ec2_asg: Add functionality to detach specified instances from ASG (#933)

ec2_asg: Add functionality to detach specified instances from ASG 

SUMMARY

Adds feature to detach specified instances from a AutoScalingGroup rather than terminating them directly.
Detached instances are not terminated and can be managed independently.

Implements #649
ISSUE TYPE


Feature Pull Request

COMPONENT NAME

ec2_asg
ADDITIONAL INFORMATION


Makes use of
https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/autoscaling.html#AutoScaling.Client.detach_instances

Reviewed-by: Alina Buzachis <None>
Reviewed-by: Mandar Kulkarni <[email protected]>
Reviewed-by: Jill R <None>
Reviewed-by: Joseph Torcasso <None>

changelogs/fragments/933-ec2_asg-detach-instances-feature.yml

@@ -0,0 +1,3 @@
+minor_changes:
+  - ec2_asg - Added functionality to detach specific instances and/or decrement desired capacity
+   from ASG without terminating instances (https://github.com/ansible-collections/community.aws/pull/933).

plugins/modules/ec2_asg.py

@@ -182,6 +182,21 @@
         matching the current launch configuration.
     type: list
     elements: str
+  detach_instances:
+    description:
+      - Removes one or more instances from the specified AutoScalingGroup.
+      - If I(decrement_desired_capacity) flag is not set, new instance(s) are launched to replace the detached instance(s).
+      - If a Classic Load Balancer is attached to the AutoScalingGroup, the instances are also deregistered from the load balancer.
+      - If there are target groups attached to the AutoScalingGroup, the instances are also deregistered from the target groups.
+    type: list
+    elements: str
+    version_added: 3.2.0
+  decrement_desired_capacity:
+    description:
+      - Indicates whether the AutoScalingGroup decrements the desired capacity value by the number of instances detached.
+    default: false
+    type: bool
+    version_added: 3.2.0
   lc_check:
     description:
       - Check to make sure instances that are being replaced with I(replace_instances) do not already have the current I(launch_config).
@@ -756,6 +771,12 @@ def terminate_asg_instance(connection, instance_id, decrement_capacity):
                                                         ShouldDecrementDesiredCapacity=decrement_capacity)
 
 
+@AWSRetry.jittered_backoff(**backoff_params)
+def detach_asg_instances(connection, instance_ids, as_group_name, decrement_capacity):
+    connection.detach_instances(InstanceIds=instance_ids, AutoScalingGroupName=as_group_name,
+                                ShouldDecrementDesiredCapacity=decrement_capacity)
+
+
 def enforce_required_arguments_for_create():
     ''' As many arguments are not required for autoscale group deletion
         they cannot be mandatory arguments for the module, so we enforce
@@ -1523,6 +1544,40 @@ def replace(connection):
     return changed, asg_properties
 
 
+def detach(connection):
+    group_name = module.params.get('name')
+    detach_instances = module.params.get('detach_instances')
+    as_group = describe_autoscaling_groups(connection, group_name)[0]
+    decrement_desired_capacity = module.params.get('decrement_desired_capacity')
+    min_size = module.params.get('min_size')
+    props = get_properties(as_group)
+    instances = props['instances']
+
+    # check if provided instance exists in asg, create list of instances to detach which exist in asg
+    instances_to_detach = []
+    for instance_id in detach_instances:
+        if instance_id in instances:
+            instances_to_detach.append(instance_id)
+
+    # check if setting decrement_desired_capacity will make desired_capacity smaller
+    # than the currently set minimum size in ASG configuration
+    if decrement_desired_capacity:
+        decremented_desired_capacity = len(instances) - len(instances_to_detach)
+        if min_size and min_size > decremented_desired_capacity:
+            module.fail_json(
+                msg="Detaching instance(s) with 'decrement_desired_capacity' flag set reduces number of instances to {0}\
+                        which is below current min_size {1}, please update AutoScalingGroup Sizes properly.".format(decremented_desired_capacity, min_size))
+
+    if instances_to_detach:
+        try:
+            detach_asg_instances(connection, instances_to_detach, group_name, decrement_desired_capacity)
+        except (botocore.exceptions.ClientError, botocore.exceptions.BotoCoreError) as e:
+            module.fail_json_aws(e, msg="Failed to detach instances from AutoScaling Group")
+
+    asg_properties = get_properties(as_group)
+    return True, asg_properties
+
+
 def get_instances_by_launch_config(props, lc_check, initial_instances):
     new_instances = []
     old_instances = []
@@ -1776,6 +1831,8 @@ def main():
         replace_batch_size=dict(type='int', default=1),
         replace_all_instances=dict(type='bool', default=False),
         replace_instances=dict(type='list', default=[], elements='str'),
+        detach_instances=dict(type='list', default=[], elements='str'),
+        decrement_desired_capacity=dict(type='bool', default=False),
         lc_check=dict(type='bool', default=True),
         lt_check=dict(type='bool', default=True),
         wait_timeout=dict(type='int', default=300),
@@ -1821,16 +1878,18 @@ def main():
         argument_spec=argument_spec,
         mutually_exclusive=[
             ['replace_all_instances', 'replace_instances'],
-            ['launch_config_name', 'launch_template']
+            ['replace_all_instances', 'detach_instances'],
+            ['launch_config_name', 'launch_template'],
         ]
     )
 
     state = module.params.get('state')
     replace_instances = module.params.get('replace_instances')
     replace_all_instances = module.params.get('replace_all_instances')
+    detach_instances = module.params.get('detach_instances')
 
     connection = module.client('autoscaling')
-    changed = create_changed = replace_changed = False
+    changed = create_changed = replace_changed = detach_changed = False
     exists = asg_exists(connection)
 
     if state == 'present':
@@ -1847,7 +1906,15 @@ def main():
     ):
         replace_changed, asg_properties = replace(connection)
 
-    if create_changed or replace_changed:
+    # Only detach instances if asg existed at start of call
+    if (
+        exists
+        and (detach_instances)
+        and (module.params.get('launch_config_name') or module.params.get('launch_template'))
+    ):
+        detach_changed, asg_properties = detach(connection)
+
+    if create_changed or replace_changed or detach_changed:
         changed = True
 
     module.exit_json(changed=changed, **asg_properties)

tests/integration/targets/ec2_asg/tasks/instance_detach.yml

@@ -0,0 +1,208 @@
+- name: Running instance detach tests
+  block:
+    #----------------------------------------------------------------------
+    - name: create a launch configuration
+      ec2_lc:
+        name: "{{ resource_prefix }}-lc-detach-test"
+        image_id: "{{ ec2_ami_image }}"
+        region: "{{ aws_region }}"
+        instance_type: t2.micro
+        assign_public_ip: yes
+      register: create_lc
+
+    - name: ensure that lc is created
+      assert:
+        that:
+          - create_lc is changed
+          - create_lc.failed is false
+          - '"autoscaling:CreateLaunchConfiguration" in create_lc.resource_actions'
+
+    #----------------------------------------------------------------------
+    - name: create a AutoScalingGroup to be used for instance_detach test
+      ec2_asg:
+        name: "{{ resource_prefix }}-asg-detach-test"
+        launch_config_name: "{{ resource_prefix }}-lc-detach-test"
+        health_check_period: 60
+        health_check_type: ELB
+        replace_all_instances: yes
+        min_size: 3
+        max_size: 6
+        desired_capacity: 3
+        region: "{{ aws_region }}"
+      register: create_asg
+
+    - name: ensure that AutoScalingGroup is created
+      assert:
+        that:
+          - create_asg is changed
+          - create_asg.failed is false
+          - create_asg.instances | length == 3
+          - create_asg.desired_capacity == 3
+          - create_asg.in_service_instances == 3
+          - '"autoscaling:CreateAutoScalingGroup" in create_asg.resource_actions'
+
+    - name: gather info about asg, get instance ids
+      ec2_asg_info:
+        name: "{{ resource_prefix }}-asg-detach-test"
+      register: asg_info
+    - set_fact:
+        init_instance_1: "{{ asg_info.results[0].instances[0].instance_id }}"
+        init_instance_2: "{{ asg_info.results[0].instances[1].instance_id }}"
+        init_instance_3: "{{ asg_info.results[0].instances[2].instance_id }}"
+
+    - name: Gather information about recently detached instances
+      amazon.aws.ec2_instance_info:
+        instance_ids:
+          - "{{ init_instance_1 }}"
+          - "{{ init_instance_2 }}"
+          - "{{ init_instance_3 }}"
+      register: instances_info
+
+    # assert that there are 3 instances running in the AutoScalingGroup
+    - assert:
+        that:
+          - asg_info.results[0].instances | length == 3
+          - "'{{ instances_info.instances[0].state.name }}' == 'running'"
+          - "'{{ instances_info.instances[1].state.name }}' == 'running'"
+          - "'{{ instances_info.instances[2].state.name }}' == 'running'"
+
+    #----------------------------------------------------------------------
+
+    - name: detach 2 instance from the asg and replace with other instances
+      ec2_asg:
+        name: "{{ resource_prefix }}-asg-detach-test"
+        launch_config_name: "{{ resource_prefix }}-lc-detach-test"
+        health_check_period: 60
+        health_check_type: ELB
+        min_size: 3
+        max_size: 3
+        desired_capacity: 3
+        region: "{{ aws_region }}"
+        detach_instances:
+          - '{{ init_instance_1 }}'
+          - '{{ init_instance_2 }}'
+
+    # pause to allow completion of instance replacement
+    - name: Pause for 1 minute
+      pause:
+        seconds: 30
+
+    # gather info about asg and get instance ids
+    - ec2_asg_info:
+        name: "{{ resource_prefix }}-asg-detach-test"
+      register: asg_info_replaced
+    - set_fact:
+        instance_replace_1: "{{ asg_info_replaced.results[0].instances[0].instance_id }}"
+        instance_replace_2: "{{ asg_info_replaced.results[0].instances[1].instance_id }}"
+        instance_replace_3: "{{ asg_info_replaced.results[0].instances[2].instance_id }}"
+
+    # create a list of instance currently attached to asg
+    - set_fact:
+        asg_instance_detach_replace: "{{ asg_info_replaced.results[0].instances | map(attribute='instance_id') | list }}"
+
+    - name: Gather information about recently detached instances
+      amazon.aws.ec2_instance_info:
+        instance_ids:
+          - "{{ init_instance_1 }}"
+          - "{{ init_instance_2 }}"
+      register: detached_instances_info
+
+    # assert that
+    #   there are 3 still instances in the AutoScalingGroup
+    #   two specified instances are detached and still running independently(not terminated)
+    - assert:
+        that:
+          - asg_info_replaced.results[0].desired_capacity == 3
+          - asg_info_replaced.results[0].instances | length == 3
+          - "'{{ init_instance_1 }}' not in {{ asg_instance_detach_replace }}"
+          - "'{{ init_instance_2 }}' not in {{ asg_instance_detach_replace }}"
+          - "'{{ detached_instances_info.instances[0].state.name }}' == 'running'"
+          - "'{{ detached_instances_info.instances[1].state.name }}' == 'running'"
+
+    #----------------------------------------------------------------------
+
+    # detach 2 instances from the asg and reduce the desired capacity from 3 to 1
+    - name: detach 2 instance from the asg and reduce the desired capacity from 3 to 1
+      ec2_asg:
+        name: "{{ resource_prefix }}-asg-detach-test"
+        launch_config_name: "{{ resource_prefix }}-lc-detach-test"
+        health_check_period: 60
+        health_check_type: ELB
+        min_size: 1
+        max_size: 5
+        desired_capacity: 3
+        region: "{{ aws_region }}"
+        decrement_desired_capacity: true
+        detach_instances:
+          - '{{ instance_replace_1 }}'
+          - '{{ instance_replace_2 }}'
+
+    - name: Pause for 1 minute to allow completion of above task
+      pause:
+        seconds: 30
+
+    # gather information about asg and get instance id
+    - ec2_asg_info:
+        name: "{{ resource_prefix }}-asg-detach-test"
+      register: asg_info_decrement
+    - set_fact:
+        instance_detach_decrement: "{{ asg_info_decrement.results[0].instances[0].instance_id }}"
+    # create a list of instance ids from info result and set variable value to instance ID
+    - set_fact:
+        asg_instance_detach_decrement: "{{ asg_info_decrement.results[0].instances | map(attribute='instance_id') | list }}"
+
+    - name: Gather information about recently detached instances
+      amazon.aws.ec2_instance_info:
+        instance_ids:
+          - "{{ instance_replace_1 }}"
+          - "{{ instance_replace_2 }}"
+      register: detached_instances_info
+
+    # assert that
+    #   detached instances are not replaced and there is only 1 instance in the AutoScalingGroup
+    #   desired capacity is reduced to 1
+    #   detached instances are not terminated
+    - assert:
+        that:
+          - asg_info_decrement.results[0].instances | length == 1
+          - asg_info_decrement.results[0].desired_capacity == 1
+          - "'{{ instance_replace_1 }}' not in {{ asg_instance_detach_decrement }}"
+          - "'{{ instance_replace_2 }}' not in {{ asg_instance_detach_decrement }}"
+          - "'{{ detached_instances_info.instances[0].state.name }}' == 'running'"
+          - "'{{ detached_instances_info.instances[1].state.name }}' == 'running'"
+          - "'{{ instance_replace_3 }}' == '{{ instance_detach_decrement }}'"
+
+    #----------------------------------------------------------------------
+
+  always:
+
+  - name: terminate any instances created during this test
+    amazon.aws.ec2_instance:
+      instance_ids:
+        - "{{ item }}"
+      state: absent
+    loop:
+      - "{{ init_instance_1 }}"
+      - "{{ init_instance_2 }}"
+      - "{{ init_instance_3 }}"
+      - "{{ instance_replace_1 }}"
+      - "{{ instance_replace_2 }}"
+      - "{{ instance_replace_3 }}"
+
+  - name: kill asg created in this test
+    ec2_asg:
+      name: "{{ resource_prefix }}-asg-detach-test"
+      state: absent
+    register: removed
+    until: removed is not failed
+    ignore_errors: yes
+    retries: 10
+
+  - name: remove launch config created in this test
+    ec2_lc:
+      name: "{{ resource_prefix }}-lc-detach-test"
+      state: absent
+    register: removed
+    until: removed is not failed
+    ignore_errors: yes
+    retries: 10

tests/integration/targets/ec2_asg/tasks/main.yml

@@ -30,7 +30,6 @@
       aws_secret_key: "{{ aws_secret_key }}"
       security_token: "{{ security_token | default(omit) }}"
       region: "{{ aws_region }}"
-
   collections:
     - amazon.aws
 
@@ -98,6 +97,8 @@
             cidr_ip: 0.0.0.0/0
       register: sg
 
+    - include_tasks: instance_detach.yml
+
     - name: ensure launch configs exist
       ec2_lc:
         name: "{{ item }}"