Titan: Lessons learned

Titan is dead. You want JanusGraph instead.

Sources for the Dockerfile and surroundings:

• efaurie/docker-titan-cassandra
• elubow/titan-gremlin

For multiple graphs in Titan, follow these links:

• How many graphs can i create in one Titan DB?
• Serving multiple Titan graphs over Gremlin Server (TinkerPop 3)
• One graph in one Titan instance

Cassandra and Elasticsearch

As per compatibility matrix, the supported Cassandra version is 2.1 and the supported Elasticsearch version is 1.5.

Shell

In the Gremin REPL examples like this one:

$  bin/gremlin.sh
         \,,,/
         (o o)
-----oOOo-(3)-oOOo-----
plugin activated: tinkerpop.server
plugin activated: tinkerpop.hadoop
plugin activated: tinkerpop.utilities
plugin activated: aurelius.titan
plugin activated: tinkerpop.tinkergraph
gremlin> :remote connect tinkerpop.server conf/remote.yaml
==>Connected - localhost/127.0.0.1:8182
gremlin> :> graph.addVertex("name", "stephen")
==>v[256]
gremlin> :> g.V().values('name')
==>stephen

The token :> is not part of the shell, but an actual command. It is required to run the command on the remote server. Also, entering invalid commands in the shell results in an exception on the server.

Channelizers

Using the HttpChannelizer

channelizer: org.apache.tinkerpop.gremlin.server.channel.HttpChannelizer

allows for HTTP access to Titan using e.g.

curl "http://localhost:8182/?gremlin=100-1"

However, this seems to prevent the Gremlin REPL shell from talking to the server:

Jul 17, 2017 10:52:00 PM java.util.prefs.FileSystemPreferences$1 run
INFO: Created user preferences directory.

         \,,,/
         (o o)
-----oOOo-(3)-oOOo-----
plugin activated: aurelius.titan
plugin activated: tinkerpop.server
plugin activated: tinkerpop.utilities
plugin activated: tinkerpop.hadoop
plugin activated: tinkerpop.tinkergraph
gremlin> :remote connect tinkerpop.server conf/remote.yaml
22:52:14 WARN  org.apache.tinkerpop.gremlin.driver.handler.WebSocketClientHandler  - Exception caught during WebSocket processing - closing connection
io.netty.handler.codec.http.websocketx.WebSocketHandshakeException: Invalid handshake response getStatus: 400 Bad Request
	at io.netty.handler.codec.http.websocketx.WebSocketClientHandshaker13.verify(WebSocketClientHandshaker13.java:182)
	at io.netty.handler.codec.http.websocketx.WebSocketClientHandshaker.finishHandshake(WebSocketClientHandshaker.java:202)
	at org.apache.tinkerpop.gremlin.driver.handler.WebSocketClientHandler.channelRead0(WebSocketClientHandler.java:73)
	at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:308)
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:294)
	at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:103)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:308)
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:294)
	at io.netty.handler.codec.ByteToMessageDecoder.channelInactive(ByteToMessageDecoder.java:241)
	at io.netty.handler.codec.http.HttpClientCodec$Decoder.channelInactive(HttpClientCodec.java:212)
	at io.netty.channel.CombinedChannelDuplexHandler.channelInactive(CombinedChannelDuplexHandler.java:132)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:208)
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelInactive(AbstractChannelHandlerContext.java:194)
	at io.netty.channel.DefaultChannelPipeline.fireChannelInactive(DefaultChannelPipeline.java:828)
	at io.netty.channel.AbstractChannel$AbstractUnsafe$5.run(AbstractChannel.java:576)
	at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:380)
	at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:357)
	at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:116)
	at java.lang.Thread.run(Thread.java:748)
22:52:14 ERROR org.apache.tinkerpop.gremlin.driver.Handler$GremlinResponseHandler  - Could not process the response - correct the problem and restart the driver.

The REPL shell does seem to work with the WebSocketChannelizer though:

channelizer: org.apache.tinkerpop.gremlin.server.channel.WebSocketChannelizer