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feat: Refine logging levels (#985)

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The logging is sometimes too verbose and uses inappropriate level. With this
change there should be less disturbing logs and less duplication.

Notable changes:

* `LifeCycleInitializer#handleException` - duplicated log, already handled in
  transports that use the initializer.
* `McpClientSession#sendRequest` - an MCP protocol level error in JSON-RPC is
  not really a reason for ERROR level log. Using INFO with more details.
* `DefaultJsonSchemaValidator` - ERROR logs in `validate` are always logged by
  the users of this method. `validateSchema` surfaces as
  `IllegalArgumentException` and can be logged at higher levels by the user.

Also: remove DEBUG logs from mcp-test module.

Signed-off-by: Dariusz Jędrzejczyk <2554306+chemicL@users.noreply.github.com>
This commit is contained in:
Dariusz Jędrzejczyk 2026-05-27 11:50:48 +02:00 • committed by GitHub
commit c8ab3411b9
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GPG key ID: B5690EEEBB952194
11 changed files with 70 additions and 33 deletions
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1
mcp-core/src/main/java/io/modelcontextprotocol/client/LifecycleInitializer.java
View file

@ -250,7 +250,6 @@ class LifecycleInitializer {
* @param t The exception to handle
*/
public void handleException(Throwable t) {
logger.warn("Handling exception", t);
if (t instanceof McpTransportSessionNotFoundException) {
DefaultInitialization previous = this.initializationRef.getAndSet(null);
if (previous != null) {

9
mcp-core/src/main/java/io/modelcontextprotocol/client/McpAsyncClient.java
View file

@ -484,9 +484,7 @@ public class McpAsyncClient {
if (this.isInitialized()) {
return this.rootsListChangedNotification();
}
else {
logger.warn("Client is not initialized, ignore sending a roots list changed notification");
}
logger.debug("Client is not initialized, ignore sending a roots list changed notification");
}
return Mono.empty();
}
@ -514,10 +512,7 @@ public class McpAsyncClient {
if (this.isInitialized()) {
return this.rootsListChangedNotification();
}
else {
logger.warn("Client is not initialized, ignore sending a roots list changed notification");
}
logger.debug("Client is not initialized, ignore sending a roots list changed notification");
}
return Mono.empty();
}

19
mcp-core/src/main/java/io/modelcontextprotocol/client/transport/StdioClientTransport.java
View file

@ -10,10 +10,13 @@ import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;
import java.time.Duration;
import java.util.ArrayList;
import java.util.EnumSet;
import java.util.List;
import java.util.Set;
import java.util.concurrent.Executors;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.stream.IntStream;
import io.modelcontextprotocol.json.TypeRef;
import io.modelcontextprotocol.json.McpJsonMapper;
@ -41,6 +44,15 @@ public class StdioClientTransport implements McpClientTransport {
private static final Logger logger = LoggerFactory.getLogger(StdioClientTransport.class);
// @formatter:off
private static final Set<Integer> EXIT_SUCCESS_CODES = Set.of(
0, // success
130, // interrupted (SIGINT)
141, // pipeline shortcut (SIGPIPE)
143 // graceful termination (SIGTERM)
);
// @formatter:on
private final Sinks.Many<JSONRPCMessage> inboundSink;
private final Sinks.Many<JSONRPCMessage> outboundSink;
@ -356,11 +368,12 @@ public class StdioClientTransport implements McpClientTransport {
return Mono.<Process>empty();
}
})).doOnNext(process -> {
if (process.exitValue() != 0) {
logger.warn("Process terminated with code {}", process.exitValue());
int exitValue = process.exitValue();
if (EXIT_SUCCESS_CODES.contains(exitValue)) {
logger.info("MCP server completed successfully with code {}", exitValue);
}
else {
logger.info("MCP server process stopped");
logger.warn("MCP server process failed with code {}", exitValue);
}
}).then(Mono.fromRunnable(() -> {
try {

9
mcp-core/src/main/java/io/modelcontextprotocol/server/McpAsyncServer.java
View file

@ -513,14 +513,13 @@ public class McpAsyncServer {
return Mono.defer(() -> {
if (this.tools.removeIf(toolSpecification -> toolSpecification.tool().name().equals(toolName))) {
logger.debug("Removed tool handler: {}", toolName);
if (this.serverCapabilities.tools().listChanged()) {
return notifyToolsListChanged();
}
}
else {
logger.warn("Ignore as a Tool with name '{}' not found", toolName);
logger.warn("Failed to remove tool with name '{}' (not found)", toolName);
}
return Mono.empty();
@ -637,7 +636,7 @@ public class McpAsyncServer {
return Mono.empty();
}
else {
logger.warn("Ignore as a Resource with URI '{}' not found", resourceUri);
logger.warn("Failed to remove resource with URI '{}' (not found)", resourceUri);
}
return Mono.empty();
});
@ -701,7 +700,7 @@ public class McpAsyncServer {
logger.debug("Removed resource template: {}", uriTemplate);
}
else {
logger.warn("Ignore as a Resource Template with URI '{}' not found", uriTemplate);
logger.warn("Failed to remove a resource template with URI '{}' (not found)", uriTemplate);
}
return Mono.empty();
});
@ -907,7 +906,7 @@ public class McpAsyncServer {
return Mono.empty();
}
else {
logger.warn("Ignore as a Prompt with name '{}' not found", promptName);
logger.warn("Failed to remove a prompt with name '{}' (not found)", promptName);
}
return Mono.empty();
});

8
mcp-core/src/main/java/io/modelcontextprotocol/server/McpStatelessAsyncServer.java
View file

@ -390,7 +390,7 @@ public class McpStatelessAsyncServer {
logger.debug("Removed tool handler: {}", toolName);
}
else {
logger.warn("Ignore as a Tool with name '{}' not found", toolName);
logger.warn("Failed to remove a tool with name '{}' (not found)", toolName);
}
return Mono.empty();
@ -492,7 +492,7 @@ public class McpStatelessAsyncServer {
logger.debug("Removed resource handler: {}", resourceUri);
}
else {
logger.warn("Resource with URI '{}' not found", resourceUri);
logger.warn("Failed to remove a resource with URI '{}' (not found)", resourceUri);
}
return Mono.empty();
});
@ -554,7 +554,7 @@ public class McpStatelessAsyncServer {
logger.debug("Removed resource template: {}", uriTemplate);
}
else {
logger.warn("Ignore as a Resource Template with URI '{}' not found", uriTemplate);
logger.warn("Failed to remove a resource template with URI '{}' (not found)", uriTemplate);
}
return Mono.empty();
});
@ -677,7 +677,7 @@ public class McpStatelessAsyncServer {
return Mono.empty();
}
else {
logger.warn("Ignore as a Prompt with name '{}' not found", promptName);
logger.warn("Failed to remove a prompt with name '{}' (not found)", promptName);
}
return Mono.empty();

5
mcp-core/src/main/java/io/modelcontextprotocol/server/transport/HttpServletStreamableServerTransportProvider.java
View file

@ -200,7 +200,7 @@ public class HttpServletStreamableServerTransportProvider extends HttpServlet
session.sendNotification(method, params).block();
}
catch (Exception e) {
logger.error("Failed to send message to session {}: {}", session.getId(), e.getMessage());
logger.info("Failed to send message to session {}: {}", session.getId(), e.getMessage());
}
});
});
@ -233,12 +233,11 @@ public class HttpServletStreamableServerTransportProvider extends HttpServlet
session.closeGracefully().block();
}
catch (Exception e) {
logger.error("Failed to close session {}: {}", session.getId(), e.getMessage());
logger.warn("Failed to close session {}: {}", session.getId(), e.getMessage());
}
});
this.sessions.clear();
logger.debug("Graceful shutdown completed");
}).then().doOnSuccess(v -> {
sessions.clear();
logger.debug("Graceful shutdown completed");

5
mcp-core/src/main/java/io/modelcontextprotocol/spec/McpClientSession.java
View file

@ -124,7 +124,7 @@ public class McpClientSession implements McpSession {
private void dismissPendingResponses() {
this.pendingResponses.forEach((id, sink) -> {
logger.warn("Abruptly terminating exchange for request {}", id);
logger.info("Abruptly terminating exchange for request {}", id);
sink.error(new RuntimeException("MCP session with server terminated"));
});
this.pendingResponses.clear();
@ -257,7 +257,8 @@ public class McpClientSession implements McpSession {
});
})).timeout(this.requestTimeout).handle((jsonRpcResponse, deliveredResponseSink) -> {
if (jsonRpcResponse.error() != null) {
logger.error("Error handling request: {}", jsonRpcResponse.error());
logger.info("Server returned a JSON-RPC error when calling method {}: {}", method,
jsonRpcResponse.error());
deliveredResponseSink.error(new McpError(jsonRpcResponse.error()));
}
else {

4
mcp-core/src/main/java/io/modelcontextprotocol/spec/McpServerSession.java
View file

@ -256,8 +256,8 @@ public class McpServerSession implements McpLoggableSession {
// happening first
logger.debug("Received notification: {}", notification);
// TODO: in case of error, should the POST request be signalled?
return handleIncomingNotification(notification, transportContext)
.doOnError(error -> logger.error("Error handling notification: {}", error.getMessage()));
return handleIncomingNotification(notification, transportContext).doOnError(
error -> logger.warn("Error handling notification {}: {}", notification, error.getMessage()));
}
else {
logger.warn("Received unknown message type: {}", message);

3
mcp-json-jackson2/src/main/java/io/modelcontextprotocol/json/schema/jackson2/DefaultJsonSchemaValidator.java
View file

@ -84,11 +84,9 @@ public class DefaultJsonSchemaValidator implements JsonSchemaValidator {
}
catch (JsonProcessingException e) {
logger.error("Failed to validate CallToolResult: Error parsing schema: {}", e);
return ValidationResponse.asInvalid("Error parsing tool JSON Schema: " + e.getMessage());
}
catch (Exception e) {
logger.error("Failed to validate CallToolResult: Unexpected error: {}", e);
return ValidationResponse.asInvalid("Unexpected validation error: " + e.getMessage());
}
}
@ -113,7 +111,6 @@ public class DefaultJsonSchemaValidator implements JsonSchemaValidator {
return ValidationResponse.asValid(null);
}
catch (Exception e) {
logger.error("Failed to validate schema definition: {}", e.getMessage());
return ValidationResponse.asInvalid("Failed to validate schema definition: " + e.getMessage());
}
}

3
mcp-json-jackson3/src/main/java/io/modelcontextprotocol/json/schema/jackson3/DefaultJsonSchemaValidator.java
View file

@ -83,11 +83,9 @@ public class DefaultJsonSchemaValidator implements JsonSchemaValidator {
}
catch (JacksonException e) {
logger.error("Failed to validate CallToolResult: Error parsing schema: {}", e);
return ValidationResponse.asInvalid("Error parsing tool JSON Schema: " + e.getMessage());
}
catch (Exception e) {
logger.error("Failed to validate CallToolResult: Unexpected error: {}", e);
return ValidationResponse.asInvalid("Unexpected validation error: " + e.getMessage());
}
}
@ -112,7 +110,6 @@ public class DefaultJsonSchemaValidator implements JsonSchemaValidator {
return ValidationResponse.asValid(null);
}
catch (Exception e) {
logger.error("Failed to validate schema definition: {}", e.getMessage());
return ValidationResponse.asInvalid("Failed to validate schema definition: " + e.getMessage());
}
}

37
mcp-test/src/test/resources/logback-test.xml Normal file
View file

@ -0,0 +1,37 @@
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration>
<configuration>
<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
<encoder>
<pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
</encoder>
</appender>
<appender name="DOCKER" class="ch.qos.logback.core.ConsoleAppender">
<encoder>
<pattern>%d{HH:mm:ss.SSS} [%thread] %-5level [DOCKER] %logger{36} - %msg%n</pattern>
</encoder>
</appender>
<!-- Testcontainers framework -->
<logger name="org.testcontainers" level="INFO" additivity="false">
<appender-ref ref="DOCKER"/>
</logger>
<!-- Docker Java client -->
<logger name="com.github.dockerjava" level="INFO" additivity="false">
<appender-ref ref="DOCKER"/>
</logger>
<!-- Container output (tc.<image-name> format used by Testcontainers) -->
<logger name="tc" level="INFO" additivity="false">
<appender-ref ref="DOCKER"/>
</logger>
<logger name="io.modelcontextprotocol" level="INFO"/>
<root level="INFO">
<appender-ref ref="STDOUT"/>
</root>
</configuration>