fix: Guard against double-free of galacticChannel objects (#71)

Signed-off-by: Josh Kim <[email protected]>

build/npm/transport.json

@@ -28,6 +28,16 @@
     ],
     "license": "BSD-2-Clause",
     "changelogHistory": [
+        {
+            "date": "5/6/22",
+            "version": "1.3.6",
+            "notes": [
+                {
+                    "description": "Guard against race condition from process sleep/wake that corrupt galacticChannels map state",
+                    "review_uri": "https://github.com/vmware/transport-typescript/pull/61"
+                }
+            ]
+        },
         {
             "date": "9/8/21",
             "version": "1.3.5",

src/bridge/broker-connector.ts

@@ -690,7 +690,16 @@ export class BrokerConnector implements EventBusEnabled {
                     const session = this.sessions.get(sessionId);
                     for (let [chan, bIds] of this.channelBrokerIdentitiesMap.entries()) {
                         // decrement connectedBrokers for the channel
-                        this._galacticChannels.get(chan).connectedBrokers--;
+                        // NOTE: in an unlikely scenario, there could be a "double free" condition of the galactic channel object
+                        // that had been already cleaned up by this.closeGalacticChannel() when an event from the _closeObservable
+                        // tried to access the object and decrement the connectedBrokers counter, leading to access to undefined.
+                        // this is an extremely hard to reproduce issue, but I suspect that it greatly has to do with the browser
+                        // tab process being put to sleep (after a long idle) and a resultant race condition that may have led to
+                        // the above chain of actions. a fix implemented here is to protect the decrement instruction against
+                        // a situation where the galactic channel object has been destroyed.
+                        if (this._galacticChannels.has(chan)) {
+                            this._galacticChannels.get(chan).connectedBrokers--;
+                        }
 
                         // If the client will not immediately try to reconnect, clean up by
                         // removing the connection string from the channelBrokerIdentitiesMap

src/bus.api.ts

@@ -21,7 +21,7 @@ import { BrokerConnector } from './bridge';
 export declare type NgZoneRef = any;
 
 // current version
-const version = '1.3.5';
+const version = '1.3.6';
 
 export type ChannelName = string;
 export type SentFrom = string;