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HugeGraph configuration

1 Overview

The directory for the configuration files is hugegraph-release/conf, and all the configurations related to the service and the graph itself are located in this directory.

The main configuration files include gremlin-server.yaml, rest-server.properties, and hugegraph.properties.

The HugeGraphServer integrates the GremlinServer and RestServer internally, and gremlin-server.yaml and rest-server.properties are used to configure these two servers.

GremlinServer: GremlinServer accepts Gremlin statements from users, parses them, and then invokes the Core code.
RestServer: It provides a RESTful API that, based on different HTTP requests, calls the corresponding Core API. If the user’s request body is a Gremlin statement, it will be forwarded to GremlinServer to perform operations on the graph data.

Now let’s introduce these three configuration files one by one.

2. gremlin-server.yaml

The default content of the gremlin-server.yaml file is as follows:

# host and port of gremlin server, need to be consistent with host and port in rest-server.properties
#host: 127.0.0.1
#port: 8182

# timeout in ms of gremlin query
evaluationTimeout: 30000

channelizer: org.apache.tinkerpop.gremlin.server.channel.WsAndHttpChannelizer
# don't set graph at here, this happens after support for dynamically adding graph
graphs: {
}
scriptEngines: {
  gremlin-groovy: {
    staticImports: [
      org.opencypher.gremlin.process.traversal.CustomPredicates.*',
      org.opencypher.gremlin.traversal.CustomFunctions.*
    ],
    plugins: {
      org.apache.hugegraph.plugin.HugeGraphGremlinPlugin: {},
      org.apache.tinkerpop.gremlin.server.jsr223.GremlinServerGremlinPlugin: {},
      org.apache.tinkerpop.gremlin.jsr223.ImportGremlinPlugin: {
        classImports: [
          java.lang.Math,
          org.apache.hugegraph.backend.id.IdGenerator,
          org.apache.hugegraph.type.define.Directions,
          org.apache.hugegraph.type.define.NodeRole,
          org.apache.hugegraph.traversal.algorithm.CollectionPathsTraverser,
          org.apache.hugegraph.traversal.algorithm.CountTraverser,
          org.apache.hugegraph.traversal.algorithm.CustomizedCrosspointsTraverser,
          org.apache.hugegraph.traversal.algorithm.CustomizePathsTraverser,
          org.apache.hugegraph.traversal.algorithm.FusiformSimilarityTraverser,
          org.apache.hugegraph.traversal.algorithm.HugeTraverser,
          org.apache.hugegraph.traversal.algorithm.JaccardSimilarTraverser,
          org.apache.hugegraph.traversal.algorithm.KneighborTraverser,
          org.apache.hugegraph.traversal.algorithm.KoutTraverser,
          org.apache.hugegraph.traversal.algorithm.MultiNodeShortestPathTraverser,
          org.apache.hugegraph.traversal.algorithm.NeighborRankTraverser,
          org.apache.hugegraph.traversal.algorithm.PathsTraverser,
          org.apache.hugegraph.traversal.algorithm.PersonalRankTraverser,
          org.apache.hugegraph.traversal.algorithm.SameNeighborTraverser,
          org.apache.hugegraph.traversal.algorithm.ShortestPathTraverser,
          org.apache.hugegraph.traversal.algorithm.SingleSourceShortestPathTraverser,
          org.apache.hugegraph.traversal.algorithm.SubGraphTraverser,
          org.apache.hugegraph.traversal.algorithm.TemplatePathsTraverser,
          org.apache.hugegraph.traversal.algorithm.steps.EdgeStep,
          org.apache.hugegraph.traversal.algorithm.steps.RepeatEdgeStep,
          org.apache.hugegraph.traversal.algorithm.steps.WeightedEdgeStep,
          org.apache.hugegraph.traversal.optimize.ConditionP,
          org.apache.hugegraph.traversal.optimize.Text,
          org.apache.hugegraph.traversal.optimize.TraversalUtil,
          org.apache.hugegraph.util.DateUtil,
          org.opencypher.gremlin.traversal.CustomFunctions,
          org.opencypher.gremlin.traversal.CustomPredicate
        ],
        methodImports: [
          java.lang.Math#*,
          org.opencypher.gremlin.traversal.CustomPredicate#*,
          org.opencypher.gremlin.traversal.CustomFunctions#*
        ]
      },
      org.apache.tinkerpop.gremlin.jsr223.ScriptFileGremlinPlugin: {
        files: [scripts/empty-sample.groovy]
      }
    }
  }
}
serializers:
  - { className: org.apache.tinkerpop.gremlin.driver.ser.GraphBinaryMessageSerializerV1,
      config: {
        serializeResultToString: false,
        ioRegistries: [org.apache.hugegraph.io.HugeGraphIoRegistry]
      }
  }
  - { className: org.apache.tinkerpop.gremlin.driver.ser.GraphSONMessageSerializerV1d0,
      config: {
        serializeResultToString: false,
        ioRegistries: [org.apache.hugegraph.io.HugeGraphIoRegistry]
      }
  }
  - { className: org.apache.tinkerpop.gremlin.driver.ser.GraphSONMessageSerializerV2d0,
      config: {
        serializeResultToString: false,
        ioRegistries: [org.apache.hugegraph.io.HugeGraphIoRegistry]
      }
  }
  - { className: org.apache.tinkerpop.gremlin.driver.ser.GraphSONMessageSerializerV3d0,
      config: {
        serializeResultToString: false,
        ioRegistries: [org.apache.hugegraph.io.HugeGraphIoRegistry]
      }
  }
metrics: {
  consoleReporter: {enabled: false, interval: 180000},
  csvReporter: {enabled: false, interval: 180000, fileName: ./metrics/gremlin-server-metrics.csv},
  jmxReporter: {enabled: false},
  slf4jReporter: {enabled: false, interval: 180000},
  gangliaReporter: {enabled: false, interval: 180000, addressingMode: MULTICAST},
  graphiteReporter: {enabled: false, interval: 180000}
}
maxInitialLineLength: 4096
maxHeaderSize: 8192
maxChunkSize: 8192
maxContentLength: 65536
maxAccumulationBufferComponents: 1024
resultIterationBatchSize: 64
writeBufferLowWaterMark: 32768
writeBufferHighWaterMark: 65536
ssl: {
  enabled: false
}

There are many configuration options mentioned above, but for now, let’s focus on the following options: channelizer and graphs.

graphs: This option specifies the graphs that need to be opened when the GremlinServer starts. It is a map structure where the key is the name of the graph and the value is the configuration file path for that graph.
channelizer: The GremlinServer supports two communication modes with clients: WebSocket and HTTP (default). If WebSocket is chosen, users can quickly experience the features of HugeGraph using Gremlin-Console, but it does not support importing large-scale data. It is recommended to use HTTP for communication, as all peripheral components of HugeGraph are implemented based on HTTP.

By default, the GremlinServer serves at localhost:8182. If you need to modify it, configure the host and port settings.

host: The hostname or IP address of the machine where the GremlinServer is deployed. Currently, HugeGraphServer does not support distributed deployment, and GremlinServer is not directly exposed to users.
port: The port number of the machine where the GremlinServer is deployed.

Additionally, you need to add the corresponding configuration gremlinserver.url=http://host:port in rest-server.properties.

3. rest-server.properties

The default content of the rest-server.properties file is as follows:

# bind url
# could use '0.0.0.0' or specified (real)IP to expose external network access
restserver.url=http://127.0.0.1:8080
#restserver.enable_graphspaces_filter=false
# gremlin server url, need to be consistent with host and port in gremlin-server.yaml
#gremlinserver.url=http://127.0.0.1:8182

graphs=./conf/graphs

# The maximum thread ratio for batch writing, only take effect if the batch.max_write_threads is 0
batch.max_write_ratio=80
batch.max_write_threads=0

# configuration of arthas
arthas.telnet_port=8562
arthas.http_port=8561
arthas.ip=127.0.0.1
arthas.disabled_commands=jad

# authentication configs
# choose 'org.apache.hugegraph.auth.StandardAuthenticator' or a custom implementation
#auth.authenticator=

# for StandardAuthenticator mode
#auth.graph_store=hugegraph
# auth client config
#auth.remote_url=127.0.0.1:8899,127.0.0.1:8898,127.0.0.1:8897

# TODO: Deprecated & removed later (useless from version 1.5.0)
# rpc server configs for multi graph-servers or raft-servers
#rpc.server_host=127.0.0.1
#rpc.server_port=8091
#rpc.server_timeout=30

# rpc client configs (like enable to keep cache consistency)
#rpc.remote_url=127.0.0.1:8091,127.0.0.1:8092,127.0.0.1:8093
#rpc.client_connect_timeout=20
#rpc.client_reconnect_period=10
#rpc.client_read_timeout=40
#rpc.client_retries=3
#rpc.client_load_balancer=consistentHash

# raft group initial peers
#raft.group_peers=127.0.0.1:8091,127.0.0.1:8092,127.0.0.1:8093

# lightweight load balancing (beta)
server.id=server-1
server.role=master

# slow query log
log.slow_query_threshold=1000

# jvm(in-heap) memory usage monitor, set 1 to disable it
memory_monitor.threshold=0.85
memory_monitor.period=2000

restserver.url: The URL at which the RestServer provides its services. Modify it according to the actual environment. If you can’t connet to server from other IP address, try to modify it as specific IP; or modify it as http://0.0.0.0 to listen all network interfaces as a convenient solution, but need to take care of the network area that might access.
graphs: The RestServer also needs to open graphs when it starts. This option is a map structure where the key is the name of the graph and the value is the configuration file path for that graph.

Note: Both gremlin-server.yaml and rest-server.properties contain the graphs configuration option, and the init-store command initializes based on the graphs specified in the graphs section of gremlin-server.yaml.

The gremlinserver.url configuration option is the URL at which the GremlinServer provides services to the RestServer. By default, it is set to http://localhost:8182. If you need to modify it, it should match the host and port settings in gremlin-server.yaml.

4. hugegraph.properties

hugegraph.properties is a type of file. If the system has multiple graphs, there will be multiple similar files. This file is used to configure parameters related to graph storage and querying. The default content of the file is as follows:

# gremlin entrence to create graph
gremlin.graph=org.apache.hugegraph.HugeFactory

# cache config
#schema.cache_capacity=100000
# vertex-cache default is 1000w, 10min expired
#vertex.cache_capacity=10000000
#vertex.cache_expire=600
# edge-cache default is 100w, 10min expired
#edge.cache_capacity=1000000
#edge.cache_expire=600

# schema illegal name template
#schema.illegal_name_regex=\s+|~.*

#vertex.default_label=vertex

backend=rocksdb
serializer=binary

store=hugegraph

raft.mode=false
raft.safe_read=false
raft.use_snapshot=false
raft.endpoint=127.0.0.1:8281
raft.group_peers=127.0.0.1:8281,127.0.0.1:8282,127.0.0.1:8283
raft.path=./raft-log
raft.use_replicator_pipeline=true
raft.election_timeout=10000
raft.snapshot_interval=3600
raft.backend_threads=48
raft.read_index_threads=8
raft.queue_size=16384
raft.queue_publish_timeout=60
raft.apply_batch=1
raft.rpc_threads=80
raft.rpc_connect_timeout=5000
raft.rpc_timeout=60000

# if use 'ikanalyzer', need download jar from 'https://github.com/apache/hugegraph-doc/raw/ik_binary/dist/server/ikanalyzer-2012_u6.jar' to lib directory
search.text_analyzer=jieba
search.text_analyzer_mode=INDEX

# rocksdb backend config
#rocksdb.data_path=/path/to/disk
#rocksdb.wal_path=/path/to/disk

# cassandra backend config
cassandra.host=localhost
cassandra.port=9042
cassandra.username=
cassandra.password=
#cassandra.connect_timeout=5
#cassandra.read_timeout=20
#cassandra.keyspace.strategy=SimpleStrategy
#cassandra.keyspace.replication=3

# hbase backend config
#hbase.hosts=localhost
#hbase.port=2181
#hbase.znode_parent=/hbase
#hbase.threads_max=64

# mysql backend config
#jdbc.driver=com.mysql.jdbc.Driver
#jdbc.url=jdbc:mysql://127.0.0.1:3306
#jdbc.username=root
#jdbc.password=
#jdbc.reconnect_max_times=3
#jdbc.reconnect_interval=3
#jdbc.ssl_mode=false

# postgresql & cockroachdb backend config
#jdbc.driver=org.postgresql.Driver
#jdbc.url=jdbc:postgresql://localhost:5432/
#jdbc.username=postgres
#jdbc.password=

# palo backend config
#palo.host=127.0.0.1
#palo.poll_interval=10
#palo.temp_dir=./palo-data
#palo.file_limit_size=32

Pay attention to the following uncommented items:

gremlin.graph: The entry point for GremlinServer startup. Users should not modify this item.
backend: The backend storage used, with options including memory, cassandra, scylladb, mysql, hbase, postgresql, and rocksdb.
serializer: Mainly for internal use, used to serialize schema, vertices, and edges to the backend. The corresponding options are text, cassandra, scylladb, and binary (Note: The rocksdb backend should have a value of binary, while for other backends, the values of backend and serializer should remain consistent. For example, for the hbase backend, the value should be hbase).
store: The name of the database used for storing the graph in the backend. In Cassandra and ScyllaDB, it corresponds to the keyspace name. The value of this item is unrelated to the graph name in GremlinServer and RestServer, but for clarity, it is recommended to use the same name.
cassandra.host: This item is only meaningful when the backend is set to cassandra or scylladb. It specifies the seeds of the Cassandra/ScyllaDB cluster.
cassandra.port: This item is only meaningful when the backend is set to cassandra or scylladb. It specifies the native port of the Cassandra/ScyllaDB cluster.
rocksdb.data_path: This item is only meaningful when the backend is set to rocksdb. It specifies the data directory for RocksDB.
rocksdb.wal_path: This item is only meaningful when the backend is set to rocksdb. It specifies the log directory for RocksDB.
admin.token: A token used to retrieve server configuration information. For example: http://localhost:8080/graphs/hugegraph/conf?token=162f7848-0b6d-4faf-b557-3a0797869c55

5. Multi-Graph Configuration

Our system can have multiple graphs, and the backend of each graph can be different, such as hugegraph_rocksdb and hugegraph_mysql, where hugegraph_rocksdb uses RocksDB as the backend, and hugegraph_mysql uses MySQL as a backend.

The configuration method is simple:

[Optional]: Modify rest-server.properties

You can modify the graph profile directory in the graphs option of rest-server.properties. The default configuration is graphs=./conf/graphs, if you want to change it to another directory then adjust the graphs option, e.g. adjust it to graphs=/etc/hugegraph/graphs, example is as follows:

graphs=./conf/graphs

Modify hugegraph_mysql_backend.properties and hugegraph_rocksdb_backend.properties based on hugegraph.properties under conf/graphs path

The modified part of hugegraph_mysql_backend.properties is as follows:

backend=mysql
serializer=mysql

store=hugegraph_mysql

# mysql backend config
jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306
jdbc.username=root
jdbc.password=xxx
jdbc.reconnect_max_times=3
jdbc.reconnect_interval=3
jdbc.ssl_mode=false

The modified part of hugegraph_rocksdb_backend.properties is as follows:

backend=rocksdb
serializer=binary

store=hugegraph_rocksdb

Stop the server, execute init-store.sh (to create a new database for the new graph), and restart the server.

$ ./bin/stop-hugegraph.sh

$ ./bin/init-store.sh

Initializing HugeGraph Store...
2023-06-11 14:16:14 [main] [INFO] o.a.h.u.ConfigUtil - Scanning option 'graphs' directory './conf/graphs'
2023-06-11 14:16:14 [main] [INFO] o.a.h.c.InitStore - Init graph with config file: ./conf/graphs/hugegraph_rocksdb_backend.properties
...
2023-06-11 14:16:15 [main] [INFO] o.a.h.StandardHugeGraph - Graph 'hugegraph_rocksdb' has been initialized
2023-06-11 14:16:15 [main] [INFO] o.a.h.c.InitStore - Init graph with config file: ./conf/graphs/hugegraph_mysql_backend.properties
...
2023-06-11 14:16:16 [main] [INFO] o.a.h.StandardHugeGraph - Graph 'hugegraph_mysql' has been initialized
2023-06-11 14:16:16 [main] [INFO] o.a.h.StandardHugeGraph - Close graph standardhugegraph[hugegraph_rocksdb]
...
2023-06-11 14:16:16 [main] [INFO] o.a.h.HugeFactory - HugeFactory shutdown
2023-06-11 14:16:16 [hugegraph-shutdown] [INFO] o.a.h.HugeFactory - HugeGraph is shutting down
Initialization finished.

$ ./bin/start-hugegraph.sh

Starting HugeGraphServer...
Connecting to HugeGraphServer (http://127.0.0.1:8080/graphs)...OK
Started [pid 21614]

Check out created graphs:

curl http://127.0.0.1:8080/graphs/

{"graphs":["hugegraph_rocksdb","hugegraph_mysql"]}

Get details of the graph

curl http://127.0.0.1:8080/graphs/hugegraph_mysql_backend

{"name":"hugegraph_mysql","backend":"mysql"}

curl http://127.0.0.1:8080/graphs/hugegraph_rocksdb_backend

{"name":"hugegraph_rocksdb","backend":"rocksdb"}