Support jvm mem percentage (#3747)

docs/configuration/jvm-options.md

@@ -10,6 +10,12 @@ By default, the image declares an initial and maximum Java memory-heap limit of
 
 The values of all three are passed directly to the JVM and support format/units as `<size>[g|G|m|M|k|K]`.
 
+To have control over heap size, without relying on absolute memory sizes percentages are also supported using `<size>%`.
+
+!!! info "RAMPercentage parameters"
+    Percentage based heap sizing is enabled using `-XX:InitialRAMPercentage` for `INIT_MEMORY` and `-XX:MaxRAMPercentage` for `MAX_MEMORY`.
+    For details on the function of these parameters look [here](https://www.baeldung.com/java-jvm-parameters-rampercentage).
+
 !!! example "Using docker run"
 
     ```
@@ -37,19 +43,7 @@ The values of all three are passed directly to the JVM and support format/units
           MAX_MEMORY: 4G
     ```
 
-To let the JVM calculate the heap size from the container declared memory limit, unset `MEMORY` with an empty value, such as `-e MEMORY=""`. By default, the JVM will use 25% of the container memory limit as the heap limit; however, as an example the following would tell the JVM to use 75% of the container limit of 4GB of memory:
+To let the JVM calculate the heap size from the container declared memory limit, unset `MEMORY` with an empty value, such as `-e MEMORY=""`. By default, the JVM will use 25% of the container memory limit as the heap limit.
-
-!!! example "MaxRAMPercentage using compose file"
-
-    ```
-        environment:
-          MEMORY: ""
-          JVM_XX_OPTS: "-XX:MaxRAMPercentage=75"
-        deploy:
-          resources:
-            limits:
-              memory: 4G
-    ```
 
 !!! important
     The settings above only set the Java **heap** limits. Memory resource requests and limits on the overall container should also account for non-heap memory usage. An extra 25% is [a general best practice](https://dzone.com/articles/best-practices-java-memory-arguments-for-container).

scripts/start-deployBukkitSpigot

@@ -28,7 +28,19 @@ function buildSpigotFromSource {
   mkdir ${tempDir}
   cd ${tempDir}
 
-  jvmOpts="-Xms${INIT_MEMORY:-$MEMORY} -Xmx${MAX_MEMORY:-$MEMORY}"
+  jvmOpts=""
+
+  if isPercentage "${INIT_MEMORY:-$MEMORY}"; then
+    jvmOpts+="-XX:InitialRAMPercentage=$(getPercentageValue "${INIT_MEMORY:-$MEMORY}") "
+  else
+    jvmOpts+="-Xms${INIT_MEMORY:-$MEMORY} "
+  fi
+
+  if isPercentage "${MAX_MEMORY:-$MEMORY}"; then
+    jvmOpts+="-XX:MaxRAMPercentage=$(getPercentageValue "${MAX_MEMORY:-$MEMORY}")"
+  else
+    jvmOpts+="-Xmx${MAX_MEMORY:-$MEMORY}"
+  fi
 
   logn ''
   curl -sSL -o ${tempDir}/BuildTools.jar https://hub.spigotmc.org/jenkins/job/BuildTools/lastSuccessfulBuild/artifact/target/BuildTools.jar && \

scripts/start-finalExec

@@ -368,10 +368,15 @@ fi
 
 if [[ ${INIT_MEMORY} || ${MAX_MEMORY} ]]; then
   log "Setting initial memory to ${INIT_MEMORY:=${MEMORY}} and max to ${MAX_MEMORY:=${MEMORY}}"
-  if [[ ${INIT_MEMORY} ]]; then
+  if isPercentage "$INIT_MEMORY"; then
+    JVM_OPTS="-XX:InitialRAMPercentage=$(getPercentageValue "${INIT_MEMORY}") ${JVM_OPTS}"
+  elif [[ ${INIT_MEMORY} ]]; then
     JVM_OPTS="-Xms${INIT_MEMORY} ${JVM_OPTS}"
   fi
-  if [[ ${MAX_MEMORY} ]]; then
+
+  if isPercentage "$MAX_MEMORY"; then
+    JVM_OPTS="-XX:MaxRAMPercentage=$(getPercentageValue "${MAX_MEMORY}") ${JVM_OPTS}"
+  elif [[ ${MAX_MEMORY} ]]; then
     JVM_OPTS="-Xmx${MAX_MEMORY} ${JVM_OPTS}"
   fi
 fi
@@ -431,15 +436,34 @@ elif [[ ${TYPE} == "CURSEFORGE" ]]; then
 
   copyFilesForCurseForge
 
+if isPercentage "$INIT_MEMORY" || isPercentage "$MAX_MEMORY"; then
+# Convert to bytes
+NORM_INIT_MEM=$(normalizeMemSize "$INIT_MEMORY")
+NORM_MAX_MEM=$(normalizeMemSize "$MAX_MEMORY")
+# Convert to MB
+((NORM_INIT_MEM*=1048576))
+((NORM_MAX_MEM*=1048576))
+
+  cat > "${FTB_DIR}/settings-local.sh" <<EOF
+export MIN_RAM="${NORM_INIT_MEM}M"
+export MAX_RAM="${NORM_MAX_MEM}M"
+export JAVA_PARAMETERS="${JVM_XX_OPTS} ${JVM_OPTS} $expandedDOpts"
+EOF
+else
   cat > "${FTB_DIR}/settings-local.sh" <<EOF
 export MIN_RAM="${INIT_MEMORY}"
 export MAX_RAM="${MAX_MEMORY}"
 export JAVA_PARAMETERS="${JVM_XX_OPTS} ${JVM_OPTS} $expandedDOpts"
 EOF
+fi
 
   # patch CurseForge cfg file, if present
   if [ -f "${FTB_DIR}/settings.cfg" ] && [[ ${MAX_MEMORY} ]]; then
-    sed -i "s/MAX_RAM=[^;]*/MAX_RAM=${MAX_MEMORY}/" "${FTB_DIR}/settings.cfg"
+    if isPercentage "$MAX_MEMORY"; then
+      sed -i "s/MAX_RAM=[^;]*/MAX_RAM=${NORM_MAX_MEM}M/" "${FTB_DIR}/settings.cfg"
+    else
+      sed -i "s/MAX_RAM=[^;]*/MAX_RAM=${MAX_MEMORY}/" "${FTB_DIR}/settings.cfg"
+    fi
   fi
 
   cd "${FTB_DIR}" || (logError "Can't go into ${FTB_DIR}"; exit 1)

scripts/start-utils

@@ -39,6 +39,23 @@ function get_major_version() {
   echo "$version" | cut -d. -f 1-2
 }
 
+function isPercentage() {
+  local value=$1
+  
+  [[ $value =~ ^[0-9]+(\.[0-9]+)?\s*%$ ]]
+}
+
+function getPercentageValue() {
+  local value=$1
+  if [[ "$value" =~ ^([0-9]+(\.[0-9]+)?)\s*%$ ]]; then
+    echo "${BASH_REMATCH[1]}"
+    return 0
+  else
+    logError "Value '$value' is not a valid percentage."
+    return 1
+  fi
+}
+
 function isURL() {
   local value=$1
 
@@ -229,6 +246,7 @@ function logRcon() {
 
 function normalizeMemSize() {
   local scale=1
+  local mem=1
   case ${1,,} in
   *k)
     scale=1024
@@ -239,10 +257,20 @@ function normalizeMemSize() {
   *g)
     scale=1073741824
     ;;
+  *%)
+    # Get system memory
+    if [ -f "/sys/fs/cgroup/memory/memory.limit_in_bytes" ]; then
+    mem=$( cat /sys/fs/cgroup/memory/memory.limit_in_bytes )
+    elif [ -f "/sys/fs/cgroup/memory.max" ]; then
+    mem=$( cat /sys/fs/cgroup/memory.max )
+    fi
+    # Scale is used to transform percentages into decimals (eg. 60 -> 0.6)
+    scale=0.01
+    ;;
   esac
 
   val=${1:0:-1}
-  echo $((val * scale))
+  echo $((val * scale * mem))
 }
 
 function compare_version() {