Gremlin Server as REST API with dynamically created data

Question

Let's say I have the following: - a node.js server that is able to query a database and receive a (possibly big) JSON - a gremlin server (configured with gremlin-server-rest-modern.yaml but maybe there must be something more in there)

My question is: is there a way to dynamically and programmatically add a new graph to be served up by the server? I want my node server to query the database and send the JSON response to the gremlin server; there, the response will be converted into a graph; from the node server, the user will be able to send other queries and receive complex responses. How can I achieve that?

I tried to use [1] but I'm not sure how can I do what I want. How do you actually send multiple (chained) commands, like a mini-script? I know how to do it using the console, but not using the server (as a REST service), since there is not an exposed API. Can you give me an advice or some examples? Thanks!

Adrian

[1] https://github.com/jbmusso/gremlin-javascript

Edit: I managed to send a POST message to the server with some simple commands. It works if I send a POST with all the commands (the graph creation and the query). However, for multiple POSTs, the context is not saved. First, I'm sending a POST with the content:

{
 "gremlin" : "graph = TinkerGraph.open(); g = graph .traversal(); graph .addVertex('name', 'adrian', 'age', 21); "
}

Then, I send another POST with

{
 "gremlin" : "v2 = graph.addVertex('name', 'gigel', 'age', 22); g.V()"
}

However, I get the following error:

{
    "message": "No such property: graf for class: Script4",
    "Exception-Class": "groovy.lang.MissingPropertyException",
    "exceptions": [
        "groovy.lang.MissingPropertyException"
    ],
    "stackTrace": "groovy.lang.MissingPropertyException: No such property: graf for class: Script4\n\tat org.codehaus.groovy.runtime.ScriptBytecodeAdapter.unwrap(ScriptBytecodeAdapter.java:53)\n\tat org.codehaus.groovy.runtime.callsite.PogoGetPropertySite.getProperty(PogoGetPropertySite.java:52)\n\tat org.codehaus.groovy.runtime.callsite.AbstractCallSite.callGroovyObjectGetProperty(AbstractCallSite.java:307)\n\tat Script4.run(Script4.groovy:1)\n\tat org.apache.tinkerpop.gremlin.groovy.jsr223.GremlinGroovyScriptEngine.eval(GremlinGroovyScriptEngine.java:834)\n\tat org.apache.tinkerpop.gremlin.groovy.jsr223.GremlinGroovyScriptEngine.eval(GremlinGroovyScriptEngine.java:547)\n\tat javax.script.AbstractScriptEngine.eval(AbstractScriptEngine.java:233)\n\tat org.apache.tinkerpop.gremlin.groovy.engine.ScriptEngines.eval(ScriptEngines.java:120)\n\tat org.apache.tinkerpop.gremlin.groovy.engine.GremlinExecutor.lambda$eval$2(GremlinExecutor.java:314)\n\tat java.util.concurrent.FutureTask.run(FutureTask.java:266)\n\tat java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)\n\tat java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)\n\tat java.lang.Thread.run(Thread.java:745)\n"
}

The context is not saved on the gremlin server? I must send the entire script to be executed? What if I want to create two graphs and query them later?

Thanks!

Answer 1

Graphs you create in scripts through sessionless requests (like REST) are not maintained. You can create graph instances that are maintained between requests in a session but then they are only maintained in that session and not reachable outside of that session.

If you want to create graphs globally for the server they must be:

1. configured in the server configuration file
2. produced as part of an initialization script
3. constructed by a custom GraphManager instance (which involves writing some Java code)

I suppose it would be also possible to build a custom endpoint that let you manage he graphs in some way, but you'd have to get more than a cursory knowledge of Gremlin Server's code to pull that off (wouldn't be too hard though).