Read container memory limit from cgroup (v1 and v2)

Uses memory.high if available (recommended way of setting a functioning soft limit), then first falls back to memory.max (e.g. from 'docker run -m'), then to memory.low (e.g. from 'docker run --memory-reservation'), and finally to memory.min.

Falls back to direct reading of '/sys/fs/cgroup/memory/memory.limit_in_bytes' for cases where that exists, but no full cgroupfs is mounted (e.g. on Heroku).

Limit enforcement (now to 8 TB) is still in place this way - a Docker v1 value will be read, and run into the limit for unrestricted containers, without hitting the fallback and getting returned.

GUS-W-16052317

Author: dzuelke

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## [Unreleased]
 
+- Support reading container memory limits from cgroups (v1 and v2)
+
 
 ## [v255] - 2024-06-21
 

lib/environment.sh

@@ -86,7 +86,13 @@ write_profile() {
   local bp_dir="$1"
   local build_dir="$2"
   mkdir -p "$build_dir/.profile.d"
-  cp "$bp_dir"/profile/* "$build_dir/.profile.d/"
+  local restore_extglob
+  restore_extglob=$(shopt -p extglob) # will return "shopt -u extglob" (or "-s"), for later
+  shopt -s extglob
+  cp "$bp_dir"/profile/!(WEB_CONCURRENCY.sh) "$build_dir/.profile.d/"
+  $restore_extglob
+  # concatenate these two together
+  cat "$bp_dir"/etc/cgroups.sh "$bp_dir"/profile/WEB_CONCURRENCY.sh > "$build_dir/.profile.d/WEB_CONCURRENCY.sh"
 }
 
 write_ci_profile() {

profile/WEB_CONCURRENCY.sh

@@ -31,17 +31,28 @@ log_concurrency() {
 detect_memory() {
   local default=$1
 
-  if [ -e /sys/fs/cgroup/memory/memory.limit_in_bytes ]; then
-    echo $(($(cat /sys/fs/cgroup/memory/memory.limit_in_bytes) / 1048576))
+  local memory_limit
+  memory_limit=$(cgroup_util_read_cgroup_memory_limit_with_fallback) && {
+    echo $(( memory_limit / 1024 / 1024 ))
+    return
+  }
+
+  if (($? == 99)); then
+    dne_memory
   else
     echo "$default"
-  fi
+	fi
+}
+
+dne_memory() {
+	echo "129024"
 }
 
 bound_memory() {
   local detected=$1
   # Memory is bound to the maximum memory of known dyno types: ~126 GB
-  local max_detected_memory=129024
+  local max_detected_memory
+  max_detected_memory=$(dne_memory)
   if (( detected > max_detected_memory )); then
     echo "$max_detected_memory"
   else