fix(gateway): derive BEAM scheduler count from the environment (#2169)

fluxer_gateway/config/vm.args.src

@@ -7,8 +7,8 @@
 -env ERL_PROCESSES 262144
 +P 262144
 +Q 65536
-+S 6:6
-+SDcpu 4:4
++S ${FLUXER_ERLANG_SCHEDULERS:-6}:${FLUXER_ERLANG_SCHEDULERS:-6}
++SDcpu ${FLUXER_ERLANG_DIRTY_CPU_SCHEDULERS:-4}:${FLUXER_ERLANG_DIRTY_CPU_SCHEDULERS:-4}
 +SDio 8
 +sbwt none
 +sbwtdcpu none

fluxer_gateway/scripts/docker_entrypoint.sh

@@ -4,13 +4,56 @@
 
 set -eu
 
+is_positive_int() {
+    case "${1:-}" in
+        '' | 0* | *[!0-9]*) return 1 ;;
+        *) [ "$1" -gt 0 ] ;;
+    esac
+}
+
+available_cpu_count() {
+    cpu_quota=""
+    cpu_period=""
+    if [ -r /sys/fs/cgroup/cpu.max ]; then
+        read -r cpu_quota cpu_period < /sys/fs/cgroup/cpu.max || true
+    else
+        for cgroup_dir in /sys/fs/cgroup/cpu /sys/fs/cgroup/cpu,cpuacct; do
+            if [ -r "$cgroup_dir/cpu.cfs_quota_us" ] && [ -r "$cgroup_dir/cpu.cfs_period_us" ]; then
+                read -r cpu_quota < "$cgroup_dir/cpu.cfs_quota_us" || true
+                read -r cpu_period < "$cgroup_dir/cpu.cfs_period_us" || true
+                break
+            fi
+        done
+    fi
+    if is_positive_int "$cpu_quota" && is_positive_int "$cpu_period"; then
+        echo "$(((cpu_quota + cpu_period - 1) / cpu_period))"
+        return 0
+    fi
+    cpu_count="$(nproc 2>/dev/null || echo 1)"
+    if is_positive_int "$cpu_count"; then
+        echo "$cpu_count"
+    else
+        echo 1
+    fi
+}
+
 : "${FLUXER_ERLANG_NODE_NAME:[email protected]}"
 : "${FLUXER_ERLANG_COOKIE:=fluxer_gateway_dev_cookie}"
 : "${FLUXER_ERLANG_DIST_PORT:=8081}"
 
+if ! is_positive_int "${FLUXER_ERLANG_SCHEDULERS:-}"; then
+    FLUXER_ERLANG_SCHEDULERS="$(available_cpu_count)"
+fi
+
+if ! is_positive_int "${FLUXER_ERLANG_DIRTY_CPU_SCHEDULERS:-}"; then
+    FLUXER_ERLANG_DIRTY_CPU_SCHEDULERS="$(((FLUXER_ERLANG_SCHEDULERS * 2 + 2) / 3))"
+fi
+
 export FLUXER_ERLANG_NODE_NAME
 export FLUXER_ERLANG_COOKIE
 export FLUXER_ERLANG_DIST_PORT
+export FLUXER_ERLANG_SCHEDULERS
+export FLUXER_ERLANG_DIRTY_CPU_SCHEDULERS
 export RELX_REPLACE_OS_VARS="${RELX_REPLACE_OS_VARS:-true}"
 
 exec /opt/fluxer_gateway/bin/fluxer_gateway foreground >/dev/null 2>&1