Object Storage Service (OSS) is a secure, cost-effective, and highly reliable cloud storage service provided by Alibaba Cloud. OSS enables you to store a large amount of data in the cloud. After OSS is integrated with Function Compute, OSS events can trigger relevant functions to customize data processing in OSS buckets.
Background information
OSS is seamlessly integrated with Function Compute by using OSS event triggers. You can define functions and trigger the functions by using OSS events to customize data processing in OSS buckets. When OSS detects an OSS event of a specified type, this event triggers a corresponding function. For example, you can define a function to process a PutObject event. When you call the PutObject operation of OSS to upload an image to OSS, this function will be automatically triggered to process the image.
After OSS is integrated with Function Compute, you can call various functions to process images or audio data and then write the results to multiple storage services. In the entire architecture, you only need to focus on defining the function logic. Function Compute can reliably process large volumes of data in real time and in parallel.
Definition of OSS events
When OSS detects an event, OSS encodes the event information as a JSON string and passes it to the corresponding event processing function. For more information about OSS event notification formats, see Notifications. The following table lists the supported OSS events.
| Code | Description |
|---|---|
| oss:ObjectCreated:PutObject | The PutObject operation is called to upload files. For more information, see PutObject. A function will be triggered after the operation is called. |
| oss:ObjectCreated:PutSymlink | The PutSymlink operation is called to create a symbolic link for TargetObject in OSS, so that you can use this symbolic link to access TargetObject. For more information, see PutSymlink. A function will be triggered after the operation is called. |
| oss:ObjectCreated:PostObject | The PostObject operation is called to upload a file to a specified bucket by using an HTML form. For more information, see PostObject. A function will be triggered after the operation is called. |
| oss:ObjectCreated:CopyObject | The CopyObject operation is called to copy an existing object in OSS. For more information, see CopyObject. A function will be triggered after the operation is called. |
| oss:ObjectCreated:InitiateMultipartUpload | Before the MultipartUpload mode is used to transmit data, the InitiateMultipartUpload operation is called to notify OSS to initialize a MultipartUpload event. For more information, see InitiateMultipartUpload. A function will be triggered after the operation is called. |
| oss:ObjectCreated:UploadPart | After a MultipartUpload event is initialized, data can be uploaded in parts based on the specified object name and upload ID. For more information, see UploadPart. A function will be triggered after the operation is called. |
| oss:ObjectCreated:UploadPartCopy | The UploadPartCopy operation is called to upload a part by copying data from an existing object. For more information, see UploadPartCopy. A function will be triggered after the operation is called. |
| oss:ObjectCreated:CompleteMultipartUpload | You can call this operation to complete multipart upload of an object. For more information, see CompleteMultipartUpload. A function will be triggered after the operation is called. |
| oss:ObjectCreated:AppendObject | The AppendObject operation is called to upload a file in append mode. For more information, see AppendObject. A function will be triggered after the operation is called. |
| oss:ObjectCreated:* | A function will be triggered when one of the preceding ObjectCreated operations is called. |
| oss:ObjectRemoved:DeleteObject | The DeleteObject operation is called to delete an object. For more information, see DeleteObject. A function will be triggered after the operation is called. |
| oss:ObjectRemoved:DeleteObjects | The DeleteObjects operation is called to delete files in batches. A function will be triggered after the operation is called. |
| oss:ObjectRemoved:AbortMultipartUpload | The AbortMultipartUpload operation is called to abort a MultipartUpload event based on the upload ID that you provide. For more information, see AbortMultipartUpload. A function will be triggered after the operation is called. |
Trigger rules
When you use OSS event triggers, make sure to avoid loops. For example, in a scenario where files are uploaded to an OSS bucket, the upload operation triggers a function. This function then generates one or more files that are written to the OSS bucket, and the write operation triggers this function again. This results in a loop.
To avoid costs incurred by loops as described in the preceding example, we recommend that you add prefixes or suffixes to directories. For example, you can set the src/ prefix for the bucket directory where a function is triggered, and the dst/ prefix for the directory to which files generated by the function are written. This prevents the function from being triggered again by the generated files.
If the same event type is specified for different triggers of a bucket, prefixes or suffixes cannot be repeated. For example, the oss:ObjectCreated:PutObject event is configured for a trigger. The prefix is source and the suffix is zip. The following table lists whether the bucket can be configured with other triggers.
| Event | Prefix | Suffix | Valid | Description |
|---|---|---|---|---|
| oss:ObjectCreated:PutObject | source | zip | No | Both the prefix and suffix are the same as the prefix and suffix configured for the existing trigger. |
| oss:ObjectCreated:PutObject | source | N/A | No | The prefix is the same as the prefix configured for the existing trigger. No suffix is set, and objects with the zip suffix are included. |
| oss:ObjectCreated:PutObject | N/A | zip | No | The suffix is the same as the suffix configured for the existing trigger. No prefix is set, and objects with the source prefix are included. |
| oss:ObjectCreated:PutObject | source1 | 1zip | Yes | The prefix and suffix are different from the existing ones. |
| oss:ObjectCreated:PutObject | source | zip1 | Yes | The suffix is different from the suffix configured for the existing trigger. |
| oss:ObjectCreated:PutObject | 1source | zip | Yes | The prefix is different from the prefix configured for the existing trigger. |
| oss:ObjectCreated:PostObject | source | zip | Yes | The event is different from the event configured for the existing trigger. |
If you want to use a trigger to trigger multiple functions, you can use Function Compute along with Serverless workflow. You can first use a trigger to trigger a function. Then, the function starts a Serverless workflow flow, in which you can call multiple functions. For more information, see Documentation.