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Setting File Decompression

Last updated: 2022-09-01 15:54:29


    The file decompression feature is a data processing solution provided by COS based on SCF. When you upload a compressed file to a bucket with a ZIP decompression rule configured, the SCF function preset by COS will be triggered automatically to decompress the file into the specified bucket and directory.

    Decompression Flow


    • File decompression supports decompressing ZIP files only.
    • If you have added a file decompression rule to your bucket in the COS console, you can view the created decompression function in the SCF console. Do not delete the function; otherwise, your rule may not take effect.
    • Regions where SCF is available support file decompression, including Guangzhou, Shanghai, Beijing, Chengdu, Hong Kong (China), Singapore, Mumbai, Toronto, and Silicon Valley. For more supported regions, see Serverless Cloud Function.
    • The directory or file name in your package must be UTF-8 or GB 2312 encoded; otherwise, the directory or file name might be garbled after decompression, or the decompression may be interrupted. If an error is reported, you can click View Log on the right of the function to redirect to the SCF console to view log details.
    • The decompression service is not supported for files stored in the ARCHIVE storage class. To decompress a package stored in the ARCHIVE storage class, restore it first. For detailed directions, see Restoring Archived Objects.
    • The maximum processing time for decompressing a compressed file is 900 seconds, beyond which the decompression task will fail. Limits of the COS file decompression feature are subject to SCF. For more limits, see Quota Limits.
    • The file decompression feature depends on the SCF service, which provides a free tier. Excessive usage will be billed at SCF prices. For more information, see Pricing. For the decompression feature, the larger your package, the higher your resource usage; the more often you decompress packages, the more invocations you will need to use.


    1. Log in to the COS console.
    2. Click Bucket List on the left sidebar.
    3. Click the name of the target bucket.
    4. Select Function Service on the left sidebar and click ZIP Decompression Function.

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

    5. Click Add Function and configure the following parameters:
    • Function Name: It uniquely identifies a function and cannot be modified after being set. You can view the function in the SCF console.
    • Event Type: An event is an operation that triggers SCF. Take upload as an example. You can initiate an upload by calling the PUT Object or POST Object API. If you select Create using Put method as the event type, decompression will be triggered only by a package uploaded via the PUT Object API.

      If you intend to upload files to the bucket in multiple ways, such as simple upload, multipart upload, and cross-region replication, we recommend you select File upload as the event type.

    • Trigger Condition: The upload path that will trigger SCF. If you select Specified prefix, SCF will be triggered only when the package is uploaded to a path with the specified prefix. If you select Not specifying prefix, SCF will be triggered as long as a package is uploaded to any location of the bucket.

      If the destination file prefix configured overlaps with the trigger condition, a loop may be triggered, which should be avoided. For example, if the destination file prefix is prefix, and the trigger condition is pre, a decompression loop will be triggered when you upload a pref package.

    • SCF Authorization: This authorization is required, because decompression requires you to authorize SCF to read the package from your bucket and upload the decompressed files to the specified location.
    1. Click Next and configure the following in the pop-up window:
    • Decompression Format: The supported compression format, which currently can be ZIP only.
    • Destination bucket: The bucket to store the decompressed files.
    • Destination path: Decompress the matched files into this destination directory. To prevent unnecessary fees from triggering the loop, we recommend you set a destination directory different from the prefix.
    • Extra prefix:
      • Compressed package name: You can decompress the compressed package to the prefix named after the compressed package
      • Full path of the compressed package: You can decompress the compressed package to a prefix named after the path of the complete compressed package.

        For example, if the compressed package is named 123.zip and is stored in the abc directory, then the compressed package name is 123.zip, and its full path is abc/123.zip.

      • None: The files in the compressed package will be directly decompressed to the destination path.
    • Forbid recursive triggering: Enabling this option does not continue to decompress ZIP packages that are decompressed from the package, while disabling it does.
    • Callback URL: Enter the callback URL as needed.
    1. Click Confirm.

      You can perform the following operations on the created function:
    • Click Log to view the historical running status of decompression. If an error is reported, you can click Log to quickly redirect to the SCF console to view its details.
    • Click More > Edit to modify the file decompression rule.
    • Click More > Delete to delete the file decompression rule.
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