Filtering ec2-instances with boto

Question

I use tags to keep track of my EC2 instances, such as (Project, Environment). I have a use case where I need to filter only those instances that belong to a specific project and to a specific environment.

When I use filter with boto and pass these two values I get a result that does a OR rather than a AND of the filters and so I am receiving a list of instances that belong to different projects but same environment.

Now I can use two lists and then compare the instances in each and get the desired set of instances, but is there a better way of getting this done?

Here is what i am doing:

conn = ec2.EC2Connection('us-east-1',aws_access_key_id='XXX',aws_secret_access_key='YYY')
reservations = conn.get_all_instances(filters={"tag-key":"project","tag-value":<project-name>,"tag-key":"env","tag-value":<env-name>})
instances = [i for r in reservations for i in r.instances]

Now the instance list that I am getting gives all the instances from the specified project irrespective of the environment and all the instances from the specified environment irrespective of the project.

Answer 1

You can use the tag:key=value syntax to do an AND search on your filters.

import boto.ec2

conn = boto.ec2.connect_to_region('us-east-1',aws_access_key_id='xx', aws_secret_access_key='xx')
reservations = conn.get_all_instances(filters={"tag:Name" : "myName", "tag:Project" : "B"})
instances = [i for r in reservations for i in r.instances]
print instances

See EC2 API for details http://docs.aws.amazon.com/AWSEC2/latest/APIReference/ApiReference-query-DescribeInstances.html

The problem with the syntax you used is that a Python dict has unique keys, so the second tag-key entry overwrites the first one :-(

Seb

Answer 2

While the documentation does not specifically say what happens with multiple filters, the ORing may be by design. In this case, pass the required attributes in sequence to the function and pass in the result of the previous invocation into the next one (using the instance_ids parameter). This will restrict the results in each step with the additional filter. The attributes are then applied in sequence returning the ANDed result you desire.