fix: prevent crash looping hello world (#2625) (#2671)

Author: biswapanda

examples/runtime/hello_world/client.py

@@ -31,10 +31,33 @@ async def worker(runtime: DistributedRuntime):
     client = await endpoint.client()
     await client.wait_for_instances()
 
-    # Issue request and process the stream
-    stream = await client.generate("world,sun,moon,star")
-    async for response in stream:
-        print(response.data())
+    idx = 0
+    base_delay = 0.1  # Start with 100ms
+    max_delay = 5.0  # Max 5 seconds
+    current_delay = base_delay
+
+    while True:
+        try:
+            # Issue request and process the stream
+            idx += 1
+            stream = await client.generate("world,sun,moon,star")
+            async for response in stream:
+                print(response.data())
+            # Reset backoff on successful iteration
+            current_delay = base_delay
+            # Sleep for 1 second
+            await asyncio.sleep(1)
+        except asyncio.CancelledError:
+            # Re-raise for graceful shutdown
+            raise
+        except Exception as e:
+            # Log the exception with context
+            print(f"Error in worker iteration {idx}: {type(e).__name__}: {e}")
+            # Perform exponential backoff
+            print(f"Retrying after {current_delay:.2f} seconds...")
+            await asyncio.sleep(current_delay)
+            # Double the delay for next time, up to max_delay
+            current_delay = min(current_delay * 2, max_delay)
 
 
 if __name__ == "__main__":

examples/runtime/hello_world/deploy/hello_world.yaml

@@ -6,6 +6,7 @@ kind: DynamoGraphDeployment
 metadata:
   name: hello-world
 spec:
+  backendFramework: vllm
   services:
     Frontend:
       livenessProbe:
@@ -60,7 +61,7 @@ spec:
           command:
             - /bin/sh
             - -c
-            - 'grep "Serving endpoint" /tmp/hello_world.log'
+            - "exit 0"
         initialDelaySeconds: 60
         periodSeconds: 60
         timeoutSeconds: 30
@@ -83,4 +84,4 @@ spec:
             - /bin/sh
             - -c
           args:
-            - python3 hello_world.py 2>&1 | tee /tmp/hello_world.log
+            - python3 hello_world.py