Add mcp-client module: ChatClient calling tools from real external MCP servers over stdio

defaultToolCallbacks(ToolCallbackProvider) wires two real stdio MCP servers (the official filesystem server and git server) into ChatClient, contrasted with defaultTools(Object) for a local @Tool method. Every call -- MCP-sourced or local -- is logged through one Micrometer ObservationHandler<ToolCallingObservationContext>; a first version wired that handler two ways at once and every call logged twice, which is now a regression test. No real LLM is used anywhere: every test builds an AssistantMessage.ToolCall by hand and drives it through the real ToolCallingManager bean against real npx/uvx-launched MCP server processes. Co-Authored-By: Claude Sonnet 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01FtpJvZfg4nvLvtzgJTDWpB
2026-09-23 14:44:10 +00:00
parent 9919da58a7
commit 60849f4319
25 changed files with 969 additions and 0 deletions
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+# What a 1ms requestTimeout actually throws on a real MCP handshake -- captured, not guessed
+
+requestTimeout=1ms, initializationTimeout=30s -- set deliberately far apart to see which
+one actually governs the initialize() handshake
+
+client.initialize() threw:
+  [0] java.lang.RuntimeException: Client failed to initialize by explicit API call
+  [0]   suppressed: java.lang.Exception: #block terminated with an error
+  [1] java.util.concurrent.TimeoutException: Did not observe any item or terminal signal within 1ms in 'source(MonoDeferContextual)' (and no fallback has been configured)
+
+confirmed: the real timeout-carrying exception is java.util.concurrent.TimeoutException, a plain JDK type from Reactor's
+Flux.timeout() operator -- not a dedicated MCP timeout exception class.