CI small fix (#797)

* add a wait and timeout for principals to be removed from an iot thing

* move certificate deletion

* f-string fix

Author: sbSteveK

utils/ci_iot_thing.py

@@ -3,8 +3,46 @@
 
 import sys
 
-import boto3
-
+import boto3, time
+from botocore.exceptions import ClientError, WaiterError
+
+class ThingDetachedWaiter:
+    """
+    Wait until principal (cert or Cognito identity) is detached from a thing.
+    Raise WaiterError after timeout seconds.
+    """
+
+    def __init__(self, client, delay=2.0, max_delay=10.0, timeout=60.0):
+        self._client = client
+        self._delay = delay
+        self._max_delay = max_delay
+        self._timeout = timeout
+
+    def wait(self, thing_name):
+        start = time.monotonic()
+        sleep = self._delay
+
+        while True:
+            try:
+                resp = self._client.list_thing_principals(thingName=thing_name)
+            except ClientError as e:
+                if e.response["Error"]["Code"] == "ResourceNotFoundException":
+                    return
+                raise
+
+            if not resp.get("principals"):
+                # No principals, we can move on.
+                return
+
+            if time.monotonic() - start > self._timeout:
+                raise WaiterError(
+                    name="ThingDetached",
+                    reason="timeout",
+                    last_response=resp,
+                )
+
+            time.sleep(sleep)
+            sleep = min(sleep * 1.6, self._max_delay) # exponential backoff on retrys
 
 def create_iot_thing(thing_name, region, policy_name, certificate_path, key_path, thing_group=None):
     """ Create IoT thing along with policy and credentials. """
@@ -57,6 +95,8 @@ def delete_iot_thing(thing_name, region):
         print(f"ERROR: Could not make Boto3 client. Credentials likely could not be sourced", file=sys.stderr)
         raise
 
+    cert_ids = []
+
     # Detach and delete thing's principals.
     try:
         thing_principals = iot_client.list_thing_principals(thingName=thing_name)
@@ -65,12 +105,24 @@ def delete_iot_thing(thing_name, region):
             certificate_id = principal.split("/")[1]
             iot_client.detach_thing_principal(thingName=thing_name, principal=principal)
             iot_client.update_certificate(certificateId=certificate_id, newStatus='INACTIVE')
-            iot_client.delete_certificate(certificateId=certificate_id, forceDelete=True)
+            cert_ids.append(certificate_id)
     except Exception:
-        print(f"ERROR: Could not delete certificate for IoT thing {thing_name}, probably thing does not exist",
+        print(f"ERROR: Could not detatch principal or set its certificate to INACTIVE for {thing_name}, probably thing does not exist",
               file=sys.stderr)
         raise
 
+    # Wait for thing to be free of principals
+    ThingDetachedWaiter(iot_client, timeout=10).wait(thing_name)
+
+    # Delete all the certificates
+    for cert in cert_ids:
+        try:
+            iot_client.delete_certificate(certificateId=cert, forceDelete=True)
+        except Exception:
+            print(f"ERROR: Could not delete certificate for IoT thing {thing_name}.",
+              file=sys.stderr)
+            raise
+
     # Delete thing.
     try:
         iot_client.delete_thing(thingName=thing_name)