How to make each JanusGraph Server within its Kubernetes Cluster communicate with the co-located Cassandra Server in its Kubernetes Cluster?

[raphael10-collab]

I opened yesterday a thread in StackOverflow : https://stackoverflow.com/questions/75659263/how-to-make-each-janusgraph-server-within-its-kubernetes-cluster-communicate-wit but didn't get any help. So I'm here, to ask for it

As far as I understand from the JanusGraph docs: https://docs.janusgraph.org/operations/deployment/ , and from this Google Group Talk: https://groups.google.com/g/janusgraph-users/c/ZOoR1vRLfvo?pli=1 , The JanusGraph Servers are standalone independent servers that do not communicate with each other, and the coordination is achieved through the underlying storage backend, which, as Cassandra, can be put into a Kubernetes Cluster.

But would it be convenient to set a Kubernetes Cluster for the JanusGraph standalone independent servers as well? How to do it, and how to make each single standalone independent JanusGraph Server within its Kubernetes Cluster communicate with the co-located Cassandra Server in its Kubernetes Cluster?

[FlorianHockmann]

I don't quite understand your question. You want to put JanusGraph Server, Cassandra, and Solr all in separate k8s clusters, but then you want JanusGraph Server to communicate only to one Cassandra node which is somehow co-located, and the same for one Solr node?
How are these services co-located in your case? Are they running in separate k8s clusters, but still on the same servers?

In general, I don't think that you gain much performance benefit, if any, by trying to limit JanusGraph Server to only Cassandra/Solr instances running on the same host. You will need to involve at least a second Cassandra node anyway to reach a QUORUM consistency level if you are using at least a replication factor of 3.
I would simply let JanusGraph connect to any of the Cassandra & Solr nodes and let it use its own load balancing. It probably also makes sense to keep them in the same k8s cluster as they are tightly coupled, but you could of course also put them in different clusters, especially if you are also using Cassandra / Solr for other use cases than JanusGraph.

But maybe I also understood your question wrong so please clarify if my answer doesn't really answer your question.

[raphael10-collab]

Hi Florian,
thanks for trying to helping me in disentagling my twisted thoughts.

What I was thinking was running JanusGraph Server, Cassandra and Solr in separate k8s clusters, so... a JanusGraph Server Cluster including the JanusGraph Servers living in three different "physical" machines, a Cassandra Cluster, and a Solr Cluster .

But actually you correctly made me think that a simpler, and, since I would use in those three machines Cassandra and Solr only for JanusGraph, more effective approach would be :

A) let JanusGraph connect to any of the Cassandra & Solr nodes, and let it use its own load balancing
B) keep JanusGraph, Cassandra and Solr in the same k8s cluster, because they are tightly coupled, and, as said, I would use in those three machines Cassandra and Solr only for JanusGraph.

In one of these three machines I've just installed :
a JanusGraph Server via docker (https://docs.janusgraph.org/getting-started/installation/),
and a single-cluster k8ssandra instance (https://docs.k8ssandra.io/install/local/single-cluster-kustomize/) :

root@vmi1231861:~# kubectl -n k8ssandra-operator describe K8ssandraCluster demo
Name:         demo
Namespace:    k8ssandra-operator
Labels:       <none>
Annotations:  k8ssandra.io/initial-system-replication: {"dc1":3}
API Version:  k8ssandra.io/v1alpha1
Kind:         K8ssandraCluster
Metadata:
  Creation Timestamp:  2023-03-08T09:15:51Z
  Finalizers:
    k8ssandracluster.k8ssandra.io/finalizer
  Generation:  2
  Managed Fields:
    API Version:  k8ssandra.io/v1alpha1
    Fields Type:  FieldsV1
    fieldsV1:
      f:metadata:
        f:annotations:
          .:
          f:kubectl.kubernetes.io/last-applied-configuration:
      f:spec:
        .:
        f:auth:
        f:cassandra:
          .:
          f:datacenters:
          f:jmxInitContainerImage:
            .:
            f:name:
            f:registry:
            f:tag:
          f:perNodeConfigInitContainerImage:
          f:serverType:
          f:serverVersion:
        f:secretsProvider:
    Manager:      kubectl-client-side-apply
    Operation:    Update
    Time:         2023-03-08T09:15:51Z
    API Version:  k8ssandra.io/v1alpha1
    Fields Type:  FieldsV1
    fieldsV1:
      f:metadata:
        f:annotations:
          f:k8ssandra.io/initial-system-replication:
        f:finalizers:
          .:
          v:"k8ssandracluster.k8ssandra.io/finalizer":
      f:spec:
        f:cassandra:
          f:superuserSecretRef:
    Manager:      manager
    Operation:    Update
    Time:         2023-03-08T09:15:51Z
    API Version:  k8ssandra.io/v1alpha1
    Fields Type:  FieldsV1
    fieldsV1:
      f:status:
        .:
        f:conditions:
        f:datacenters:
          .:
          f:dc1:
            .:
            f:cassandra:
              .:
              f:cassandraOperatorProgress:
              f:conditions:
              f:datacenterName:
              f:lastServerNodeStarted:
              f:nodeStatuses:
                .:
                f:demo-dc1-default-sts-0:
                  .:
                  f:hostID:
                f:demo-dc1-default-sts-1:
                  .:
                  f:hostID:
                f:demo-dc1-default-sts-2:
                  .:
                  f:hostID:
              f:observedGeneration:
              f:quietPeriod:
              f:superUserUpserted:
              f:usersUpserted:
            f:stargate:
              .:
              f:availableReplicas:
              f:conditions:
              f:deploymentRefs:
              f:progress:
              f:readyReplicas:
              f:readyReplicasRatio:
              f:replicas:
              f:serviceRef:
              f:updatedReplicas:
        f:error:
    Manager:         manager
    Operation:       Update
    Subresource:     status
    Time:            2023-03-08T09:22:22Z
  Resource Version:  12773
  UID:               86044015-d3b7-4a0a-9655-2e5c4dee082e
Spec:
  Auth:  true
  Cassandra:
    Datacenters:
      Config:
        Jvm Options:
          Gc:         G1GC
          Heap Size:  512M
      Jmx Init Container Image:
        Name:      busybox
        Registry:  docker.io
        Tag:       1.34.1
      Metadata:
        Name:                                dc1
      Per Node Config Init Container Image:  mikefarah/yq:4
      Size:                                  3
      Stargate:
        Allow Stargate On Data Nodes:  false
        Container Image:
          Registry:        docker.io
          Repository:      stargateio
          Tag:             v1.0.67
        Heap Size:         256M
        Secrets Provider:  internal
        Service Account:   default
        Size:              1
      Stopped:             false
      Storage Config:
        Cassandra Data Volume Claim Spec:
          Access Modes:
            ReadWriteOnce
          Resources:
            Requests:
              Storage:         5Gi
          Storage Class Name:  standard
    Jmx Init Container Image:
      Name:                                busybox
      Registry:                            docker.io
      Tag:                                 1.34.1
    Per Node Config Init Container Image:  mikefarah/yq:4
    Server Type:                           cassandra
    Server Version:                        4.0.3
    Superuser Secret Ref:
      Name:          demo-superuser
  Secrets Provider:  internal
Status:
  Conditions:
    Last Transition Time:  2023-03-08T09:21:06Z
    Status:                True
    Type:                  CassandraInitialized
  Datacenters:
    dc1:
      Cassandra:
        Cassandra Operator Progress:  Ready
        Conditions:
          Last Transition Time:    2023-03-08T09:18:09Z
          Message:                 
          Reason:                  
          Status:                  True
          Type:                    Healthy
          Last Transition Time:    2023-03-08T09:21:04Z
          Message:                 
          Reason:                  
          Status:                  False
          Type:                    Stopped
          Last Transition Time:    2023-03-08T09:21:04Z
          Message:                 
          Reason:                  
          Status:                  False
          Type:                    ReplacingNodes
          Last Transition Time:    2023-03-08T09:21:04Z
          Message:                 
          Reason:                  
          Status:                  False
          Type:                    Updating
          Last Transition Time:    2023-03-08T09:21:04Z
          Message:                 
          Reason:                  
          Status:                  False
          Type:                    RollingRestart
          Last Transition Time:    2023-03-08T09:21:04Z
          Message:                 
          Reason:                  
          Status:                  False
          Type:                    Resuming
          Last Transition Time:    2023-03-08T09:21:04Z
          Message:                 
          Reason:                  
          Status:                  False
          Type:                    ScalingDown
          Last Transition Time:    2023-03-08T09:21:04Z
          Message:                 
          Reason:                  
          Status:                  True
          Type:                    Valid
          Last Transition Time:    2023-03-08T09:21:05Z
          Message:                 
          Reason:                  
          Status:                  True
          Type:                    Initialized
          Last Transition Time:    2023-03-08T09:21:05Z
          Message:                 
          Reason:                  
          Status:                  True
          Type:                    Ready
        Datacenter Name:           
        Last Server Node Started:  2023-03-08T09:19:31Z
        Node Statuses:
          demo-dc1-default-sts-0:
            Host ID:  ba284c01-deb8-47b8-8f2f-b8d1c67abe96
          demo-dc1-default-sts-1:
            Host ID:  5c48bb71-f80f-4571-8556-ab546c7e2a00
          demo-dc1-default-sts-2:
            Host ID:          193798c1-81c1-42a1-b69e-b2f4ee8ca7ef
        Observed Generation:  1
        Quiet Period:         2023-03-08T09:21:10Z
        Super User Upserted:  2023-03-08T09:21:05Z
        Users Upserted:       2023-03-08T09:21:05Z
      Stargate:
        Available Replicas:  1
        Conditions:
          Last Transition Time:  2023-03-08T09:22:20Z
          Status:                True
          Type:                  Ready
        Deployment Refs:
          demo-dc1-default-stargate-deployment
        Progress:              Running
        Ready Replicas:        1
        Ready Replicas Ratio:  1/1
        Replicas:              1
        Service Ref:           demo-dc1-stargate-service
        Updated Replicas:      1
  Error:                       None
Events:                        <none>

Could you be so kind in pointing me to the specific docs parts of JanusGraph Docs and of k8ssandra Docs which explain how to correctly deploy point A) : let JanusGraph connect to any of the Cassandra & Solr nodes, and let it use its own load balancing
and point B) : keep JanusGraph, Cassandra and Solr in the same k8s cluster
?

[FlorianHockmann]

I haven't used k8ssandra myself, so I unfortunately can't really help you there. But setting up Cassandra isn't specific in any way for JanusGraph so you should be able to just follow their documentation. I would recommend to start with a three node cluster and configure JanusGraph to use 3 replicas.

For JanusGraph in k8s, it's important to get to know the JanusGraph Docker image and how that can be configured. This is documented mostly in the README.md of janusgraph-docker.
The important part is that you can configure the image completely via environment variables, e.g., janusgraph.storage.hostname configures the hostname(s) of the storage backend which is Cassandra in your case.

[raphael10-collab]

Thank you very much @FlorianHockmann for your kind help and suggestions

[raphael10-collab]

I take advantage of the fact you are an expert of janus-docker to ask you here one more thing ( for other issues, that likely will occur, I will open new threads)

I've put in a file some environment variables : janusgraph-env.txt :

storage.backend=cql
storage.hostname=127.0.0.1, xx.xxx.xxx.xx, xx.xxx.xxx.xxx
cluster.max-partitions=32
index.search.backend=solr

Running the janusgraph docker I don't get any errors:

root@vmi1231861:~# docker run --env-file ./janusgraph-env.txt --name janusgraph-default janusgraph/janusgraph:latest
/etc/opt/janusgraph/janusgraph-server.yaml will be used to start JanusGraph Server in foreground
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/opt/janusgraph/lib/logback-classic-1.2.11.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/opt/janusgraph/lib/slf4j-reload4j-1.7.36.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 [ch.qos.logback.classic.util.ContextSelectorStaticBinder]
18:51:23 WARN  org.apache.tinkerpop.gremlin.server.AbstractChannelizer - The org.apache.tinkerpop.gremlin.driver.ser.GryoMessageSerializerV3d0 serialization class is deprecated.
18:51:24 WARN  org.apache.tinkerpop.gremlin.server.AbstractChannelizer - The org.apache.tinkerpop.gremlin.driver.ser.GryoMessageSerializerV3d0 serialization class is deprecated.

But it is strange that there are no errors, since solr is not even installed, as stand-alone nor as kubernetes cluster :

CONTAINER ID   IMAGE                  COMMAND                  CREATED        STATUS        PORTS                                                                                                     NAMES
2c83d209be03   kindest/node:v1.25.3   "/usr/local/bin/entr…"   12 hours ago   Up 12 hours   0.0.0.0:30080->30080/tcp, 0.0.0.0:30443->30443/tcp, 0.0.0.0:30942->30942/tcp, 127.0.0.1:43263->6443/tcp   k8ssandra-0-control-plane
0c1548e123a1   kindest/node:v1.25.3   "/usr/local/bin/entr…"   12 hours ago   Up 12 hours                                                                                                             k8ssandra-0-worker3
ae0e54a2f510   kindest/node:v1.25.3   "/usr/local/bin/entr…"   12 hours ago   Up 12 hours                                                                                                             k8ssandra-0-worker2
f683494db5f5   kindest/node:v1.25.3   "/usr/local/bin/entr…"   12 hours ago   Up 12 hours                                                                                                             k8ssandra-0-worker
74738f0ee6ff   kindest/node:v1.25.3   "/usr/local/bin/entr…"   12 hours ago   Up 12 hours                                                                                                             k8ssandra-0-worker4
ed00413b9b98   registry:2             "/entrypoint.sh /etc…"   12 hours ago   Up 12 hours   0.0.0.0:5000->5000/tcp                                                                                    kind-registry

Does the absence of any errors mean that the whole configuration does not actually work?
And why it does not complain for the other two storage.hostname IP addresses, xx.xxx.xxx.xx, xx.xxx.xxx.xxx , since in those two other machines I have not yet installed and run anything?

[FlorianHockmann]

Please check the linked README.md of janusgraph-docker again. All config options for JanusGraph need to be prefixed with janusgraph.. So, storage.backend for example won't work. It needs to be janusgraph.storage.backend instead. The same applies to the other env vars in your janusgraph-env.txt file.
This also explains why JanusGraph doesn't complain about not being able to contact Cassandra / Solr. It simply didn't try to and instead used its default config which is Berkeley & Lucene.

[raphael10-collab]

With :

janusgraph.storage.backend=cql
janusgraph.storage.hostname=127.0.0.1
janusgraph.cluster.max-partitions=32

I get :

root@vmi1231861:~# docker run --env-file ./janusgraph-env.txt --name janusgraph-default janusgraph/janusgraph:latest
waiting for storage...
waiting for storage...
waiting for storage...
/etc/opt/janusgraph/janusgraph-server.yaml will be used to start JanusGraph Server in foreground
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/opt/janusgraph/lib/logback-classic-1.2.11.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/opt/janusgraph/lib/slf4j-reload4j-1.7.36.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 [ch.qos.logback.classic.util.ContextSelectorStaticBinder]
08:54:02 WARN  com.datastax.oss.driver.internal.core.control.ControlConnection - [JanusGraph Session] Error connecting to Node(endPoint=/127.0.0.1:9042, hostId=null, hashCode=2712615d), trying next node (ConnectionInitException: [JanusGraph Session|control|connecting...] Protocol initialization request, step 1 (OPTIONS): failed to send request (io.netty.channel.StacklessClosedChannelException))
08:54:03 WARN  org.apache.tinkerpop.gremlin.server.util.DefaultGraphManager - Graph [graph] configured at [/etc/opt/janusgraph/janusgraph.properties] could not be instantiated and will not be available in Gremlin Server.  GraphFactory message: GraphFactory could not instantiate this Graph implementation [class org.janusgraph.core.JanusGraphFactory]
java.lang.RuntimeException: GraphFactory could not instantiate this Graph implementation [class org.janusgraph.core.JanusGraphFactory]
    at org.apache.tinkerpop.gremlin.structure.util.GraphFactory.open(GraphFactory.java:84)
    at org.apache.tinkerpop.gremlin.structure.util.GraphFactory.open(GraphFactory.java:72)
    at org.apache.tinkerpop.gremlin.structure.util.GraphFactory.open(GraphFactory.java:106)
    at org.apache.tinkerpop.gremlin.server.util.DefaultGraphManager.addGraph(DefaultGraphManager.java:63)
    at java.util.LinkedHashMap.forEach(LinkedHashMap.java:684)
    at org.apache.tinkerpop.gremlin.server.util.DefaultGraphManager.<init>(DefaultGraphManager.java:58)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at org.apache.tinkerpop.gremlin.server.util.ServerGremlinExecutor.<init>(ServerGremlinExecutor.java:86)
    at org.apache.tinkerpop.gremlin.server.GremlinServer.<init>(GremlinServer.java:127)
    at org.apache.tinkerpop.gremlin.server.GremlinServer.<init>(GremlinServer.java:90)
    at org.janusgraph.graphdb.server.JanusGraphServer.start(JanusGraphServer.java:85)
    at org.janusgraph.graphdb.server.JanusGraphServer.main(JanusGraphServer.java:53)
Caused by: java.lang.reflect.InvocationTargetException: null
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.apache.tinkerpop.gremlin.structure.util.GraphFactory.open(GraphFactory.java:80)
    ... 14 common frames omitted
Caused by: java.lang.IllegalArgumentException: Could not instantiate implementation: org.janusgraph.diskstorage.cql.CQLStoreManager
    at org.janusgraph.util.system.ConfigurationUtil.instantiate(ConfigurationUtil.java:79)
    at org.janusgraph.diskstorage.Backend.getImplementationClass(Backend.java:527)
    at org.janusgraph.diskstorage.Backend.getStorageManager(Backend.java:491)
    at org.janusgraph.graphdb.configuration.builder.GraphDatabaseConfigurationBuilder.build(GraphDatabaseConfigurationBuilder.java:64)
    at org.janusgraph.core.JanusGraphFactory.open(JanusGraphFactory.java:176)
    at org.janusgraph.core.JanusGraphFactory.open(JanusGraphFactory.java:147)
    at org.janusgraph.core.JanusGraphFactory.open(JanusGraphFactory.java:127)
    ... 19 common frames omitted
Caused by: java.lang.reflect.InvocationTargetException: null
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at org.janusgraph.util.system.ConfigurationUtil.instantiate(ConfigurationUtil.java:73)
    ... 25 common frames omitted
Caused by: com.datastax.oss.driver.api.core.AllNodesFailedException: Could not reach any contact point, make sure you've provided valid addresses (showing first 1 nodes, use getAllErrors() for more): Node(endPoint=/127.0.0.1:9042, hostId=null, hashCode=2712615d): [com.datastax.oss.driver.api.core.connection.ConnectionInitException: [JanusGraph Session|control|connecting...] Protocol initialization request, step 1 (OPTIONS): failed to send request (io.netty.channel.StacklessClosedChannelException)]
    at com.datastax.oss.driver.api.core.AllNodesFailedException.copy(AllNodesFailedException.java:141)
    at com.datastax.oss.driver.internal.core.util.concurrent.CompletableFutures.getUninterruptibly(CompletableFutures.java:149)
    at com.datastax.oss.driver.api.core.session.SessionBuilder.build(SessionBuilder.java:835)
    at org.janusgraph.diskstorage.cql.builder.CQLSessionBuilder.build(CQLSessionBuilder.java:81)
    at org.janusgraph.diskstorage.cql.CQLStoreManager.<init>(CQLStoreManager.java:135)
    at org.janusgraph.diskstorage.cql.CQLStoreManager.<init>(CQLStoreManager.java:116)
    ... 30 common frames omitted
    Suppressed: com.datastax.oss.driver.api.core.connection.ConnectionInitException: [JanusGraph Session|control|connecting...] Protocol initialization request, step 1 (OPTIONS): failed to send request (io.netty.channel.StacklessClosedChannelException)
	    at com.datastax.oss.driver.internal.core.channel.ProtocolInitHandler$InitRequest.fail(ProtocolInitHandler.java:356)
	    at com.datastax.oss.driver.internal.core.channel.ChannelHandlerRequest.writeListener(ChannelHandlerRequest.java:87)
	    at io.netty.util.concurrent.DefaultPromise.notifyListener0(DefaultPromise.java:590)
	    at io.netty.util.concurrent.DefaultPromise.notifyListenersNow(DefaultPromise.java:557)
	    at io.netty.util.concurrent.DefaultPromise.notifyListeners(DefaultPromise.java:492)
	    at io.netty.util.concurrent.DefaultPromise.addListener(DefaultPromise.java:185)
	    at io.netty.channel.DefaultChannelPromise.addListener(DefaultChannelPromise.java:95)
	    at io.netty.channel.DefaultChannelPromise.addListener(DefaultChannelPromise.java:30)
	    at com.datastax.oss.driver.internal.core.channel.ChannelHandlerRequest.send(ChannelHandlerRequest.java:76)
	    at com.datastax.oss.driver.internal.core.channel.ProtocolInitHandler$InitRequest.send(ProtocolInitHandler.java:193)
	    at com.datastax.oss.driver.internal.core.channel.ProtocolInitHandler.onRealConnect(ProtocolInitHandler.java:124)
	    at com.datastax.oss.driver.internal.core.channel.ConnectInitHandler.lambda$connect$0(ConnectInitHandler.java:57)
	    at io.netty.util.concurrent.DefaultPromise.notifyListener0(DefaultPromise.java:590)
	    at io.netty.util.concurrent.DefaultPromise.notifyListeners0(DefaultPromise.java:583)
	    at io.netty.util.concurrent.DefaultPromise.notifyListenersNow(DefaultPromise.java:559)
	    at io.netty.util.concurrent.DefaultPromise.notifyListeners(DefaultPromise.java:492)
	    at io.netty.util.concurrent.DefaultPromise.setValue0(DefaultPromise.java:636)
	    at io.netty.util.concurrent.DefaultPromise.setFailure0(DefaultPromise.java:629)
	    at io.netty.util.concurrent.DefaultPromise.tryFailure(DefaultPromise.java:118)
	    at io.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe.fulfillConnectPromise(AbstractNioChannel.java:321)
	    at io.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe.finishConnect(AbstractNioChannel.java:337)
	    at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:776)
	    at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:724)
	    at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:650)
	    at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:562)
	    at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997)
	    at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
	    at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
	    at java.lang.Thread.run(Thread.java:750)
	    Suppressed: io.netty.channel.AbstractChannel$AnnotatedConnectException: Connection refused: /127.0.0.1:9042
	    Caused by: java.net.ConnectException: Connection refused
		    at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
		    at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:716)
		    at io.netty.channel.socket.nio.NioSocketChannel.doFinishConnect(NioSocketChannel.java:337)
		    at io.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe.finishConnect(AbstractNioChannel.java:334)
		    at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:776)
		    at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:724)
		    at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:650)
		    at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:562)
		    at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997)
		    at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
		    at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
		    at java.lang.Thread.run(Thread.java:750)
    Caused by: io.netty.channel.StacklessClosedChannelException: null
	    at io.netty.channel.AbstractChannel$AbstractUnsafe.flush0()(Unknown Source)
08:54:07 ERROR org.apache.tinkerpop.gremlin.jsr223.DefaultGremlinScriptEngineManager - Could not create GremlinScriptEngine for gremlin-groovy
java.lang.IllegalStateException: javax.script.ScriptException: javax.script.ScriptException: groovy.lang.MissingPropertyException: No such property: graph for class: Script1
    at org.apache.tinkerpop.gremlin.jsr223.DefaultGremlinScriptEngineManager.lambda$createGremlinScriptEngine$16(DefaultGremlinScriptEngineManager.java:464)
    at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:183)
    at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
    at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1384)
    at java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:647)
    at java.util.stream.ReferencePipeline$7$1.accept(ReferencePipeline.java:272)
    at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1384)
    at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:482)
    at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:472)
    at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:150)
    at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:173)
    at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
    at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:485)
    at org.apache.tinkerpop.gremlin.jsr223.DefaultGremlinScriptEngineManager.createGremlinScriptEngine(DefaultGremlinScriptEngineManager.java:450)
    at org.apache.tinkerpop.gremlin.jsr223.DefaultGremlinScriptEngineManager.getEngineByName(DefaultGremlinScriptEngineManager.java:219)
    at org.apache.tinkerpop.gremlin.jsr223.CachedGremlinScriptEngineManager.lambda$getEngineByName$0(CachedGremlinScriptEngineManager.java:57)
    at java.util.concurrent.ConcurrentHashMap.computeIfAbsent(ConcurrentHashMap.java:1660)
    at org.apache.tinkerpop.gremlin.jsr223.CachedGremlinScriptEngineManager.getEngineByName(CachedGremlinScriptEngineManager.java:57)
    at org.apache.tinkerpop.gremlin.groovy.engine.GremlinExecutor.lambda$eval$0(GremlinExecutor.java:272)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:750)
Caused by: javax.script.ScriptException: javax.script.ScriptException: groovy.lang.MissingPropertyException: No such property: graph for class: Script1
    at org.apache.tinkerpop.gremlin.groovy.jsr223.GremlinGroovyScriptEngine.eval(GremlinGroovyScriptEngine.java:381)
    at javax.script.AbstractScriptEngine.eval(AbstractScriptEngine.java:264)
    at org.apache.tinkerpop.gremlin.jsr223.DefaultGremlinScriptEngineManager.lambda$createGremlinScriptEngine$16(DefaultGremlinScriptEngineManager.java:460)
    ... 24 common frames omitted
Caused by: javax.script.ScriptException: groovy.lang.MissingPropertyException: No such property: graph for class: Script1
    at org.apache.tinkerpop.gremlin.groovy.jsr223.GremlinGroovyScriptEngine.eval(GremlinGroovyScriptEngine.java:700)
    at org.apache.tinkerpop.gremlin.groovy.jsr223.GremlinGroovyScriptEngine.eval(GremlinGroovyScriptEngine.java:379)
    ... 26 common frames omitted
Caused by: groovy.lang.MissingPropertyException: No such property: graph for class: Script1
    at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.unwrap(ScriptBytecodeAdapter.java:65)
    at org.codehaus.groovy.runtime.callsite.PogoGetPropertySite.getProperty(PogoGetPropertySite.java:51)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callGroovyObjectGetProperty(AbstractCallSite.java:309)
    at Script1.run(Script1.groovy:30)
    at org.apache.tinkerpop.gremlin.groovy.jsr223.GremlinGroovyScriptEngine.eval(GremlinGroovyScriptEngine.java:677)
    ... 27 common frames omitted
08:54:07 WARN  org.apache.tinkerpop.gremlin.server.util.ServerGremlinExecutor - Could not initialize gremlin-groovy GremlinScriptEngine as init script could not be evaluated
java.util.concurrent.CompletionException: java.lang.IllegalArgumentException: gremlin-groovy is not an available GremlinScriptEngine
    at java.util.concurrent.CompletableFuture.reportJoin(CompletableFuture.java:375)
    at java.util.concurrent.CompletableFuture.join(CompletableFuture.java:1947)
    at org.apache.tinkerpop.gremlin.server.util.ServerGremlinExecutor.lambda$new$4(ServerGremlinExecutor.java:153)
    at java.util.LinkedHashMap$LinkedKeySet.forEach(LinkedHashMap.java:559)
    at org.apache.tinkerpop.gremlin.server.util.ServerGremlinExecutor.<init>(ServerGremlinExecutor.java:145)
    at org.apache.tinkerpop.gremlin.server.GremlinServer.<init>(GremlinServer.java:127)
    at org.apache.tinkerpop.gremlin.server.GremlinServer.<init>(GremlinServer.java:90)
    at org.janusgraph.graphdb.server.JanusGraphServer.start(JanusGraphServer.java:85)
    at org.janusgraph.graphdb.server.JanusGraphServer.main(JanusGraphServer.java:53)
Caused by: java.lang.IllegalArgumentException: gremlin-groovy is not an available GremlinScriptEngine
    at org.apache.tinkerpop.gremlin.jsr223.CachedGremlinScriptEngineManager.registerLookUpInfo(CachedGremlinScriptEngineManager.java:95)
    at org.apache.tinkerpop.gremlin.jsr223.CachedGremlinScriptEngineManager.getEngineByName(CachedGremlinScriptEngineManager.java:58)
    at org.apache.tinkerpop.gremlin.groovy.engine.GremlinExecutor.lambda$eval$0(GremlinExecutor.java:272)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:750)
08:54:07 WARN  org.apache.tinkerpop.gremlin.server.AbstractChannelizer - The org.apache.tinkerpop.gremlin.driver.ser.GryoMessageSerializerV3d0 serialization class is deprecated.
08:54:07 WARN  org.apache.tinkerpop.gremlin.server.AbstractChannelizer - The org.apache.tinkerpop.gremlin.driver.ser.GryoMessageSerializerV3d0 serialization class is deprecated.

Why it does not recognize the local host 127.0.0.1 : Error connecting to Node(endPoint=/127.0.0.1:9042, hostId=null, hashCode=2712615d) ? For this issue I open a second question into janusgraph-discussions