FallbackSTT

The FallbackSTT class provides automatic failover between multiple STT providers for improved reliability. When one provider fails after exhausting its retries, it automatically switches to the next provider in the list.

Features

• Automatic failover: Seamlessly switches between providers when failures occur
• Audio buffering: Retains audio chunks during failures and replays them to the next provider
• Circular rotation: Cycles through providers indefinitely until transcription succeeds
• Zero configuration: Works with any STT implementation

Usage

import { FallbackSTT } from '@micdrop/server'
import { OpenaiSTT } from '@micdrop/openai'
import { GladiaSTT } from '@micdrop/gladia'

// Create a fallback STT with multiple providers
const stt = new FallbackSTT({
  factories: [
    // Primary provider: OpenAI with low retry count
    () =>
      new OpenaiSTT({
        apiKey: process.env.OPENAI_API_KEY || '',
        maxRetry: 2, // Fail faster to switch to backup
      }),
    // Backup provider: Gladia
    () =>
      new GladiaSTT({
        apiKey: process.env.GLADIA_API_KEY || '',
        maxRetry: 3,
      }),
  ],
})

// Use with MicdropServer
const server = new MicdropServer(socket, {
  stt,
  // ... other options
})

Options

Option	Type	Description
factories	Array<() => STT>	Array of factory functions that create STT instances

How It Works

1. Initialization: Starts with the first provider in the list
2. Normal operation: Forwards all audio to the current provider and emits transcripts
3. On failure: When a provider emits the Failed event:
   • Destroys the current provider
   • Moves to the next provider (wraps around to first if at end)
   • Replays buffered audio chunks to the new provider
4. Logging: Inherits logger configuration and applies it to child providers