prestodb/presto · error · PrestoException

KAFKA_SCHEMA_ERROR

KAFKA_SCHEMA_ERROR

Error message

Unable to read data schema at '%s'

What it means

getDataSchema reads the table's configured dataSchemaLocation from local disk; if Files.readAllBytes throws IOException (missing file, permissions, path is a directory), the connector wraps it in a PrestoException with code KAFKA_SCHEMA_ERROR. The connector cannot build the Avro data schema needed to encode/decode records.

Source

Thrown at presto-kafka/src/main/java/com/facebook/presto/kafka/KafkaPageSinkProvider.java:110

        return new KafkaPageSink(
                handle.getSchemaName(),
                handle.getTopicName(),
                handle.getColumns(),
                keyEncoder,
                messageEncoder,
                producerFactory,
                kafkaClusterMetadataSupplier);
    }

    private Optional<String> getDataSchema(Optional<String> dataSchemaLocation)
    {
        return dataSchemaLocation.map(location -> {
            try {
                return new String(Files.readAllBytes(Paths.get(location)));
            }
            catch (IOException e) {
                throw new PrestoException(KAFKA_SCHEMA_ERROR, format("Unable to read data schema at '%s'", dataSchemaLocation.get()), e);
            }
        });
    }
}

View on GitHub (pinned to 55bb57d202)

Solutions

1. Verify the file exists and is readable on every node that runs the query: ls -l <dataSchemaLocation>
2. Use a URI-based (hdfs/http) schema location or ship the schema inside the table description JSON instead of a local file path
3. Fix permissions/ownership of the schema file
4. Correct the dataSchemaLocation value in the Kafka table description

Example fix

// before (table description)
"dataSchema": "/etc/kafka/schemas/order.avsc"
// after - inline schema or valid path
"dataSchema": {"type":"record","name":"order","fields":[...]}

java.nio.file.Path p = java.nio.file.Paths.get(dataSchemaLocation);
if (!java.nio.file.Files.isReadable(p))
    throw new IllegalStateException("Data schema not readable: " + p);

null

try { ... } catch (PrestoException e) {
  if (KAFKA_SCHEMA_ERROR.toErrorCode().getCode().equals(e.getErrorCode().getCode())) {
    // fix/verify dataSchemaLocation, then retry
  }
}

When it happens

Trigger: kafka.table-description data schema location (or table's dataSchemaLocation property) points to a file that does not exist or is unreadable at the moment keyEncoder/messageEncoder request the schema.

Common situations: Typo or wrong absolute path in table description JSON; schema file deleted from workers (file only exists on coordinator); permissions after container image change; relative path resolved against a different working directory on a worker node.

Related errors

• Failed to append record
• Failed to close ByteArrayOutputStream
• BIGQUERY_ERROR_END_OF_AVRO_BUFFER
• BIGQUERY_ERROR_READING_NEXT_AVRO_RECORD
• unexpected internal column '%s'

AI-assisted analysis of prestodb/presto@55bb57d202 (2026-09-04). Data as JSON: /api/errors/33bc5ed9350a09b9. Report an issue: GitHub.