From 675db17ace22d6554292d51afbed1c0dac445de7 Mon Sep 17 00:00:00 2001
From: acsbendi <acsbendi28@gmail.com>
Date: Fri, 30 Aug 2019 18:21:11 +0200
Subject: [PATCH] Implemented deregistering terminated instances from ELB
 target groups.

---
 moto/ec2/responses/instances.py |  2 +
 moto/elbv2/models.py            |  9 ++++
 tests/test_elbv2/test_elbv2.py  | 77 +++++++++++++++++++++++++++++++++
 3 files changed, 88 insertions(+)

diff --git a/moto/ec2/responses/instances.py b/moto/ec2/responses/instances.py
index 82c2b1997..28123b995 100644
--- a/moto/ec2/responses/instances.py
+++ b/moto/ec2/responses/instances.py
@@ -6,6 +6,7 @@ from moto.core.responses import BaseResponse
 from moto.core.utils import camelcase_to_underscores
 from moto.ec2.utils import filters_from_querystring, \
     dict_from_querystring
+from moto.elbv2 import elbv2_backends
 
 
 class InstanceResponse(BaseResponse):
@@ -68,6 +69,7 @@ class InstanceResponse(BaseResponse):
         if self.is_not_dryrun('TerminateInstance'):
             instances = self.ec2_backend.terminate_instances(instance_ids)
             autoscaling_backends[self.region].notify_terminate_instances(instance_ids)
+            elbv2_backends[self.region].notify_terminate_instances(instance_ids)
             template = self.response_template(EC2_TERMINATE_INSTANCES)
             return template.render(instances=instances)
 
diff --git a/moto/elbv2/models.py b/moto/elbv2/models.py
index 7e73c7042..726799fe5 100644
--- a/moto/elbv2/models.py
+++ b/moto/elbv2/models.py
@@ -110,6 +110,11 @@ class FakeTargetGroup(BaseModel):
             if not t:
                 raise InvalidTargetError()
 
+    def deregister_terminated_instances(self, instance_ids):
+        for target_id in list(self.targets.keys()):
+            if target_id in instance_ids:
+                del self.targets[target_id]
+
     def add_tag(self, key, value):
         if len(self.tags) >= 10 and key not in self.tags:
             raise TooManyTagsError()
@@ -936,6 +941,10 @@ class ELBv2Backend(BaseBackend):
                             return True
         return False
 
+    def notify_terminate_instances(self, instance_ids):
+        for target_group in self.target_groups.values():
+            target_group.deregister_terminated_instances(instance_ids)
+
 
 elbv2_backends = {}
 for region in ec2_backends.keys():
diff --git a/tests/test_elbv2/test_elbv2.py b/tests/test_elbv2/test_elbv2.py
index 36772c02e..b2512a3f1 100644
--- a/tests/test_elbv2/test_elbv2.py
+++ b/tests/test_elbv2/test_elbv2.py
@@ -752,6 +752,83 @@ def test_stopped_instance_target():
     })
 
 
+@mock_ec2
+@mock_elbv2
+def test_terminated_instance_target():
+    target_group_port = 8080
+
+    conn = boto3.client('elbv2', region_name='us-east-1')
+    ec2 = boto3.resource('ec2', region_name='us-east-1')
+
+    security_group = ec2.create_security_group(
+        GroupName='a-security-group', Description='First One')
+    vpc = ec2.create_vpc(CidrBlock='172.28.7.0/24', InstanceTenancy='default')
+    subnet1 = ec2.create_subnet(
+        VpcId=vpc.id,
+        CidrBlock='172.28.7.192/26',
+        AvailabilityZone='us-east-1a')
+    subnet2 = ec2.create_subnet(
+        VpcId=vpc.id,
+        CidrBlock='172.28.7.0/26',
+        AvailabilityZone='us-east-1b')
+
+    conn.create_load_balancer(
+        Name='my-lb',
+        Subnets=[subnet1.id, subnet2.id],
+        SecurityGroups=[security_group.id],
+        Scheme='internal',
+        Tags=[{'Key': 'key_name', 'Value': 'a_value'}])
+
+    response = conn.create_target_group(
+        Name='a-target',
+        Protocol='HTTP',
+        Port=target_group_port,
+        VpcId=vpc.id,
+        HealthCheckProtocol='HTTP',
+        HealthCheckPath='/',
+        HealthCheckIntervalSeconds=5,
+        HealthCheckTimeoutSeconds=5,
+        HealthyThresholdCount=5,
+        UnhealthyThresholdCount=2,
+        Matcher={'HttpCode': '200'})
+    target_group = response.get('TargetGroups')[0]
+
+    # No targets registered yet
+    response = conn.describe_target_health(
+        TargetGroupArn=target_group.get('TargetGroupArn'))
+    response.get('TargetHealthDescriptions').should.have.length_of(0)
+
+    response = ec2.create_instances(
+        ImageId='ami-1234abcd', MinCount=1, MaxCount=1)
+    instance = response[0]
+
+    target_dict = {
+        'Id': instance.id,
+        'Port': 500
+    }
+
+    response = conn.register_targets(
+        TargetGroupArn=target_group.get('TargetGroupArn'),
+        Targets=[target_dict])
+
+    response = conn.describe_target_health(
+        TargetGroupArn=target_group.get('TargetGroupArn'))
+    response.get('TargetHealthDescriptions').should.have.length_of(1)
+    target_health_description = response.get('TargetHealthDescriptions')[0]
+
+    target_health_description['Target'].should.equal(target_dict)
+    target_health_description['HealthCheckPort'].should.equal(str(target_group_port))
+    target_health_description['TargetHealth'].should.equal({
+        'State': 'healthy'
+    })
+
+    instance.terminate()
+
+    response = conn.describe_target_health(
+        TargetGroupArn=target_group.get('TargetGroupArn'))
+    response.get('TargetHealthDescriptions').should.have.length_of(0)
+
+
 @mock_ec2
 @mock_elbv2
 def test_target_group_attributes():