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feat(mcp): add notification handlers support for async client #568
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3ef7d5d
feat(mcp): add notification handlers support for async client
JGoP-L 5b9582d
Merge branch 'main' into feat/add-notification-handlers-support-for-a…
JGoP-L ae06223
feat(mcp): add notification handlers support for sync client
JGoP-L b966d99
feat(mcp): add notification handlers support for sync client
JGoP-L 378b7b1
Merge branch 'main' into feat/add-notification-handlers-support-for-a…
JGoP-L 9a23888
add synchronized
JGoP-L e9df304
Merge remote-tracking branch 'origin/feat/add-notification-handlers-s…
JGoP-L fa1e155
Merge branch 'main' into feat/add-notification-handlers-support-for-a…
JGoP-L 3e95f85
add volatile
JGoP-L 2d086ef
Merge branch 'main' into feat/add-notification-handlers-support-for-a…
JGoP-L 7c97c55
fix Spotless
JGoP-L e99b485
Merge branch 'main' into feat/add-notification-handlers-support-for-a…
JGoP-L e34c3fd
Merge branch 'main' into feat/add-notification-handlers-support-for-a…
JGoP-L 5d37bda
Merge branch 'main' into feat/add-notification-handlers-support-for-a…
JGoP-L 3839079
Merge branch 'main' into feat/add-notification-handlers-support-for-a…
JGoP-L 5733e57
fix
JGoP-L a8292de
Merge branch 'main' into feat/add-notification-handlers-support-for-a…
JGoP-L e72373d
fix higress
JGoP-L 20724d9
Merge branch 'main' into feat/add-notification-handlers-support-for-a…
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| Original file line number | Diff line number | Diff line change | ||||||
|---|---|---|---|---|---|---|---|---|
|
|
@@ -19,17 +19,16 @@ | |||||||
| import io.modelcontextprotocol.spec.McpSchema; | ||||||||
| import java.util.List; | ||||||||
| import java.util.Map; | ||||||||
| import java.util.concurrent.atomic.AtomicReference; | ||||||||
| import org.slf4j.Logger; | ||||||||
| import org.slf4j.LoggerFactory; | ||||||||
| import reactor.core.publisher.Mono; | ||||||||
|
|
||||||||
| /** | ||||||||
| * Wrapper for asynchronous MCP clients using Project Reactor. | ||||||||
| * This implementation delegates to {@link McpAsyncClient} and provides | ||||||||
| * reactive operations that return Mono types. | ||||||||
| * Wrapper for asynchronous MCP clients using Project Reactor. This implementation delegates to | ||||||||
| * {@link McpAsyncClient} and provides reactive operations that return Mono types. | ||||||||
| * | ||||||||
| * <p>Example usage: | ||||||||
| * <pre>{@code | ||||||||
| * <p>Example usage: <pre>{@code | ||||||||
| * McpAsyncClient client = ... // created via McpClient.async() | ||||||||
| * McpAsyncClientWrapper wrapper = new McpAsyncClientWrapper("my-mcp", client); | ||||||||
| * wrapper.initialize() | ||||||||
|
|
@@ -41,7 +40,7 @@ public class McpAsyncClientWrapper extends McpClientWrapper { | |||||||
|
|
||||||||
| private static final Logger logger = LoggerFactory.getLogger(McpAsyncClientWrapper.class); | ||||||||
|
|
||||||||
| private final McpAsyncClient client; | ||||||||
| private final AtomicReference<McpAsyncClient> clientRef; | ||||||||
|
|
||||||||
| /** | ||||||||
| * Constructs a new asynchronous MCP client wrapper. | ||||||||
|
|
@@ -51,7 +50,32 @@ public class McpAsyncClientWrapper extends McpClientWrapper { | |||||||
| */ | ||||||||
| public McpAsyncClientWrapper(String name, McpAsyncClient client) { | ||||||||
| super(name); | ||||||||
| this.client = client; | ||||||||
| this.clientRef = new AtomicReference<>(client); | ||||||||
| } | ||||||||
|
|
||||||||
| /** | ||||||||
| * Sets the underlying MCP async client. This is called by McpClientBuilder after the client | ||||||||
| * is created with notification handlers. | ||||||||
| * | ||||||||
| * @param client the MCP async client | ||||||||
| */ | ||||||||
| void setClient(McpAsyncClient client) { | ||||||||
| this.clientRef.set(client); | ||||||||
| } | ||||||||
|
|
||||||||
| /** | ||||||||
| * Updates the cached tools map with new tools from the server. This method is called when the | ||||||||
| * server sends a tools/list_changed notification. | ||||||||
| * | ||||||||
| * @param tools the new list of tools from the server (empty list clears cache) | ||||||||
| */ | ||||||||
| void updateCachedTools(List<McpSchema.Tool> tools) { | ||||||||
| if (tools != null) { | ||||||||
| // Clear and rebuild cache | ||||||||
| cachedTools.clear(); | ||||||||
| tools.forEach(tool -> cachedTools.put(tool.name(), tool)); | ||||||||
| logger.info("[MCP-{}] Updated cached tools, total: {}", name, tools.size()); | ||||||||
| } | ||||||||
| } | ||||||||
|
|
||||||||
| /** | ||||||||
|
|
@@ -68,6 +92,12 @@ public Mono<Void> initialize() { | |||||||
| return Mono.empty(); | ||||||||
| } | ||||||||
|
|
||||||||
| McpAsyncClient client = clientRef.get(); | ||||||||
| if (client == null) { | ||||||||
| return Mono.error( | ||||||||
| new IllegalStateException("McpAsyncClient not set. Call setClient() first.")); | ||||||||
|
||||||||
| return Mono.error( | |
| new IllegalStateException("McpAsyncClient not set. Call setClient() first.")); | |
| return Mono.error(new IllegalStateException("MCP client not available")); |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
|
|
@@ -38,6 +38,8 @@ | |
| import java.util.Map; | ||
| import java.util.function.Consumer; | ||
| import java.util.stream.Collectors; | ||
| import org.slf4j.Logger; | ||
| import org.slf4j.LoggerFactory; | ||
| import reactor.core.publisher.Mono; | ||
|
|
||
| /** | ||
|
|
@@ -78,6 +80,7 @@ public class McpClientBuilder { | |
|
|
||
| private static final Duration DEFAULT_REQUEST_TIMEOUT = Duration.ofSeconds(120); | ||
| private static final Duration DEFAULT_INIT_TIMEOUT = Duration.ofSeconds(30); | ||
| private static final Logger logger = LoggerFactory.getLogger(McpClientBuilder.class); | ||
|
|
||
| private final String name; | ||
| private TransportConfig transportConfig; | ||
|
|
@@ -283,6 +286,10 @@ public McpClientBuilder initializationTimeout(Duration timeout) { | |
| /** | ||
| * Builds an asynchronous MCP client wrapper. | ||
| * | ||
| * <p>This method uses a two-phase build pattern to support notification handlers. | ||
| * The wrapper is created first, then the MCP client is built with notification consumers | ||
| * that can reference the wrapper. | ||
| * | ||
| * @return Mono emitting the async client wrapper | ||
| */ | ||
| public Mono<McpClientWrapper> buildAsync() { | ||
|
|
@@ -303,15 +310,76 @@ public Mono<McpClientWrapper> buildAsync() { | |
| McpSchema.ClientCapabilities clientCapabilities = | ||
| McpSchema.ClientCapabilities.builder().build(); | ||
|
|
||
| // ========== Phase 1: Create wrapper (client is temporarily null) ========== | ||
| McpAsyncClientWrapper wrapper = new McpAsyncClientWrapper(name, null); | ||
|
|
||
| // ========== Phase 2: Build client (can reference wrapper) ========== | ||
| McpAsyncClient mcpClient = | ||
| McpClient.async(transport) | ||
| .requestTimeout(requestTimeout) | ||
| .initializationTimeout(initializationTimeout) | ||
| .clientInfo(clientInfo) | ||
| .capabilities(clientCapabilities) | ||
|
|
||
| // ----- Log notification Consumer ----- | ||
| .loggingConsumer( | ||
| notification -> { | ||
| // Parse notification content | ||
| String level = | ||
| notification.level() != null | ||
| ? notification.level().toString() | ||
| : "info"; | ||
| String loggerName = | ||
| notification.logger() != null | ||
| ? notification.logger() | ||
| : "mcp"; | ||
| String data = | ||
| notification.data() != null | ||
| ? notification.data() | ||
| : ""; | ||
|
|
||
| // Log to SLF4J by level | ||
| switch (level.toLowerCase()) { | ||
| case "error" -> | ||
| logger.error( | ||
| "[MCP-{}] [{}] {}", | ||
| name, | ||
| loggerName, | ||
| data); | ||
| case "warning" -> | ||
| logger.warn( | ||
| "[MCP-{}] [{}] {}", | ||
| name, | ||
| loggerName, | ||
| data); | ||
| case "debug" -> | ||
| logger.debug( | ||
| "[MCP-{}] [{}] {}", | ||
| name, | ||
| loggerName, | ||
| data); | ||
| default -> | ||
| logger.info( | ||
| "[MCP-{}] [{}] {}", | ||
| name, | ||
|
||
| loggerName, | ||
| data); | ||
| } | ||
| return Mono.empty(); | ||
| }) | ||
|
|
||
| // ----- Tools change notification Consumer ----- | ||
| .toolsChangeConsumer( | ||
| tools -> { | ||
| // Call wrapper method to update cache | ||
| wrapper.updateCachedTools(tools); | ||
| return Mono.empty(); | ||
| }) | ||
| .build(); | ||
|
|
||
| return new McpAsyncClientWrapper(name, mcpClient); | ||
| // ========== Phase 3: Link MCP client to wrapper ========== | ||
| wrapper.setClient(mcpClient); | ||
| return wrapper; | ||
| }); | ||
| } | ||
|
|
||
|
|
||
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| Original file line number | Diff line number | Diff line change | ||||||
|---|---|---|---|---|---|---|---|---|
|
|
@@ -19,18 +19,18 @@ | |||||||
| import io.modelcontextprotocol.spec.McpSchema; | ||||||||
| import java.util.List; | ||||||||
| import java.util.Map; | ||||||||
| import java.util.concurrent.atomic.AtomicReference; | ||||||||
| import org.slf4j.Logger; | ||||||||
| import org.slf4j.LoggerFactory; | ||||||||
| import reactor.core.publisher.Mono; | ||||||||
| import reactor.core.scheduler.Schedulers; | ||||||||
|
|
||||||||
| /** | ||||||||
| * Wrapper for synchronous MCP clients that converts blocking calls to reactive Mono types. | ||||||||
| * This implementation delegates to {@link McpSyncClient} and wraps blocking operations | ||||||||
| * in Reactor's boundedElastic scheduler to avoid blocking the event loop. | ||||||||
| * Wrapper for synchronous MCP clients that converts blocking calls to reactive Mono types. This | ||||||||
| * implementation delegates to {@link McpSyncClient} and wraps blocking operations in Reactor's | ||||||||
| * boundedElastic scheduler to avoid blocking the event loop. | ||||||||
| * | ||||||||
| * <p>Example usage: | ||||||||
| * <pre>{@code | ||||||||
| * <p>Example usage: <pre>{@code | ||||||||
| * McpSyncClient client = ... // created via McpClient.sync() | ||||||||
| * McpSyncClientWrapper wrapper = new McpSyncClientWrapper("my-mcp", client); | ||||||||
| * wrapper.initialize() | ||||||||
|
|
@@ -42,7 +42,7 @@ public class McpSyncClientWrapper extends McpClientWrapper { | |||||||
|
|
||||||||
| private static final Logger logger = LoggerFactory.getLogger(McpSyncClientWrapper.class); | ||||||||
|
|
||||||||
| private final McpSyncClient client; | ||||||||
| private final AtomicReference<McpSyncClient> clientRef; | ||||||||
|
|
||||||||
| /** | ||||||||
| * Constructs a new synchronous MCP client wrapper. | ||||||||
|
|
@@ -52,7 +52,7 @@ public class McpSyncClientWrapper extends McpClientWrapper { | |||||||
| */ | ||||||||
| public McpSyncClientWrapper(String name, McpSyncClient client) { | ||||||||
| super(name); | ||||||||
| this.client = client; | ||||||||
| this.clientRef = new AtomicReference<>(client); | ||||||||
| } | ||||||||
|
|
||||||||
| /** | ||||||||
|
|
@@ -70,10 +70,16 @@ public Mono<Void> initialize() { | |||||||
| return Mono.empty(); | ||||||||
| } | ||||||||
|
|
||||||||
| logger.info("Initializing MCP sync client: {}", name); | ||||||||
|
|
||||||||
| return Mono.fromCallable( | ||||||||
| () -> { | ||||||||
| McpSyncClient client = clientRef.get(); | ||||||||
| if (client == null) { | ||||||||
| throw new IllegalStateException( | ||||||||
| "McpSyncClient not set. Call setClient() first."); | ||||||||
|
||||||||
| throw new IllegalStateException( | |
| "McpSyncClient not set. Call setClient() first."); | |
| throw new IllegalStateException("MCP client not available"); |
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The
updateCachedTools()method performs a non-atomic clear-and-rebuild operation oncachedTools. Since this can be called asynchronously via notification handlers while other threads may be reading from the cache (e.g., viagetCachedTool()or during initialization), this creates a race condition. WhileConcurrentHashMapis thread-safe for individual operations, the clear-then-add pattern is not atomic. Consider synchronizing this method or using other concurrency patterns to ensure atomicity.