Fixed transcribe 2 legs cannot fallback (#1451)

* fixed transcribe cannot fallback for specific endpoint

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lib/tasks/gather.js

@@ -1161,7 +1161,7 @@ class TaskGather extends SttTask {
   }
 
   async _startFallback(cs, ep, evt) {
-    if (this.canFallback) {
+    if (this.canFallback()) {
       this._stopTranscribing(ep);
       try {
         this.logger.debug('gather:_startFallback');

lib/tasks/stt-task.js

@@ -171,7 +171,7 @@ class SttTask extends Task {
       try {
         this.sttCredentials = await this._initSpeechCredentials(this.cs, this.vendor, this.label);
       } catch (error) {
-        if (this.canFallback) {
+        if (this.canFallback()) {
           this.notifyError(
             {
               msg: 'ASR error', details:`Invalid vendor ${this.vendor}, Error: ${error}`,
@@ -260,8 +260,19 @@ class SttTask extends Task {
     ep.addCustomEventListener(event, handler);
   }
 
-  removeCustomEventListeners() {
+  removeCustomEventListeners(ep) {
+    if (ep) {
+      // for specific endpoint
+      this.eventHandlers.filter((h) => h.ep === ep).forEach((h) => {
+        h.ep.removeCustomEventListener(h.event, h.handler);
+      });
+      this.eventHandlers = this.eventHandlers.filter((h) => h.ep !== ep);
+      return;
+    } else {
+      // for all endpoints
       this.eventHandlers.forEach((h) => h.ep.removeCustomEventListener(h.event, h.handler));
+      this.eventHandlers = [];
+    }
   }
 
   async _initSpeechCredentials(cs, vendor, label) {
@@ -329,11 +340,13 @@ class SttTask extends Task {
     return credentials;
   }
 
-  get canFallback() {
+  canFallback() {
     return this.fallbackVendor && this.isHandledByPrimaryProvider && !this.cs.hasFallbackAsr;
   }
 
-  async _initFallback() {
+  // ep is optional for gather or any verb that have single ep,
+  // but transcribe does need as it might has 2 eps
+  async _initFallback(ep) {
     assert(this.fallbackVendor, 'fallback failed without fallbackVendor configuration');
     this.logger.info(`Failed to use primary STT provider, fallback to ${this.fallbackVendor}`);
     this.isHandledByPrimaryProvider = false;
@@ -346,7 +359,7 @@ class SttTask extends Task {
     this.data.recognizer.label = this.label;
     this.sttCredentials = await this._initSpeechCredentials(this.cs, this.vendor, this.label);
     // cleanup previous listener from previous vendor
-    this.removeCustomEventListeners();
+    this.removeCustomEventListeners(ep);
   }
 
   async compileHintsForCobalt(ep, hostport, model, token, hints) {

lib/tasks/transcribe.js

@@ -70,6 +70,9 @@ class TaskTranscribe extends SttTask {
     this._bufferedTranscripts = [ [], [] ];  // for channel 1 and 2
     this.bugname_prefix = 'transcribe_';
     this.paused = false;
+    // fallback flags
+    this.isHandledByPrimaryProviderForEp1 = true;
+    this.isHandledByPrimaryProviderForEp2 = true;
   }
 
   get name() { return TaskName.Transcribe; }
@@ -776,7 +779,7 @@ class TaskTranscribe extends SttTask {
   }
 
   async _startFallback(cs, _ep, evt) {
-    if (this.canFallback) {
+    if (this.canFallback(_ep)) {
       _ep.stopTranscription({
         vendor: this.vendor,
         bugname: this.bugname,
@@ -786,7 +789,7 @@ class TaskTranscribe extends SttTask {
       try {
         this.notifyError({ msg: 'ASR error',
           details:`STT Vendor ${this.vendor} error: ${evt.error || evt.reason}`, failover: 'in progress'});
-        await this._initFallback();
+        await this._initFallback(_ep);
         let channel = 1;
         if (this.ep !== _ep) {
           channel = 2;
@@ -895,6 +898,41 @@ class TaskTranscribe extends SttTask {
     if (this._asrTimer) clearTimeout(this._asrTimer);
     this._asrTimer = null;
   }
+
+  // We need to keep track the fallback is happened for each endpoint
+  // override the canFallback and _initFallback methods to make sure that
+  // we only fallback once per endpoint
+  // we want to keep track this on task level instead of endpoint level
+  // because the endpoint instance is used across multiple tasks.
+  canFallback(ep) {
+    let isHandledByPrimaryProvider = this.isHandledByPrimaryProvider;
+    if (ep === this.ep) {
+      isHandledByPrimaryProvider = this.isHandledByPrimaryProviderForEp1;
+    } else if (ep === this.ep2) {
+      isHandledByPrimaryProvider = this.isHandledByPrimaryProviderForEp2;
+    }
+
+    const isOneOfEndpointAlreadyFallenBack = !!this.ep && !!this.ep2 &&
+      this.isHandledByPrimaryProviderForEp1 !== this.isHandledByPrimaryProviderForEp2;
+
+    // fallback is configured
+    return this.fallbackVendor &&
+      // has this endpoint already fallen back
+      isHandledByPrimaryProvider &&
+      // in global level, is there any fallback is already happened
+      // one fallen endpoint will mark cs.hasFallbackAsr to true,
+      // so if one endpoint was fallen, the other endpoint would be able to fallback.
+      (isOneOfEndpointAlreadyFallenBack || !this.cs.hasFallbackAsr);
+  }
+
+  _initFallback(ep) {
+    if (ep === this.ep) {
+      this.isHandledByPrimaryProviderForEp1 = false;
+    } else if (ep === this.ep2) {
+      this.isHandledByPrimaryProviderForEp2 = false;
+    }
+    return super._initFallback(ep);
+  }
 }
 
 module.exports = TaskTranscribe;