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    Object Storage Service:Message notification

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    Object Storage Service:Message notification

    Last Updated:Jun 21, 2026

    Asynchronous processing requests return only a task ID. To obtain the result of a task after data processing is complete, you must add message notification parameters to the processing request.

    Usage notes

    • Message notification is supported only for asynchronous processing.

    • Message notification supports only topics for Simple Message Queue (SMQ). SMQ was formerly known as MNS. For more information about SMQ, see SMQ Quick Start.

    Parameter description

    When you use the notify parameter, include the following option:

    Parameter

    Required

    Description

    topic

    Yes

    The name of the SMQ topic.

    • The SMQ topic must be in the same region as the bucket.

    • The topic name must be URL-safe Base64 encoded. For example, a topic named test must be entered as dGVzdA==. You can use a Base64 URL encoding tool to encode the name.

    To learn how to obtain the SMQ topic name, see How do I view the name of my SMQ topic in the console?

    Use REST APIs

    If your program requires a high level of customization, you can directly initiate REST API requests. To do this, you must manually write code to calculate signatures.

    When you call the PostObject operation to process an object, pass the x-oss-async-process parameter in the request body. Then, add the notify parameter to the request to receive message notifications about the results. Message notification supports only SMQ topics. For more information about using SMQ, see Python SDK version guide.

    The following sections provide examples of receiving SMQ message notifications in different scenarios.

    Use processing parameters to convert a document and receive SMQ message notifications

    Conversion information

    • Before conversion

      • File type: DOCX

      • File name: example.docx

    • After conversion

      • File type: PNG

      • Storage path: oss://test-bucket/doc_images/

    • Message notification

      The conversion result notification is sent to the SMQ topic named test-topic.

    Processing example

    POST /exmaple.docx?x-oss-async-process HTTP/1.1
Host: doc-demo.oss-cn-hangzhou.aliyuncs.com
Date: Fri, 28 Oct 2022 06:40:10 GMT
Authorization: OSS4-HMAC-SHA256 Credential=LTAI********************/20250417/cn-hangzhou/oss/aliyun_v4_request,Signature=a7c3554c729d71929e0b84489addee6b2e8d5cb48595adfc51868c299c0c218e
// Converts example.docx to PNG, saves it to oss://test-bucket/doc_images/, and sends a notification to the test-topic SMQ topic.
x-oss-async-process=doc/convert,target_png,source_docx|sys/saveas,b_dGVzdC1idWNrZXQ,o_ZG9jX2ltYWdlcy97aW5kZXh9LnBuZw/notify,topic_dGVzdC10b3BpYw

    Use style parameters to transcode a video and save it to a specified bucket

    Transcoding information

    • Before transcoding

      • Video format: AVI

      • Video name: example.avi

    • After transcoding

      • Video format: MP4

      • Video name: outobjprefix.mp4

      • Storage path: oss://outbucket/outobjprefix.mp4

    • Message notification

      The transcoding result notification is sent to the SMQ topic named test-topic.

    POST /exmaple.avi?x-oss-async-process HTTP/1.1
Host: video-demo.oss-cn-hangzhou.aliyuncs.com
Date: Fri, 28 Oct 2022 06:40:10 GMT
Authorization: OSS4-HMAC-SHA256 Credential=LTAI********************/20250417/cn-hangzhou/oss/aliyun_v4_request,Signature=a7c3554c729d71929e0b84489addee6b2e8d5cb48595adfc51868c299c0c218e
 // Transcodes example.avi using the examplestyle style, saves the output to oss://outbucket/outobjprefix.mp4, and sends a notification to the test-topic SMQ topic.
x-oss-async-process=style/examplestyle|sys/saveas,b_b3V0YnVja2V0,o_b3V0b2JqcHJlZml4LnthdXRvZXh0fQ/notify,topic_dGVzdC10b3BpYw

    Message formats for x-oss-process operations

    Feature module

    x-oss-process operation

    Message format

    Document processing

    doc/convert

    Sample MNS message for the CreateOfficeConversionTask operation

    ApsaraVideo Media Processing

    Sample MNS message for the CreateMediaConvertTask operation

    File processing

    pointcloud/compress

    Sample MNS message for the CreateCompressPointCloudTask operation

    Image processing

    image/deblindwatermark

    Sample MNS message for the CreateDecodeBlindWatermarkTask operation

    FAQ

    How do I view the name of my SMQ topic in the console?

    To configure a Simple Message Queue (SMQ) topic for OSS event notifications, you must use a topic that is in the same region as your OSS bucket. Follow these steps to find the name of an SMQ topic. SMQ was formerly known as MNS.

    1. Log on to the Simple Message Queue (SMQ), formerly MNS, console.

    2. In the top navigation bar of the console, make sure that you select the same region as your OSS bucket.

    3. In the navigation pane on the left, click Topic-based Model > Topic List to view all created topics in the current region.

    4. Browse the topic list to find the name of the topic that you want to use for your OSS event notification configuration.

    By following these steps, you can find the name of the SMQ topic in the same region as your OSS bucket. Using the correct topic name ensures that OSS events are sent to the message queue for processing.