[8.19] Add Hugging Face Chat Completion support to Inference Plugin (#127254)

docs/changelog/127254.yaml

@@ -0,0 +1,5 @@
+pr: 127254
+summary: "[ML] Add HuggingFace Chat Completion support to the Inference Plugin"
+area: Machine Learning
+type: enhancement
+issues: []

server/src/main/java/org/elasticsearch/TransportVersions.java

@@ -219,6 +219,7 @@ static TransportVersion def(int id) {
     public static final TransportVersion INFERENCE_ADD_TIMEOUT_PUT_ENDPOINT_8_19 = def(8_841_0_28);
     public static final TransportVersion ESQL_REPORT_SHARD_PARTITIONING_8_19 = def(8_841_0_29);
     public static final TransportVersion ESQL_DRIVER_TASK_DESCRIPTION_8_19 = def(8_841_0_30);
+    public static final TransportVersion ML_INFERENCE_HUGGING_FACE_CHAT_COMPLETION_ADDED_8_19 = def(8_841_0_31);
 
     /*
      * STOP! READ THIS FIRST! No, really,

x-pack/plugin/inference/qa/inference-service-tests/src/javaRestTest/java/org/elasticsearch/xpack/inference/InferenceGetServicesIT.java

@@ -123,7 +123,7 @@ public void testGetServicesWithRerankTaskType() throws IOException {
 
     public void testGetServicesWithCompletionTaskType() throws IOException {
         List<Object> services = getServices(TaskType.COMPLETION);
-        assertThat(services.size(), equalTo(10));
+        assertThat(services.size(), equalTo(11));
 
         var providers = providers(services);
 
@@ -140,19 +140,23 @@ public void testGetServicesWithCompletionTaskType() throws IOException {
                     "deepseek",
                     "googleaistudio",
                     "openai",
-                    "streaming_completion_test_service"
+                    "streaming_completion_test_service",
+                    "hugging_face"
                 ).toArray()
             )
         );
     }
 
     public void testGetServicesWithChatCompletionTaskType() throws IOException {
         List<Object> services = getServices(TaskType.CHAT_COMPLETION);
-        assertThat(services.size(), equalTo(4));
+        assertThat(services.size(), equalTo(5));
 
         var providers = providers(services);
 
-        assertThat(providers, containsInAnyOrder(List.of("deepseek", "elastic", "openai", "streaming_completion_test_service").toArray()));
+        assertThat(
+            providers,
+            containsInAnyOrder(List.of("deepseek", "elastic", "openai", "streaming_completion_test_service", "hugging_face").toArray())
+        );
     }
 
     public void testGetServicesWithSparseEmbeddingTaskType() throws IOException {

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/InferenceNamedWriteablesProvider.java

@@ -78,6 +78,7 @@
 import org.elasticsearch.xpack.inference.services.googlevertexai.rerank.GoogleVertexAiRerankServiceSettings;
 import org.elasticsearch.xpack.inference.services.googlevertexai.rerank.GoogleVertexAiRerankTaskSettings;
 import org.elasticsearch.xpack.inference.services.huggingface.HuggingFaceServiceSettings;
+import org.elasticsearch.xpack.inference.services.huggingface.completion.HuggingFaceChatCompletionServiceSettings;
 import org.elasticsearch.xpack.inference.services.huggingface.elser.HuggingFaceElserServiceSettings;
 import org.elasticsearch.xpack.inference.services.ibmwatsonx.embeddings.IbmWatsonxEmbeddingsServiceSettings;
 import org.elasticsearch.xpack.inference.services.ibmwatsonx.rerank.IbmWatsonxRerankServiceSettings;
@@ -357,6 +358,13 @@ private static void addHuggingFaceNamedWriteables(List<NamedWriteableRegistry.En
         namedWriteables.add(
             new NamedWriteableRegistry.Entry(ServiceSettings.class, HuggingFaceServiceSettings.NAME, HuggingFaceServiceSettings::new)
         );
+        namedWriteables.add(
+            new NamedWriteableRegistry.Entry(
+                ServiceSettings.class,
+                HuggingFaceChatCompletionServiceSettings.NAME,
+                HuggingFaceChatCompletionServiceSettings::new
+            )
+        );
     }
 
     private static void addGoogleAiStudioNamedWritables(List<NamedWriteableRegistry.Entry> namedWriteables) {

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/huggingface/HuggingFaceChatCompletionResponseHandler.java

@@ -0,0 +1,171 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+package org.elasticsearch.xpack.inference.services.huggingface;
+
+import org.elasticsearch.core.Nullable;
+import org.elasticsearch.rest.RestStatus;
+import org.elasticsearch.xcontent.ConstructingObjectParser;
+import org.elasticsearch.xcontent.ParseField;
+import org.elasticsearch.xcontent.XContentFactory;
+import org.elasticsearch.xcontent.XContentParser;
+import org.elasticsearch.xcontent.XContentParserConfiguration;
+import org.elasticsearch.xcontent.XContentType;
+import org.elasticsearch.xpack.core.inference.results.UnifiedChatCompletionException;
+import org.elasticsearch.xpack.inference.external.http.HttpResult;
+import org.elasticsearch.xpack.inference.external.http.retry.ErrorResponse;
+import org.elasticsearch.xpack.inference.external.http.retry.ResponseParser;
+import org.elasticsearch.xpack.inference.external.request.Request;
+import org.elasticsearch.xpack.inference.services.huggingface.response.HuggingFaceErrorResponseEntity;
+import org.elasticsearch.xpack.inference.services.openai.OpenAiUnifiedChatCompletionResponseHandler;
+
+import java.util.Locale;
+import java.util.Optional;
+
+import static org.elasticsearch.core.Strings.format;
+
+/**
+ * Handles streaming chat completion responses and error parsing for Hugging Face inference endpoints.
+ * Adapts the OpenAI handler to support Hugging Face's simpler error schema with fields like "message" and "http_status_code".
+ */
+public class HuggingFaceChatCompletionResponseHandler extends OpenAiUnifiedChatCompletionResponseHandler {
+
+    private static final String HUGGING_FACE_ERROR = "hugging_face_error";
+
+    public HuggingFaceChatCompletionResponseHandler(String requestType, ResponseParser parseFunction) {
+        super(requestType, parseFunction, HuggingFaceErrorResponseEntity::fromResponse);
+    }
+
+    @Override
+    protected Exception buildError(String message, Request request, HttpResult result, ErrorResponse errorResponse) {
+        assert request.isStreaming() : "Only streaming requests support this format";
+        var responseStatusCode = result.response().getStatusLine().getStatusCode();
+        if (request.isStreaming()) {
+            var errorMessage = errorMessage(message, request, result, errorResponse, responseStatusCode);
+            var restStatus = toRestStatus(responseStatusCode);
+            return errorResponse instanceof HuggingFaceErrorResponseEntity
+                ? new UnifiedChatCompletionException(
+                    restStatus,
+                    errorMessage,
+                    HUGGING_FACE_ERROR,
+                    restStatus.name().toLowerCase(Locale.ROOT)
+                )
+                : new UnifiedChatCompletionException(
+                    restStatus,
+                    errorMessage,
+                    createErrorType(errorResponse),
+                    restStatus.name().toLowerCase(Locale.ROOT)
+                );
+        } else {
+            return super.buildError(message, request, result, errorResponse);
+        }
+    }
+
+    @Override
+    protected Exception buildMidStreamError(Request request, String message, Exception e) {
+        var errorResponse = StreamingHuggingFaceErrorResponseEntity.fromString(message);
+        if (errorResponse instanceof StreamingHuggingFaceErrorResponseEntity streamingHuggingFaceErrorResponseEntity) {
+            return new UnifiedChatCompletionException(
+                RestStatus.INTERNAL_SERVER_ERROR,
+                format(
+                    "%s for request from inference entity id [%s]. Error message: [%s]",
+                    SERVER_ERROR_OBJECT,
+                    request.getInferenceEntityId(),
+                    errorResponse.getErrorMessage()
+                ),
+                HUGGING_FACE_ERROR,
+                extractErrorCode(streamingHuggingFaceErrorResponseEntity)
+            );
+        } else if (e != null) {
+            return UnifiedChatCompletionException.fromThrowable(e);
+        } else {
+            return new UnifiedChatCompletionException(
+                RestStatus.INTERNAL_SERVER_ERROR,
+                format("%s for request from inference entity id [%s]", SERVER_ERROR_OBJECT, request.getInferenceEntityId()),
+                createErrorType(errorResponse),
+                "stream_error"
+            );
+        }
+    }
+
+    private static String extractErrorCode(StreamingHuggingFaceErrorResponseEntity streamingHuggingFaceErrorResponseEntity) {
+        return streamingHuggingFaceErrorResponseEntity.httpStatusCode() != null
+            ? String.valueOf(streamingHuggingFaceErrorResponseEntity.httpStatusCode())
+            : null;
+    }
+
+    /**
+     * Represents a structured error response specifically for streaming operations
+     * using HuggingFace APIs. This is separate from non-streaming error responses,
+     * which are handled by {@link HuggingFaceErrorResponseEntity}.
+     * An example error response for failed field validation for streaming operation would look like
+     * <code>
+     *     {
+     *       "error": "Input validation error: cannot compile regex from schema",
+     *       "http_status_code": 422
+     *     }
+     * </code>
+     */
+    private static class StreamingHuggingFaceErrorResponseEntity extends ErrorResponse {
+        private static final ConstructingObjectParser<Optional<ErrorResponse>, Void> ERROR_PARSER = new ConstructingObjectParser<>(
+            HUGGING_FACE_ERROR,
+            true,
+            args -> Optional.ofNullable((StreamingHuggingFaceErrorResponseEntity) args[0])
+        );
+        private static final ConstructingObjectParser<StreamingHuggingFaceErrorResponseEntity, Void> ERROR_BODY_PARSER =
+            new ConstructingObjectParser<>(
+                HUGGING_FACE_ERROR,
+                true,
+                args -> new StreamingHuggingFaceErrorResponseEntity(args[0] != null ? (String) args[0] : "unknown", (Integer) args[1])
+            );
+
+        static {
+            ERROR_BODY_PARSER.declareString(ConstructingObjectParser.optionalConstructorArg(), new ParseField("message"));
+            ERROR_BODY_PARSER.declareInt(ConstructingObjectParser.optionalConstructorArg(), new ParseField("http_status_code"));
+
+            ERROR_PARSER.declareObjectOrNull(
+                ConstructingObjectParser.optionalConstructorArg(),
+                ERROR_BODY_PARSER,
+                null,
+                new ParseField("error")
+            );
+        }
+
+        /**
+         * Parses a streaming HuggingFace error response from a JSON string.
+         *
+         * @param response the raw JSON string representing an error
+         * @return a parsed {@link ErrorResponse} or {@link ErrorResponse#UNDEFINED_ERROR} if parsing fails
+         */
+        private static ErrorResponse fromString(String response) {
+            try (
+                XContentParser parser = XContentFactory.xContent(XContentType.JSON)
+                    .createParser(XContentParserConfiguration.EMPTY, response)
+            ) {
+                return ERROR_PARSER.apply(parser, null).orElse(ErrorResponse.UNDEFINED_ERROR);
+            } catch (Exception e) {
+                // swallow the error
+            }
+
+            return ErrorResponse.UNDEFINED_ERROR;
+        }
+
+        @Nullable
+        private final Integer httpStatusCode;
+
+        StreamingHuggingFaceErrorResponseEntity(String errorMessage, @Nullable Integer httpStatusCode) {
+            super(errorMessage);
+            this.httpStatusCode = httpStatusCode;
+        }
+
+        @Nullable
+        public Integer httpStatusCode() {
+            return httpStatusCode;
+        }
+
+    }
+}

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/huggingface/HuggingFaceModel.java

@@ -9,17 +9,18 @@
 
 import org.elasticsearch.common.settings.SecureString;
 import org.elasticsearch.core.Nullable;
-import org.elasticsearch.inference.Model;
 import org.elasticsearch.inference.ModelConfigurations;
 import org.elasticsearch.inference.ModelSecrets;
 import org.elasticsearch.xpack.inference.external.action.ExecutableAction;
+import org.elasticsearch.xpack.inference.services.RateLimitGroupingModel;
 import org.elasticsearch.xpack.inference.services.ServiceUtils;
 import org.elasticsearch.xpack.inference.services.huggingface.action.HuggingFaceActionVisitor;
 import org.elasticsearch.xpack.inference.services.settings.ApiKeySecrets;
+import org.elasticsearch.xpack.inference.services.settings.RateLimitSettings;
 
 import java.util.Objects;
 
-public abstract class HuggingFaceModel extends Model {
+public abstract class HuggingFaceModel extends RateLimitGroupingModel {
     private final HuggingFaceRateLimitServiceSettings rateLimitServiceSettings;
     private final SecureString apiKey;
 
@@ -38,6 +39,16 @@ public HuggingFaceRateLimitServiceSettings rateLimitServiceSettings() {
         return rateLimitServiceSettings;
     }
 
+    @Override
+    public int rateLimitGroupingHash() {
+        return Objects.hash(rateLimitServiceSettings.uri(), apiKey);
+    }
+
+    @Override
+    public RateLimitSettings rateLimitSettings() {
+        return rateLimitServiceSettings.rateLimitSettings();
+    }
+
     public SecureString apiKey() {
         return apiKey;
     }

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/huggingface/HuggingFaceRequestManager.java

@@ -19,7 +19,7 @@
 import org.elasticsearch.xpack.inference.external.http.sender.EmbeddingsInput;
 import org.elasticsearch.xpack.inference.external.http.sender.ExecutableInferenceRequest;
 import org.elasticsearch.xpack.inference.external.http.sender.InferenceInputs;
-import org.elasticsearch.xpack.inference.services.huggingface.request.HuggingFaceInferenceRequest;
+import org.elasticsearch.xpack.inference.services.huggingface.request.embeddings.HuggingFaceEmbeddingsRequest;
 
 import java.util.List;
 import java.util.Objects;
@@ -64,7 +64,7 @@ public void execute(
     ) {
         List<String> docsInput = EmbeddingsInput.of(inferenceInputs).getStringInputs();
         var truncatedInput = truncate(docsInput, model.getTokenLimit());
-        var request = new HuggingFaceInferenceRequest(truncator, truncatedInput, model);
+        var request = new HuggingFaceEmbeddingsRequest(truncator, truncatedInput, model);
 
         execute(new ExecutableInferenceRequest(requestSender, logger, request, responseHandler, hasRequestCompletedFunction, listener));
     }