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Configuration

For the purposes of the following examples, no additional configuration is necessary. But for deploying a production Neo4j server, there are settings within the conf/neo4j.conf file that are desirable or necessary to be altered.

The underlying database filename can be changed from its default setting of graph.db:

# The name of the database to mount
  dbms.active_database=graph.db

The section after the database name configuration is where things such as the data, certificates, and log directories can be defined. Remember that all locations defined here are relative, so make sure to explicitly define any paths that may be required to be located somewhere other than the Neo4j home directory:

# Paths of directories in the installation.
#dbms.directories.data=data
#dbms.directories.plugins=plugins
#dbms.directories.certificates=certificates
#dbms.directories.logs=logs
#dbms.directories.lib=lib
#dbms.directories.run=run

The configuration properties in the preceding example are all prefaced with a hash sign (#) or commented out. To change them, first remove the hash sign, and then alter the value. If you're changing these properties on an already-running instance, be sure to restart the Neo4j process as well.

For instance, if we wanted to put the data or log location on a different directory or mount point (data0 off of root and /var/log, respectively), we could define them like this:

dbms.directories.data=/data0
dbms.directories.logs=/var/log/neo4j

Our instance should be able to accept connections from machines other than the localhost (127.0.0.1), so we'll also set the default_listen_address and default_advertised_address. These settings can be modified in the network connector configuration section of the neo4j.conf file:

dbms.connectors.default_listen_address=192.168.0.100
dbms.connectors.default_advertised_address=192.168.0.100

The default connector ports can be changed as well. Client connections will need the Bolt protocol enabled. By default, it is defined to connect on port 7687:

#Bolt connector
dbms.connector.bolt.enabled=true
dbms.connector.bolt.listen_address=:7687

Note that if you disable the bolt connector, then client applications will only be able to connect to Neo4j using the REST API. The web management interface and REST API use HTTP/HTTPS, so they connect (by default) on ports 7474 and 7473, respectively. These ports can also be altered:

# HTTP Connector. There must be exactly one HTTP connector.
dbms.connector.http.enabled=true
dbms.connector.http.listen_address=:7474
# HTTPS Connector. There can be zero or one HTTPS connectors.
dbms.connector.https.enabled=true
dbms.connector.https.listen_address=:7473

Now is also a good time to change the initial password. Neo4j installs with a single default admin username and password of neo4j/neo4j. To change the password, we can use the following command:

bin/neo4j-admin set-initial-password flynnLives

This command only works if you have not yet started Neo4j for the first time.

By default, Neo4j installs with the Usage Data Collector (UDC) enabled.^[7] The UDC collects data concerning your usage and installation, tars it up and sends it to udc.neo4j.org. A full description of the data collected can be found at http://neo4j.com/docs/operations-manual/current/configuration/usage-data-collector/.

To disable this feature, simply add this line to the bottom of your neo4j.conf file:

dbms.udc.enabled=false

While the default JVM settings should be fine for most single-instance Neo4j clusters, larger operational workloads may require the tuning of various settings. Some bulk-load operations may not complete successfully if the JVM stack size is too small. To adjust it (say, to 1 MB), add the following line to the end of the neo4j.conf file:

dbms.jvm.additional=-Xss1M

The default garbage collector for Neo4j is the Concurrent Mark and Sweep (CMS) garbage collector. As Neo4j typically recommends larger heap sizes for production (20 GB+), performance can be improved by using the garbage-first garbage collector (G1GC). For example, to enable G1GC with a 24 GB heap and a target pause time of 200 ms, add the following settings to your neo4j.conf file:

dbms.memory.heap.max_size=24G
dbms.memory.heap.initial_size=24G
dbms.jvm.additional=-XX:+UseG1GC
dbms.jvm.additional=-XX:MaxGCPauseMillis=200

Note that regardless of the choice of the garbage collector and its settings, Neo4j should be tested under the production load to ensure that performance is within desirable levels. Be sure to keep track of GC behaviors and trends, and make adjustments as necessary.