alibaba/canal · error · CanalClientException

compression is not supported in this connector

Error message

compression is not supported in this connector

What it means

Thrown by CanalMessageSerializerUtil.deserializer when a parsed CanalPacket.Packet reports a Compression value other than NONE or COMPRESSIONCOMPATIBLEPROTO2. The canal client connector does not implement payload decompression, so any non-NONE compression flag is rejected outright (it then gets wrapped by the outer catch into 'deserializer failed by ...').

Source

Thrown at connector/core/src/main/java/com/alibaba/otter/canal/connector/core/util/CanalMessageSerializerUtil.java:101

        }
        return null;
    }

    public static Message deserializer(byte[] data) {
        return deserializer(data, false);
    }

    public static Message deserializer(byte[] data, boolean lazyParseEntry) {
        try {
            if (data == null) {
                return null;
            } else {
                CanalPacket.Packet p = CanalPacket.Packet.parseFrom(data);
                switch (p.getType()) {
                    case MESSAGES: {
                        if (!p.getCompression().equals(CanalPacket.Compression.NONE)
                            && !p.getCompression().equals(CanalPacket.Compression.COMPRESSIONCOMPATIBLEPROTO2)) {
                            throw new CanalClientException("compression is not supported in this connector");
                        }

                        CanalPacket.Messages messages = CanalPacket.Messages.parseFrom(p.getBody());
                        Message result = new Message(messages.getBatchId());
                        if (lazyParseEntry) {
                            // byteString
                            result.setRawEntries(messages.getMessagesList());
                            result.setRaw(true);
                        } else {
                            for (ByteString byteString : messages.getMessagesList()) {
                                result.addEntry(CanalEntry.Entry.parseFrom(byteString));
                            }
                            result.setRaw(false);
                        }
                        return result;
                    }
                    case ACK: {
                        CanalPacket.Ack ack = CanalPacket.Ack.parseFrom(p.getBody());

View on GitHub (pinned to 87be50e876)

Solutions

1. Align canal server and client connector versions so both treat Compression as NONE.
2. Ensure the byte[] passed to deserializer is a genuine canal Packet produced by CanalMessageSerializerUtil.serializer (not a foreign payload).
3. Disable any compression flag on the producer side (canal protocol uses NONE).

Example fix

// before
byte[] payload = readFromForeignSource();
deserializer(payload, false);  // unsupported compression
// after
byte[] payload = readFromCanalProducer();
deserializer(payload, false);  // Compression == NONE

// Inspect packet type/compression before deserializing as MESSAGES
CanalPacket.Packet p = CanalPacket.Packet.parseFrom(data);
if (!CanalPacket.Compression.NONE.equals(p.getCompression())
    && !CanalPacket.Compression.COMPRESSIONCOMPATIBLEPROTO2.equals(p.getCompression())) {
    throw new CanalClientException("unsupported compression: " + p.getCompression());
}
if (p.getType() != CanalPacket.PacketType.MESSAGES) {
    throw new CanalClientException("not a MESSAGES packet: " + p.getType());
}

boolean isDecompressible(CanalPacket.Packet p) {
    return p.getCompression().equals(CanalPacket.Compression.NONE)
        || p.getCompression().equals(CanalPacket.Compression.COMPRESSIONCOMPATIBLEPROTO2);
}

try {
    Message m = CanalMessageSerializerUtil.deserializer(data, lazyParse);
} catch (CanalClientException e) {
    if (e.getMessage().contains("compression is not supported")) {
        // version mismatch: align canal server and client versions
    } else throw e;
}

When it happens

Trigger: Receiving a packet whose Compression field is set to a compressed mode; producer/sender and consumer running different canal protocol versions where one side sets compression the other cannot decode; corrupted bytes being misparsed as a Packet with a stray compression enum value.

Common situations: Version mismatch between canal server (producer) and client connector (consumer) introducing a compression flag; cross-system interoperability where a non-canal sender populates the Compression field; truncated/corrupt byte array parsed into a bogus Packet.

Related errors

• unsupported version at this client.
• Error when serializing message to byte[] by ${e.getMessage()
• something goes wrong with reason: ${ack.getErrorMessage()}
• unexpected packet type: ${p.getType()}
• deserializer failed by ${e.getMessage()}

AI-assisted analysis of alibaba/canal@87be50e876 (2026-08-14). Data as JSON: /api/errors/8cc688b7473c33d2. Report an issue: GitHub.