Repository: cloud-custodian/cloud-custodian

Issue:
aws:asg propagte-tags action errors on asgs without instances
The error message when I try to use the propagate-tags action is the following:

```
[ERROR] 2019-11-19T02:56:38.336Z b1c8af86-d773-412d-b755-638faf7698e8 Error while executing policy
20:56:38 Traceback (most recent call last):
20:56:38 File "/var/task/c7n/policy.py", line 320, in run
20:56:38 results = a.process(resources)
20:56:38 File "/var/task/c7n/resources/asg.py", line 1200, in process
20:56:38 instance_count = sum(list(w.map(self.process_asg, asgs)))
20:56:38 File "/var/lang/lib/python3.7/concurrent/futures/_base.py", line 598, in result_iterator
20:56:38 yield fs.pop().result()
20:56:38 File "/var/lang/lib/python3.7/concurrent/futures/_base.py", line 435, in result
20:56:38 return self.__get_result()
20:56:38 File "/var/lang/lib/python3.7/concurrent/futures/_base.py", line 384, in __get_result
20:56:38 raise self._exception
20:56:38 File "/var/lang/lib/python3.7/concurrent/futures/thread.py", line 57, in run
20:56:38 result = self.fn(*self.args, **self.kwargs)
20:56:38 File "/var/task/c7n/resources/asg.py", line 1221, in process_asg
20:56:38 Tags=[{'Key': k, 'Value': v} for k, v in tag_map.items()])
20:56:38 File "/var/runtime/botocore/client.py", line 357, in _api_call
20:56:38 return self._make_api_call(operation_name, kwargs)
20:56:38 File "/var/runtime/botocore/client.py", line 661, in _make_api_call
20:56:38 raise error_class(parsed_response, operation_name)
20:56:38 botocore.exceptions.ClientError: An error occurred (MissingParameter) when calling the CreateTags operation: The request must contain the parameter resourceIdSet
20:56:38 [ERROR] 2019-11-19T02:56:38.338Z b1c8af86-d773-412d-b755-638faf7698e8 error during policy execution
20:56:38 Traceback (most recent call last):
20:56:38 File "/var/task/c7n/handler.py", line 168, in dispatch_event
20:56:38 p.push(event, context)
20:56:38 File "/var/task/c7n/policy.py", line 991, in push
20:56:38 return mode.run(event, lambda_ctx)
20:56:38 File "/var/task/c7n/policy.py", line 591, in run
20:56:38 return PullMode.run(self)
20:56:38 File "/var/task/c7n/policy.py", line 320, in run
20:56:38 results = a.process(resources)
20:56:38 File "/var/task/c7n/resources/asg.py", line 1200, in process
20:56:38 instance_count = sum(list(w.map(self.process_asg, asgs)))
20:56:38 File "/var/lang/lib/python3.7/concurrent/futures/_base.py", line 598, in result_iterator
20:56:38 yield fs.pop().result()
20:56:38 File "/var/lang/lib/python3.7/concurrent/futures/_base.py", line 435, in result
20:56:38 return self.__get_result()
20:56:38 File "/var/lang/lib/python3.7/concurrent/futures/_base.py", line 384, in __get_result
20:56:38 raise self._exception
20:56:38 File "/var/lang/lib/python3.7/concurrent/futures/thread.py", line 57, in run
20:56:38 result = self.fn(*self.args, **self.kwargs)
20:56:38 File "/var/task/c7n/resources/asg.py", line 1221, in process_asg
20:56:38 Tags=[{'Key': k, 'Value': v} for k, v in tag_map.items()])
20:56:38 File "/var/runtime/botocore/client.py", line 357, in _api_call
20:56:38 return self._make_api_call(operation_name, kwargs)
20:56:38 File "/var/runtime/botocore/client.py", line 661, in _make_api_call
20:56:38 raise error_class(parsed_response, operation_name)
20:56:38 botocore.exceptions.ClientError: An error occurred (MissingParameter) when calling the CreateTags operation: The request must contain the parameter resourceIdSet
20:56:38 [ERROR] ClientError: An error occurred (MissingParameter) when calling the CreateTags operation: The request must contain the parameter resourceIdSet Traceback (most recent call last):   File "/var/task/custodian_policy.py", line 4, in run     return handler.dispatch_event(event, context)   File "/var/task/c7n/handler.py", line 168, in dispatch_event     p.push(event, context)   File "/var/task/c7
20:56:38 END RequestId: b1c8af86-d773-412d-b755-638faf7698e8
```

Discussion:
kapilt: Thanks for the pull request!  If you don't mind could you sign the CLA per the developer docs? Direct link here: https://docs.google.com/forms/d/e/1FAIpQLSfwtl1s6KmpLhCY6CjiY8nFZshDwf_wrmNYx1ahpsNFXXmHKw/viewform
kapilt: can you switch the account id here in the recorded output to the one we use in other test data and rebase.
fussybeaver: Thanks for the feedback. Rebased master, removed trailing whitespace and changed account id.

Patch:
diff --git a/c7n/resources/asg.py b/c7n/resources/asg.py
index 9d01ee426..181141dd9 100644
--- a/c7n/resources/asg.py
+++ b/c7n/resources/asg.py
@@ -1215,7 +1215,7 @@ class PropagateTags(Action):
         if self.data.get('trim', False):
             instances = [self.instance_map[i] for i in instance_ids]
             self.prune_instance_tags(client, asg, tag_set, instances)
-        if not self.manager.config.dryrun:
+        if not self.manager.config.dryrun and instances:
             client.create_tags(
                 Resources=instance_ids,
                 Tags=[{'Key': k, 'Value': v} for k, v in tag_map.items()])


Test patch:
diff --git a/tests/data/placebo/test_asg_propagate_tag_no_instances/autoscaling.DescribeAutoScalingGroups_1.json b/tests/data/placebo/test_asg_propagate_tag_no_instances/autoscaling.DescribeAutoScalingGroups_1.json
new file mode 100644
index 000000000..3e8368da5
--- /dev/null
+++ b/tests/data/placebo/test_asg_propagate_tag_no_instances/autoscaling.DescribeAutoScalingGroups_1.json
@@ -0,0 +1,64 @@
+{
+    "status_code": 200,
+    "data": {
+        "AutoScalingGroups": [
+            {
+                "AutoScalingGroupARN": "arn:aws:autoscaling:us-east-1:123456789012:autoScalingGroup:5fd42b45-825e-45c1-b02a-6a97d9512f30:autoScalingGroupName/c7n.asg.ec2.01",
+                "TargetGroupARNs": [],
+                "SuspendedProcesses": [],
+                "DesiredCapacity": 1,
+                "Tags": [
+                    {
+                        "ResourceType": "auto-scaling-group",
+                        "ResourceId": "CustodianASG",
+                        "PropagateAtLaunch": true,
+                        "Value": "ubuntu",
+                        "Key": "Platform"
+                    }
+                ],
+                "EnabledMetrics": [],
+                "LoadBalancerNames": [],
+                "AutoScalingGroupName": "c7n.asg.ec2.01",
+                "DefaultCooldown": 300,
+                "MinSize": 1,
+                "Instances": [
+                ],
+                "MaxSize": 1,
+                "VPCZoneIdentifier": "subnet-ea6429a3,subnet-2c5dcf01",
+                "HealthCheckGracePeriod": 300,
+                "TerminationPolicies": [
+                    "Default"
+                ],
+                "LaunchConfigurationName": "c7n.asg.01",
+                "CreatedTime": {
+                    "hour": 19,
+                    "__class__": "datetime",
+                    "month": 2,
+                    "second": 3,
+                    "microsecond": 171000,
+                    "year": 2017,
+                    "day": 24,
+                    "minute": 0
+                },
+                "AvailabilityZones": [
+                    "us-east-1a",
+                    "us-east-1b"
+                ],
+                "HealthCheckType": "EC2",
+                "NewInstancesProtectedFromScaleIn": false
+            }
+        ],
+        "ResponseMetadata": {
+            "RetryAttempts": 0,
+            "HTTPStatusCode": 200,
+            "RequestId": "770b2115-fac8-11e6-ac2c-5ff00137fb8b",
+            "HTTPHeaders": {
+                "x-amzn-requestid": "770b2115-fac8-11e6-ac2c-5ff00137fb8b",
+                "vary": "Accept-Encoding",
+                "content-length": "7006",
+                "content-type": "text/xml",
+                "date": "Fri, 24 Feb 2017 19:35:57 GMT"
+            }
+        }
+    }
+}
diff --git a/tests/data/placebo/test_asg_propagate_tag_no_instances/ec2.CreateTags_1.json b/tests/data/placebo/test_asg_propagate_tag_no_instances/ec2.CreateTags_1.json
new file mode 100644
index 000000000..420881faf
--- /dev/null
+++ b/tests/data/placebo/test_asg_propagate_tag_no_instances/ec2.CreateTags_1.json
@@ -0,0 +1,20 @@
+{
+    "status_code": 400,
+    "data": {
+        "Error": {
+            "Code": "MissingParameter",
+            "Message": "The request must contain the parameter resourceIdSet"
+        },
+        "ResponseMetadata": {
+            "RequestId": "f229a23a-def5-4288-8ee0-f754ea63eda2",
+            "HTTPStatusCode": 400,
+            "HTTPHeaders": {
+                "transfer-encoding": "chunked",
+                "date": "Thu, 21 Nov 2019 18:49:02 GMT",
+                "connection": "close",
+                "server": "AmazonEC2"
+            },
+            "RetryAttempts": 0
+        }
+    }
+}
diff --git a/tests/data/placebo/test_asg_propagate_tag_no_instances/ec2.DeleteTags_1.json b/tests/data/placebo/test_asg_propagate_tag_no_instances/ec2.DeleteTags_1.json
new file mode 100644
index 000000000..8a17226c3
--- /dev/null
+++ b/tests/data/placebo/test_asg_propagate_tag_no_instances/ec2.DeleteTags_1.json
@@ -0,0 +1,9 @@
+{
+    "status_code": 200,
+    "data": {
+        "ResponseMetadata": {
+            "HTTPStatusCode": 200,
+            "RequestId": "1b312937-e532-443a-99bd-1dab530b4a84"
+        }
+    }
+}
diff --git a/tests/test_asg.py b/tests/test_asg.py
index a4b7d75b5..a7c3d5b41 100644
--- a/tests/test_asg.py
+++ b/tests/test_asg.py
@@ -819,6 +819,28 @@ class AutoScalingTest(BaseTest):
         self.assertEqual(len(resources), 1)
         self.assertEqual(resources[0]["AutoScalingGroupName"], "c7n-asg-np-missing")
 
+    def test_asg_propagate_tag_no_instances(self):
+        factory = self.replay_flight_data("test_asg_propagate_tag_no_instances")
+        p = self.load_policy(
+            {
+                "name": "asg-tag",
+                "resource": "asg",
+                "filters": [{"tag:Platform": "ubuntu"}],
+                "actions": [
+                    {
+                        "type": "propagate-tags",
+                        "trim": True,
+                        "tags": ["CustomerId", "Platform"],
+                    },
+                ],
+            },
+            session_factory=factory,
+        )
+
+        resources = p.run()
+        self.assertEqual(len(resources), 1)
+        self.assertEqual(resources[0]["AutoScalingGroupName"], "c7n.asg.ec2.01")
+
     def test_asg_filter_capacity_delta_match(self):
         factory = self.replay_flight_data("test_asg_filter_capacity_delta_match")
         p = self.load_policy(