Add "vm_memory_high_watermark" to the generated config, sourced from the value of the "memory.limit_in_bytes" cgroup restriction

Author: tianon

3.6/alpine/docker-entrypoint.sh

@@ -95,6 +95,10 @@ for conf in "${allConfigKeys[@]}"; do
 	var="RABBITMQ_${conf^^}"
 	val="${!var:-}"
 	if [ "$val" ]; then
+		if [ "${configDefaults[$conf]:-}" ] && [ "${configDefaults[$conf]}" = "$val" ]; then
+			# if the value set is the same as the default, treat it as if it isn't set
+			continue
+		fi
 		haveConfig=1
 		case "$conf" in
 			ssl_*) haveSslConfig=1 ;;
@@ -235,13 +239,26 @@ rabbit_env_config() {
 	join $'\n' "${ret[@]}"
 }
 
-if [ "$1" = 'rabbitmq-server' ] && [ "$haveConfig" ]; then
+shouldWriteConfig="$haveConfig"
+if [ ! -f /etc/rabbitmq/rabbitmq.config ]; then
+	shouldWriteConfig=1
+fi
+
+if [ "$1" = 'rabbitmq-server' ] && [ "$shouldWriteConfig" ]; then
 	fullConfig=()
 
 	rabbitConfig=(
 		"{ loopback_users, $(rabbit_array) }"
 	)
 
+	# https://www.rabbitmq.com/memory.html#memsup-usage
+	# "If the absolute limit is larger than the installed RAM or available virtual address space, the threshold is set to whichever limit is smaller."
+	# specifically, if a memory limit isn't supplied to the container and "memory.limit_in_bytes" is thus an enormous constant, RabbitMQ will ignore it and use maximum available memory or address space instead
+	if [ -r /sys/fs/cgroup/memory/memory.limit_in_bytes ]; then
+		memLimit="$(< /sys/fs/cgroup/memory/memory.limit_in_bytes)"
+		rabbitConfig+=( "{ vm_memory_high_watermark, { absolute, $memLimit } }" )
+	fi
+
 	if [ "$haveSslConfig" ]; then
 		IFS=$'\n'
 		rabbitSslOptions=( $(rabbit_env_config 'ssl' "${sslConfigKeys[@]}") )

3.6/debian/docker-entrypoint.sh

@@ -95,6 +95,10 @@ for conf in "${allConfigKeys[@]}"; do
 	var="RABBITMQ_${conf^^}"
 	val="${!var:-}"
 	if [ "$val" ]; then
+		if [ "${configDefaults[$conf]:-}" ] && [ "${configDefaults[$conf]}" = "$val" ]; then
+			# if the value set is the same as the default, treat it as if it isn't set
+			continue
+		fi
 		haveConfig=1
 		case "$conf" in
 			ssl_*) haveSslConfig=1 ;;
@@ -235,13 +239,26 @@ rabbit_env_config() {
 	join $'\n' "${ret[@]}"
 }
 
-if [ "$1" = 'rabbitmq-server' ] && [ "$haveConfig" ]; then
+shouldWriteConfig="$haveConfig"
+if [ ! -f /etc/rabbitmq/rabbitmq.config ]; then
+	shouldWriteConfig=1
+fi
+
+if [ "$1" = 'rabbitmq-server' ] && [ "$shouldWriteConfig" ]; then
 	fullConfig=()
 
 	rabbitConfig=(
 		"{ loopback_users, $(rabbit_array) }"
 	)
 
+	# https://www.rabbitmq.com/memory.html#memsup-usage
+	# "If the absolute limit is larger than the installed RAM or available virtual address space, the threshold is set to whichever limit is smaller."
+	# specifically, if a memory limit isn't supplied to the container and "memory.limit_in_bytes" is thus an enormous constant, RabbitMQ will ignore it and use maximum available memory or address space instead
+	if [ -r /sys/fs/cgroup/memory/memory.limit_in_bytes ]; then
+		memLimit="$(< /sys/fs/cgroup/memory/memory.limit_in_bytes)"
+		rabbitConfig+=( "{ vm_memory_high_watermark, { absolute, $memLimit } }" )
+	fi
+
 	if [ "$haveSslConfig" ]; then
 		IFS=$'\n'
 		rabbitSslOptions=( $(rabbit_env_config 'ssl' "${sslConfigKeys[@]}") )