Recommendations for recovery upon Out Of Memory error

It is possible to configure the JVM (Java Virtual Machine) such that upon encountering an OOM (Out-Of-Memory) error it will force an exception and crash or simply shut down the application. Taking action upon first OOM occurrence can help in… Read more →

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Retired: Changing your Garbage Collection Method to G1

Note This is already the default Garbage Collector in Neo4j 2.3+. This guide is only intended for previous versions. When to Use G1: By default, Neo4j versions 2.2 and earlier use Concurrent Mark and Sweep (CMS) for garbage collection. Customers… Read more →

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How to estimate initial memory configuration

The initial and eventual memory configuration parameters can be a moving target, based on how your store changes in size and how your workload increases or changes over time. This guidance is meant for the initial configuration. In order to… Read more →

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Long GC Pauses caused by application code calling System.gc()

When investigating the cause of long garbage collection cycles, it is often useful to enable GC logging. You can do so by following the product documentation. Once this is enabled, you can look through the GC log file for signs… Read more →

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Getting a JVM heap dump

This document provides the process of creating a heap-dump on a java machine to investigate potential memory leaks. Although a heap dump will be auto generated when OutOfMemoryError is thrown by specifying -XX:+HeapDumpOnOutOfMemoryError VM option, we can use the jmap… Read more →

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How do I enable Java Flight Recorder and view the Results

Java Flight Recorder can be used to capture low level Java properties and run-time data about Java processes, for example Neo4j. Per https://docs.oracle.com/javase/8/docs/technotes/guides/troubleshoot/tooldescr002.html The Java Flight Recorder (JFR) is a commercial feature. You can use it for free on developer… Read more →

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Enabling GC Logging

What is Garbage collection and why enabling it? A garbage collection event is a complete pause of the java application (ie: neo4j-server). It can be identified in the debug.log as a stop-the-world event. For example: If you notice issues with… Read more →

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