Cannot query neo4j from console

[Dave Bloodworth]

Hi,

I'd like to migrate an existing java web app to Gremlin from Cypher. I'd like to be able to use other graph dbs rather than be locked into neo4j.

I am trying to start working with gremlin and, after reading the docs, decided to start with gremlin-console (3.4.0)

I was running neo4j version 3.4.9, and tried to connect to it, but got an error similar to the following (note this may not be the exact error - I may have copied this from another post):

• Failed to start Neo4j with an older data store version. To enable automatic upgrade, please set configuration parameter "allow_store_upgrade=true"

Anyway, after playing around with config options as directed I then got the error:

• Not possible to upgrade a store with version 'v0.A.9' to current store version `v0.A.8` (Neo4j 3.2.3).

Assuming this means that my neo4j installation is too new (3.4.9, data store v0.A.9), I downgraded to 3.2.3 (data store v0.A.8).
I then reloaded all of my data (using my Cypher scripts through neo4j server) and checked it was complete using the neo4j browser.

I started gremlin console, setting config as follows:

gremlin> conf = new BaseConfiguration()

==>org.apache.commons.configuration.BaseConfiguration@7ac9af2a

gremlin> conf.setProperty('gremlin.neo4j.directory','C:\\Users\\me\\work\\docker\\neo4j\\volumes\\neo4j\\data\\databases\\graph.db\\')

==>null

gremlin> graph = Neo4jGraph.open(conf)
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/C:/Users/me/work/tools/TinkerPop/apache-tinkerpop-gremlin-console-3.4.0/lib/slf4j-log4j12-1.7.21.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/C:/Users/me/work/tools/TinkerPop/apache-tinkerpop-gremlin-console-3.4.0/ext/neo4j-gremlin/lib/slf4j-nop-1.7.22.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.slf4j.impl.Log4jLoggerFactory]

==>neo4jgraph[community single [C:\Users\me\work\docker\neo4j\volumes\neo4j\data\databases\graph.db]]

gremlin> g = graph.traversal()

==>graphtraversalsource[neo4jgraph[community single [C:\Users\me\work\docker\neo4j\volumes\neo4j\data\databases\graph.db]], standard]

As you can see the graph appears to open successfully (albeit with a warning from slf4j) and I can create the graphtraversal instance.

However, it doesn't matter which queries I use, I cannot get any response to be shown in the console.

gremlin> g.V()
gremlin> g.V(133)


As you can tell, I'm very new to gremlin (and console) and would really appreciate any advice on what to try next, log file locations, anything ...

Also, is this a valid approach, should I just forget trying to start with a neo4j instance and just opt for a db that directly supports gremlin? The (main) reason I ask, because it already appears to be necessary to downgrade the data store version in order to get rid of the startup errors.

Thanks,

Dave

[Stephen Mallette]

As of 3.4.0 TinkerPop is using Neo4j  3.2.3:

https://github.com/neo4j-contrib/neo4j-tinkerpop-api-impl/blob/0.7-3.2.3/pom.xml#L23

so whatever Neo4j allows in terms of connecting various versions of their datastore will simply apply based on that. There is an open PR for a neo4j upgrade to 3.4.0:

https://github.com/apache/tinkerpop/pull/1042

so hopefully that's on it's way for TinkerPop 3.4.1. As for why you can't connect I'd guess that the reason is related to your pathing. 

gremlin> conf.setProperty('gremlin.neo4j.directory','C:\\Users\\me\\work\\docker\\neo4j\\volumes\\neo4j\\data\\databases\\graph.db\\')

isn't "graph.db" a file and not a directory? if so, i think you just want this:

gremlin> conf.setProperty('gremlin.neo4j.directory','C:\\Users\\me\\work\\docker\\neo4j\\volumes\\neo4j\\data\\databases\\)

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[Dave Bloodworth]

Hi Stephen

Thanks for the quick response and the info regarding neo4j version support.

You were right, it was the path, but not 'graph.db' as that is a folder, it was the trailing backslash that caused the problem.

Thanks for your help.

Dave