mvnd - the Maven Daemon

Table of Contents

• Introduction
• Additional features
• How to install mvnd
  • Install using SDKMAN!
  • Install using Homebrew
  • Other installers
  • Set up completion
  • Note for oh-my-zsh users
  • Install manually
• Usage
• mvnd specific options
• Configuration
• Build mvnd from source
  • Prerequisites:
  • Build mvnd
  • Install mvnd

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 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 finished, 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

Other installers

We’re looking for contribution to support MacPorts, Chocolatey, Scoop or asdf. If you’re fancy helping us…​

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://downloads.apache.org/maven/mvnd/

• 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.

  If you are on macOS, you’ll need to remove the quarantine flags from all the files after unpacking the archive:

$ xattr -r -d com.apple.quarantine mvnd-x.y.z-darwin-amd64

Usage

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

mvnd verify

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/apache/maven-mvnd.git
$ cd maven-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

Please note that if you are using Windows as your operating system you will need the following prerequisites for building maven-mvnd: a version of Visual Studio with the workload "Desktop development with C++" and the individual component "Windows Universal CRT SDK".

Install mvnd

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

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

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