clients/src/main/resources/common/message/RequestHeader.json

// Licensed to the Apache Software Foundation (ASF) under one or more
// contributor license agreements.  See the NOTICE file distributed with
// this work for additional information regarding copyright ownership.
// The ASF licenses this file to You under the Apache License, Version 2.0
// (the "License"); you may not use this file except in compliance with
// the License.  You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
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// distributed under the License is distributed on an "AS IS" BASIS,
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{
  "type": "header",
  "name": "RequestHeader",
  // Version 0 was removed in Apache Kafka 4.0, Version 1 is the new baseline.
  //
  // Version 0 of the RequestHeader is only used by v0 of ControlledShutdownRequest.
  //
  // Version 1 is the first version with ClientId.
  //
  // Version 2 is the first flexible version.
  "validVersions": "1-2",
  "flexibleVersions": "2+",
  "fields": [
    { "name": "RequestApiKey", "type": "int16", "versions": "0+",
      "about": "The API key of this request." },
    { "name": "RequestApiVersion", "type": "int16", "versions": "0+",
      "about": "The API version of this request." },
    { "name": "CorrelationId", "type": "int32", "versions": "0+",
      "about": "The correlation ID of this request." },

    // The ClientId string must be serialized with the old-style two-byte length prefix.
    // The reason is that older brokers must be able to read the request header for any
    // ApiVersionsRequest, even if it is from a newer version.
    // Since the client is sending the ApiVersionsRequest in order to discover what
    // versions are supported, the client does not know the best version to use.
    { "name": "ClientId", "type": "string", "versions": "1+", "nullableVersions": "1+", "flexibleVersions": "none",
      "about": "The client ID string." }
  ]
}