feat fallback speech

lib/tasks/say.js

@@ -59,15 +59,28 @@ class TaskSay extends Task {
     const vendor = this.synthesizer.vendor && this.synthesizer.vendor !== 'default' ?
       this.synthesizer.vendor :
       cs.speechSynthesisVendor;
+    const fallbackVendor = this.synthesizer.fallbackVendor && this.synthesizer.fallbackVendor !== 'default' ?
+    this.synthesizer.fallbackVendor :
+    cs.fallbackSpeechSynthesisVendor;
     const language = this.synthesizer.language && this.synthesizer.language !== 'default' ?
       this.synthesizer.language :
       cs.speechSynthesisLanguage ;
+    const fallbackLanguage = this.synthesizer.fallbackLanguage && this.synthesizer.fallbackLanguage !== 'default' ?
+    this.synthesizer.fallbackLanguage :
+    cs.fallbackSpeechSynthesisLanguage ;
     let voice =  this.synthesizer.voice && this.synthesizer.voice !== 'default' ?
       this.synthesizer.voice :
       cs.speechSynthesisVoice;
+    const fallbackVoice = this.synthesizer.fallbackVoice && this.synthesizer.fallbackVoice !== 'default' ?
+    this.synthesizer.fallbackVoice :
+    cs.fallbackSpeechSynthesisVoice;
+    const fallbackLabel = this.synthesizer.fallbackLabel && this.synthesizer.fallbackLabel !== 'default' ?
+    this.synthesizer.fallbackLabel :
+    cs.fallbackSpeechSynthesisLabel;
     const engine = this.synthesizer.engine || 'standard';
     const salt = cs.callSid;
-    let credentials = cs.getSpeechCredentials(vendor, 'tts', this.data.synthesizer?.label || cs.speechSynthesisLabel);
+    let credentials = cs.getSpeechCredentials(vendor, 'tts', this.data.synthesizer ?
+      this.data.synthesizer?.label : cs.speechSynthesisLabel);
 
     /* parse Nuance voices into name and model */
     let model;
@@ -118,6 +131,8 @@ class TaskSay extends Task {
           'tts.language': language,
           'tts.voice': voice
         });
+        let filePathUrl, isFromCache, roundTripTime;
+        let executedVendor, executedLanguage;
         try {
           const {filePath, servedFromCache, rtt} = await synthAudio(stats, {
             account_sid: cs.accountSid,
@@ -131,37 +146,98 @@ class TaskSay extends Task {
             credentials,
             disableTtsCache : this.disableTtsCache
           });
-          this.logger.debug(`file ${filePath}, served from cache ${servedFromCache}`);
-          if (filePath) cs.trackTmpFile(filePath);
+
+          span.setAttributes({'tts.cached': servedFromCache});
+          span.end();
+
           if (!servedFromCache && !lastUpdated) {
             lastUpdated = true;
             updateSpeechCredentialLastUsed(credentials.speech_credential_sid)
               .catch(() => {/*already logged error */});
           }
-          span.setAttributes({'tts.cached': servedFromCache});
-          span.end();
-          if (!servedFromCache && rtt) {
-            this.notifyStatus({
-              event: 'synthesized-audio',
-              vendor,
-              language,
-              characters: text.length,
-              elapsedTime: rtt
+
+          filePathUrl = filePath;
+          isFromCache = servedFromCache;
+          roundTripTime = rtt;
+          executedVendor = vendor;
+          executedLanguage = language;
+
+        } catch (error) {
+          if (fallbackVendor) {
+            const fallbackcredentials = cs.getSpeechCredentials(fallbackVendor, 'tts', fallbackLabel); 
+            const {span: fallbackSpan} = this.startChildSpan('fallback-tts-generation', {
+              'tts.vendor': fallbackVendor,
+              'tts.language': fallbackLanguage,
+              'tts.voice': fallbackVoice
             });
+
+            try {
+              const {filePath, servedFromCache, rtt} = await synthAudio(stats, {
+                account_sid: cs.accountSid,
+                text,
+                fallbackVendor,
+                fallbackLanguage,
+                fallbackVoice,
+                engine,
+                model,
+                salt,
+                credentials: fallbackcredentials,
+                disableTtsCache : this.disableTtsCache
+              });
+
+              fallbackSpan.setAttributes({'tts.cached': servedFromCache});
+              fallbackSpan.end();
+
+              if (!servedFromCache && !lastUpdated) {
+                lastUpdated = true;
+                updateSpeechCredentialLastUsed(credentials.speech_credential_sid)
+                  .catch(() => {/*already logged error */});
+              }
+
+              filePathUrl = filePath;
+              isFromCache = servedFromCache;
+              roundTripTime = rtt;
+              executedVendor = fallbackVendor;
+              executedLanguage = fallbackLanguage;
+
+            } catch (err){
+              this.logger.info({err}, 'fallback Speech failed to synthesize audio');
+              fallbackSpan.end();
+              writeAlerts({
+                account_sid: cs.accountSid,
+                alert_type: AlertType.TTS_FAILURE,
+                vendor: fallbackVendor,
+                detail: err.message
+              }).catch((err) => this.logger.info({err}, 'Error generating alert for fallback tts failure'));
+            }
           }
-          return filePath;
-        } catch (err) {
-          this.logger.info({err}, 'Error synthesizing tts');
+
+          this.logger.info({error}, 'Error synthesizing tts');
           span.end();
           writeAlerts({
             account_sid: cs.accountSid,
             alert_type: AlertType.TTS_FAILURE,
             vendor,
-            detail: err.message
+            detail: error.message
           }).catch((err) => this.logger.info({err}, 'Error generating alert for tts failure'));
-          this.notifyError({msg: 'TTS error', details: err.message || err});
+          this.notifyError({msg: 'TTS error', details: error.message || error});
           return;
         }
+
+        this.logger.debug(`file ${filePathUrl}, served from cache ${isFromCache}`);
+        if (filePathUrl) cs.trackTmpFile(filePathUrl);
+
+        if (!isFromCache && roundTripTime) {
+          this.notifyStatus({
+            event: 'synthesized-audio',
+            vendor: executedVendor,
+            language: executedLanguage,
+            characters: text.length,
+            elapsedTime: roundTripTime
+          });
+        }
+
+        return filePathUrl;
       };
 
       const arr = this.text.map((t) => generateAudio(t));