apache/pulsar · error · IllegalArgumentException

Function class %s must be in class path

Error message

Function class %s must be in class path

What it means

While resolving the configured function class via the NAR package TypePool, the type could not be found, so doJavaChecks throws IllegalArgumentException with the cause NoSuchTypeException. The class name resolved syntactically but the bytecode is not present in the function package.

Source

Thrown at pulsar-functions/utils/src/main/java/org/apache/pulsar/functions/utils/FunctionConfigUtils.java:655

                    throw new IllegalArgumentException("Function class name is not provided.");
                }
                functionClassName = functionDefinition.getFunctionClass();
                if (functionClassName == null) {
                    throw new IllegalArgumentException("Function class name is not provided.");
                }
            }
            functionClass = validatableFunctionPackage.resolveType(functionClassName);

            if (!functionClass.asErasure().isAssignableTo(org.apache.pulsar.functions.api.Function.class)
                    && !functionClass.asErasure().isAssignableTo(java.util.function.Function.class)
                    && !functionClass.asErasure()
                    .isAssignableTo(org.apache.pulsar.functions.api.WindowFunction.class)) {
                throw new IllegalArgumentException(
                        String.format("Function class %s does not implement the correct interface",
                                functionClassName));
            }
        } catch (TypePool.Resolution.NoSuchTypeException e) {
            throw new IllegalArgumentException(
                    String.format("Function class %s must be in class path", functionClassName), e);
        }

        TypeDefinition[] typeArgs = FunctionCommon.getFunctionTypes(functionConfig, functionClass);
        // inputs use default schema, so there is no check needed there

        // Check if the Input serialization/deserialization class exists in jar or already loaded and that it
        // implements SerDe class
        if (functionConfig.getCustomSerdeInputs() != null) {
            functionConfig.getCustomSerdeInputs().forEach((topicName, inputSerializer) -> {
                ValidatorUtils.validateSerde(inputSerializer, typeArgs[0], validatableFunctionPackage.getTypePool(),
                        true);
            });
        }

        // Check if the Input serialization/deserialization class exists in jar or already loaded and that it
        // implements SerDe class
        if (functionConfig.getCustomSchemaInputs() != null) {

View on GitHub (pinned to 820761864e)

Solutions

1. Ensure the class named in className exists in the submitted archive (check jar tf / unzip -l)
2. Correct any typo in the fully qualified class name
3. Rebuild the fat/NAR package so the function class and its dependencies are bundled

Example fix

// before
config.setClassName("org.example.MyFuntion"); // typo, class not in jar
// after
config.setClassName("org.example.MyFunction"); // present in the submitted jar

try (JarFile jar = new JarFile(archivePath)) { if (jar.getJarEntry(config.getClassName().replace('.', '/') + ".class") == null) { throw new IllegalArgumentException("Class " + config.getClassName() + " not present in archive"); } }

boolean classInArchive(String archive, String fqcn) throws IOException { try (JarFile jf = new JarFile(archive)) { return jf.getJarEntry(fqcn.replace('.', '/') + ".class") != null; } }

try { ... } catch (IllegalArgumentException e) { Throwable cause = e.getCause(); if (cause instanceof TypePool.Resolution.NoSuchTypeException) { log.error("Bundle the missing class into the function archive"); } }

When it happens

Trigger: className references a class that is not contained in the submitted JAR/NAR (resolution by TypePool fails), including classes whose dependencies were not bundled.

Common situations: Shading/proguard stripped or renamed the class; fat JAR missing the function class; class name typo that still resolves as a valid binary name; dependency-only JAR submitted instead of the function JAR.

Related errors

• Function class name is not provided.
• Function class %s does not implement the correct interface
• Could not find sink config class
• Entry filter `${name}` cannot be loaded, see the broker logs
• Failed to load an authorization provider.

AI-assisted analysis of apache/pulsar@820761864e (2026-09-06). Data as JSON: /api/errors/36748f0d1ab15a8b. Report an issue: GitHub.