feat: report call count to redis for server-wide drain coordination

A server may run several sbc-inbound and sbc-outbound processes.  When
one of the sbc-inbound processes handles an AWS autoscale drain it must
complete the terminating lifecycle hook only when the whole server is
idle, not just its own process — otherwise the instance is terminated
while sibling processes still have calls in progress.

Each process now writes its own call count to a per-pid redis key
(120s expiry, refreshed every 15s from activeCallIds.size) and
registers that key in a per-host set, which the draining process
enumerates and sums.  See the companion change in sbc-inbound.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app.js

@@ -70,7 +70,8 @@ const {
   isMemberOfSet,
   addKey,
   deleteKey,
-  retrieveKey
+  retrieveKey,
+  addToSet
 } = require('@jambonz/realtimedb-helpers')({}, logger);
 
 const activeCallIds = new Map();
@@ -124,6 +125,17 @@ const {getRtpEngine, setRtpEngines} = require('@jambonz/rtpengine-utils')([], lo
 });
 srf.locals.getRtpEngine = getRtpEngine;
 
+/* report our call count to redis so a draining sbc-inbound process can count
+   calls across all sbc-inbound and sbc-outbound processes on this server */
+if (!process.env.K8S && 'test' !== process.env.NODE_ENV) {
+  srf.locals.callCountReporter = require('./lib/call-count-reporter')({
+    logger,
+    addKey,
+    addToSet,
+    getCount: () => activeCallIds.size
+  });
+}
+
 if (process.env.DRACHTIO_HOST && !process.env.K8S) {
   const cidrs = process.env.JAMBONES_NETWORK_CIDR
     .split(',')

lib/call-count-reporter.js

@@ -0,0 +1,31 @@
+const os = require('os');
+
+/**
+ * Periodically report this process's count of calls in progress to redis.
+ * A server may host several sbc-inbound and sbc-outbound processes; when one
+ * of them handles an autoscale drain it needs to know when the entire server
+ * has no calls in progress, not just its own process.  Each process writes
+ * its own count under a per-pid key (with a short expiry, so keys from dead
+ * processes evaporate) and registers that key in a per-host set that the
+ * draining process can enumerate.
+ */
+const REPORT_INTERVAL = 15000;
+const KEY_EXPIRY_SECS = 120;
+
+module.exports = ({logger, addKey, addToSet, getCount}) => {
+  const prefix = process.env.JAMBONES_CLUSTER_ID || 'default';
+  const setName = `${prefix}:call-count-keys:${os.hostname()}`;
+  const key = `${prefix}:call-count:${os.hostname()}:${process.pid}`;
+
+  const report = () => {
+    addKey(key, `${getCount()}`, KEY_EXPIRY_SECS)
+      .catch((err) => logger.error({err}, 'call-count-reporter: error writing call count'));
+  };
+
+  addToSet(setName, key)
+    .catch((err) => logger.error({err}, `call-count-reporter: error adding ${key} to ${setName}`));
+  setInterval(report, REPORT_INTERVAL);
+  report();
+
+  return {key, setName};
+};

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "sbc-outbound",
-  "version": "0.9.8",
+  "version": "0.9.9",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "sbc-outbound",
-      "version": "0.9.8",
+      "version": "0.9.9",
       "license": "MIT",
       "dependencies": {
         "@babel/helpers": "^7.26.10",

package.json

@@ -1,6 +1,6 @@
 {
   "name": "sbc-outbound",
-  "version": "0.9.8",
+  "version": "0.9.9",
   "main": "app.js",
   "engines": {
     "node": ">= 20.0.0"