Add functionality to ping AI2 InferD endpoints for tulu 2 (#2832)

Co-authored-by: Sam Skjonsberg <sams@allenai.org>

fastchat/serve/api_provider.py

@@ -147,3 +147,78 @@ def palm_api_stream_iter(chat, message, temperature, top_p, max_new_tokens):
             "error_code": 0,
         }
         yield data
+
+
+def ai2_api_stream_iter(
+    model_name,
+    messages,
+    temperature,
+    top_p,
+    max_new_tokens,
+    api_key=None,
+    api_base=None,
+):
+    from requests import post
+    from json import loads
+
+    # get keys and needed values
+    ai2_key = api_key or os.environ.get("AI2_API_KEY")
+    api_base = api_base or "https://inferd.allen.ai/api/v1/infer"
+    model_id = "mod_01hhgcga70c91402r9ssyxekan"
+
+    # Make requests
+    gen_params = {
+        "model": model_name,
+        "prompt": messages,
+        "temperature": temperature,
+        "top_p": top_p,
+        "max_new_tokens": max_new_tokens,
+    }
+    logger.info(f"==== request ====\n{gen_params}")
+
+    # AI2 uses vLLM, which requires that `top_p` be 1.0 for greedy sampling:
+    # https://github.com/vllm-project/vllm/blob/v0.1.7/vllm/sampling_params.py#L156-L157
+    if temperature == 0.0 and top_p < 1.0:
+        raise ValueError("top_p must be 1 when temperature is 0.0")
+
+    res = post(
+        api_base,
+        stream=True,
+        headers={"Authorization": f"Bearer {ai2_key}"},
+        json={
+            "model_id": model_id,
+            # This input format is specific to the Tulu2 model. Other models
+            # may require different input formats. See the model's schema
+            # documentation on InferD for more information.
+            "input": {
+                "messages": messages,
+                "opts": {
+                    "max_tokens": max_new_tokens,
+                    "temperature": temperature,
+                    "top_p": top_p,
+                    "logprobs": 1,  # increase for more choices
+                },
+            },
+        },
+    )
+
+    if res.status_code != 200:
+        logger.error(f"unexpected response ({res.status_code}): {res.text}")
+        raise ValueError("unexpected response from InferD", res)
+
+    text = ""
+    for line in res.iter_lines():
+        if line:
+            part = loads(line)
+            if "result" in part and "output" in part["result"]:
+                for t in part["result"]["output"]["text"]:
+                    text += t
+            else:
+                logger.error(f"unexpected part: {part}")
+                raise ValueError("empty result in InferD response")
+
+            data = {
+                "text": text,
+                "error_code": 0,
+            }
+            yield data