[Dashboard] Add Ray Config API to Reporter Head (#11010)

* Add Ray Config API to the backend for fetching config

* Address PR comments.

* Make reporter cache whole payload

* lint

Co-authored-by: Max Fitton <max@semprehealth.com>

dashboard/modules/reporter/reporter_head.py

@@ -1,6 +1,7 @@
 import json
 import logging
-
+import yaml
+import os
 import aiohttp.web
 from aioredis.pubsub import Receiver
 from grpc.experimental import aio as aiogrpc
@@ -52,6 +53,49 @@ class ReportHead(dashboard_utils.DashboardHeadModule):
             message="Profiling success.",
             profiling_info=profiling_info)
 
+    @routes.get("/api/ray_config")
+    async def get_ray_config(self, req) -> aiohttp.web.Response:
+        if self._ray_config is None:
+            try:
+                config_path = os.path.expanduser("~/ray_bootstrap_config.yaml")
+                with open(config_path) as f:
+                    cfg = yaml.safe_load(f)
+            except yaml.YAMLError:
+                return await dashboard_utils.rest_response(
+                    success=False,
+                    message=f"No config found at {config_path}.",
+                )
+            except FileNotFoundError:
+                return await dashboard_utils.rest_response(
+                    success=False,
+                    message=f"Invalid config, could not load YAML.")
+
+            payload = {
+                "min_workers": cfg["min_workers"],
+                "max_workers": cfg["max_workers"],
+                "initial_workers": cfg["initial_workers"],
+                "autoscaling_mode": cfg["autoscaling_mode"],
+                "idle_timeout_minutes": cfg["idle_timeout_minutes"],
+            }
+
+            try:
+                payload["head_type"] = cfg["head_node"]["InstanceType"]
+            except KeyError:
+                payload["head_type"] = "unknown"
+
+            try:
+                payload["worker_type"] = cfg["worker_nodes"]["InstanceType"]
+            except KeyError:
+                payload["worker_type"] = "unknown"
+
+            self._ray_config = payload
+
+        return await dashboard_utils.rest_response(
+            success=True,
+            message="Fetched ray config.",
+            **self._ray_config,
+        )
+
     async def run(self, server):
         aioredis_client = self._dashboard_head.aioredis_client
         receiver = Receiver()