Send SIGUSR2 signal to Node to snapshot

Signed-off-by: Christina Ying Wang <christina@balena.io>

Dockerfile.template

@@ -86,6 +86,8 @@ COPY --from=journal /sysroot /
 # Copy mount script for mounting host partitions into container
 COPY mount-partitions.sh .
 
+COPY profile.sh .
+
 # Runtime dependencies
 RUN apk add --update --no-cache \
 	$NODE \

entry.sh

@@ -75,5 +75,5 @@ if [ "${LIVEPUSH}" = "1" ]; then
 	exec npx nodemon --watch src --watch typings --ignore tests -e js,ts,json \
 		--exec node -r ts-node/register/transpile-only src/app.ts
 else
-	exec node /usr/src/app/dist/app.js
+	exec node --heapsnapshot-signal=SIGUSR2 /usr/src/app/dist/app.js
 fi

profile.sh

@@ -0,0 +1,13 @@
+#!/bin/sh
+
+set -o errexit
+
+SUPERVISOR_PID=1
+# Snapshot interval in seconds (default: 3600s = 1h)
+INTERVAL="${INTERVAL:-3600}"
+
+# Send a SIGUSR2 signal to the supervisor process once every INTERVAL
+while true; do
+    kill -USR2 "${SUPERVISOR_PID}"
+    sleep "${INTERVAL}"
+done