默认Titan是作为一个jar包依赖，本地调用。但是通过Titan Server可以提供远程服务。
Titan使用了Gremlin Server引擎作为服务器来提供服务，默认配置是使用WebSockets，但是我们可以配置成其他协议或者自己扩展实现。
下面是如何配置Titan Server，让其提供HTTP REST API：
1、If you’re starting from the titan-1.0.0-hadoop1.zip, I’d suggest making a copy of conf/gremlin-server/gremlin-server.yaml into conf/rest-gremlin-server.yaml. Also, copy conf/titan-cassandra.properties to conf/gremlin-server/titan-cassandra-server.properties
cp conf/gremlin-server/gremlin-server.yaml conf/rest-gremlin-server.yaml
cp conf/titan-cassandra.properties conf/gremlin-server/titan-cassandra-server.properties
2、If you’re planning to connect to Gremlin Server from something other than localhost, you’ll want to update the host with its IP address or 0.0.0.0 in rest-gremlin-server.yaml
host: 0.0.0.0
3、Configure the Gremlin Server for REST instead of WebSockets (refer to the Gremlin Server documentation). In the rest-gremlin-server.yaml, update the channelizer
channelizer: org.apache.tinkerpop.gremlin.server.channel.HttpChannelizer
4、Configure the Gremlin Server mapping with the Cassandra properties file with your graph configuration
graphs: {
graph: conf/gremlin-server/titan-cassandra-server.properties}
And also, be sure to start Gremlin Server with the configuration file：
./bin/gremlin-server.sh ./conf/gremlin-server/rest-gremlin-server.yaml
5、Update the titan-cassandra-server.properties with your specific Cassandra properties. In particular, you’ll want to update the keyspace name and possibly storage.hostname if Cassandra isn’t running on localhost.
storage.hostname=127.0.0.1
storage.cassandra.keyspace=TITAN_DEMO
6、Sending Gremlin to the Gremlin Server configured for REST is the same, regardless of the actual Gremlin query. Do a HTTP POST of a JSON object with a pair { “gremlin”: “g.V().count()” } to the Gremlin Server. Here’s what it looks like with a curl:
curl -XPOST -Hcontent-type:application/json -d '{"gremlin":"g.V().count()"}' http://localhost:8182
