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Proposed Changes

This proposal will generalize all remove the code in TopicConfigManager to make it possible to handle any kind of config change TopicConfigManager and introduce a "DynamicConfigManager" to handle config changes for all entities via Zookeeper. Initially, we will have only 2 specific entities:

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entities Topic and Clients.

ZNode Structure:

There will be 2 paths within config
/config/clients/<client_id>
/config/topics/<topic_name>

Internally, the znodes are comma-separated key-value pairs where key represents the configuration property to change.
{"version": x, "config" : {X1 : Y1, X2 : Y2..}}

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The notification data can be:
{"version" : 1, "entity":"topic/client", "value" : "topic_name/client_id"}

Config API

This proposal also adds broker APIs to alter and view configs for any entity. These requests can be sent to any broker within the cluster. See KIP-4 for more details on the implementation. Once work for KIP-4 completes, we can add these API's as described below. 

AlterConfig

• AddedConfigEntry is an array of configs that will be added for that entity
• DeletedConfig is an array of configs that will be deleted for that entity. For deletion on the config property name needs to be specified and not the value. Also, when a config property is deleted, that entity will reapply the default value for that property. For example: if you delete the quota for a clientId, the quota for that client will be set to the default quota.
  
  

// EntityType can be either topic or client. AddedConfigEntry and DeletedConfig will be an array.
AlterConfigRequest => [EntityType EntityName [AddedConfigEntry] [DeletedConfig]]
 EntityType => string
 EntityName => string
AddedConfigEntry => ConfigKey ConfigValue
   ConfigKey => string
   ConfigValue => string
DeletedConfig => string
 
AlterConfigResponse => [EntityType EntityName ErrorCode]
	EntityType => string
  	EntityName => string
	ErrorCode => int16

DescribeConfig

The DescribeConfig request is used to query configs for entities.

DescribeConfigRequest => [EntityType EntityName]
    EntityType => string
	EntityName => string
 
// ConfigEntry is an array. It will be empty if there is an error. ErrorCode will be non-zero in case of error
DescribeConfigResponse => [EntityType EntityName ConfigEntry]
    EntityType => string
    EntityName => string
	ErrorCode => int16
    ConfigEntry => ConfigKey ConfigValue
       ConfigKey => string
       ConfigValue => string

CLI and Interactive Shell

As described in KIP-4, these commands will have scripts and an interactive shell.

# Topic Commands - options are ported from TopicCommand.scala
bin/kafka.sh --alter-config --entityType [topic/client] --entityName name --added-config key=value,key=value --deleted-config key,key,key --broker-list <host : port>
bin/kafka.sh --describe-config --entityType [topic/client] --entityName name --broker-list <host : port>

Compatibility, Deprecation, and Migration Plan

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