Table of Contents

Status

Current state: Under DiscussionAccepted

Discussion thread: here

JIRA: https://issues.apache.org/jira/browse/

Jira

server	ASF JIRA
serverId	5aa69414-a9e9-3523-82ec-879b028fb15b
key	KAFKA-9494

PR:

Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).

...

This KIP proposes to include 2 additional metadata information - dataType, and documentation and validator for the individual config entries.

The motivation behind extending the schema to include dataType of the configuration entry including dataType is to enable the client to provide better validation to the user. In the absence of dataType the only way to know if the user specified value is correct is to make an `alter` call and check if there is no error, which is a suboptimal sub-optimal experience. Including the dataType could open up potentially other use cases as well.

Including documentation would enable the client to provide latest information about the config and would also act as a single source of truth.

Including validator would enable the client to further improve upon the validation provided by dataType. Validator here is the serialized version of Range, ValidList, ValidString, CaseInsensitiveValidString, NonNullValidator, NonEmptyString to name a few.

In this proposal we modify the DescribeConfigsResponse schema to include the field type.

Public Interfaces

Network protocol

Request

There is no change in the request schema except

Bump up the valid versions range

Public Interfaces

Network protocol

Request

The changes to the Request schema include

Bump up the valid versions range
New field IncludeDocumentation - with default value of false

Code Block

{
  "apiKey": 32,
  "type": "request",
  "name": "DescribeConfigsRequest",
  // Version 1 adds IncludeSynoyms.
  // Version 2 is the same as version 1.
  // Version 3 is the same as version 2.
  "validVersions": "0-3", <--- Updated Field
  "flexibleVersions": "none",
  "fields": [
    { "name": "Resources", "type": "[]DescribeConfigsResource", "versions": "0+",
      "about": "The resources whose configurations we want to describe.", "fields": [
      { "name": "ResourceType", "type": "int8", "versions": "0+",
        "about": "The resource type." },
      { "name": "ResourceName", "type": "string", "versions": "0+",
        "about": "The resource name." },
      { "name": "ConfigurationKeys", "type": "[]string", "versions": "0+", "nullableVersions": "0+",
        "about": "The configuration keys to list, or null to list all configuration keys." }
    ]},
    { "name": "IncludeSynoyms", "type": "bool", "versions": "1+", "default": "false", "ignorable": false,
      "about": "True if we should include all synonyms." }
	{  ]
}

Response

The changes to the Response schema include

Bump valid versions range
Add new Fields - ConfigValueType, Documentation & Validator

Code Block

{
  "apiKey": 32,
  "type": "response",
  "name": "DescribeConfigsResponse",
  "validVersions": "0-3", "name": "IncludeDocumentation", "type": "bool", "versions": "1+", "default": "false", "ignorable": false,  <--- UpdatedNew Field
   "flexibleVersions": "none",
  "fieldsabout": [
"True if we should include configuration documentation." }
  ]
}

Response

The changes to the Response schema include

Bump valid versions range
Add new Fields - ConfigValueType and Documentation

Code Block

{
  "apiKey": 32,
  "type": "response",
  "name": "DescribeConfigsResponse",
  "validVersions": "0-3", <--- Updated Field
  "flexibleVersions": "none",
  "fields": [{ "name": "ThrottleTimeMs", "type": "int32", "versions": "0+",
      "about": "The duration in milliseconds for which the request was throttled due to a quota violation, or zero if the request did not violate any quota." },
    { "name": "ResultsThrottleTimeMs", "type": "[]DescribeConfigsResultint32", "versions": "0+",
      "about": "The resultsduration for each resource.", "fields": [
  in milliseconds for which the request was throttled due to a quota violation, or zero if the request did not violate any quota." },
    { "name": "ErrorCodeResults", "type": "int16[]DescribeConfigsResult", "versions": "0+",
        "about": "The errorresults code,for or 0 if we were able to successfully describe the configurations." },each resource.", "fields": [
      { "name": "ErrorMessageErrorCode", "type": "stringint16", "versions": "0+", "nullableVersions": "0+",
        "about": "The error messagecode, or null0 if we were able to successfully describe the configurations." },
      { "name": "ResourceTypeErrorMessage", "type": "int8string", "versions": "0+",
   "nullableVersions": "0+",
        "about": "The resource type error message, or null if we were able to successfully describe the configurations." },
      { "name": "ResourceNameResourceType", "type": "stringint8", "versions": "0+",
        "about": "The resource nametype." },
      { "name": "ConfigsResourceName", "type": "[]DescribeConfigsResourceResultstring", "versions": "0+",
        "about": "EachThe listedresource configurationname." }, "
      { "name": "Configs", "type": "[]DescribeConfigsResourceResult", "versions": "0+",
        "about": "Each listed configuration.", "fields": [
        { "name": "Name", "type": "string", "versions": "0+",
          "about": "The configuration name." },
        { "name": "Value", "type": "string", "versions": "0+", "nullableVersions": "0+",
          "about": "The configuration value." },
        { "name": "ReadOnly", "type": "bool", "versions": "0+",
          "about": "True if the configuration is read-only." },
        { "name": "IsDefault", "type": "bool", "versions": "0",
          "about": "True if the configuration is not set." },
        // Note: the v0 default for this field that should be exposed to callers is
        // context-dependent. For example, if the resource is a broker, this should default to 4.
        // -1 is just a placeholder value.
        { "name": "ConfigSource", "type": "int8", "versions": "1+", "default": "-1", "ignorable": true,
          "about": "The configuration source." },
        { "name": "IsSensitive", "type": "bool", "versions": "0+",
          "about": "True if this configuration is sensitive." },
        { "name": "Synonyms", "type": "[]DescribeConfigsSynonym", "versions": "1+", "ignorable": true,
          "about": "The synonyms for this configuration key.", "fields": [
          { "name": "Name", "type": "string", "versions": "1+",
            "about": "The synonym name." },
          { "name": "Value", "type": "string", "versions": "1+", "nullableVersions": "0+",
            "about": "The synonym value." },
          { "name": "Source", "type": "int8", "versions": "1+",
            "about": "The synonym source." }
        ]},
<--- New Field
        { "name": "ConfigValueType", "type": "stringint8", "versions": "3+", "nullableVersionsdefault": "0+",     <--- New Field
          "about": "The configuration data type." },
        { "name": "Documentation", "type": "string", "versions": "3+", "nullableVersions": "0+",    <--- New Field
          "about": "The configuration documentation." },
      ]}
  { "name": "Validator", "type": "string", "versions": "3+", "nullableVersions": "0+",
          "about": "The valid values for the configuration." }
<---- End of New Field
      ]}
    ]}
  ]
}

 ]}
  ]
}

AdminClient Class

No new method will be added or updated to the AdminCient class.

Proposed Changes

Under the proposed change, AdminClient.describeConfigs response (DescribeConfigsResponse.ConfigEntry) would include following new properties

...

AbstractConfig Class

As part of this KIP, a new method will be added to AbstractConfig to return the documentation of the given Config

Code Block
public String documentationOf(String key)
Code Block
/** * The config types */ public enum Type { BOOLEAN, STRING, INT, SHORT, LONG, DOUBLE, LIST, CLASS, PASSWORD }

2. Documentation - field's documentation

3. Validator - Serialized version of Range, ValidList, ValidString, CaseInsensitiveValidString, NonNullValidator, NonEmptyString, and CompositeValidator.

DescribeConfigsResponse.ConfigEntry

Code Block

public class ConfigEntry {
    private final String name;
    private final String value;
    private final ConfigSource source;
    private final boolean isSensitive;
    private final boolean isReadOnly;
    private final String type; // This is the new property
    private final List<ConfigSynonym> synonyms;
	private final String documentation; // This is the new property
    private final String validator; // This is the new property
.....

Rest of the changes would be plumbing this new property in AdminManager class to be eventually consumed by AdminClient class

Sample Response

A few examples of DescribeConfigResponse

...

language	js

...

 ConfigDef.ConfigKey configKey = definition.configKeys().get(key);
        if (configKey == null)
            return null;
        return configKey.documentation;
    }

Proposed Changes

Under the proposed change, response for AdminClient.describeConfigs would include following new properties, which would be part of DescribeConfigsResponse.ConfigEntry class.

Type: ConfigType - This is an Enum of all the supported data type.

Code Block
/** * Data type of configuration entry. */ public enum ConfigType { UNKNOWN, BOOLEAN, STRING, INT, SHORT, LONG, DOUBLE, LIST, CLASS, PASSWORD }

ConfigType.Unknown is for ensuring backward compatibility (explained is Compatibility section below)

The values in above Enum is derived from existing Type Enum defined in ConfigDef.java below

Code Block
/** * The config types */ public enum Type { BOOLEAN, STRING, INT, SHORT, LONG, DOUBLE, LIST, CLASS, PASSWORD }

2. Documentation: String - field's documentation

DescribeConfigsResponse.ConfigEntry with the above new fields

Code Block

public class ConfigEntry {
    private final String name;
    private final String value;
    private final ConfigSource source;
    private final boolean isSensitive;
    private final boolean isReadOnly;
    private final List<ConfigSynonym> synonyms;

.....
    private final ConfigType type; // This is the new property
	private final String documentation; // This is the new property
.....

Rest of the changes would be plumbing this new property in AdminManager class to be eventually consumed by AdminClient class

Sample Response

Following example show how the response would look like in JSON format.
Note: Kafka uses binary protocol over TCP. ConfigType Enum is serialized as byte instead of string.

Code Block

language	js

{
  "name": "logoffsets.messagetopic.timestampnum.typepartitions",
  "value": "CreateTime50",
  "source": "DEFAULT_CONFIG",
  "type": "STRINGINT",   // <---- New Field
  "synonyms": [
    {
      "name": "logoffsets.messagetopic.timestampnum.typepartitions",
      "value": "CreateTime50",
      "source": "DEFAULT_CONFIG"
    }
  ],
  "documentation": "DefineThe whethernumber theof timestamppartitions infor the messageoffset iscommit messagetopic create(should timenot orchange log append time. The value should be either `CreateTime` or `LogAppendTime`", // Newafter deployment)", //  <---- New Field
  "isReadOnly": falsetrue,
  "isSensitive": false,
  "validValues": {  // New
    "caseSensitive": false,
    "values": [
 }

Default Behavior

By default, the `documentation` field will not be included in the response to describeConfigs. This is to avoid the response from boating up as the value for documentation field can be quite large.

Below example shows how client can include the new fields in the response

Code Block

title	Example

KafkaAdminClient.describeConfigs(
  resources,
  new DescribeConfigsOptions()
      "CreateTime",
      "LogAppendTime"
 .includeSynonyms(true)
     ]
  }
},

Note on Recommender interface

Instead of serializing the Validator, we could leverage Recommender in org.apache.kafka.common.config.ConfigDef.ConfigKey. Few reason for not doing that

Recommender is not used by any of the KafkaConfig today.
Recommender.validValues() which returns valid set of values has limited expressiveness when it comes to defining Range, nullability, case sensitiveness that comes with Validator

Compatibility, Deprecation, and Migration Plan

The proposed change is backward compatible in a sense that for same version of Kafka server and client response would include additional fields

Code Block
replication.quota.window.num=11 type=INT sensitive=false synonyms={}

...

Code Block
request.timeout.ms=30000 type=null sensitive=false synonyms={}

...

.includeDocumentation(true)
)

Compatibility, Deprecation, and Migration Plan

For backward compatibility we rely on existing schema versioning technique. Under this, client sends its version information in the request header. This in turn is used on the server to select the schema for that version.

	Server version	Client version	Expected Behavior
1	X	X	Both `Type` and `Documentation` is visible to the client.
2	X	X-1	`Type` and `Documentation` are not visible to the client. Not serialized as part of the response.
3	X-1	X	IllegalArgumentException: Invalid version for API key...
4	X+1	X	Both `Type` and `Documentation` is visible to the client. If version X+1 has new value in enum `ConfigType`, client would get `ConfigType.Unknown` instead for that new value.

Rejected Alternatives

NA

Space shortcuts

Child pages

Versions Compared

Old Version 10

New Version Current

Key

Status

Public Interfaces

Network protocol

Request

Public Interfaces

Network protocol

Request

Response

Response

AdminClient Class

Proposed Changes

AbstractConfig Class

Sample Response

Proposed Changes

Sample Response

Default Behavior

Note on Recommender interface

Compatibility, Deprecation, and Migration Plan

Compatibility, Deprecation, and Migration Plan

Rejected Alternatives

Space shortcuts

Child pages

Page History

Versions Compared

Old Version 10

New Version Current

Key

Status

Public Interfaces

Network protocol

Request

Public Interfaces

Network protocol

Request

Response

Response

AdminClient Class

Proposed Changes

AbstractConfig Class

Sample Response

Proposed Changes

Sample Response

Default Behavior

Note on Recommender interface

Compatibility, Deprecation, and Migration Plan

Compatibility, Deprecation, and Migration Plan

Rejected Alternatives