= mvnd - the Maven Daemon :toc: macro

image::https://img.shields.io/twitter/url/https/twitter.com/mvndaemon.svg?style=social&label=Follow%20%40mvndaemon[link="https://twitter.com/mvndaemon"]

toc::[]

== Introduction

This project aims at providing faster https://maven.apache.org/[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 https://www.graalvm.org/reference-manual/native-image/[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 into the command line to make your build serial.
Improved console output: we believe that the output of a parallel build on 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:

image::https://user-images.githubusercontent.com/1826249/103917178-94ee4500-510d-11eb-9abb-f52dae58a544.gif[] + Once the build is finished, the complete Maven output is forwarded to the console.

== How to install mvnd

=== Install using https://sdkman.io/[SDKMAN!]

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

[source,shell]

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 https://brew.sh/[Homebrew]

[source,shell]

brew install mvndaemon/homebrew-mvnd/mvnd

Note: There are two formulae: the mvnd that install latest, and mvnd@1 that installs 1.x line.

=== Install using https://www.macports.org[MacPorts]

[source,shell]

sudo port install mvnd

=== Other installers

We're looking for contribution to support https://community.chocolatey.org/packages/mvndaemon/[Chocolatey], https://scoop.sh/[Scoop] or https://github.com/joschi/asdf-mvnd#install[asdf]. If you fancy helping us...

//// === Install using https://www.macports.org[MacPorts]

[source,shell]

$ sudo port install mvnd

=== Install using https://community.chocolatey.org/packages/mvndaemon/[Chocolatey]

[source,shell]

$ choco install mvndaemon

=== Install using https://scoop.sh/[Scoop]

[source,shell]

$ scoop install mvndaemon

=== Install using https://github.com/joschi/asdf-mvnd#install[asdf]

[source,shell]

$ asdf plugin-add mvnd
$ asdf install mvnd latest

////

=== Set up completion

Optionally, you can set up completion as follows:
[source,shell]

ensure that MVND_HOME points 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.

=== 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 the JAVA_HOME environment variable.
Test whether mvnd works:

[source,shell]

$ 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 https://github.com/oracle/graal/issues/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:
[source,shell]

$ 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.:

[source,shell]

mvnd verify

== mvnd specific options

--status lists running daemons

--stop kills all running daemons

mvnd --help prints the complete list of options

== Configuration Configuration can be provided through the properties file. Mvnd reads the 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 https://github.com/apache/maven-mvnd/blob/master/dist/src/main/distro/conf/mvnd.properties[/dist/src/main/distro/conf/mvnd.properties].

== Build mvnd from source

=== Prerequisites:

git
Maven
Download and unpack GraalVM CE from https://github.com/graalvm/graalvm-ce-builds/releases[GitHub]
Set JAVA_HOME to where you unpacked GraalVM in the previous step. Check that java -version output is as
expected:

[source,shell]

$ $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:

[source,shell]

$ $JAVA_HOME/bin/gu install native-image

native-image may require additional software to be installed depending on your platform - see the
https://www.graalvm.org/reference-manual/native-image/#prerequisites[`native-image` documentation].

=== Build mvnd

[source,shell]

$ 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