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janusgraphgremlin-server

Janusgraph doesn't allow to set vertex Id even after setting this property `graph.set-vertex-id=true`

I'm running janusgraph server backed by Cassandra. It doesn't allow me to use custom vertex ids.

I do see the following log when the janusgraph gremlin server is starting.

Local setting graph.set-vertex-id=true (Type: FIXED) is overridden by globally managed value (false).  Use the ManagementSystem interface instead of the local configuration to control this setting

Even tried to set this property via management API and still no luck.

gremlin> mgmt = graph.openManagement()
gremlin> mgmt.set('graph.set-vertex-id', true)
Solution

  • As the log message already states, this config option has the mutability FIXED which means that it is a global configuration option. Global configuration is described in this section of the JanusGraph documentation.

    It states that:

    Global configuration options apply to all instances in a cluster.

    JanusGraph stores these configuration options in its storage backend which is Cassandra in your case. This ensures that all JanusGraph instances have the same values for these configuration values. Any changes that are made to these options in a local file are ignored because of this. Instead, you have to use the management API to change them which will update them in the storage backend.

    But that is already what you tried with mgmt.set(). This doesn't work in this case however because this specific config option has the mutability level FIXED. The JanusGraph documentation describes this as:

    FIXED: Like GLOBAL, but the value cannot be changed once the JanusGraph cluster is initialized.

    So, this value can really not be changed in an existing JanusGraph cluster. Your only option is to start with a new cluster if you really need to change this value.

    It is of course unfortunate that the error message suggested to use the management API even though it doesn't work in this case. I have created an issue with the JanusGraph project to improve this error message to avoid such confusion in the future: https://github.com/JanusGraph/janusgraph/issues/3206