README.adoc - maven-mvnd - Git at Google

 = `mvnd` - the Maven Daemon

 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:

 * `-T1C` is used by default. This means builing in parallel using as many threads as CPU cores on your machine. 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:
 +
 image::src/main/images/console-output.png[]
 +
 Once the build is finshed, 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 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:
 +
 [source,shell]
 ----
 $ mvnd --version
 Maven Daemon 0.0.0 (native)
 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.


 == Usage

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

 [source,shell]
 ----
 mvnd clean install
 ----

 == `mvnd` specific options

 `--status` lists running daemons

 `--stop` kills all running daemons

 == 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 "11.0.7" 2020-04-14
 OpenJDK Runtime Environment GraalVM CE 20.1.0 (build 11.0.7+10-jvmci-20.1-b02)
 OpenJDK 64-Bit Server VM GraalVM CE 20.1.0 (build 11.0.7+10-jvmci-20.1-b02, 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/docs/reference-manual/native-image/#prerequisites[`native-image` documentation].

 === Build `mvnd`

 [source,shell]
 ----
 $ 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
 ----

 This project is still in prototype mode, so feedback is most welcomed!
	= `mvnd` - the Maven Daemon

	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:

	* `-T1C` is used by default. This means builing in parallel using as many threads as CPU cores on your machine. 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:
	+
	image::src/main/images/console-output.png[]
	+
	Once the build is finshed, 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 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:
	+
	[source,shell]
	----
	$ mvnd --version
	Maven Daemon 0.0.0 (native)
	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.


	== Usage

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

	[source,shell]
	----
	mvnd clean install
	----

	== `mvnd` specific options

	`--status` lists running daemons

	`--stop` kills all running daemons

	== 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 "11.0.7" 2020-04-14
	OpenJDK Runtime Environment GraalVM CE 20.1.0 (build 11.0.7+10-jvmci-20.1-b02)
	OpenJDK 64-Bit Server VM GraalVM CE 20.1.0 (build 11.0.7+10-jvmci-20.1-b02, 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/docs/reference-manual/native-image/#prerequisites[`native-image` documentation].

	=== Build `mvnd`

	[source,shell]
	----
	$ 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
	----

	This project is still in prototype mode, so feedback is most welcomed!