Knowledge Base

Use Java Runtime 11 with Neo4J 3.5.x

Neo4j 3.5.x supports Java 11 as runtime, however custom code should still be compiled against Java 8. As a best practice, it is recommended to maintain your infrastructure environment on supported components (Hypervisor, Operating System, Java Virtual Machine). In this example, we will show you how to upgrade the Java JDK from version 8 to Java JDK 11 on Linux.

Java JDK 11 Installation

The first step is to install Java 11, you can refer to your preferred vendor instructions. We recommend to use a JDK to be able to run Neo4j in production. Java diagnostic commands might be required when engaging Neo4J support:

  • neo4j-admin report command requires a JDK.

  • jstack or jmap dumps the heap memory into a file which can be requested to troubleshoot issues.

  • jfr : profiling tool used to gather diagnostics and profiling data from a running Java application. It is available for free since java 11.

At this stage, Java 8 will still be used. It is allowed to have multiple JVM installations on the same machine.

java -version will still display Java 8.

Switch to Java 11 as default

To use Java 11 runtime by default,

For RedHat, CentOS, Fedora, Amazon AMI: run sudo alternatives --config java For Debian-based systems, Debian, Ubuntu, Suse: run sudo update-alternatives --config java

Pick the right version and press enter. There are 2 installed binaries that provides 'java' in this example:

$ sudo alternatives --config java

Selection    Command
1           java-1.8.0-openjdk.x86_64 (/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.252.b09-2.amzn2.0.1.x86_64/jre/bin/java)
2           /usr/lib/jvm/java-11-amazon-corretto/bin/java

Choose the second option and press enter to validate.

java -version should now display Java 11.

Edit Neo4J.conf

  • Comment or remove the following line:

dbms.logs.gc.options=-XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+PrintGCApplicationStoppedTime -XX:+PrintPromotionFailure -XX:+PrintTenuringDistribution

  • Uncomment the following setting:

dbms.logs.gc.options=-Xlog:gc,safepoint,age=trace

Start Neo4J

You will immediately see WARNING messages in your neo4j.log You can safely disregard them as shown below:

WARNING: Please consider reporting this to the maintainers of org.eclipse.collections.impl.utility.ArrayListIterate
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release