Add option for Flare flags (#827)

Dockerfile

@@ -1,4 +1,4 @@
-FROM openjdk:8u212-jre-alpine
+FROM adoptopenjdk/openjdk11:alpine-jre
 
 LABEL org.opencontainers.image.authors="Geoff Bourne <itzgeoff@gmail.com>"
 

README.md

@@ -327,6 +327,10 @@ An [Airplane](https://github.com/TECHNOVE/Airplane) server, which is a fork of T
 
 > **NOTE** only Java 8 and 11 are supported
 
+Extra variables:
+- `FORCE_REDOWNLOAD=false` : set to true to force the located server jar to be re-downloaded
+- `USE_FLARE_FLAGS=false` : set to true to add appropriate flags for the [Flare](https://blog.airplane.gg/flare) profiler
+
 ## Running a Purpur server
 
 A [Purpur](https://purpur.pl3x.net/) server, which is "a fork of Paper, Tuinity, Airplane with the goal of providing new and interesting configuration options".
@@ -338,6 +342,7 @@ A [Purpur](https://purpur.pl3x.net/) server, which is "a fork of Paper, Tuinity,
 Extra variables:
 - `PURPUR_BUILD=LATEST` : set a specific Purpur build to use
 - `FORCE_REDOWNLOAD=false` : set to true to force the located server jar to be re-downloaded
+- `USE_FLARE_FLAGS=false` : set to true to add appropriate flags for the [Flare](https://blog.airplane.gg/flare) profiler
 
 ## Running a Yatopia server
 
@@ -350,6 +355,7 @@ A [Yatopia](https://github.com/YatopiaMC/Yatopia) server, which is a "blazing fa
 Extra variables:
 - `RELEASE=stable` : set to `stable` or `latest`
 - `FORCE_REDOWNLOAD=false` : set to true to force the located server jar to be re-downloaded
+- `USE_FLARE_FLAGS=false` : set to true to add appropriate flags for the [Flare](https://blog.airplane.gg/flare) profiler
 
 ## Running a Magma server
 

start-configuration

@@ -63,7 +63,7 @@ fi
 
 if ! which java > /dev/null; then
   log "Fixing PATH to include java"
-  PATH="${PATH}:/usr/bin"
+  PATH="${PATH}:/opt/java/openjdk/bin"
 fi
 
 export VERSIONS_JSON=https://launchermeta.mojang.com/mc/game/version_manifest.json
@@ -105,6 +105,12 @@ case "${TYPE^^}" in
   ;;
 
   FORGE)
+    log "**********************************************************************"
+    log "WARNING: The image tag itzg/minecraft-server:java8 is recommended"
+    log "         since some mods require Java 8"
+    log "         Exception traces reporting ClassCastException: class jdk.internal.loader.ClassLoaders\$AppClassLoader"
+    log "         can be fixed with java8"
+    log "**********************************************************************"
     exec ${SCRIPTS:-/}start-deployForge "$@"
   ;;
 
@@ -113,6 +119,12 @@ case "${TYPE^^}" in
   ;;
 
   FTB|CURSEFORGE)
+    log "**********************************************************************"
+    log "WARNING: The image tag itzg/minecraft-server:java8 is recommended"
+    log "         since some mods require Java 8"
+    log "         Exception traces reporting ClassCastException: class jdk.internal.loader.ClassLoaders\$AppClassLoader"
+    log "         can be fixed with java8"
+    log "**********************************************************************"
     exec ${SCRIPTS:-/}start-deployCF "$@"
   ;;
 

start-deployAirplane

@@ -19,7 +19,7 @@ fi
 
 export SERVER=airplane-${VANILLA_VERSION}-jdk${JAVA_VER}.jar
 
-if [ ! -f "$SERVER" ] || [ -n "$FORCE_REDOWNLOAD" ]; then
+if [ ! -f "$SERVER" ] || isTrue "$FORCE_REDOWNLOAD"; then
     downloadUrl="https://dl.airplane.gg/latest/Airplane-JDK${JAVA_VER}/launcher-airplane.jar"
     log "Downloading Airplane from $downloadUrl ..."
     curl -fsSL -o "$SERVER" "$downloadUrl"

start-minecraftFinalSetup

@@ -144,6 +144,13 @@ if isTrue "${USE_LARGE_PAGES}"; then
   "
 fi
 
+if isTrue "${USE_FLARE_FLAGS}"; then
+  JVM_XX_OPTS="${JVM_XX_OPTS}
+  -XX:+UnlockDiagnosticVMOptions
+  -XX:+DebugNonSafepoints
+  "
+fi
+
 if isTrue "${DEBUG_MEMORY}"; then
   log "Memory usage and availability (in MB)"
   uname -a