Adjust WEB_CONCURRENCY for memory heavy instances (#1196)

* Update concurrency calculations for larger memory footprints

* Use 2048 MB WEB_MEMORY for memory heavy dynos

* Drop duplicate line from WEB_CONCURRENCY

* Adjust tests for memory heavy WEB_CONCURRENCY

* Adjust web concurrency test value

* Add changelog entry for web concurrency changes

* Fix typo in changelog

CHANGELOG.md

@@ -2,7 +2,9 @@
 
 ## main
 
+- Adjust WEB_CONCURRENCY calculations to support larger, memory heavy instances. ([#1196](https://github.com/heroku/heroku-buildpack-nodejs/pull/1196))
 - Added Node.js version 21.6.1.
+
 ## v234 (2024-01-16)
 
 - Added Node.js version 21.6.0.

profile/WEB_CONCURRENCY.sh

@@ -4,7 +4,7 @@ calculate_concurrency() {
   local available=$1
   local web_memory=$2
 
-  echo $(($available/$web_memory))
+  echo $(( available / web_memory ))
 }
 
 validate_concurrency() {
@@ -13,11 +13,10 @@ validate_concurrency() {
 
   if (( concurrency < 1 )); then
     concurrency=1
-    ret=1
   elif (( concurrency > 200 )); then
     # Ex: This will happen on Dokku on DO
     concurrency=1
-    ret=2
+    ret=1
   fi
 
   echo "$concurrency"
@@ -41,19 +40,28 @@ detect_memory() {
 
 bound_memory() {
   local detected=$1
-  local max_detected_memory=14336
-
-  # The hardcoded value is 16GB of memory
+  # Memory is bound to the maximum memory of known dyno types: ~126 GB
+  local max_detected_memory=129024
   if (( detected > max_detected_memory )); then
     echo "$max_detected_memory"
   else
     echo "$detected"
   fi
 }
 
-warn_high_web_concurrency() {
+default_web_memory() {
+    local available_memory=$1
+    # Allow more memory per process on memory heavy dyno types.
+    if (( available_memory > 16384 )); then
+        echo 2048
+    else
+        echo 512
+    fi
+}
+
+warn_web_concurrency() {
   echo "Could not determine a reasonable value for WEB_CONCURRENCY.
-This is likely due to running the Heroku NodeJS buildpack on a non-Heroku
+This is likely due to running the Heroku Node.js buildpack on a non-Heroku
 platform.
 
 WEB_CONCURRENCY has been set to ${1}. Please review whether this value is
@@ -62,24 +70,17 @@ appropriate for your application.
 }
 
 DETECTED=$(detect_memory 512)
-export MEMORY_AVAILABLE=${MEMORY_AVAILABLE-$(bound_memory $DETECTED)}
-export WEB_MEMORY=${WEB_MEMORY-512}
-WEB_CONCURRENCY=${WEB_CONCURRENCY-$(calculate_concurrency "$MEMORY_AVAILABLE" "$WEB_MEMORY")}
-validated_concurrency=$(validate_concurrency "$WEB_CONCURRENCY")
-case $? in # validate_concurrency exit code indicates result
-  1)
-    # too low
-    export WEB_CONCURRENCY=$validated_concurrency
-    ;;
-  2)
-    # too high
-    warn_high_web_concurrency "$validated_concurrency" "$WEB_CONCURRENCY"
+export MEMORY_AVAILABLE=${MEMORY_AVAILABLE-$(bound_memory "$DETECTED")}
+export WEB_MEMORY=${WEB_MEMORY-$(default_web_memory "$MEMORY_AVAILABLE")}
+
+# Calculate/validate WEB_CONCURRENCY if not already set
+if [ -z "${WEB_CONCURRENCY}" ]; then
+    calculated_concurrency=$(calculate_concurrency "$MEMORY_AVAILABLE" "$WEB_MEMORY")
+    if ! validated_concurrency=$(validate_concurrency "$calculated_concurrency"); then
+        warn_web_concurrency "$validated_concurrency"
+    fi
     export WEB_CONCURRENCY=$validated_concurrency
-    ;;
-  0)
-    export WEB_CONCURRENCY
-    ;;
-esac
+fi
 
 if [[ "${LOG_CONCURRENCY+isset}" && "$LOG_CONCURRENCY" == "true" ]]; then
   log_concurrency

test/unit

@@ -315,12 +315,12 @@ testWebConcurrencyProfileScript() {
   # memory in MB of a Peformance-L dyno
   assertEquals "14336" "$(bound_memory 14336)"
 
-  # one more MB
-  assertEquals "14336" "$(bound_memory 14337)"
-
   # On non-Heroku systems `detect_memory` can return non-sensically large values
-  # In this case, we should bound
-  assertEquals "14336" "$(bound_memory 1000000)"
+  # so bound to largest known dyno size
+  assertEquals "129024" "$(bound_memory 129024)"
+
+  # One larger than largest known
+  assertEquals "129024" "$(bound_memory 129025)"
 
   # test calculate_concurrency
 
@@ -332,6 +332,8 @@ testWebConcurrencyProfileScript() {
   assertEquals "5" "$(calculate_concurrency 2560 512)"
   # Performance-L
   assertEquals "28" "$(calculate_concurrency 14336 512)"
+  # Memory heavy
+  assertEquals "31" "$(calculate_concurrency 63488 2048)"
 
   # In case some very large memory available value gets passed in
   assertEquals "1" "$(validate_concurrency $(calculate_concurrency 103401 512))"