Object Concatenation

Last updated: 2021-11-19 14:48:50


    COS launched the object concatenation feature based on Serverless Cloud Function (SCF) to allow users to concatenate the binary of multiple objects in a specific order to get a new object.

    You need to add an object concatenation rule to a bucket, specify the URLs of objects to concatenate, trigger SCF to perform the concatenation, and store the concatenated object to a specified path in the bucket.


    • The concatenated object cannot be larger than 50 TB.
    • This feature can concatenate only binary of objects and cannot be used to splice audio, videos, or images.
    • If you have added an object concatenation rule to your bucket via the COS console, the function will appear in the SCF console. DO NOT delete the function. Otherwise, your rule may not take effect.
    • Regions where SCF is available support object concatenation, including Guangzhou, Shanghai, Beijing, Chengdu, Hong Kong, Singapore, Mumbai, Toronto, and Silicon Valley, and more. For more supported regions, please see SCF Documentation.
    • If an error is reported when you concatenate objects, click View Log on the right of the function to quickly redirect to the SCF console to view the error logs.
    • Object concatenation is not supported for objects stored in the ARCHIVE or DEEP ARCHIVE storage classes. To concatenate these objects, you need to restore them first. For detailed directions, please see Restoring Archived Objects.
    • Object concatenation depends on the SCF service, which provides users with a free tier. You will be billed for the part exceeding the free tier limit according to SCF Pricing. Note that the more objects you concatenate, the more resources will be used; the more often you concatenate objects, the more calling times will be incurred.


    1. Log in to the COS console.

    2. Click Application Integration on the left sidebar and then select the Data Processing tab.

    3. Click Object Concatenation.


      If you haven’t activated SCF, please go to the SCF console to activate it and authorize the service as instructed.

    4. Click Add Function and configure the following parameters:

      • Function Name: uniquely identifies a function and cannot be modified after it is created. You can view the function in the SCF console.

      • Execution Method: execution method for the function. If you set this field to Sync, the execution results will be returned after the concatenation task is complete. If you set this field to Async, the function will respond directly and execute the concatenation task in the background.

      • Authentication Method: authentication method for the function

        • If you select SCF, you need to trigger the function using a role that has permission to call the function.
        • If you select No, you need to select an appropriate API gateway to receive requests. If you don’t have an API gateway in this region, click Create API Gateway service, and we will configure an API gateway suitable for this function in this region.
      • API Gateway Service/API Path/Request Method: For more information about API gateway configurations, please see API Gateway Overview.

      • SCF Authorization: You need to authorize SCF so that it can read objects in your bucket and save the concatenated object to the specified path.

    5. Click Confirm.

    6. Click Instructions to view the field description, where Request Body is in JSON format. For the configuration demo, please see Using APIs to Concatenate Objects.

    7. Click Next to go to Calling Test page.

    8. Click Start, and the function will be called as configured. You can view the response of the function in Response.

    9. You can perform the following operations on the created function:

      • Click View Log to view the historical running status of object concatenation. If an error is reported, you can click View Log to quickly redirect to the SCF console to view the error log details.
      • Click Edit to modify an object concatenation function.
      • Click Delete to delete an unwanted object concatenation function.