apache/cassandra · error · ConfigurationException

ICompressor.serializedAs() of a compressor created by provid

Error message

ICompressor.serializedAs() of a compressor created by provider %s returned %s. It must return a non-anonymous built-in compressor class in package org.apache.cassandra.io.compress.

What it means

CompressorRegistry.getCompressor() resolves a compressor via a registered provider, then validates that ICompressor.serializedAs() returns a real class equal to the requested built-in compressor class. If it returns null, an empty/anonymous class name, a class outside org.apache.cassandra.io.compress, or a different class than requested, a ConfigurationException is thrown because the on-disk format would record a compressor name peers could never resolve.

Source

Thrown at src/java/org/apache/cassandra/io/compress/CompressorRegistry.java:183

            if (provider == DEFAULT_COMPRESSION_PROVIDER)
                throw t;

            logger.warn("Failed to create compressor {}. Will attempt fallback to default if enabled. Message: {}",
                        compressorClass.getName(),
                        t.getMessage());

            if (provider.isFailOnMissingProvider())
                throw t;

            compressor = DEFAULT_COMPRESSION_PROVIDER.createCompressor(compressorClass, compressionOptions);
        }

        // Validate the masquerade target for both the provider and the fallback path: whatever is
        // returned must serialize as exactly the compressor class that was requested, otherwise the
        // schema / on-disk format would record a name that cannot be resolved on peers and restarts.
        Class<? extends ICompressor> serializedAs = compressor.serializedAs();
        if (serializedAs == null || serializedAs.getSimpleName().isEmpty())
            throw new ConfigurationException(String.format("ICompressor.serializedAs() of a compressor created by provider %s returned %s. " +
                                                           "It must return a non-anonymous built-in compressor class in package " +
                                                           "org.apache.cassandra.io.compress.",
                                                           provider.getClass(),
                                                           serializedAs));
        if (serializedAs != compressorClass)
            throw new ConfigurationException(String.format("The result of ICompressor.serializedAs(), %s, of a compressor object created " +
                                                           "by a compressor provider %s does not match the compressor class to get a compressor for. " +
                                                           "You need to override serializedAs() method of your custom compressor and return " +
                                                           "base compressor class it is the substitute for.",
                                                           serializedAs,
                                                           provider.getClass()));
        return compressor;
    }

    /**
     * Populates the registry with compression providers specified in the configuration.
     * Should be called once during initialization to ensure providers are registered and available
     * for use. If a provider fails to initialize and fallback is enabled, the default provider is used.

View on GitHub (pinned to 88fd0f6a0e)

Solutions

1. Make the provider return a compressor whose serializedAs() is the exact built-in class requested (e.g. LZ4Compressor.class) in package org.apache.cassandra.io.compress
2. Fix anonymous/wrapper compressors to delegate serializedAs() to the underlying built-in compressor
3. Unregister/fix the offending provider and reconfigure the table to a built-in compressor class
4. Add a startup self-check that calls getCompressor() for each configured compression class and fails fast

Example fix

// before
public Class<? extends ICompressor> serializedAs() { return this.getClass(); } // anonymous wrapper
// after
public Class<? extends ICompressor> serializedAs() { return LZ4Compressor.class; } // exact built-in target

// Java: pre-validate a provider's compressor before registering
Class<? extends ICompressor> sa = compressor.serializedAs();
if (sa == null || sa.getName().startsWith("org.apache.cassandra.io.compress.$")
    || !sa.getName().startsWith("org.apache.cassandra.io.compress."))
    throw new ConfigurationException("Provider compressor serializes as non-builtin: " + sa);

static boolean isMasqueradeSafe(ICompressor c, Class<? extends ICompressor> requested) {
    Class<? extends ICompressor> sa = c.serializedAs();
    return sa != null && !sa.getSimpleName().isEmpty() && sa == requested;
}

try { ICompressor c = CompressorRegistry.instance.getCompressor(LZ4Compressor.class, provider); }
catch (ConfigurationException e) { logger.error("Invalid compressor provider", e); useDefaultCompressor(); }

When it happens

Trigger: Registering a custom ICompressorProvider whose created compressor's serializedAs() returns null, an empty-named or anonymous class, a class not in the org.apache.cassandra.io.compress package, or a class differing from the one requested (masquerade failure).

Common situations: Custom compressor plugins implemented as anonymous or wrapper classes; providers returning repackaged compressors whose serializedAs points at the wrapper; typos in the registered class mapping; plugin version drift after upgrade.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

• compressed_read_ahead_buffer_size must be at least 256KiB (s
• commitlog_disk_access_mode =
• SSTable format name in %s cannot be null
• SSTable format name for %s must be non-empty, lower-case let
• compressed_read_ahead_buffer_size_in_kb must be at least 256

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/5c7b155a349861fd. Report an issue: GitHub.