systemProperties.adoc

Chronicle System Properties Guide

This document lists Java system properties that influence Chronicle libraries such as Chronicle Wire and Chronicle Core. These options are commonly used for debugging or performance tuning.

Note	Boolean properties are parsed with net.openhft.chronicle.core.Jvm.getBoolean(String, boolean). A property is true when the key is present (e.g. -Dprop) or set to true/yes. To change a non-default value, provide the opposite value explicitly.

Warning

Changing these settings can affect behaviour and performance. Use them mainly for development and debugging unless advised otherwise.

Table of Contents

• 1. Core and Wire System Properties
• 2. Important Considerations

1. Core and Wire System Properties

Table 1. System Properties Details

Property Key (System Property Name)	Default Value	Description & Use Case	Corresponding Java Variable (Conceptual)
dumpCode	false	Prints generated bytecode or other internals such as WireMarshaller implementations when enabled. Useful for in depth debugging of dynamic code generation.	Jvm.getBoolean("dumpCode") → DUMP_CODE
mappedFile.retain	false	When enabled, mapped file components attempt to retain file mappings which can alter cleanup on JVM exit (notably on Windows where files may remain locked).	Jvm.getBoolean("mappedFile.retain") → RETAIN
regress.tests	false	Activates behaviour used by regression tests within the Chronicle test suites.	Jvm.getBoolean("regress.tests") → REGRESS_TESTS
wire.generate.tuples	false	Alters serialisation of some complex Marshallable objects to use a tuple style representation. Useful for inspecting field order in text based wire formats.	Wires.GENERATE_TUPLES
wire.method.prependPackage	false	Generated MethodWriter proxies will have their package name prefixed, aiding in debugging generated classes.	Wires.PREPEND_PACKAGE
wire.testAsYaml	false	Forces certain tests to write data in YAML instead of binary formats, making messages human readable.	Wires.TEXT_AS_YAML
wire.usePadding	true	Controls alignment padding in binary wire formats. Disable with -Dwire.usePadding=false if message size is critical at the cost of potential performance impact.	Wires.DEFAULT_USE_PADDING
yaml.logging	false	Enables logging of YAML formatted messages for debugging or documentation purposes.	YamlLogging.getYamlLogging() (or similar)

2. Important Considerations

Version Specificity

Defaults and behaviour can change between Chronicle releases. Check the version of the library you use.

Performance Impact

Properties that enable additional logging or code generation tracing (like dumpCode or yaml.logging) can slow down your application.

Testing

Include any required system property values in your test configuration to ensure consistent behaviour.