24.2. Server Configuration

Important server configurations parameters

The main configuration file for the server can be found at conf/neo4j-server.properties. This file contains several important settings, and although the defaults are sensible administrators might choose to make changes (especially to the port settings).

Set the location on disk of the database directory like this:

org.neo4j.server.database.location=data/graph.db
[Note]Note

On Windows systems, absolute locations including drive letters need to read "c:/data/db".

Specify the HTTP server port supporting data, administrative, and UI access:

org.neo4j.server.webserver.port=7474

Specify the client accept pattern for the webserver (default is 127.0.0.1, localhost only):

#allow any client to connect
org.neo4j.server.webserver.address=0.0.0.0

For securing the Neo4j Server, see also Chapter 27, Security

Set the location of the round-robin database directory which gathers metrics on the running server instance:

org.neo4j.server.webadmin.rrdb.location=data/graph.db/../rrd

Set the URI path for the REST data API through which the database is accessed. This should be a relative path.

org.neo4j.server.webadmin.data.uri=/db/data/

Setting the management URI for the administration API that the Webadmin tool uses. This should be a relative path.

org.neo4j.server.webadmin.management.uri=/db/manage

Force the server to use IPv4 network addresses, in conf/neo4j-wrapper.conf under the section Java Additional Parameters add a new paramter:

wrapper.java.additional.3=-Djava.net.preferIPv4Stack=true

Specify the number of threads used by the Neo4j Web server to control the level of concurrent HTTP requests that the server will service.

org.neo4j.server.webserver.maxthreads=200
[Note]Note

The default value is the number of CPUs reported available by the JVM, limited to a maximum of 500. The limit can be exceeded by specifying a larger value.

The server guards against orphaned transactions by using a timeout. If there are no requests for a given transaction within the timeout period, the server will roll it back. You can configure the timeout period by setting the following property to the number of seconds before timeout. The default timeout is 60 seconds.

org.neo4j.server.transaction.timeout=60

Low-level performance tuning parameters can be explicitly set by referring to the following property:

org.neo4j.server.db.tuning.properties=neo4j.properties

If this property isn’t set, the server will look for a file called neo4j.properties in the same directory as the neo4j-server.properties file.

If this property isn’t set, and there is no neo4j.properties file in the default configuration directory, then the server will log a warning. Subsequently at runtime the database engine will attempt tune itself based on the prevailing conditions.

Neo4j Database performance configuration

The fine-tuning of the low-level Neo4j graph database engine is specified in a separate properties file, conf/neo4j.properties.

The graph database engine has a range of performance tuning options which are enumerated in Section 24.3, “Server Performance Tuning”. Note that other factors than Neo4j tuning should be considered when performance tuning a server, including general server load, memory and file contention, and even garbage collection penalties on the JVM, though such considerations are beyond the scope of this configuration document.

Server logging configuration

Application events within Neo4j server are processed with java.util.logging and configured in the file conf/logging.properties.

By default it is setup to print INFO level messages both on screen and in a rolling file in data/log. Most deployments will choose to use their own configuration here to meet local standards. During development, much useful information can be found in the logs so some form of logging to disk is well worth keeping. On the other hand, if you want to completely silence the console output, set:

java.util.logging.ConsoleHandler.level=OFF

By default log files are rotated at approximately 10Mb and named consecutively neo4j.<id>.<rotation sequence #>.log To change the naming scheme, rotation frequency and backlog size modify

java.util.logging.FileHandler.pattern
java.util.logging.FileHandler.limit
java.util.logging.FileHandler.count

respectively to your needs. Details are available at the Javadoc for java.util.logging.FileHandler.

Apart from log statements originating from the Neo4j server, other libraries report their messages through various frameworks.

HTTP logging configuration

As well as logging events happening within the Neo4j server, it is possible to log the HTTP requests and responses that the server consumes and produces. Configuring HTTP logging requires operators to enable and configure the logger and where it will log; and then to optionally configure the log format.

[Warning]Warning

By default the HTTP logger uses Common Log Format meaning that most Web server tooling can automtically consume such logs. In general users should only enable HTTP logging, select an output directory, and if necessary alter the rollover and retention policies.

To enable HTTP logging, edit the conf/neo4j-server.properties file to resemble the following:

org.neo4j.server.http.log.enabled=true
org.neo4j.server.http.log.config=conf/neo4j-http-logging.xml

org.neo4j.server.http.log.enabled=true tells the server that HTTP logging is enabled. HTTP logging can be totally disabled by setting this property to false. org.neo4j.server.http.log.config=conf/neo4j-http-logging.xml specifies the logging format and rollover policy file that governs how HTTP log output is presented and archived. The defaults provided with Neo4j server uses an hourly log rotation and Common Log Format.

If logging is set up to use log files then the server will check that the log file directory exists and is writable. If this check fails, then the server will not startup and wil report the failure another available channel like standard out.

Using X-Forwarded-Proto and X-Forwarded-Host to parameterize the base URI for REST responses

There are occasions, for example when you want to host Neo4j server behind a proxy (e.g. one that handles HTTPS traffic), and still have Neo4j respect the base URI of that externally visible proxy.

Ordinarily Neo4j uses the HOST header of the HTTP request to construct URIs in its responses. Where a proxy is involved however, this is often undesirable. Instead Neo4j, uses the X-Forwarded-Host and X-Forwarded-Proto headers provided by proxies to parameterize the URIs in the responses from the database’s REST API. From the outside it looks as if the proxy generated that payload. If an X-Forwarded-Host header value contains more than one address (X-Forwarded-Host allows comma-and-space separated lists of addresses), Neo4j picks the first, which represents the client request.

In order to take advantage of this functionality, your proxy server must be configured to transmit these headers to the Neo4j server. Failure to transmit both X-Forwarded-Host and X-Forwarded-Proto headers will result in the original base URI being used.

Other configuration options

Enabling logging from the garbage collector

To get garbage collection logging output you have to pass the corresponding option to the server JVM executable by setting in conf/neo4j-wrapper.conf the value

wrapper.java.additional.3=-Xloggc:data/log/neo4j-gc.log

This line is already present and needs uncommenting. Note also that logging is not directed to console ; You will find the logging statements in data/log/ne4j-gc.log or whatever directory you set at the option.

Disabling console types in Webadmin

You may, for security reasons, want to disable the the Neo4j Shell in Webadmin. Shells allow arbitrary code execution, and so they could constitute a security risk if you do not trust all users of your Neo4j Server.

In the conf/neo4j-server.properties file:

# To disable all shells:
org.neo4j.server.manage.console_engines=

# To enable only the Neo4j Shell:
org.neo4j.server.manage.console_engines=shell