如何根据ec2资源实例获取public_dns_name？

Question

现在我想获取public_dns_name，然后登录到一个aws实例来获取CPU利用率。我知道用cloudwatch可以查，但是现在不想依赖amazon提供的功能直接基于linux查。我怎样才能得到它？

ec2 = boto3.resource('ec2',
                     aws_access_key_id=settings.AWS.get("aws_access_key_id"),
                     aws_secret_access_key=settings.AWS.get("aws_secret_access_key"),
                     region_name=settings.AWS.get("region_name"))

user_data_script = """#cloud-config
   runcmd:
    - sudo systemctl start docker
    - cd /srv/app/kfquantum
    - sudo docker run --env broker=%s \
                      --env result=redis://10.0.0.245:6379/0 \
                      --env host=kf-db.cluster-crietao0wrdu.rds.cn-northwest-1.amazonaws.com.cn \
                      --env user=db \
                      --env pw=y6y83aGagY8hgXZ \
                      -w /kfquantum -d --restart unless-stopped --name kf-celery kf-celery \
                      celery -A kfquantum worker --pool=solo -l info
   """ % settings.BROKER_URL
instance_type = "c5.large"
instance = ec2.create_instances(
    BlockDeviceMappings=[
        {
            "DeviceName": "/dev/xvda",
            'Ebs': {
                'DeleteOnTermination': True,
                'VolumeSize': 8
            },
        },
    ],
    ImageId="ami-09feea664bfc54194",
    MinCount=1,
    MaxCount=1,
    Placement={'AvailabilityZone': 'cn-northwest-1a'},
    InstanceType=instance_type,
    UserData=user_data_script,
    NetworkInterfaces=[
        {
            'DeviceIndex': 0,
            'SubnetId': "subnet-093161e8b00deb367",
            'AssociatePublicIpAddress': True
        },
    ]
)
instance = instance[0]
print("1",instance.private_ip_address)
print("2",instance.public_dns_name)

控制台

1,10.0.0.73
2

Answer 1

试试这个...

instance= instance[0]
print('***Success!! instance:', instance.id, 'created, and instance-state-name:', instance.state['Name'])           

instance.wait_until_running()           
instance.reload()

print('***instance:', instance.id, 'is now up, and instance-state-name:', instance.state['Name'])
print('***private ipa:', instance.private_ip_address)
print('***public ipa:', instance.public_dns_name)

希望对您有所帮助...
r0ck

Answer 2

public_dns_name 的值尚未分配。

这可能是由于

1. 实例还不是running。您正在尝试在调用 create_instances 方法后立即获取 DNS 名称。实例需要几秒钟才能达到running 状态。在实例达到running 状态之前，public_dns_name 不可用。检查实例状态并等待它运行，然后再尝试获取公共 DNS 名称。

在不干扰其余代码的情况下，一个简单的修复方法是，

更新： instance 对象必须在等待检测到更新的实例属性之后重新加载。

instance = instance[0]
instance.wait_until_running()
instance.reload()
print("1",instance.private_ip_address)
print("2",instance.public_dns_name)

1. 您的 VPC 中未启用 DNS 主机名。