[Frontend] Support OpenAI batch file format (#4794)

Co-authored-by: Robert Shaw <114415538+robertgshaw2-neuralmagic@users.noreply.github.com>

tests/entrypoints/test_openai_run_batch.py

@@ -0,0 +1,53 @@
+import subprocess
+import sys
+import tempfile
+
+from vllm.entrypoints.openai.protocol import BatchRequestOutput
+
+# ruff: noqa: E501
+INPUT_BATCH = """{"custom_id": "request-1", "method": "POST", "url": "/v1/chat/completions", "body": {"model": "NousResearch/Meta-Llama-3-8B-Instruct", "messages": [{"role": "system", "content": "You are a helpful assistant."},{"role": "user", "content": "Hello world!"}],"max_tokens": 1000}}
+{"custom_id": "request-2", "method": "POST", "url": "/v1/chat/completions", "body": {"model": "NousResearch/Meta-Llama-3-8B-Instruct", "messages": [{"role": "system", "content": "You are an unhelpful assistant."},{"role": "user", "content": "Hello world!"}],"max_tokens": 1000}}"""
+
+INVALID_INPUT_BATCH = """{"invalid_field": "request-1", "method": "POST", "url": "/v1/chat/completions", "body": {"model": "NousResearch/Meta-Llama-3-8B-Instruct", "messages": [{"role": "system", "content": "You are a helpful assistant."},{"role": "user", "content": "Hello world!"}],"max_tokens": 1000}}
+{"custom_id": "request-2", "method": "POST", "url": "/v1/chat/completions", "body": {"model": "NousResearch/Meta-Llama-3-8B-Instruct", "messages": [{"role": "system", "content": "You are an unhelpful assistant."},{"role": "user", "content": "Hello world!"}],"max_tokens": 1000}}"""
+
+
+def test_e2e():
+    with tempfile.NamedTemporaryFile(
+            "w") as input_file, tempfile.NamedTemporaryFile(
+                "r") as output_file:
+        input_file.write(INPUT_BATCH)
+        input_file.flush()
+        proc = subprocess.Popen([
+            sys.executable, "-m", "vllm.entrypoints.openai.run_batch", "-i",
+            input_file.name, "-o", output_file.name, "--model",
+            "NousResearch/Meta-Llama-3-8B-Instruct"
+        ], )
+        proc.communicate()
+        proc.wait()
+        assert proc.returncode == 0, f"{proc=}"
+
+        contents = output_file.read()
+        for line in contents.strip().split("\n"):
+            # Ensure that the output format conforms to the openai api.
+            # Validation should throw if the schema is wrong.
+            BatchRequestOutput.model_validate_json(line)
+
+
+def test_e2e_invalid_input():
+    """
+    Ensure that we fail when the input doesn't conform to the openai api.
+    """
+    with tempfile.NamedTemporaryFile(
+            "w") as input_file, tempfile.NamedTemporaryFile(
+                "r") as output_file:
+        input_file.write(INVALID_INPUT_BATCH)
+        input_file.flush()
+        proc = subprocess.Popen([
+            sys.executable, "-m", "vllm.entrypoints.openai.run_batch", "-i",
+            input_file.name, "-o", output_file.name, "--model",
+            "NousResearch/Meta-Llama-3-8B-Instruct"
+        ], )
+        proc.communicate()
+        proc.wait()
+        assert proc.returncode != 0, f"{proc=}"