EC2: Waiting until a new instance is in running state

Question

I would like to create a new instance based on my stored AMI.

I achieve this by the following code:

RunInstancesRequest rir = new RunInstancesRequest(ima         


        

Answer 1

You can use boto3 waiters, https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/ec2.html#waiters

for this ex: https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/ec2.html#EC2.Waiter.InstanceRunning

Or in Java https://docs.aws.amazon.com/AWSJavaSDK/latest/javadoc/ I am sure there are waiters implemented in all the AWS sdks.

Answer 2

boto3 has:

instance.wait_until_running()

From the boto3 docs:

Waits until this Instance is running. This method calls EC2.Waiter.instance_running.wait() which polls EC2.Client.describe_instances() every 15 seconds until a successful state is reached. An error is returned after 40 failed checks.

Answer 3

From the AWS CLI changelog for v1.6.0:

Add a wait subcommand that allows for a command to block until an AWS resource reaches a given state (issue 992, issue 985)

I don't see this mentioned in the documentation, but the following worked for me:

aws ec2 start-instances --instance-ids "i-XXXXXXXX"
aws ec2 wait instance-running --instance-ids "i-XXXXXXXX"

The wait instance-running line did not finish until the EC2 instance was running.

I don't use Python/boto/botocore but assume it has something similar. Check out waiter.py on Github.

Answer 4

Waiting for the EC2 instance to get ready is a common pattern. In the Python library boto you also solve this with sleep calls:

   reservation = conn.run_instances([Instance configuration here])
   instance = reservation.instances[0]

   while instance.state != 'running':
       print '...instance is %s' % instance.state
       time.sleep(10)
       instance.update()

With this mechanism you will be able to poll when your new instance will come up.

Answer 5

Go use Boto3's wait_until_running method:

http://boto3.readthedocs.io/en/latest/reference/services/ec2.html#EC2.Instance.wait_until_running

Answer 6

Depending on what you are trying to do (and how many servers you plan on starting), instead of polling for the instance start events, you could install on the AMI a simple program/script that runs once when the instance starts and sends out a notification to that effect, i.e. to an AWS SNS Topic.

The process that needs to know about new servers starting could then subscribe to this SNS topic, and would receive a push notifications each time a server starts.

Solves the same problem from a different angle; your mileage may vary.