如何获取AWS实例的公共DNS?

Question

我获取了某个特定地区，比如欧洲的负载均衡器（ELB）的详细信息。接着，我能够找到与这个负载均衡器相关的实例。但是，我遇到的问题是无法获取这些实例的公共DNS。我的做法是：

conn = regions[3].connect(aws_access_key_id= access, aws_secret_access_key = secret_key)
loadbalancers = conn.get_all_load_balancers()
for lb in loadbalancers:
    print lb.instances

那么，如何才能获取这些实例的公共DNS名称呢？

当我尝试这样做时：

for i in lb.instances:
    i.public_dns_name

我遇到了一个错误：'InstanceInfo'对象没有'public_dns_name'这个属性。

Answer 1

LoadBalancer类中的“instances”属性只包含了一点点关于实例的信息，并不是完整的实例对象。如果想要获取完整的实例对象，就需要使用可用的instanceId来查询更多的信息。下面的代码片段是在你的代码基础上增加了所需的调用：

#Create connection to ec2, credentials stored in environment
ec2_conn = connect_ec2()

conn = regions[3].connect(aws_access_key_id= access, aws_secret_access_key = secret_key)
loadbalancers = conn.get_all_load_balancers()
for lb in loadbalancers:
    for i in lb.instances:
        #Here, 'i' is an InstanceInfo object, not a full Instance
        instance_id = i.id

        #Query based on the instance_id we've got
        #This function actually gives reservations, not instances
        reservations = ec2_conn.get_all_instances(instance_ids=[instance_id])
        #pull out our single instance
        instance = reservations[0].instances[0]

        #Now we've got the full instance and we can get parameters from here
        print(instance.public_dns_name)