quarkusio/quarkus · warning · ClassLoaderLimiterConsistencyException

resource listed multiple times to produce a stacktrace:

Error message

resource listed multiple times to produce a stacktrace: 

What it means

Thrown by ClassLoaderLimiter.Builder.produceStackTraceOnLoad when the same resource is registered more than once for stacktrace-on-load debugging. Each registered resource should appear once so the limiter's debug sets stay consistent. This only affects debug/diagnostic configuration of the class loader.

Source

Thrown at independent-projects/bootstrap/core/src/main/java/io/quarkus/bootstrap/classloading/ClassLoaderLimiter.java:209

                throw new ClassLoaderLimiterConsistencyException(
                        resourceFullName + " is being listed both as never loaded and as at most once");
            }
            return this;
        }

        /**
         * When the specified resource is loaded, print a full stack trace on System out.
         * This is not useful for testing, but handy to trace were a certain load is coming from,
         * should you need to diagnose a failing expectation.
         *
         * @param resourceFullName
         * @return this, for method chaining.
         */
        public Builder produceStackTraceOnLoad(String resourceFullName) {
            Objects.requireNonNull(resourceFullName);
            final boolean add = onHitPrintStacktrace.add(resourceFullName);
            if (!add)
                throw new ClassLoaderLimiterConsistencyException(
                        "resource listed multiple times to produce a stacktrace: " + resourceFullName);
            return this;
        }

        /**
         * Simply log all resource loading events. Useful to get an idea of which resources are being loaded;
         * Note it includes resources being used to load classes.
         *
         * @param enable
         * @return this, for method chaining.
         */
        public Builder traceAllResourceLoad(boolean enable) {
            traceAllResourceLoad = enable;
            return this;
        }

        public ClassLoaderLimiter build() {
            return new ClassLoaderLimiter(this);

View on GitHub (pinned to e1c734241f)

Solutions

1. Deduplicate resource names before registering them for stacktrace logging
2. Remove the duplicate produceStackTraceOnLoad call
3. Guard the call with a Set to make registration idempotent

Example fix

// before
builder.produceStackTraceOnLoad("quarkus-run.jar");
builder.produceStackTraceOnLoad("quarkus-run.jar"); // throws
// after
if (debugSeen.add("quarkus-run.jar")) builder.produceStackTraceOnLoad("quarkus-run.jar");

if (!debugResources.add(name)) { /* skip duplicate */ }

When it happens

Trigger: Calling builder.produceStackTraceOnLoad(name) twice for the same resourceFullName (Set.add returns false).

Common situations: Debugging classloading leaks where multiple diagnostic registrations of the same resource accumulate, e.g. from repeated builder configuration.

Related errors

• is being listed both as never loaded and as at most once
• never loaded class listed multiple times:
• resource listed multiple times as loaded at most once:
• Failed to load steps from %s
• The class (${name}) cannot be created during deployment.

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/3fc08d8052f89dba. Report an issue: GitHub.