add support for running in AWS autoscale cluster with graceful scale-in and standby

lib/utils/sbc-pinger.js

@@ -1,5 +1,7 @@
 const assert = require('assert');
 const noopLogger = {info: () => {}, error: () => {}};
+const {LifeCycleEvents} = require('./constants');
+const Emitter = require('events');
 const debug = require('debug')('jambonz:feature-server');
 
 module.exports = (logger) => {
@@ -13,6 +15,58 @@ module.exports = (logger) => {
   assert.ok(sbcs.length, 'JAMBONES_SBCS env var is empty or misconfigured');
   logger.info({sbcs}, 'SBC inventory');
 
+  // listen for SNS lifecycle changes
+  let lifecycleEmitter = new Emitter();
+  let dryUpCalls = false;
+  if (process.env.AWS_SNS_TOPIC_ARM &&
+    process.env.AWS_ACCESS_KEY_ID && process.env.AWS_SECRET_ACCESS_KEY && process.env.AWS_REGION) {
+
+    (async function() {
+      try {
+        lifecycleEmitter = await require('./aws-sns-lifecycle')(logger);
+
+        lifecycleEmitter
+          .on(LifeCycleEvents.ScaleIn, () => {
+            logger.info('AWS scale-in notification: begin drying up calls');
+            dryUpCalls = true;
+            lifecycleEmitter.operationalState = LifeCycleEvents.ScaleIn;
+
+            const {srf} = require('../..');
+            pingProxies(srf);
+
+            // if we have zero calls, we can complete the scale-in right
+            setTimeout(() => {
+              const calls = srf.locals.sessionTracker.count;
+              if (calls === 0) {
+                logger.info('scale-in can complete immediately as we have no calls in progress');
+                lifecycleEmitter.completeScaleIn();
+              }
+              else {
+                logger.info(`${calls} calls in progress; scale-in will complete when they are done`);
+              }
+            }, 5000);
+          })
+          .on(LifeCycleEvents.StandbyEnter, () => {
+            dryUpCalls = true;
+            const {srf} = require('../..');
+            pingProxies(srf);
+
+            logger.info('AWS enter pending state notification: begin drying up calls');
+          })
+          .on(LifeCycleEvents.StandbyExit, () => {
+            dryUpCalls = false;
+            const {srf} = require('../..');
+            pingProxies(srf);
+
+            logger.info('AWS enter pending state notification: re-enable calls');
+          });
+      } catch (err) {
+        logger.error({err}, 'Failure creating SNS notifier, lifecycle events will be disabled');
+      }
+    })();
+  }
+
+  // send OPTIONS pings to SBCs
   async function pingProxies(srf) {
     for (const sbc of sbcs) {
       try {
@@ -21,7 +75,7 @@ module.exports = (logger) => {
           uri: `sip:${sbc}`,
           method: 'OPTIONS',
           headers: {
-            'X-FS-Status': ms ? 'open' : 'closed'
+            'X-FS-Status': ms && !dryUpCalls ? 'open' : 'closed'
           }
         });
         req.on('response', (res) => {
@@ -40,6 +94,7 @@ module.exports = (logger) => {
   }, 60000);
 
   return {
+    lifecycleEmitter,
     getSBC: () => sbcs[idxSbc++ % sbcs.length]
   };
 };