Add initial attempts to automatically clean up dangling hosts

Now, when workflows fail, Broker will attempt to find a handgling host
and check it in if found.

broker/providers/ansible_tower.py

@@ -168,7 +168,7 @@ def __init__(self, **kwargs):
         # Init the class itself
         config = kwargs.get("config")
         root = kwargs.get("root")
-        self._v2, self.username = get_awxkit_and_uname(
+        self._v2, self.uname = get_awxkit_and_uname(
             config=config,
             root=root,
             url=self.url,
@@ -374,6 +374,33 @@ def _get_failure_messages(self, workflow):
         else:
             return failure_messages
 
+    def _try_get_dangling_hosts(self, failed_workflow):
+        """Get one or more hosts that may have been left behind by a failed workflow."""
+        hosts = []
+        for node in failed_workflow.get_related("workflow_nodes").results:
+            if not (job_fields := node.summary_fields.get("job", {})) or job_fields.get(
+                "failed"
+            ):  # skip jobs with no summary fields and failed jobs
+                continue
+            if jobs := self._v2.jobs.get(id=job_fields["id"]).results:
+                if vm_name := jobs[0].artifacts.get("vm_name"):
+                    hosts.append(vm_name)
+        return list(set(hosts))
+
+    def _try_checkin_dangling_host(self, job):
+        """Attempt to check in dangling hosts associated with the given job."""
+        dangling_hosts = self._try_get_dangling_hosts(job)
+        if not dangling_hosts:
+            logger.debug("No dangling hosts found for the failed job.")
+            return
+        for dangling_host in dangling_hosts:
+            logger.info(f"Found dangling host: {dangling_host}. Attempting to check in.")
+            try:
+                self.release(dangling_host)
+                logger.debug(f"Successfully checked in dangling host: {dangling_host}")
+            except exceptions.BrokerError:
+                logger.warning(f"Failed to check in dangling host: {dangling_host}")
+
     def _compile_host_info(self, host):
         try:
             host_facts = host.related.ansible_facts.get()
@@ -607,14 +634,15 @@ def execute(self, **kwargs):  # noqa: PLR0912,PLR0915 - Possible TODO refactor
                 "URL": job_ui_url,
             }
             helpers.emit(message_data)
+            self._try_checkin_dangling_host(job)
             raise JobExecutionError(message_data=message_data["Reason(s)"])
         if strategy := kwargs.pop("artifacts", None):
             return self._merge_artifacts(job, strategy=strategy)
         return job
 
     def get_inventory(self, user=None):
         """Compile a list of hosts based on any inventory a user's name is mentioned."""
-        user = user or self.username
+        user = user or self.uname
         invs = [
             inv
             for inv in self._v2.inventory.get(page_size=200).results