[Frontend] Rerank API (Jina- and Cohere-compatible API)

docs/source/serving/openai_compatible_server.md

@@ -50,6 +50,11 @@ In addition, we have the following custom APIs:
   - Applicable to all [pooling models](../models/pooling_models.md).
 - [Score API](#score-api) (`/score`)
   - Only applicable to [cross-encoder models](../models/pooling_models.md) (`--task score`).
+- [Re-rank API](#rerank-api) (`/rerank`, `/v1/rerank`)
+  - Implements [Jina AI's v1 re-rank API](https://jina.ai/reranker/)
+  - Also compatible with [Cohere's v1 & v2 re-rank APIs](https://docs.cohere.com/v2/reference/rerank)
+  - Jina and Cohere's APIs are very similar; Jina's includes extra information in the rerank endpoint's response.
+  - Only applicable to [cross-encoder models](../models/pooling_models.md) (`--task score`).
 
 (chat-template)=
 
@@ -473,3 +478,90 @@ The following extra parameters are supported:
 :start-after: begin-score-extra-params
 :end-before: end-score-extra-params
 ```
+
+(rerank-api)=
+
+### Re-rank API
+
+Our Re-rank API applies a cross-encoder model to predict relevant scores between a single query, and
+each of a list of documents. Usually, the score for a sentence pair refers to the similarity between two sentences, on
+a scale of 0 to 1.
+
+You can find the documentation for these kind of models at [sbert.net](https://www.sbert.net/docs/package_reference/cross_encoder/cross_encoder.html).
+
+The rerank endpoints support popular re-rank models such as `BAAI/bge-reranker-base` and other models supporting the
+`score` task. Additionally, both `/rerank` and `/v1/rerank` endpoints
+endpoints are compatible with both [Jina AI's re-rank API interface](https://jina.ai/reranker/) and
+[Cohere's re-rank API interface](https://docs.cohere.com/v2/reference/rerank) to ensure compatibility with
+popular open-source tools.
+
+Code example: <gh-file:examples/online_serving/jinaai_rerank_client.py>
+
+#### Example Request
+
+Note that the `top_n` request parameter is optional and will default to the length of the `documents` field.
+Result documents will be sorted by relevance, and the `index` property can be used to determine original order.
+
+Request:
+
+```bash
+curl -X 'POST' \
+  'http://127.0.0.1:8000/v1/rerank' \
+  -H 'accept: application/json' \
+  -H 'Content-Type: application/json' \
+  -d '{
+  "model": "BAAI/bge-reranker-base",
+  "query": "What is the capital of France?",
+  "documents": [
+    "The capital of Brazil is Brasilia.",
+    "The capital of France is Paris.",
+    "Horses and cows are both animals"
+  ]
+}'
+```
+
+Response:
+
+```bash
+{
+  "id": "rerank-fae51b2b664d4ed38f5969b612edff77",
+  "model": "BAAI/bge-reranker-base",
+  "usage": {
+    "total_tokens": 56
+  },
+  "results": [
+    {
+      "index": 1,
+      "document": {
+        "text": "The capital of France is Paris."
+      },
+      "relevance_score": 0.99853515625
+    },
+    {
+      "index": 0,
+      "document": {
+        "text": "The capital of Brazil is Brasilia."
+      },
+      "relevance_score": 0.0005860328674316406
+    }
+  ]
+}
+```
+
+#### Extra parameters
+
+The following [pooling parameters](#pooling-params) are supported.
+
+```{literalinclude} ../../../vllm/entrypoints/openai/protocol.py
+:language: python
+:start-after: begin-rerank-pooling-params
+:end-before: end-rerank-pooling-params
+```
+
+The following extra parameters are supported:
+
+```{literalinclude} ../../../vllm/entrypoints/openai/protocol.py
+:language: python
+:start-after: begin-rerank-extra-params
+:end-before: end-rerank-extra-params
+```

examples/online_serving/cohere_rerank_client.py

@@ -0,0 +1,37 @@
+"""
+Example of using the OpenAI entrypoint's rerank API which is compatible with
+the Cohere SDK: https://github.com/cohere-ai/cohere-python
+
+run: vllm serve --model BAAI/bge-reranker-base
+"""
+import cohere
+
+# cohere v1 client
+co = cohere.Client(base_url="http://localhost:8000", api_key="sk-fake-key")
+rerank_v1_result = co.rerank(
+    model="BAAI/bge-reranker-base",
+    query="What is the capital of France?",
+    documents=[
+        "The capital of France is Paris",
+        "Reranking is fun!",
+        "vLLM is an open-source framework for fast AI serving"
+    ]
+)
+
+print(rerank_v1_result)
+
+# or the v2
+co2 = cohere.ClientV2("sk-fake-key", base_url="http://localhost:8000")
+
+v2_rerank_result = co2.rerank(
+    model="BAAI/bge-reranker-base",
+    query="What is the capital of France?",
+    documents=[
+        "The capital of France is Paris",
+        "Reranking is fun!",
+        "vLLM is an open-source framework for fast AI serving"
+    ]
+)
+
+print(v2_rerank_result)
+

examples/online_serving/jinjaai_rerank_client.py

@@ -0,0 +1,33 @@
+"""
+Example of using the OpenAI entrypoint's rerank API which is compatible with
+Jina and Cohere https://jina.ai/reranker
+
+run: vllm serve --model BAAI/bge-reranker-base
+"""
+import json
+
+import requests
+
+url = "http://127.0.0.1:8000/rerank"
+
+headers = {"accept": "application/json", "Content-Type": "application/json"}
+
+data = {
+    "model":
+    "BAAI/bge-reranker-base",
+    "query":
+    "What is the capital of France?",
+    "documents": [
+        "The capital of Brazil is Brasilia.",
+        "The capital of France is Paris.", "Horses and cows are both animals"
+    ]
+}
+response = requests.post(url, headers=headers, json=data)
+
+# Check the response
+if response.status_code == 200:
+    print("Request successful!")
+    print(json.dumps(response.json(), indent=2))
+else:
+    print(f"Request failed with status code: {response.status_code}")
+    print(response.text)

tests/entrypoints/openai/test_rerank.py

@@ -0,0 +1,98 @@
+import pytest
+import requests
+
+from vllm.entrypoints.openai.protocol import RerankResponse
+
+from ...utils import RemoteOpenAIServer
+
+MODEL_NAME = "BAAI/bge-reranker-base"
+
+
+@pytest.fixture(scope="module")
+def server():
+    args = ["--enforce-eager", "--max-model-len", "100"]
+
+    with RemoteOpenAIServer(MODEL_NAME, args) as remote_server:
+        yield remote_server
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("model_name", [MODEL_NAME])
+def test_rerank_texts(server: RemoteOpenAIServer, model_name: str):
+    query = "What is the capital of France?"
+    documents = [
+        "The capital of Brazil is Brasilia.", "The capital of France is Paris."
+    ]
+
+    rerank_response = requests.post(server.url_for("rerank"),
+                                    json={
+                                        "model": model_name,
+                                        "query": query,
+                                        "documents": documents,
+                                    })
+    rerank_response.raise_for_status()
+    rerank = RerankResponse.model_validate(rerank_response.json())
+
+    assert rerank.id is not None
+    assert rerank.results is not None
+    assert len(rerank.results) == 2
+    assert rerank.results[1].relevance_score <= 0.01
+    assert rerank.results[0].relevance_score >= 0.9
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("model_name", [MODEL_NAME])
+def test_top_n(server: RemoteOpenAIServer, model_name: str):
+    query = "What is the capital of France?"
+    documents = [
+        "The capital of Brazil is Brasilia.",
+        "The capital of France is Paris.", "Cross-encoder models are neat"
+    ]
+
+    rerank_response = requests.post(server.url_for("score"),
+                                    json={
+                                        "model": model_name,
+                                        "query": query,
+                                        "documents": documents,
+                                        "top_n": 2
+                                    })
+    rerank_response.raise_for_status()
+    rerank = RerankResponse.model_validate(rerank_response.json())
+
+    assert rerank.id is not None
+    assert rerank.results is not None
+    assert len(rerank.results) == 2
+    assert rerank.results[1].relevance_score <= 0.01
+    assert rerank.results[0].relevance_score >= 0.9
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("model_name", [MODEL_NAME])
+def test_score_max_model_len(server: RemoteOpenAIServer, model_name: str):
+
+    query = "What is the capital of France?" * 100
+    documents = [
+        "The capital of Brazil is Brasilia.", "The capital of France is Paris."
+    ]
+
+    rerank_response = requests.post(server.url_for("rerank"),
+                                    json={
+                                        "model": model_name,
+                                        "query": query,
+                                        "documents": documents
+                                    })
+    assert rerank_response.status_code == 400
+    # Assert just a small fragments of the response
+    assert "Please reduce the length of the input." in \
+        rerank_response.text
+
+    # Test truncation
+    rerank_response = requests.post(server.url_for("rerank"),
+                                    json={
+                                        "model": model_name,
+                                        "query": query,
+                                        "documents": documents
+                                    })
+    assert rerank_response.status_code == 400
+    assert "Please, select a smaller truncation size." in \
+        rerank_response.text

vllm/entrypoints/openai/api_server.py

@@ -56,6 +56,7 @@
                                               PoolingChatRequest,
                                               PoolingCompletionRequest,
                                               PoolingRequest, PoolingResponse,
+                                              RerankRequest, RerankResponse,
                                               ScoreRequest, ScoreResponse,
                                               TokenizeRequest,
                                               TokenizeResponse,
@@ -68,6 +69,7 @@
 from vllm.entrypoints.openai.serving_models import (BaseModelPath,
                                                     OpenAIServingModels)
 from vllm.entrypoints.openai.serving_pooling import OpenAIServingPooling
+from vllm.entrypoints.openai.serving_rerank import JinaAIServingRerank
 from vllm.entrypoints.openai.serving_score import OpenAIServingScores
 from vllm.entrypoints.openai.serving_tokenization import (
     OpenAIServingTokenization)
@@ -306,6 +308,10 @@ def score(request: Request) -> Optional[OpenAIServingScores]:
     return request.app.state.openai_serving_scores
 
 
+def rerank(request: Request) -> Optional[JinaAIServingRerank]:
+    return request.app.state.jinaai_serving_reranking
+
+
 def tokenization(request: Request) -> OpenAIServingTokenization:
     return request.app.state.openai_serving_tokenization
 
@@ -502,6 +508,43 @@ async def create_score_v1(request: ScoreRequest, raw_request: Request):
     return await create_score(request, raw_request)
 
 
+@router.post("/rerank")
+@with_cancellation
+async def do_rerank(request: RerankRequest, raw_request: Request):
+    handler = rerank(raw_request)
+    if handler is None:
+        return base(raw_request).create_error_response(
+            message="The model does not support Rerank (Score) API")
+    generator = await handler.do_rerank(request, raw_request)
+    if isinstance(generator, ErrorResponse):
+        return JSONResponse(content=generator.model_dump(),
+                            status_code=generator.code)
+    elif isinstance(generator, RerankResponse):
+        return JSONResponse(content=generator.model_dump())
+
+    assert_never(generator)
+
+
+@router.post("/v1/rerank")
+@with_cancellation
+async def do_rerank_v1(request: RerankRequest, raw_request: Request):
+    logger.warning(
+        "To indicate that the rerank API is not part of the standard OpenAI"
+        " API, we have located it at `/rerank`. Please update your client"
+        "accordingly. (Note: Conforms to JinaAI rerank API)")
+    return await do_rerank(request, raw_request)
+
+
+@router.post("/v2/rerank")
+@with_cancellation
+async def do_rerank_v2(request: RerankRequest, raw_request: Request):
+    logger.warning(
+        "To indicate that the rerank API is not part of the standard OpenAI"
+        " API, we have located it at `/rerank`. Please update your client"
+        "accordingly. (Note: Conforms to JinaAI rerank API)")
+    return await do_rerank(request, raw_request)
+
+
 TASK_HANDLERS: Dict[str, Dict[str, tuple]] = {
     "generate": {
         "messages": (ChatCompletionRequest, create_chat_completion),
@@ -514,6 +557,9 @@ async def create_score_v1(request: ScoreRequest, raw_request: Request):
     "score": {
         "default": (ScoreRequest, create_score),
     },
+    "rerank": {
+        "default": (RerankRequest, do_rerank)
+    },
     "reward": {
         "messages": (PoolingChatRequest, create_pooling),
         "default": (PoolingCompletionRequest, create_pooling),
@@ -759,6 +805,11 @@ async def init_app_state(
         state.openai_serving_models,
         request_logger=request_logger
     ) if model_config.task == "score" else None
+    state.jinaai_serving_reranking = JinaAIServingRerank(
+        engine_client,
+        model_config,
+        state.openai_serving_models,
+        request_logger=request_logger)
     state.openai_serving_tokenization = OpenAIServingTokenization(
         engine_client,
         model_config,