boto 3 - EC2 Linux instance - need to capture device name as variable - amazon-web-services

Question

I need to capture variable value for Linux EC2 instances.
'Name': 'device',
'Value': "xvdg"
The value Disk Name(device name) changes for EC2 Linux instances e.g sdh,xvdg, etc..
I am using boto3 SDK
Any help is much appreciated.
Current Code (Hard coded the Device Name):
cloudwatch.put_metric_alarm(
AlarmName=prefix + ' - Elastic Search Disc % Availabilty is less than the configured threshold value - Please increase size of EBS Volume',
ComparisonOperator='LowerThanThreshold',
EvaluationPeriods=3,
MetricName='disk_used_percent',
Namespace='CWAgent',
Period=300,
Statistic='Average',
Threshold=75,
AlarmActions=[snstopicarn],
AlarmDescription='Standard Disc Alert - Elastic Search Disc % Availabilty is less than the configured threshold value - Please increase size of EBS Volume',
Dimensions=[
{
'Name': 'InstanceId',
'Value': instance["InstanceId"]
},
{
'Name': 'path',
'Value': "/mnt/elasticsearch"
},
{
'Name': 'device',
'Value': "xvdi"
},
{
'Name': 'fstype',
'Value': "ext4"
},
]
)

Answer 1

You can use describe_instances and extract DeviceName. (boto3 doc)
import boto3
instance_id = <instance_id>
client = boto3.client('ec2')
response = client.describe_instances(
InstanceIds=[
instance_id,
],
)
device_name = response['Reservations'][0]['Instances'][0]['BlockDeviceMappings'][0]['DeviceName']
#/dev/xvda
print(device_name)
When using describe_alarms_for_metric, the code would be like this.
response = client.describe_alarms_for_metric(
MetricName='string',
Namespace='string',
Statistic='SampleCount'|'Average'|'Sum'|'Minimum'|'Maximum',
ExtendedStatistic='string',
Dimensions=[
{
'Name': 'string',
'Value': 'string'
},
],
Period=123,
Unit='Seconds'|'Microseconds'|'Milliseconds'|'Bytes'|'Kilobytes'|'Megabytes'|'Gigabytes'|'Terabytes'|'Bits'|'Kilobits'|'Megabits'|'Gigabits'|'Terabits'|'Percent'|'Count'|'Bytes/Second'|'Kilobytes/Second'|'Megabytes/Second'|'Gigabytes/Second'|'Terabytes/Second'|'Bits/Second'|'Kilobits/Second'|'Megabits/Second'|'Gigabits/Second'|'Terabits/Second'|'Count/Second'|'None'
)
response = cloudwatch.put_metric_alarm(....)
for i in response['MetricAlarms'][0]['Dimensions'][0]:
if i['Name'] == 'device':
print(i['Value']) # xvdi