Bug description Unable to use embedding functionality when integrating Spring AI with VLLM using OpenAI API format. The issue appears to be related to HTTP protocol version compatibility.

Environment Spring AI: 1.0.0-M4 JDK: 22 VLLM: 0.6.6.post1

Steps to reproduce 1. Set up VLLM server 

vllm serve Alibaba-NLP/gte-Qwen2-1.5B-instruct --task embed --tokenizer Alibaba-NLP/gte-Qwen2-1.5B-instruct
  1. Configure Spring AI to use VLLM endpoint
  2. Attempt to use embedding functionality
@RestController
@RequestMapping("/ai")
public class EmbeddingController {
    private final EmbeddingModel embeddingModel;

    @Autowired
    public EmbeddingController(EmbeddingModel embeddingModel) {
        this.embeddingModel = embeddingModel;
    }

    @GetMapping("/embedding")
    public Map embed(@RequestParam(value = "message", defaultValue = "Tell me a joke") String message) {
        EmbeddingResponse embeddingResponse = this.embeddingModel.embedForResponse(List.of(message));
        return Map.of("embedding", embeddingResponse);
    }

}

Expected behavior Return embedding results.

Current Behavior When sending requests to VLLM using Spring AI's OpenAI API implementation: 1. VLLM logs:

WARNING: Unsupported upgrade request.
INFO: - "POST /v1/embeddings HTTP/1.1" 400 Bad Request
  1. Spring AI throws:
org.springframework.ai.retry.NonTransientAiException: 400 - {
    "object": "error",
    "message": "[{'type': 'missing', 'loc': ('body',), 'msg': 'Field required', 'input': None}]",
    "type": "BadRequestError",
    "param": null,
    "code": 400
}

The request being sent contains:

{
    "method": "POST",
    "headers": {
        "Connection": "Upgrade, HTTP2-Settings",
        "Host": "127.0.0.1:8080",
        "Http2-Settings": "AAEAAEAAAAIAAAABAAMAAABkAAQBAAAAAAUAAEAA",
        "Transfer-Encoding": "chunked",
        "Upgrade": "h2c",
        "User-Agent": "Java-http-client/22.0.1",
        "Authorization": "Bearer test",
        "Content-Type": "application/json"
    }
}

Current Workaround I've implemented a temporary solution by forcing HTTP/1.1:

@Component
public class RestClientCustomizer {
    @Bean
    @Primary
    public RestClient.Builder customRestClientBuilder() {
        HttpClient httpClient = HttpClient.newBuilder()
                .version(HttpClient.Version.HTTP_1_1)
                .build();
        return RestClient.builder()
                .requestFactory(new JdkClientHttpRequestFactory(httpClient));
    }
}

🤔Perhaps a better solution would be for VLLM to provide support.

Comment From: dev-jonghoonpark

@icyclv Which Vector Databases are you experiencing this issue in? In my case, I am experiencing the above issue in chroma.

Comment From: icyclv

@dev-jonghoonpark I am using Elasticsearch as the vector database, but the issue I'm encountering isn't occurring during the storage-to-database phase, but rather during the stage of embedding text into vectors.

Comment From: dev-jonghoonpark

ChromaVectorStoreAutoConfiguration.java

When a ChromaApi instance is created, RestClient.builder() is used as follows:

var chromaApi = new ChromaApi(chromaUrl, restClientBuilderProvider.getIfAvailable(RestClient::builder), objectMapper);

The RestClient.builder() returns DefaultRestClientBuilder:

static Builder builder() {
    return new DefaultRestClientBuilder();
}

DefaultRestClientBuilder.java

when build() method of DefaultRestClientBuilder is invoked, it call initRequestFactory() method

private ClientHttpRequestFactory initRequestFactory() {
    if (this.requestFactory != null) {
        return this.requestFactory;
    } else if (httpComponentsClientPresent) {
        return new HttpComponentsClientHttpRequestFactory();
    } else if (jettyClientPresent) {
        return new JettyClientHttpRequestFactory();
    } else if (reactorNettyClientPresent) {
        return new ReactorClientHttpRequestFactory();
    } else {
        return (ClientHttpRequestFactory)(jdkClientPresent ? new JdkClientHttpRequestFactory() : new SimpleClientHttpRequestFactory());
    }
}

finally, a JdkClientHttpRequestFactory instance selected.

JdkClientHttpRequestFactory.java

The JdkClientHttpRequestFactory uses HttpClient, witch is created by calling HttpClient.newHttpClient(). By default, it uses HTTP/2.

Refer to HttpClient.html#newHttpClient() for more details:

The default settings include: the "GET" request method, a preference of HTTP/2, a redirection policy of NEVER, the default proxy selector, and the default SSL context.