= mvnd: Maven Daemon

The mvnd project aims to provide a daemon infrastructure for maven based builds.  It borrows techniques from Gradle and Takari to provide a simple and efficient system.

== Install `mvnd`

If you are on Linux or Mac, you can use the following shell commands. On Windows, you can perform the steps manually.

[source,shell]
----
cd ~/bin # <1>
os=$(uname | tr '[:upper:]' '[:lower:]') # <2>
curl https://github.com/mvndaemon/mvnd/releases/latest/download/mvnd-${os}-amd64 -o mvnd # <3>
chmod +x mvnd # <4>
mvnd --install # <5>
----
<1> Change to `~/bin` or any other location already included in `PATH`; otherwise, you'll need to add `mvnd` to
  `PATH` manually
<2> Detect the name of the current operating system and turn it to lower case
<3> Download the latest `mvnd` executable for the given OS from https://github.com/mvndaemon/mvnd/releases[`mvnd` releases page]; store the executable as `mvnd` (or `mvnd.exe` on Windows)
<4> Make it executable (not required on Windows)
<5> Run `mvnd --install` to download and install the server part. This will:
+
* Download `mvnd-dist.zip`
* Unpack it to `~/.m2/mvnd/<version>`
* Create `~/.m2/mvnd.properties`
+
If your 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.

Optionally, you can open `~/.m2/mvnd.properties` and set the `java.home` property in case you do not want to bother with setting `JAVA_HOME` environment variable.
+
Now you can 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"
----


== 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

`--install` installs the server part

`--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!