Using EG Event Notifications to Automate Image Processing in OBS

Buckets are containers that store objects in OBS. In this example, the uploaded image is stored in the source bucket. The watermarked image is stored in the target bucket. If you already have the source and target buckets, go to Step 2: Create a Function.

Objects in Archive or Deep Archive buckets can be downloaded or accessed via URLs only after they are manually restored. Therefore, this practice does not support Archive or Deep Archive buckets.

1. Go to the bucket creation page of OBS Console.
2. On the bucket creation page, configure the parameters as described in the following table. Keep the default settings for other parameters. The example values in the table are for reference only.
   For more information, see Creating a Bucket.

   Parameter	Example Value	Description
   Region	ME-Riyadh	The region where the bucket is located. For lower latency and faster access, select the region nearest to where the data will be accessed. Once the bucket is created, its region cannot be changed. The source and target buckets must be in the same region.
   Bucket Name	piccomp	The name of the bucket. Once the bucket is created, its name cannot be changed. A bucket name: Must be globally unique. It cannot be the same as the name of any existing bucket, including those created by other users. You must wait at least 30 minutes before you can reuse the name of a deleted bucket or parallel file system, or the creation will fail. Must be 3 to 63 characters long. Only lowercase letters, digits, hyphens (-), and periods (.) are allowed. Cannot start or end with a period (.) or hyphen (-). It also cannot contain two consecutive periods (..) or have a period (.) and a hyphen (-) adjacent to each other. Cannot be formatted as an IP address.
   Data Redundancy Policy	Multi-AZ storage	You can choose to store data in a single AZ or multiple AZs. With Multi-AZ storage, data is stored in multiple AZs within a region. This storage policy costs more but provides higher reliability. Once a bucket is created, its data redundancy policy cannot be changed. Multi-AZ storage is not available for buckets in the Archive or Deep Archive storage class.
   Storage Class	Standard	The storage class of the bucket. The storage classes can meet different performance and cost requirements. The Standard storage class is for storing a large number of hot files or small files that are frequently accessed (multiple times per month on average) and require fast access. For more information, see Storage Classes.
   Bucket Policy	Private	Controls read and write permissions for the bucket. Private: Only users granted permissions by the bucket ACL can access the bucket.
   Enterprise Project	default	You can add the bucket to an enterprise project for unified management. If you do not have any specific needs for enterprise project division and management, choose the default enterprise project. To learn more about how to manage OBS buckets using enterprise projects, see the Enterprise Project parameter in Creating a Bucket.

3. In the lower right corner of the page, click Create Now. Then, confirm the prompt message.

   If the bucket is created successfully, a success message will be displayed. Then, you can see the bucket in the bucket list.

4. Repeat 1 to 3 to create the target bucket piccomp-output.

When an image is uploaded to the source OBS bucket, the EG event subscription triggers function execution. Therefore, you need a function that adds a watermark to the image.

1. Click in the upper left corner of the page. Then, choose Compute > FunctionGraph to go to the FunctionGraph console.
2. In the navigation pane, choose Functions > Function List.
3. Click Create Function.
4. On the Create Function page, configure the parameters as described in the following table. Keep the default settings for other parameters.

   For more information, see Creating an Event Function.

   Table 3 Function parameters

   Parameter	Example Value	Description
   Create With	Create from scratch	Select a method for creating the function. Create from scratch means creating a custom function from the ground up.
   Function Type	Event Function	Defines how the function is triggered. Event Function indicates that the function is invoked by a trigger.
   Region	ME-Riyadh	Select a region where you will deploy your function code. Select the region where both the source and target buckets are located.
   Function Name	FG_Test	The name of the function. A function name: Can contain only letters, digits, underscores (_), and hyphens (-). Must start with a letter and end with a letter or digit. Can be up to 60 characters long.
   Enterprise Project	default	You can add the function to an enterprise project for unified management. If you do not have any specific needs for enterprise project division and management, choose the default enterprise project. For details about how to use enterprise projects, see Enterprise User Permissions and Project Management.
   Agency	OBS_Agency	An agency that authorizes FunctionGraph to access other cloud services. This agency must have the OBS Administrator permission for all resources. For details about how to create an agency, see Delegating Another Service for Resource Management.
   Runtime	Python 3.9	Select a language to compile the function.

   Figure 3 Creating a function
   

5. Click Create Function.
6. In the function list, click the function name to go to the function details page.
7. Upload the code file. For the sample code file used in this example, see Using a Function to Add Watermarks to Images.
   1. On the Code tab, choose Upload > Local ZIP.
   2. In the Upload ZIP File dialog box, click Add, select the downloaded sample code file watermark.zip, and click OK.

      In the code area, you can see the index.py file. This file serves as the entry point for function execution. The key parameters in the file are as follows:

      • obs_output_bucket: the OBS bucket (the target bucket in this example) for storing the watermarked image
      • obs_region: the ID of the region where the target bucket is located

8. Add code dependencies. The sample code depends on the Pillow package, which must be added as a dependency. Follow the following steps to add it:
   1. At the bottom of the Code tab, click Add under Dependencies.
   2. In the Select Dependency dialog box, add the public dependency package pillow-7.1.2 and click OK.

9. Configure environment variables. They are used to configure the target bucket for storing the watermarked image.
   1. On the Configuration tab, choose Environment Variables in the navigation pane.
   2. Click Edit Environment Variable. In the dialog box displayed on the right, click Add.
   3. Add the environment variables listed in the following table and click OK.

      Table 4 Environment variables

      Key	Value	Description
      obs_output_bucket	piccomp-output	The target OBS bucket for storing the watermarked image The value is the name of the target bucket created in Step 1: Create Source and Target OBS Buckets.
      obs_region	me-east-1	The ID of the region where the target bucket is located For details, refer to Regions and Endpoints.

      

      The keys obs_output_bucket and obs_region are the target bucket's key parameters in the sample code in 7.

      Figure 4 Configuring environment variables
      

Use an EG notification as the event trigger to trigger function execution. An EG event subscription connects an event source, a channel, and an event target. The event source (an OBS event) uses the channel to trigger the event target (the function) to run.

1. Click in the upper left corner of the page. Then, choose Storage > Object Storage Service. The bucket list page is displayed.
2. Click the name of the source bucket. The object list page is displayed.
3. In the navigation pane, choose Data Management > Event Notification.
4. On the EG tab, click Create. The EG event subscription details page is displayed.
5. Change the subscription name.

   Click next to the subscription name in the upper right corner. In the displayed dialog box, change the subscription name and click OK. In this example, change the subscription name to subscription-obs.

6. Configure an event source.
   1. Click Event Source. In the displayed dialog box, configure the parameters as described in the following table. Keep the default settings for other parameters.
      For more information, see Creating an Event Subscription.

      Table 5 Event source parameters

      Parameter	Example Value	Description
      Provider	Cloud services	Select an event source provider. Cloud services indicates that Huawei Cloud services are the event source providers.
      Event Source	OBS Application Service	Select a cloud service event source. OBS Application Service indicates that certain operations on objects in the bucket will generate events.
      Bucket	piccomp	Select the OBS bucket (the source bucket in this example) for which events are generated.
      Event Type	OBS:DWR:ObjectCreated:PUT OBS:DWR:ObjectCreated:POST OBS:DWR:ObjectCreated:COPY OBS:DWR:ObjectCreated:CompleteMultipartUpload	There will be events when the following operations happen: OBS:DWR:ObjectCreated:PUT: Creates or overwrites objects using the console or Put requests. OBS:DWR:ObjectCreated:POST: Creates or overwrites objects using Post requests. OBS:DWR:ObjectCreated:COPY: Creates or overwrites objects using Copy requests. OBS:DWR:ObjectCreated:CompleteMultipartUpload: Completes multipart uploads through the console or APIs.

      Figure 5 Configuring an event source
      
   2. Click OK.

7. Configure an event target.
   1. Click Event Target. In the displayed dialog box, configure the parameters as described in the following table. Keep the default settings for other parameters.

      For more information, see Creating an Event Subscription.

      Table 6 Event target parameters

      Parameter	Example Value	Description
      Provider	Cloud services	Select an event target provider. Cloud services indicates that Huawei Cloud services are the event target providers.
      Event Target	FunctionGraph (function computing)	Select a cloud service event target. FunctionGraph (function computing) indicates that FunctionGraph executes specific operations.
      Function	FG-Test	Select the required function. In this example, select the created function FG-Test that adds a watermark to the image.
      Agency	EG_TARGET_AGENCY	An agency that authorizes EG to access other cloud services. In this example, EG needs to access FunctionGraph. If no agency is available, click Create Agency to automatically create one named EG_TARGET_AGENCY.
      Transform Type	Variables	EG transforms event parameters by extracting them with JSONPath and routing them to the target.
      Parameters	As shown below	The parameters that need to be transformed
      Template	As shown below	Create a custom template that includes the required variables. EG will transform event parameters according to the template.

      In this example, configure Parameters as follows:

      {
        "eventVersion": "$.data.eventVersion",
        "eventTime": "$.data.eventTime",
        "requestParameters": "$.data.requestParameters.sourceIPAddress",
        "configurationId": "$.data.obs.configurationId",
        "eTag": "$.data.obs.object.eTag",
        "sequencer": "$.data.obs.object.sequencer",
        "key": "$.data.obs.object.key",
        "size": "$.data.obs.object.size",
        "arn": "$.data.obs.bucket.arn",
        "name": "$.data.obs.bucket.name",
        "ownerIdentity": "$.data.obs.bucket.ownerIdentity.ID",
        "eventRegion": "$.data.eventRegion",
        "eventName": "$.type",
        "userIdentity": "$.data.userIdentity.ID"
      }

      In this example, define the template as follows:

      {
          "Records": [
              {
                  "eventVersion": "${eventVersion}",
                  "eventTime": "${eventTime}",
                  "requestParameters": {
                      "sourceIPAddress": "${requestParameters}"
                  },
                  "b1": {
                      "configurationId": "${configurationId}",
                      "object": {
                          "eTag": "${eTag}",
                          "sequencer": "${sequencer}",
                          "key": "${key}",
                          "size": "${size}"
                      },
                      "bucket": {
                          "arn": "${arn}",
                          "name": "${name}",
                          "ownerIdentity": {
                              "PrincipalId": "${ownerIdentity}"
                          }
                      }
                  },
                  "eventRegion": "${eventRegion}",
                  "eventName": "${eventName}",
                  "userIdentity": {
                      "principalId": "${userIdentity}"
                  }
              }
          ]
      }

      Figure 6 Configuring an event target
      
   2. Click OK.

8. Click Save in the upper right corner of the page.

Upload an image to the OBS source bucket to generate an OBS event. EG then notifies the function to add a watermark to the image and store the processed image in the target bucket.

1. Click in the upper left corner of the page. Then, choose Storage > Object Storage Service. The bucket list page is displayed.
2. Click the name of the source bucket. The object list page is displayed.
3. On the Objects page, click Upload Object above the search box.
4. In the Upload Object dialog box, click add files and select the image you want to upload. Keep the default settings for other parameters.

   For more information, see Uploading an Object.

5. Click Upload.

   You can see the image you uploaded in the object list.

   Figure 7 Object uploaded successfully
   

Verify that the watermark is added to the image in the target bucket.

1. On the Buckets page, click the target bucket name.
2. On the object list page, click the name of the watermarked image.
3. Switch to the Preview Image tab and verify that the watermark appears on the image.
   Figure 8 Checking the watermarked image