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Don't silently swallow proxy initialization failures #982

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Merged
adwsingh merged 1 commit into from
Dec 11, 2025
Merged

Don't silently swallow proxy initialization failures #982

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29 changes: 18 additions & 11 deletions mcp/mcp-server/src/main/java/software/amazon/smithy/java/mcp/server/McpService.java
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,9 @@
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.CompletionException;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Consumer;
import java.util.stream.Collectors;
Expand Down Expand Up @@ -333,17 +335,13 @@ public void initializeProxies(Consumer<JsonRpcResponse> responseWriter) {
}

for (McpServerProxy proxy : proxies.values()) {
try {
if (initRequest != null) {
proxy.initialize(responseWriter, initRequest, protocolVersion);
}
if (initRequest != null) {
proxy.initialize(responseWriter, initRequest, protocolVersion);
}

List<ToolInfo> proxyTools = proxy.listTools();
for (var toolInfo : proxyTools) {
tools.put(toolInfo.getName(), new Tool(toolInfo, proxy.name(), proxy));
}
} catch (Exception e) {
LOG.error("Failed to initialize proxy: " + proxy.name(), e);
List<ToolInfo> proxyTools = proxy.listTools();
for (var toolInfo : proxyTools) {
tools.put(toolInfo.getName(), new Tool(toolInfo, proxy.name(), proxy));
}
}
}
Expand Down Expand Up @@ -457,8 +455,9 @@ private JsonRpcResponse createErrorResponse(JsonRpcRequest req, Exception except
return createErrorResponse(req, exception, true); //TODO change the default to false.
}

private JsonRpcResponse createErrorResponse(JsonRpcRequest req, Exception exception, boolean sendStackTrace) {
private JsonRpcResponse createErrorResponse(JsonRpcRequest req, Throwable exception, boolean sendStackTrace) {
String s;
exception = unwrapException(exception);
if (sendStackTrace) {
try (var sw = new StringWriter();
var pw = new PrintWriter(sw)) {
Expand All @@ -474,6 +473,14 @@ private JsonRpcResponse createErrorResponse(JsonRpcRequest req, Exception except
return createErrorResponse(req, s);
}

private Throwable unwrapException(Throwable exception) {
return switch (exception) {
case CompletionException ce when ce.getCause() != null -> ce.getCause();
case ExecutionException ee when ee.getCause() != null -> ee.getCause();
default -> exception;
};
}

private JsonRpcResponse createErrorResponse(JsonRpcRequest req, String s) {
var error = JsonRpcErrorResponse.builder()
.code(500)
Expand Down