[docker] Allow to change default sysctl parameters using environment …

…variables (#3689)

docker/sysctl-setter/Dockerfile

@@ -5,20 +5,23 @@ RUN apk add --no-cache procps && echo $'#!/bin/ash\n\
 set -e\n\
 while true; do\n\
   MVAL=$(sysctl -n vm.max_map_count)\n\
-  if [ "$MVAL" -lt 3000000 ]; then\n\
-    sysctl -w vm.max_map_count=3000000\n\
+  MIN_MVAL=${SYSCTL_VM_MAX_MAP_COUNT:-3000000}\n\
+  if [ "$MVAL" -lt "$MIN_MVAL" ]; then\n\
+    sysctl -w vm.max_map_count=${MIN_MVAL}\n\
   fi\n\
   SVAL=$(sysctl -n vm.swappiness)\n\
   if [ "$SVAL" -ne 1 ]; then\n\
     sysctl -w vm.swappiness=1\n\
   fi\n\
   FVAL=$(sysctl -n fs.file-max)\n\
-  if [ "$FVAL" -lt 3000000 ]; then\n\
-    sysctl -w fs.file-max=3000000\n\
+  MIN_FVAL=${SYSCTL_FS_FILE_MAX:-3000000}\n\
+  if [ "$FVAL" -lt "$MIN_FVAL" ]; then\n\
+    sysctl -w fs.file-max=${MIN_FVAL}\n\
   fi\n\
   OVAL=$(sysctl -n fs.nr_open)\n\
-  if [ "$OVAL" -lt 3000000 ]; then\n\
-    sysctl -w fs.nr_open=3000000\n\
+  MIN_OVAL=${SYSCTL_FS_NR_OPEN:-3000000}\n\
+  if [ "$OVAL" -lt "$MIN_OVAL" ]; then\n\
+    sysctl -w fs.nr_open=${MIN_OVAL}\n\
   fi\n\
   sleep 60\n\
 done' > /bin/m3dbnode_sysctl.sh &&\