When you submit a task to the Lyrics Generation API, you can use the callBackUrl parameter to set a callback URL. When the task is completed, the system will automatically push the results to your specified address.

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Callback Mechanism Overview

The callback mechanism eliminates the need to poll the API for task status. The system will proactively push task completion results to your server.

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Callback Timing

The system will send callback notifications in the following situations:
  • Lyrics generation task completed successfully
  • Lyrics generation task failed
  • Errors occurred during task processing

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Callback Method

  • HTTP Method: POST
  • Content Type: application/json
  • Timeout Setting: 15 seconds
  • Retry Mechanism: Retry 3 times after failure, with intervals of 1 minute, 5 minutes, and 15 minutes respectively

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Callback Request Format

When the task is completed, the system will send a POST request to your callBackUrl in the following format: 
{
  "code": 200,
  "msg": "All generated successfully.",
  "data": {
    "callbackType": "complete",
    "taskId": "11dc****8b0f",
    "lyricsData": [
      {
        "text": "[Verse]\nWalking through the city's darkest night\nWith dreams burning like a blazing fire",
        "title": "Iron Man",
        "status": "complete",
        "errorMessage": ""
      },
      {
        "text": "[Verse]\nWind is calling out my name\nSteel armor shining in the light",
        "title": "Iron Man",
        "status": "complete",
        "errorMessage": ""
      }
    ]
  }
}

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Status Code Description

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code
integer
required
Callback status code indicating task processing result:
Status CodeDescription
200Success - Lyrics generation completed
400Bad Request - Parameter error, content violation, etc.
451Download Failed - Unable to download related files
500Server Error - Please try again later
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msg
string
required
Status message providing detailed status description
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data.callbackType
string
required
Callback type indicating the current callback stage:
  • complete: Lyrics generation completed
  • error: Task failed
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data.taskId
string
required
Task ID, consistent with the taskId returned when you submitted the task
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data.lyricsData
array
Lyrics generation result information, returns multiple lyrics variants on success
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data.lyricsData[].text
string
Generated lyrics content, including song structure markers (e.g., [Verse], [Chorus], etc.)
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data.lyricsData[].title
string
Lyrics title
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data.lyricsData[].status
string
Lyrics generation status:
  • complete: Generation completed
  • failed: Generation failed
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data.lyricsData[].errorMessage
string
Error message, contains specific error description when status is failed

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Callback Reception Examples

Here are example codes for receiving callbacks in popular programming languages: 
const express = require('express');
const app = express();

app.use(express.json());

app.post('/generate-lyrics-callback', (req, res) => {
  const { code, msg, data } = req.body;
  
  console.log('Received lyrics generation callback:', {
    taskId: data.taskId,
    callbackType: data.callbackType,
    status: code,
    message: msg
  });
  
  if (code === 200) {
    // Task completed successfully
    console.log('Lyrics generation completed');
    const lyricsData = data.lyricsData || [];
    
    console.log(`Generated ${lyricsData.length} lyrics variants:`);
    lyricsData.forEach((lyrics, index) => {
      console.log(`Lyrics variant ${index + 1}:`);
      console.log(`  Title: ${lyrics.title}`);
      console.log(`  Status: ${lyrics.status}`);
      if (lyrics.status === 'complete') {
        console.log(`  Lyrics content:\n${lyrics.text}`);
      } else {
        console.log(`  Error message: ${lyrics.errorMessage}`);
      }
    });
    
    // Process generated lyrics
    // Can save to database, files, etc.
    
  } else {
    // Task failed
    console.log('Lyrics generation failed:', msg);
    
    // Handle failure cases...
    if (code === 400) {
      console.log('Parameter error or content violation');
    } else if (code === 451) {
      console.log('File download failed');
    } else if (code === 500) {
      console.log('Server internal error');
    }
  }
  
  // Return 200 status code to confirm callback received
  res.status(200).json({ status: 'received' });
});

app.listen(3000, () => {
  console.log('Callback server running on port 3000');
});

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Best Practices

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Callback URL Configuration Recommendations

  1. Use HTTPS: Ensure your callback URL uses HTTPS protocol for secure data transmission
  2. Verify Source: Verify the legitimacy of the request source in callback processing
  3. Idempotent Processing: The same taskId may receive multiple callbacks, ensure processing logic is idempotent
  4. Quick Response: Callback processing should return a 200 status code as quickly as possible to avoid timeout
  5. Asynchronous Processing: Complex business logic should be processed asynchronously to avoid blocking callback response
  6. Lyrics Storage: Lyrics content should be saved to database or file system promptly

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Important Reminders

  • Callback URL must be a publicly accessible address
  • Server must respond within 15 seconds, otherwise it will be considered a timeout
  • If 3 consecutive retries fail, the system will stop sending callbacks
  • Please ensure the stability of callback processing logic to avoid callback failures due to exceptions
  • Pay attention to content policy compliance to avoid generation failures due to policy violations
  • Lyrics content may contain special characters, pay attention to encoding handling

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Troubleshooting

If you do not receive callback notifications, please check the following:

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Alternative Solution

If you cannot use the callback mechanism, you can also use polling:

Poll Query Results

Use the get lyrics generation details endpoint to regularly query task status. We recommend querying every 30 seconds.