCycleHook]

// define the default ReadOnly TraversalSource to bind queries to - this one will be named "g".

globals << [g : graph.traversal(GraphTraversalSource.build().with(ReadOnlyStrategy.instance()))]

After I connect via gremlin console (3.2.0-incubating) and remote into the gremlin server,

it is indeed read only, given this command / result

gremlin> g.E(0).property('anything',1)
The provided traversal has a mutating step and thus is not read only: AddPropertyStep({key=[anything], value=[1]})
Display stack trace? [yN]

But when I try to read the edges via a progam websocket connection using this query:

            const string query = "g.E().by(valueMap(true)).toList()";

The gremlin server response has

code:597

message:"org.apache.tinkerpop.gremlin.process.traversal.step.map.GraphStep cannot be cast to org.apache.tinkerpop.gremlin.process.traversal.step.ByModulating"

Yet, from my remote gremlin console, the query works

gremlin> g.E().valueMap(true).toList()

==>{nullArcDescription=self-loop-on-nullNode, label=nullArc, id=0}

==>{takePcs=40, givePcs=40, vdest=888, label=flowArc, id=1}

==>{takePcs=40, givePcs=40, vdest=888, label=flowArc, id=2}

==>{takePcs=60, givePcs=60, vdest=888, label=ovFlowArc, id=3}

==>{takePcs=40, givePcs=40, vdest=888, label=ovFlowArc, id=4}

==>{takePcs=40, givePcs=40, vdest=888, label=ovFlowArc, id=5}

==>{takePcs=20, givePcs=20, vdest=888, label=flowArc, id=6}

==>{takePcs=60, givePcs=60, vdest=888, label=flowArc, id=7}

==>{takePcs=100, givePcs=100, vdest=888, label=endDlvArc, id=8}

==>{takePcs=100, givePcs=100, vdest=888, label=dlvArc, id=9}

[Lee Mitchell]

The solution was to change my program query to

g.E().valueMap(true).toList()




Instead of 

g.E().by(valueMap(true)).toList()