LamiumAmplexicaule commented on code in PR #8665: URL: https://github.com/apache/hadoop/pull/8665#discussion_r3792489312
########## hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/mcp/McpRequestHandler.java: ########## @@ -0,0 +1,181 @@ +/** + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package org.apache.hadoop.mcp; + +import java.util.ArrayList; +import java.util.Collections; +import java.util.HashMap; +import java.util.LinkedHashMap; +import java.util.List; +import java.util.Map; +import java.util.UUID; + +import org.apache.hadoop.classification.InterfaceAudience; +import org.apache.hadoop.classification.InterfaceStability; +import org.apache.hadoop.mcp.McpSchema.ServerCapabilities; +import org.apache.hadoop.mcp.McpSchema.Tool; +import org.apache.hadoop.mcp.McpServer.RegisteredTool; + +import com.fasterxml.jackson.core.type.TypeReference; +import com.fasterxml.jackson.databind.JsonNode; +import com.fasterxml.jackson.databind.ObjectMapper; + +/** + * Transport-neutral MCP JSON-RPC request handler. + */ [email protected] [email protected] +public final class McpRequestHandler { + + public static final String SESSION_HEADER = "Mcp-Session-Id"; + + public static final String METHOD_INITIALIZE = "initialize"; + public static final String METHOD_TOOLS_LIST = "tools/list"; + public static final String METHOD_TOOLS_CALL = "tools/call"; + + private static final TypeReference<Map<String, Object>> PARAMS_TYPE = new TypeReference<>() {}; + + private final ObjectMapper objectMapper; + private final String serverName; + private final String serverVersion; + private final ServerCapabilities capabilities; + private final Map<String, RegisteredTool> tools; + private final McpJsonRpcResponses jsonRpcResponses; + + McpRequestHandler(ObjectMapper objectMapper, String serverName, String serverVersion, + ServerCapabilities capabilities, Map<String, RegisteredTool> tools) { + this.objectMapper = objectMapper; + this.serverName = serverName; + this.serverVersion = serverVersion; + this.capabilities = capabilities; + this.tools = Collections.unmodifiableMap(new LinkedHashMap<>(tools)); + this.jsonRpcResponses = new McpJsonRpcResponses(objectMapper); + } + + public McpHttpResponse handle(JsonNode requestNode) { + return handle(requestNode, new McpCallContext(null)); + } + + public McpHttpResponse parseErrorResponse() { + return jsonRpcResponses.error(null, McpJsonRpc.PARSE_ERROR, McpJsonRpc.PARSE_ERROR_MESSAGE); + } + + public McpHttpResponse requestBodyTooLargeResponse() { + return jsonRpcResponses.error(null, McpJsonRpc.INVALID_REQUEST, + McpJsonRpc.REQUEST_BODY_TOO_LARGE_MESSAGE); + } + + public McpHttpResponse handle(JsonNode requestNode, McpCallContext context) { + McpHttpResponse error = McpJsonRpcValidator.validate(requestNode, jsonRpcResponses); + if (error != null) { + return error; + } + + String method = requestNode.get("method").asText(); + if (McpJsonRpcValidator.isNotification(method)) { + return McpHttpResponse.notification(); + } + + JsonNode idNode = requestNode.get("id"); + JsonNode paramsNode = requestNode.get("params"); + if (paramsNode != null && !paramsNode.isNull() && !paramsNode.isObject()) { + return jsonRpcResponses.error(idNode, McpJsonRpc.INVALID_PARAMS, + "params must be a JSON object"); + } + Map<String, Object> params = paramsNode == null || paramsNode.isNull() + ? Collections.emptyMap() + : objectMapper.convertValue(paramsNode, PARAMS_TYPE); + + switch (method) { + case METHOD_INITIALIZE: + return initializeResponse(idNode); + case METHOD_TOOLS_LIST: + return jsonRpcResponses.success(idNode, buildToolsListResult()); + case METHOD_TOOLS_CALL: + return toolsCallResponse(idNode, params, context); + default: + return jsonRpcResponses.error(idNode, McpJsonRpc.METHOD_NOT_FOUND, + "Method not found: " + method); + } + } + + private McpHttpResponse initializeResponse(JsonNode idNode) { + Map<String, Object> result = new HashMap<>(); + result.put("protocolVersion", McpJsonRpc.PROTOCOL_VERSION); + result.put("capabilities", capabilities.toMap()); + Map<String, Object> serverInfo = new HashMap<>(); + serverInfo.put("name", serverName); + serverInfo.put("version", serverVersion); + result.put("serverInfo", serverInfo); + + Map<String, String> headers = new HashMap<>(); + headers.put(SESSION_HEADER, UUID.randomUUID().toString()); + return jsonRpcResponses.success(idNode, result, headers); + } + + private Map<String, Object> buildToolsListResult() { + List<Map<String, Object>> toolList = new ArrayList<>(); + for (RegisteredTool registeredTool : tools.values()) { + Tool tool = registeredTool.tool(); + Map<String, Object> toolMap = new LinkedHashMap<>(); + toolMap.put("name", tool.name()); + toolMap.put("description", tool.description()); + toolMap.put("inputSchema", tool.inputSchema()); + toolList.add(toolMap); + } + Map<String, Object> result = new HashMap<>(); + result.put("tools", toolList); + return result; + } + + private McpHttpResponse toolsCallResponse(JsonNode idNode, Map<String, Object> params, + McpCallContext context) { + Object nameObject = params.get("name"); + if (!(nameObject instanceof String)) { + return jsonRpcResponses.error(idNode, McpJsonRpc.INVALID_PARAMS, "Missing tool name"); + } + + RegisteredTool registeredTool = tools.get(nameObject); + if (registeredTool == null) { + return jsonRpcResponses.error(idNode, McpJsonRpc.INVALID_PARAMS, + "Unknown tool: " + nameObject); + } + + Object argumentsObject = params.get("arguments"); + Map<String, Object> arguments; + if (argumentsObject == null) { + arguments = Collections.emptyMap(); + } else if (!(argumentsObject instanceof Map)) { + return jsonRpcResponses.error(idNode, McpJsonRpc.INVALID_PARAMS, + "arguments must be a JSON object"); + } else { + arguments = objectMapper.convertValue( + objectMapper.valueToTree(argumentsObject), PARAMS_TYPE); + } + + final McpSchema.CallToolResult callResult; + try { + callResult = registeredTool.call(context, arguments); + } catch (Exception e) { + return jsonRpcResponses.success(idNode, McpJsonRpcResponses.toResultMap( + McpSchema.CallToolResult.error(e.getMessage()))); Review Comment: If an exception doesn’t include a message, the response ends up with `"text": null`. Should we allow that? If `e.getMessage()` is null, it might be better to display a fallback error message instead. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
