Elastic Compute Service:Create application-consistent snapshots

Linux instance

On a Linux instance, compile custom shell scripts, including prescript.sh and postscript.sh, based on the deployed application to ensure application consistency. The following section describes how to create application-consistent snapshots for a Linux instance.

1. Prepare the scripts based on the application on the ECS instance and upload the scripts to the ECS instance in advance.

   Script	Description	Path	Type	Permissions	Content
   prescript.sh	Used to suspend all write operations to an application before you perform operations that may affect the application. This prevents data inconsistency due to new data generated during the operations.	/tmp/prescript.sh	Shell	Only the root user has read, write, and execute permissions on the scripts.	The script content is compiled based on your business requirements. For more information, see Best practices for creating application-consistent snapshots for a Linux instance on which MySQL is deployed.
   postscript.sh	After an operation that may affect an application, such as data backup, is complete, the postscript.sh script is run to restore the application and resume write operations.	/tmp/postscript.sh

   For information about how to upload files to an ECS instance, see Use Workbench to upload a file to and download a file from an instance.

   Note

   If the script settings, such as the permissions, storage path, or script name, are invalid, file system-consistent snapshots are created instead of application-consistent snapshots.

2. Navigate to the Create Snapshot-Consistent Group page.

   1. Log on to the ECS console.

   2. In the left-side navigation pane, choose Storage & Snapshots > Snapshots.

   3. In the top navigation bar, select the region where the ECS instance resides.

   4. Click the Snapshot-consistent Group tab, then click Create Snapshot-consistent Group.

3. In the Create Snapshot dialog box, configure the parameters described in the following table to create a snapshot-consistent group.

   1. By default, the Resource Type parameter is set to Instance.

   2. Select a Linux instance from the Select Instances drop-down list. Then, in the Select Cloud Disks section, select the ESSDs for which you want to create snapshots from the instance.

   3. Configure the parameters in the Application-consistent Snapshot section.

      • If you select Enable Application-consistent Snapshot and correctly configure scripts, application-consistent snapshots are created.

      • If you select Enable Application-consistent Snapshot but do not configure or incorrectly configure scripts, file system-consistent snapshots are created.

        Note

        If you do not install Cloud Assistant on the instance and you select Enable Application-consistent Snapshot, the required Cloud Assistant plug-in is automatically installed on the instance.

      • You can also select Enable to enable the File System I/O Suspension and Resume feature and specify a timeout period.

        Note

        If you enable the File System I/O Suspension and Resume feature, the system suspends I/O operations to file systems when snapshots are being created to prevent data inconsistency caused by ongoing I/O operations. If you set the Timeout Period parameter to a value greater than 16 and the I/O operation suspension is not complete within the period, the I/O operation suspension fails, which may cause data inconsistency issues.

4. Click OK.

   After the snapshot-consistent group is created, a message that contains the Cloud Assistant command ID and the task ID is displayed. You can check whether application-consistent snapshots are created based on the task ID.

Navigate to the Create Snapshot-Consistent Group page.

1. Log on to the ECS console.

2. In the left-side navigation pane, choose Storage & Snapshots > Snapshots.

3. In the top navigation bar, select the region where the ECS instance resides.

4. Click the Snapshot-consistent Group tab, then click Create Snapshot-consistent Group.

Windows instance

Windows instances use VSS to ensure application consistency. This section describes how to enable the application-consistent snapshot feature for a Windows instance.

1. Navigate to the Create Snapshot-Consistent Group page.

   1. Log on to the ECS console.

   2. In the left-side navigation pane, choose Storage & Snapshots > Snapshots.

   3. In the top navigation bar, select the region where the ECS instance resides.

   4. Click the Snapshot-consistent Group tab, then click Create Snapshot-consistent Group.

2. In the Create Snapshot dialog box, configure the parameters described in the following table to create a snapshot-consistent group.

   1. By default, the Resource Type parameter is set to Instance.

   2. Select a Windows instance from the Select Instances drop-down list. Then, in the Select Cloud Disks section, select the ESSDs for which you want to create snapshots from the instance.

   3. Configure the parameters in the Application-consistent Snapshot section.

      • If you select Enable Application-consistent Snapshot and Contain Writers by Default, application-consistent snapshots are created.

      • If you select only Enable Application-consistent Snapshot, file system-consistent snapshots are created.

      Note

      If you do not install Cloud Assistant on the instance and you select Enable Application-consistent Snapshot, the required Cloud Assistant plug-in is automatically installed on the instance.

3. Click OK.

   After the snapshot-consistent group is created, a message that contains the Cloud Assistant command ID and the task ID is displayed. You can check whether application-consistent snapshots are created based on the task ID.

Linux instance

Call the RunCommand operation to use Cloud Assistant to create application-consistent snapshots for one or more Linux instances.

package main

import (
    "fmt"
    "os"
    "github.com/aliyun/alibaba-cloud-sdk-go/services/ecs"
)

func main() {
		// Make sure that the ALIBABA_CLOUD_ACCESS_KEY_ID and ALIBABA_CLOUD_ACCESS_KEY_SECRET environment variables are configured in the code runtime. 
    // If the project code is leaked, the AccessKey pair may be leaked and the security of all resources in your account is compromised. The following sample code provides an example on how to use environment variables to obtain an AccessKey pair and use the AccessKey pair to call API operations. We recommend that you use STS tokens, which provide higher security. 
    client, err := ecs.NewClientWithAccessKey(
        "cn-hangzhou",    // Specify the region ID of the instance.
        os.Getenv("ALIBABA_CLOUD_ACCESS_KEY_ID"),     
        os.Getenv("ALIBABA_CLOUD_ACCESS_KEY_SECRET"))

    // Call the RunCommand operation to create application-consistent snapshots for the instance. 
    request := ecs.CreateRunCommandRequest()
    request.Scheme = "https"

    request.Type = "RunShellScript"
    // Specify the command content used to create application-consistent snapshots. For more information, see the following description of the CommandContent parameter. 
    request.CommandContent = "acs-plugin-manager --exec --plugin app-snapshot-plugin --params=-RamRoleName=\"AppSnapshotRoleName\",-EnableFsFreeze=true,-TimeoutInSeconds=30,-PreScriptPath=\"/tmp/prescript.sh\",-PostScriptPath=\"/tmp/postscript.sh\",-ExcludeDiskId=\"\",-Name=\"LinuxApp1\""
    request.InstanceId = &[]string{"i-bp17r83nppqf141v****"} // Specify the ID of the instance.

    response, err := client.RunCommand(request)
    if err != nil {
        fmt.Print(err.Error())
    }
    fmt.Printf("response is %#v\n", response)
}

Windows instance

Call the RunCommand operation to use Cloud Assistant to create application-consistent snapshots for one or more Windows instances.

package main

import (
    "fmt"
  	"os"
    "github.com/aliyun/alibaba-cloud-sdk-go/services/ecs"
)

func main() {
    // Make sure that the ALIBABA_CLOUD_ACCESS_KEY_ID and ALIBABA_CLOUD_ACCESS_KEY_SECRET environment variables are configured in the code runtime. 
    // If the project code is leaked, the AccessKey pair may be leaked and the security of all resources in your account is compromised. The following sample code provides an example on how to use environment variables to obtain an AccessKey pair and use the AccessKey pair to call API operations. We recommend that you use STS tokens, which provide higher security. 
    client, err := ecs.NewClientWithAccessKey(
        "cn-hangzhou",       // Specify the region ID of the instance.
        os.Getenv("ALIBABA_CLOUD_ACCESS_KEY_ID"),     
        os.Getenv("ALIBABA_CLOUD_ACCESS_KEY_SECRET"))

    request := ecs.CreateRunCommandRequest()
    request.Scheme = "https"

    request.Type = "RunBatScript"
    // Specify the command content used to create application-consistent snapshots. For more information, see the following description of the CommandContent parameter. 
    request.CommandContent = "acs-plugin-manager --exec --plugin app-snapshot-plugin-win --params=-RamRoleName=\"AppSnapshotRoleName\",-EnableWriters=true,-Description=\"AppSnapshot\",-ExcludeDiskId=\"\",-Name=\"APPSnapshot-1\""
    request.InstanceId = &[]string{"i-bp11vqwgh574****"} // Specify the ID of the instance.
    request.Timeout = "1800"

    response, err := client.RunCommand(request)
    if err != nil {
        fmt.Print(err.Error())
    }
    fmt.Printf("response is %#v\n", response)
}

Description of the CommandContent parameter:

• acs-plugin-manager --exec --plugin app-snapshot-plugin-win: runs the app-snapshot-plugin-win Cloud Assistant plug-in.

• --params=: the parameters of the plug-in. The following table describes the parameters.

  Parameter	Type	Required	Description
  ExcludeDiskId	String	No	The cloud disks to exclude from the snapshots.
  Name	String	Yes	The name of the snapshot-consistent group.
  Description	String	No	The description of the snapshot-consistent group.
  RamRoleName	String	Yes	The RAM role attached to the instance. For information about the name of the RAM role, see Configure a RAM role for an ECS instance.
  EnableWriters	Boolen	No	Specifies whether to create application-consistent snapshots. Valid values: true false Default value: true.

A response similar to the following one is returned. For information about the parameters in the response, see RunCommand.