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Cluster Server 7.4.2 Bundled Agents Reference Guide - Windows

Last Published: 2020-07-06

Product(s): InfoScale & Storage Foundation (7.4.2)

Platform: Windows

AWS EBSVol agent

A dedicated agent is required to provide high availability of the Amazon EBS volumes across nodes in an InfoScale cluster within the same availability zone. The EBSVol agent provides high availability of the EBS volumes during the failover of an application.

The EBSVol agent attaches EBS volumes to Amazon EC2 instances, monitors the volumes, and detaches them from the instances. It uses AWS CLI commands to determine the state of the EBS volumes.

Note:

The EBS volumes should not be configured in a parallel service group.

Prerequisites

Install the AWS CLI package.
For details, refer to the InfoScale Solutions in Cloud Environments document.

Create an IAM role with the requisite permissions, and attach the roles to the EC2 instances that form the cluster nodes.

On the AWS Management Console, navigate to IAM > Create Policy > Role, and create the role.

The following is a sample of the policy (.json) file:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Action": [
                 "ec2:DescribeVolumes",
                 "ec2:AttachVolume",
                 "ec2:DetachVolume"
            ],
            "Effect": "Allow",
            "Resource": "*"
        }
    ]

Dependencies

The EBS volume resource does not depend on any other resources.

Figure: Sample service group with an EBS volume resource

Agent functions

Online	Attaches the EBS volume to an EC2 instance using the attach-volume command.
Offline	Detaches the EBS volume from the EC2 instance using the detach-volume command.
Monitor	Determines if the EBS volume is attached to the EC2 instance or not using the describe-volume command.
Clean	Adds the following warning in the agent log if the EBS volume is busy or cannot be detached. Administrative intervention required. Administrator should take corrective actions to detach the EBS volume.

State definitions

ONLINE	Indicates one of the following: The volume is attached to an EC2 instance or is in the Busy state on the same instance. The attach operation is in progress and the volume gets successfully attached to the instance within the duration that is specified in the MONITOR_TIMEOUT attribute.
OFFLINE	Indicates one of the following states: The detach operation is in progress and the volume gets successfully detached from the EC2 instance within the duration that is specified in the MONITOR_TIMEOUT attribute. The volume is not attached to any instance. The volume is attached to a different instance The volume is in the Busy state on another instance.
FAULTED	Indicates that the EBS volume has unexpectedly got detached from an EC2 instance.
UNKNOWN	Indicates one of the following conditions: AWS CLI is not installed. The AWSBinDir attribute is not configured correctly. For example, if AWS CLI is installed at `C:\Program Files\Amazon\AWSCLI`, the AWSBinDir attribute should be set to the same value. The required roles are not configured or are not attached to the instance correctly. The ID that is specified in the VolumeID attribute is invalid. The volume that is specified using the VolumeID attribute belongs to a different zone. An attach operation is in progress, and the volume is not successfully attached to the instance within the duration that is specified in the MONITOR_TIMEOUT attribute. A detach operation is in progress, and the volume is not successfully detached from the instance within the duration that is specified in the MONITOR_TIMEOUT attribute. The EC2 instance metadata is not accessible, for example, via the following command: curl "http://169.254.169.254/latest/meta-data/"

Attributes

Table: Required attribute

Attribute	Description
VolumeId	The ID of the EBS volume. The volume and the EC2 instance must be within the same availability zone. Type and dimension: string-scalar

Attribute

Description

VolumeId

The ID of the EBS volume. The volume and the EC2 instance must be within the same availability zone.

Type and dimension: string-scalar

Table: Optional attribute

Attribute	Description
AWSBinDir	Location of the AWS EC2 commands and binaries. Type and dimension: string-scalar

Attribute

Description

AWSBinDir

Location of the AWS EC2 commands and binaries.

Type and dimension: string-scalar

Table: Internal attributes

Attribute	Description
Device	Name of the device to make the device visible to the instance. For example, xvdf through xvdp. This attribute is reserved for internal use only.
NumThreads	The number of threads that are used within the agent process for managing resources. This number does not include the number of threads that are used for other internal purposes. Setting the NumThreads attribute to a higher value may decrease the time required to go online or the time required to monitor a large number of EBS volume resources. Type and dimension: static integer-scalar Default: 1

Attribute

Description

Device

Name of the device to make the device visible to the instance.

For example, xvdf through xvdp.

This attribute is reserved for internal use only.

NumThreads

The number of threads that are used within the agent process for managing resources. This number does not include the number of threads that are used for other internal purposes.

Setting the NumThreads attribute to a higher value may decrease the time required to go online or the time required to monitor a large number of EBS volume resources.

Type and dimension: static integer-scalar

Default: 1

Resource type definition

type EBSVol (
   	static int FaultOnMonitorTimeouts = 0
   	static int NumThreads = 1
   	static i18nstr ArgList[] = { VolumeId, AWSBinDir, AWSDevice }
   	static boolean AEPTimeout = 1
   	str VolumeId
   	str AWSBinDir
   	temp str AWSDevice
)

Sample configuration

EBSVol res (
    VolumeId = vol-061516adc454d7e05
    AWSBinDir = "C:\Program Files\Amazon\AWSCLI"
)

Debug log levels

The EBSVol agent uses the DBG_1 debug log level.