apache/skywalking · critical · ModuleStartException

LAL rule '{}' declares inputType '{}' but the class was not

Error message

LAL rule '{}' declares inputType '{}' but the class was not found.

What it means

Thrown when a LAL rule's YAML declares inputType: <FQCN> and Class.forName() cannot load that class. The class must be on the OAP server classpath at rule-compile time, because the compiler reflects over it to generate typed parsed.* getter calls. Reported as ModuleStartException with rule name and the offending class name.

Source

Thrown at oap-server/analyzer/log-analyzer/src/main/java/org/apache/skywalking/oap/log/analyzer/v2/provider/log/listener/LogFilterListener.java:490

                return;
            }
            throw new IllegalStateException(
                "LALSourceTypeProvider " + provider.getClass().getName() + " for layer "
                    + provider.layer() + " declared inputType " + inputType.getName()
                    + " — LAL accepts only LogData / LogData.Builder (default agent path), "
                    + "a protobuf Message subclass, or a type implementing "
                    + ToJson.class.getName() + ". Update the provider's inputType() or "
                    + "implement ToJson on " + inputType.getName() + ".");
        }

        private static Class<?> resolveInputType(final LALConfig config,
                                                  final LALSourceTypeProvider spiProvider) throws ModuleStartException {
            final String yamlType = config.getInputType();
            if (yamlType != null && !yamlType.isEmpty()) {
                try {
                    return Class.forName(yamlType);
                } catch (ClassNotFoundException e) {
                    throw new ModuleStartException(
                        "LAL rule '" + config.getName() + "' declares inputType '"
                            + yamlType + "' but the class was not found.", e);
                }
            }
            return spiProvider != null ? spiProvider.inputType() : null;
        }

        /**
         * Short name → implementation class map built from {@link ServiceLoader}{@code <LALOutputBuilder>}.
         * Populated once on first call to {@link #resolveOutputType}.
         */
        private static volatile Map<String, Class<?>> OUTPUT_BUILDER_NAMES;

        private static Map<String, Class<?>> loadOutputBuilderNames() {
            if (OUTPUT_BUILDER_NAMES != null) {
                return OUTPUT_BUILDER_NAMES;
            }
            synchronized (Factory.class) {

View on GitHub (pinned to 102af09b4a)

Solutions

1. Correct the FQCN — copy it from the class's actual package (mind protobuf generated-code nesting)
2. Ship the jar containing the class into the OAP classpath (oap-libs/ for the dist)
3. If the type comes from a receiver plugin, verify that receiver module is enabled and loaded before log-analyzer compiles rules
4. Drop inputType: to fall back to the SPI default or LogMetadata

Example fix

# before
inputType: io.envoyproxy.envoy.data.accesslog.v3.HTTPAccessLogEntry2

# after
inputType: io.envoyproxy.envoy.data.accesslog.v3.HTTPAccessLogEntry

// Pre-deploy: resolve every declared inputType the way the loader will:
try {
    Class.forName(declaredInputType);
} catch (ClassNotFoundException e) {
    // fix the FQCN or ship the jar before enabling the rule
}

try {
    Class<?> t = Class.forName(yamlType);
} catch (ClassNotFoundException e) {
    // names rule + class; correct the YAML or add the dependency, then restart
}

When it happens

Trigger: Typo in the FQCN; class lives in an agent/probe jar not shipped with OAP; a receiver plugin providing the type is not enabled/present; version skew where the class moved or was renamed between releases.

Common situations: Writing inputType: io.envoyproxy... with wrong package casing; referencing a custom DTO whose jar was not added to oap-libs; upgrading Envoy/OTel protos where generated classes relocated.

Related errors

• Failed to compile LAL expression: {dsl}
• Failed to load LAL config rules
• LAL rule {ruleName} layerDefinitions entry rejected: {def}
• Failed to create LAL listener factory.
• Failed to load static LAL rules.

AI-assisted analysis of apache/skywalking@102af09b4a (2026-08-14). Data as JSON: /api/errors/1d308aa50fef23c8. Report an issue: GitHub.