aeron-io/aeron · error · IllegalArgumentException

Invalid typeCode=

Error message

Invalid typeCode=${typeCode}

What it means

EventCodeType.get maps a numeric typeCode to an EventCodeType enum constant (DRIVER=0, ARCHIVE=1, CLUSTER=2, STANDBY=3, SEQUENCER=4, USER=0xFFFF). An unknown code throws IllegalArgumentException('Invalid typeCode=...'), meaning the event log contains a type code this Aeron version does not recognize.

Solutions

1. Upgrade to the Aeron version matching the one that produced the event log.
2. Log and skip records with unknown type codes instead of failing the whole decode.
3. Verify the type code is read from the correct header offset.
4. If adding a custom type, register it in the EventCodeType switch.

Example fix

// before
final EventCodeType type = EventCodeType.get(typeCode); // throws on unknown
// after
try
{
    final EventCodeType type = EventCodeType.get(typeCode);
}
catch (final IllegalArgumentException ex)
{
    LOGGER.warn("skipping unknown event typeCode=" + typeCode);
    return;
}

static boolean isKnownTypeCode(final int typeCode)
{
    return typeCode >= 0 && typeCode <= 4 || typeCode == 0xFFFF;
}

boolean isValidEventCodeType(final int typeCode)
{
    return (typeCode >= 0 && typeCode <= 4) || typeCode == 0xFFFF;
}

try
{
    final EventCodeType type = EventCodeType.get(typeCode);
    // process record
}
catch (final IllegalArgumentException ex)
{
    LOGGER.warn("unknown event typeCode=" + typeCode + ", skipping record");
}

When it happens

Trigger: Decoding an event log written by a newer Aeron version that introduced a new type code; passing a raw byte/int from user data as a type code; reading a corrupted header byte.

Common situations: Version mismatch between capture tooling and this library; manually constructed event headers with bad codes; forward-compatibility gaps after an Aeron upgrade.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• ClusterBackup.Context.sourceType=
• CnC version not compatible: app=
• - code must equal ordinal value: code=
• driverVersion= insufficient for clientVersion=
• EINVAL

AI-assisted analysis of aeron-io/aeron@6d60124e15 (2026-09-12). Data as JSON: /api/errors/52e0594bd66d6b97. Report an issue: GitHub.

Appendix: source

Thrown at aeron-client/src/main/java/io/aeron/logging/EventCodeType.java:87

    /**
     * Get the EventTypeCode based on the matching typeCode value.
     *
     * @param typeCode used to resolve the EventTypeCode.
     * @return the resolved EventTypeCode.
     * @throws IllegalArgumentException if the typeCode does not match one of the enum values.
     */
    public static EventCodeType get(final int typeCode)
    {
        return switch (typeCode)
        {
            case 0 -> DRIVER;
            case 1 -> ARCHIVE;
            case 2 -> CLUSTER;
            case 3 -> STANDBY;
            case 4 -> SEQUENCER;
            case 0xFFFF -> USER;
            default -> throw new IllegalArgumentException("Invalid typeCode=" + typeCode);
        };
    }
}

View on GitHub (pinned to 6d60124e15)