Make AsyncLLMEngine more robust & fix batched abort (#969)

Signed-off-by: Antoni Baum <antoni.baum@protonmail.com>
Co-authored-by: Avnish Narayan <38871737+avnishn@users.noreply.github.com>

tests/async_engine/test_api_server.py

@@ -0,0 +1,86 @@
+import subprocess
+import sys
+import time
+from multiprocessing import Pool
+from pathlib import Path
+
+import pytest
+import requests
+
+
+def _query_server(prompt: str) -> dict:
+    response = requests.post("http://localhost:8000/generate",
+                             json={
+                                 "prompt": prompt,
+                                 "max_tokens": 100,
+                                 "temperature": 0,
+                                 "ignore_eos": True
+                             })
+    response.raise_for_status()
+    return response.json()
+
+
+@pytest.fixture
+def api_server():
+    script_path = Path(__file__).parent.joinpath(
+        "api_server_async_engine.py").absolute()
+    uvicorn_process = subprocess.Popen([
+        sys.executable, "-u",
+        str(script_path), "--model", "facebook/opt-125m"
+    ])
+    yield
+    uvicorn_process.terminate()
+
+
+def test_api_server(api_server):
+    """
+    Run the API server and test it.
+
+    We run both the server and requests in separate processes.
+
+    We test that the server can handle incoming requests, including
+    multiple requests at the same time, and that it can handle requests
+    being cancelled without crashing.
+    """
+    with Pool(32) as pool:
+        # Wait until the server is ready
+        prompts = ["Hello world"] * 1
+        result = None
+        while not result:
+            try:
+                for result in pool.map(_query_server, prompts):
+                    break
+            except:
+                time.sleep(1)
+
+        # Actual tests start here
+        # Try with 1 prompt
+        for result in pool.map(_query_server, prompts):
+            assert result
+
+        num_aborted_requests = requests.get(
+            "http://localhost:8000/stats").json()["num_aborted_requests"]
+        assert num_aborted_requests == 0
+
+        # Try with 100 prompts
+        prompts = ["Hello world"] * 100
+        for result in pool.map(_query_server, prompts):
+            assert result
+
+        # Cancel requests
+        pool.map_async(_query_server, prompts)
+        time.sleep(0.01)
+        pool.terminate()
+        pool.join()
+
+        # check cancellation stats
+        num_aborted_requests = requests.get(
+            "http://localhost:8000/stats").json()["num_aborted_requests"]
+        assert num_aborted_requests > 0
+
+    # check that server still runs after cancellations
+    with Pool(32) as pool:
+        # Try with 100 prompts
+        prompts = ["Hello world"] * 100
+        for result in pool.map(_query_server, prompts):
+            assert result