support drain/undrain feature server from cluster

lib/http-routes/api/cluster.js

@@ -0,0 +1,24 @@
+const router = require('express').Router();
+const {srf} = require('../../..');
+
+router.post('/drain', async(req, res) => {
+  const {logger} = req.app.locals;
+  const {setDryUpCalls} = srf.locals;
+
+  logger.info('Received drain request via HTTP API');
+  setDryUpCalls();
+
+  res.sendStatus(201);
+});
+
+router.post('/undrain', async(req, res) => {
+  const {logger} = req.app.locals;
+  const {clearDryUpCalls} = srf.locals;
+
+  logger.info('Received undrain request via HTTP API');
+  clearDryUpCalls();
+
+  res.sendStatus(201);
+});
+
+module.exports = router;

lib/http-routes/api/index.js

@@ -8,5 +8,6 @@ api.use('/enqueue', require('./enqueue'));
 
 api.use('/messaging', require('./messaging'));            // inbound SMS
 api.use('/createMessage', require('./create-message'));   // outbound SMS (REST)
+api.use('/cluster', require('./cluster'));
 
 module.exports = api;

lib/utils/install-srf-locals.js

@@ -71,7 +71,7 @@ function installSrfLocals(srf, logger, {
   logger.debug('installing srf locals');
   assert(!srf.locals.dbHelpers);
   const {tracer} = srf.locals.otel;
-  const {getSBC, lifecycleEmitter} = require('./sbc-pinger')(logger);
+  const {getSBC, lifecycleEmitter, setDryUpCalls, clearDryUpCalls} = require('./sbc-pinger')(logger);
   const StatsCollector = require('@jambonz/stats-collector');
   const stats = srf.locals.stats = new StatsCollector(logger);
 
@@ -285,6 +285,8 @@ function installSrfLocals(srf, logger, {
     },
     parentLogger: logger,
     getSBC,
+    setDryUpCalls,
+    clearDryUpCalls,
     getSmpp: () => {
       return SMPP_URL;
     },

lib/utils/sbc-pinger.js

@@ -166,9 +166,23 @@ module.exports = (logger) => {
     }, 1000);
   }
 
+  const setDryUpCalls = () => {
+    logger.info('setting dryUpCalls flag');
+    dryUpCalls = true;
+  };
+
+  const clearDryUpCalls = () => {
+    if (lifecycleEmitter.operationalState !== LifeCycleEvents.ScaleIn) {
+      logger.info('clearing dryUpCalls flag');
+      dryUpCalls = false;
+    }
+  };
+
   return {
     lifecycleEmitter,
-    getSBC: () => sbcs[idxSbc++ % sbcs.length]
+    getSBC: () => sbcs[idxSbc++ % sbcs.length],
+    setDryUpCalls,
+    clearDryUpCalls,
   };
 };