使用BOTO3检索EC2实例的公共DNS [英] Retrieving public dns of EC2 instance with BOTO3

问题描述

我正在使用ipython了解Boto3并与EC2实例进行交互。这是我用来创建实例的代码：

I'm using ipython to get an understanding of Boto3 and interacting with EC2 instances. Here is the code I'm using to create an instance:

import boto3

ec2 = boto3.resource('ec2')
client = boto3.client('ec2')


new_instance = ec2.create_instances(
    ImageId='ami-d05e75b8',
    MinCount=1,
    MaxCount=1,
    InstanceType='t2.micro',
    KeyName=<name_of_my_key>,
    SecurityGroups=['<security_group_name>'],
    DryRun = False
    )

这将启动EC2实例很好，我可以从AWS控制台获取公共DNS名称，ip和其他信息。但是，当我尝试使用Boto获取公共DNS时，可以这样做：

This starts an EC2 instance fine, and I can get the public DNS name, ip and other info from the AWS console. But, when I try to get the public DNS using Boto, by doing this:

new_instance[0].public_dns_name

返回空引号。但是，其他实例详细信息，例如：

Returns blank quotes. Yet, other instance details, such as:

new_instance[0].instance_type

返回正确的信息。

有什么想法吗？谢谢。

Any ideas? Thanks.

编辑：

所以，如果我这样做：

def get_name(inst):
    client = boto3.client('ec2')
    response = client.describe_instances(InstanceIds = [inst[0].instance_id])
    foo = response['Reservations'][0]['Instances'][0]['NetworkInterfaces'][0]['Association']['PublicDnsName']
    return foo


foo = get_name(new_instance)
print foo

然后它将返回公共DNS。但是对我来说，为什么我需要做所有这些事情没有意义。

Then it will return the public DNS. But it doesn't make sense to me why I need to do all of this.

推荐答案

您返回的实例对象仅与响应混合在一起 create_instances 调用中的属性。由于DNS名称在实例达到运行状态之前不可用，因此 [1] ，它将不会立即显示。我想您从创建实例到调用describe实例之间的时间足以使微实例启动。

The Instance object you get back is only hydrated with the response attributes from the create_instances call. Since the DNS name is not available until the instance has reached the running state [1], it will not be immediately present. I imagine the time between you creating the instance and calling describe instances is long enough for the micro instance to start.

import boto3

ec2 = boto3.resource('ec2')
instances = ec2.create_instances(
    ImageId='ami-f0091d91',
    MinCount=1,
    MaxCount=1,
    InstanceType='t2.micro',
    KeyName='<KEY-NAME>',
    SecurityGroups=['<GROUP-NAME>'])
instance = instances[0]

# Wait for the instance to enter the running state
instance.wait_until_running()

# Reload the instance attributes
instance.load()
print(instance.public_dns_name)

这篇关于使用BOTO3检索EC2实例的公共DNS的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！