`mvnd` - the Maven Daemon

Table of Contents

Introduction
Additional features
How to install mvnd
Usage
mvnd specific options
Configuration
Build mvnd from source

Introduction

This project aims at providing faster Maven builds using techniques known from Gradle and Takari.

Architecture overview:

mvnd embeds Maven (so there is no need to install Maven separately).
The actual builds happen inside a long living background process, a.k.a. daemon.
One daemon instance can serve multiple consecutive requests from the mvnd client.
The mvnd client is a native executable built using GraalVM. It starts faster and uses less memory compared to starting a traditional JVM.
Multiple daemons can be spawned in parallel if there is no idle daemon to serve a build request.

This architecture brings the following advantages:

The JVM for running the actual builds does not need to get started anew for each build.
The classloaders holding classes of Maven plugins are cached over multiple builds. The plugin jars are thus read and parsed just once. SNAPSHOT versions of Maven plugins are not cached.
The native code produced by the Just-In-Time (JIT) compiler inside the JVM is kept too. Compared to stock Maven, less time is spent by the JIT compilation. During the repeated builds the JIT-optimized code is available immediately. This applies not only to the code coming from Maven plugins and Maven Core, but also to all code coming from the JDK itself.

Additional features

mvnd brings the following features on top of the stock Maven:

By default, mvnd is building your modules in parallel using multiple CPU cores. The number of utilized cores is given by the formula Math.max(Runtime.getRuntime().availableProcessors() - 1, 1). If your source tree does not support parallel builds, pass -T1 on the command line to make your build serial.
Improved console output: we believe that the output of a parallel build on a stock Maven is hard to follow. Therefore, we implemented a simplified a non-rolling view showing the status of each build thread on a separate line. This is what it looks like on a machine with 24 cores:

Once the build is finshed, the complete Maven output is forwarded to the console.

How to install `mvnd`

Install using SDKMAN!

If SDKMAN! supports your operating system, it is as easy as

$ sdk install mvnd

If you used the manual install in the past, please make sure that the settings in ~/.m2/mvnd.properties still make sense. With SDKMAN!, the ~/.m2/mvnd.properties file is typically not needed at all, because both JAVA_HOME and MVND_HOME are managed by SDKMAN!.

Install using Homebrew

$ brew install mvndaemon/homebrew-mvnd/mvnd

Install using MacPorts

$ sudo port install mvnd

Install using Chocolatey

$ choco install mvndaemon

Set up completion

Optionally, you can set up completion as follows:

# ensure to set MVND_HOME to point to your mvnd distribution, note that sdkman does it for you
$ echo 'source $MVND_HOME/bin/mvnd-bash-completion.bash' >> ~/.bashrc

bash is the only shell supported at this time.

Note for oh-my-zsh users

Users that use oh-my-zsh often use completion for maven. The default maven completion plugin defines mvnd as an alias to mvn deploy. So before being able to use mvnd, you need to unalias using the following command:

$ unalias mvnd

Install manually

Download the latest ZIP suitable for your platform from https://github.com/mvndaemon/mvnd/releases
Unzip to a directory of your choice
Add the bin directory to PATH
Optionally, you can create ~/.m2/mvnd.properties and set the java.home property in case you do not want to bother with setting JAVA_HOME environment variable.

Test whether mvnd works:

$ mvnd --version
Maven Daemon 0.0.11-linux-amd64 (native)
Terminal: org.jline.terminal.impl.PosixSysTerminal with pty org.jline.terminal.impl.jansi.osx.OsXNativePty
Apache Maven 3.6.3 (cecedd343002696d0abb50b32b541b8a6ba2883f)
Maven home: /home/ppalaga/orgs/mvnd/mvnd/daemon/target/maven-distro
Java version: 11.0.1, vendor: AdoptOpenJDK, runtime: /home/data/jvm/adopt-openjdk/jdk-11.0.1+13
Default locale: en_IE, platform encoding: UTF-8
OS name: "linux", version: "5.6.13-200.fc31.x86_64", arch: "amd64", family: "unix"

If you are on Windows and see a message that VCRUNTIME140.dll was not found, you need to install vc_redist.x64.exe from https://support.microsoft.com/en-us/help/2977003/the-latest-supported-visual-c-downloads. See oracle/graal#1762 for more information.

Usage

mvnd is designed to accept the same command line options like stock mvn (plus some extras - see below), e.g.:

mvnd clean install

`mvnd` specific options

--status lists running daemons

--stop kills all running daemons

The complete list of options is printed when executing mvnd --help.

Configuration

Configuration can be provided through properties file. Mvnd read properties file from the following locations:

the properties path supplied using MVND_PROPERTIES_PATH environment variable or mvnd.propertiesPath system variable
the local properties path located at [PROJECT_HOME]/.mvn/mvnd.properties
the user properties path located at: [USER_HOME]/.m2/mvnd.properties
the system properties path located at: [MVND_HOME]/conf/mvnd.properties

Properties defined in the first files will take precedence over properties specified in a lower ranked file.

A few special properties do not follow the above mechanism:

mvnd.daemonStorage: this property defines the location where mvnd stores its files (registry and daemon logs). This property can only be defined as a system property on the command line
mvnd.id: this property is used internally to identify the daemon being created
mvnd.extClasspath: internal option to specify the maven extension classpath
mvnd.coreExtensions: internal option to specify the list of maven extension to register

For a full list of available properties please see /dist/src/main/distro/conf/mvnd.properties.

Build `mvnd` from source

Prerequisites:

git
Maven
Download and unpack GraalVM CE from GitHub

Set JAVA_HOME to where you unpacked GraalVM in the previous step. Check that java -version output is as expected:

$ $JAVA_HOME/bin/java -version
openjdk version "11.0.9" 2020-10-20
OpenJDK Runtime Environment GraalVM CE 20.3.0 (build 11.0.9+10-jvmci-20.3-b06)
OpenJDK 64-Bit Server VM GraalVM CE 20.3.0 (build 11.0.9+10-jvmci-20.3-b06, mixed mode, sharing)

Install the native-image tool:

$ $JAVA_HOME/bin/gu install native-image

native-image may require additional software to be installed depending on your platform - see the native-image documentation.

Build `mvnd`

$ git clone https://github.com/mvndaemon/mvnd.git
$ cd mvnd
$ mvn clean verify -Pnative
...
$ cd client
$ file target/mvnd
target/mvnd: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=93a554f3807550a13c986d2af9a311ef299bdc5a, for GNU/Linux 3.2.0, with debug_info, not stripped
$ ls -lh target/mvnd
-rwxrwxr-x. 1 ppalaga ppalaga 25M Jun  2 13:23 target/mvnd

Install `mvnd`

$ cp -R dist/target/mvnd-[version] [target-dir]

Then you can simply run add [target-dir]/bin to your PATH and run mvnd.

We’re happy to improve mvnd, so feedback is most welcomed!

sweetcard/maven-mvnd

mvnd - the Maven Daemon