Dynamic Java options on Minecraft systemd service

Vagrantfile

@@ -35,7 +35,7 @@ Vagrant.configure("2") do |config|
   end
 
   config.vm.provider "virtualbox" do |vbox|
-    vbox.memory = 2048
+    vbox.memory = 4096
   end
 
   # Provision with Ansible

dev/host_vars/minecraft.yml

@@ -8,9 +8,16 @@ manage_network: false
 #minecraft_eula: true
 
 minecraft_onboot: vanilla
+minecraft_onboot_run: true
 minecraft:
   - name: vanilla # 1.16.5 (https://mcversions.net/download/1.16.5)
     sha1: 1b557e7b033b583cd9f66746b7a9ab1ec1673ced
+    java:
+      Xms: 1G
+      Xmx: 1G
   - name: revelation # 3.4.0 (https://api.modpacks.ch/public/modpack/35/174)
     modpack: 35/174
-    java: 8
+    java:
+      version: 8
+      Xms: 4G
+      Xmx: 4G

roles/minecraft/defaults/main.yml

@@ -2,6 +2,7 @@ minecraft_eula: false
 minecraft_home: "/opt/minecraft"
 minecraft_java: 11
 minecraft_modpack_url: "https://api.modpacks.ch/public/modpack/{{ item.modpack }}/server/linux"
+minecraft_onboot_run: false
 minecraft_url: "https://launcher.mojang.com/v1/objects/{{ item.sha1 }}/server.jar"
 minecraft_user: minecraft
 minecraft_xms: 1G

roles/minecraft/tasks/java.yml

@@ -2,14 +2,14 @@
   apt:
     name: gpg
     state: present
-  when: item.java is defined and item.java == 8
+  when: item.java.version is defined and item.java.version == 8
   loop: "{{ minecraft }}"
 
 - name: Add AdoptOpenJDK's signing key
   apt_key:
     id: 8ED17AF5D7E675EB3EE3BCE98AC3B29174885C03
     url: https://adoptopenjdk.jfrog.io/adoptopenjdk/api/gpg/key/public
-  when: item.java is defined and item.java == 8
+  when: item.java.version is defined and item.java.version == 8
   loop: "{{ minecraft }}"
 
 - name: Install AdoptOpenJDK repository
@@ -17,21 +17,21 @@
     repo: deb https://adoptopenjdk.jfrog.io/adoptopenjdk/deb/ buster main
     mode: 0644
     state: present
-  when: item.java is defined and item.java == 8
+  when: item.java.version is defined and item.java.version == 8
   loop: "{{ minecraft }}"
 
 - name: Install Java 8
   apt:
     name: adoptopenjdk-8-hotspot
     state: present
-  when: item.java is defined and item.java == 8
+  when: item.java.version is defined and item.java.version == 8
   loop: "{{ minecraft }}"
 
 - name: Install Java 11
   apt:
     name: openjdk-11-jre
     state: present
-  when: item.java is not defined or item.java == 11
+  when: item.java.version is not defined or item.java.version == 11
   loop: "{{ minecraft }}"
 
 - name: Activate Java 8

roles/minecraft/tasks/modpacks.yml

@@ -28,6 +28,8 @@
   file:
     src: "{{ item.files[0].path }}"
     dest: "{{ minecraft_home }}/{{ item.item.name }}/minecraft_server.jar"
+    owner: "{{ minecraft_user }}"
+    group: "{{ minecraft_user }}"
     state: link
   loop: "{{ minecraft_forge.results }}"
   when: minecraft_forge is defined and item.files[0].path is defined

roles/minecraft/tasks/service.yml

@@ -4,14 +4,34 @@
     dest: "/etc/systemd/system/minecraft@.service"
   register: minecraft_systemd
 
+- name: Deploy service environmental variables
+  template:
+    src: environment.conf.j2
+    dest: "{{ minecraft_home }}/{{ item.name }}/environment.conf"
+    owner: "{{ minecraft_user }}"
+    group: "{{ minecraft_user }}"
+  loop: "{{ minecraft }}"
+
 - name: Reload systemd manager configuration
   systemd:
     daemon_reload: true
   when: minecraft_systemd.changed
 
-- name: Start Service
+- name: Disable non-default service instances
+  service:
+    name: "minecraft@{{ item.name }}"
+    enabled: false
+  loop: "{{ minecraft }}"
+  when: item.name != minecraft_onboot
+
+- name: Enable default service instance
+  service:
+    name: "minecraft@{{ minecraft_onboot }}"
+    enabled: true
+  when: minecraft_eula and minecraft_onboot is defined
+
+- name: Run default service instance
   service:
     name: "minecraft@{{ minecraft_onboot }}"
     state: started
-    enabled: true
+  when: minecraft_eula and minecraft_onboot is defined and minecraft_onboot_run
-  when: minecraft_eula and minecraft_onboot is defined

roles/minecraft/templates/environment.conf.j2

@@ -0,0 +1,8 @@
+{% if item.java.version is defined and item.java.version == 8 %}
+JAVA_HOME=/usr/lib/jvm/adoptopenjdk-8-hotspot-amd64/jre
+{% else %}
+JAVA_HOME=/usr/lib/jvm/java-11-openjdk-amd64
+{% endif %}
+JAVA_XMS={{ item.java.Xms }}
+JAVA_XMX={{ item.java.Xmx }}
+

roles/minecraft/templates/minecraft.service.j2

@@ -8,9 +8,10 @@ WorkingDirectory={{ minecraft_home }}/%i
 User={{ minecraft_user }}
 Group={{ minecraft_user }}
 Restart=always
+EnvironmentFile={{ minecraft_home }}/%i/environment.conf
 
 ExecStart=/usr/bin/screen -DmS minecraft-%i \
-  /usr/bin/java -Xms{{ minecraft_xms }} -Xmx{{ minecraft_xmx }} -jar minecraft_server.jar nogui
+  ${JAVA_HOME}/bin/java -Xms${JAVA_XMS} -Xmx${JAVA_XMX} -jar minecraft_server.jar nogui
 ExecReload=/usr/bin/screen -p 0 -S minecraft-%i -X eval 'stuff "reload"\\015'
 ExecStop=/usr/bin/screen -p 0 -S minecraft-%i -X eval 'stuff "say SERVER SHUTDOWN IN 30 SECONDS"\015'
 ExecStop=/bin/sleep 15