apache/pulsar · error · SchemaSerializationException

Size of data received by IntSchema is not 4

Error message

Size of data received by IntSchema is not 4

What it means

IntSchema.validate(byte[]) requires the payload to be exactly 4 bytes (a 32-bit int). Any other length cannot be decoded as an INT32, so a SchemaSerializationException is thrown from validate, reached via decode().

Source

Thrown at pulsar-client/src/main/java/org/apache/pulsar/client/impl/schema/IntSchema.java:49

    private static final IntSchema INSTANCE;
    private static final SchemaInfo SCHEMA_INFO;

    static {
        SCHEMA_INFO = SchemaInfoImpl.builder()
            .name("INT32")
            .type(SchemaType.INT32)
            .schema(new byte[0]).build();
        INSTANCE = new IntSchema();
    }

    public static IntSchema of() {
        return INSTANCE;
    }

    @Override
    public void validate(byte[] message) {
        if (message.length != 4) {
            throw new SchemaSerializationException("Size of data received by IntSchema is not 4");
        }
    }

    @Override
    public void validate(ByteBuf message) {
        if (message.readableBytes() != 4) {
            throw new SchemaSerializationException("Size of data received by IntSchema is not 4");
        }
    }

    @Override
    public byte[] encode(Integer message) {
        if (null == message) {
            return null;
        } else {
            return new byte[] {
                (byte) (message >>> 24),
                (byte) (message >>> 16),

View on GitHub (pinned to 820761864e)

Solutions

1. Ensure the producer encodes with Schema.INT32 (4 bytes), not INT8/INT16/INT64/STRING
2. Confirm the topic's schema is INT32 via the admin schema API and align the consumer
3. Guard with message.length == 4 before decode when processing raw bytes

Example fix

// before
int v = Schema.INT32.decode(data);
// after
if (data != null && data.length == 4) { int v = Schema.INT32.decode(data); } else { /* handle mismatch */ }

if (payload == null || payload.length != 4) throw new IllegalArgumentException("INT32 payload must be 4 bytes, got " + (payload == null ? "null" : payload.length));

boolean isIntPayload(byte[] b) { return b != null && b.length == 4; }

try { int v = Schema.INT32.decode(payload); } catch (SchemaSerializationException e) { if (e.getMessage().contains("not 4")) { routeToDlq(msg); } else throw e; }

When it happens

Trigger: Calling Schema.INT32.decode(byte[]) or consuming with INT32 schema a message whose payload byte[] length != 4 (e.g. 8-byte long, 1-byte byte, or text).

Common situations: Producer/consumer schema mismatch (producer used INT64/STRING); raw-byte consumers on an INT32 topic; messages written by a different client version or language binding with wrong width.

Related errors

• This method is not supported
• Not implemented for ${this.getClass}
• Unknown version ${BytesSchemaVersion.of(schemaVersion)}
• Can't get accurate schema information for topic ${topicName}
• Size of data received by BooleanSchema is not 1

AI-assisted analysis of apache/pulsar@820761864e (2026-09-06). Data as JSON: /api/errors/6dd6547a70d544a0. Report an issue: GitHub.