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(imageId,1, 1);
// Code for configuring the settings of the new instance
...
RunInstancesResult runResult = ec2.runInstances(rir);

However, I cannot find a wait to "block"/wait until the instance is up and running apart from Thread.currentThread().sleep(xxxx) command.

On the other hand, StartInstancesResult and TerminateInstancesResult gives you a way to have access on the state of the instances and be able to monitor any changes. But, what about the state of a completely new instance?

Answer 1

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 2

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 3

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.