kafkacfg: Kafka configuration inspector

Kafka has a lot of parameters, tunables and knobs, and the configuration page isn't the easiest to parse. kafkacfg allows you to parse your kafka configuration file help you understand what it does.

kafkacfg explain

This command is used to display extra information about each configuration tunable used in your configuration file.

$ cat test.properties
num.io.threads = 10
broker.id = 1001
auto.create.topics.enable = false
background.threads = 10

$ kafkacfg explain -k 3.4 test.properties | jq .
[
  {
    "name": "num.io.threads",
    "override": "10",
    "description": "The number of threads that the server uses for processing requests, which may include disk I/O",
    "scope": "broker",
    "type": "int",
    "default": "8",
    "valid_values": "[1,...]",
    "importance": "high",
    "update_mode": "cluster-wide"
  },
  {
    "name": "broker.id",
    "override": "1001",
    "description": "The broker id for this server. If unset, a unique broker id will be generated.To avoid conflicts between zookeeper generated broker id's and user configured broker id's, generated broker ids start from reserved.broker.max.id + 1.",
    "scope": "broker",
    "type": "int",
    "default": "-1",
    "valid_values": null,
    "importance": "high",
    "update_mode": "read-only"
  },
  {
    "name": "auto.create.topics.enable",
    "override": "false",
    "description": "Enable auto creation of topic on the server",
    "scope": "broker",
    "type": "boolean",
    "default": "true",
    "valid_values": null,
    "importance": "high",
    "update_mode": "read-only"
  },
  {
    "name": "background.threads",
    "override": "10",
    "description": "The number of threads to use for various background processing tasks",
    "scope": "broker",
    "type": "int",
    "default": "10",
    "valid_values": "[1,...]",
    "importance": "high",
    "update_mode": "cluster-wide"
  }
]

This format makes it easy to pipe it through table formatting tools such as jtbl:

$ kafkacfg explain -k 3.4 test.properties | jtbl
╒═══════════════════════════╤════════════╤═══════════════════════════════════════════════════════════════════════╤═════════╤═════════╤═══════════╤════════════════╤══════════════╤═══════════════╕
│ name                      │ override   │ description                                                           │ scope   │ type    │ default   │ valid_values   │ importance   │ update_mode   │
╞═══════════════════════════╪════════════╪═══════════════════════════════════════════════════════════════════════╪═════════╪═════════╪═══════════╪════════════════╪══════════════╪═══════════════╡
│ num.io.threads            │ 10         │ The number of threads that the server uses for processing requests, w │ broker  │ int     │ 8         │ [1,...]        │ high         │ cluster-wide  │
│                           │            │ hich may include disk I/O                                             │         │         │           │                │              │               │
├───────────────────────────┼────────────┼───────────────────────────────────────────────────────────────────────┼─────────┼─────────┼───────────┼────────────────┼──────────────┼───────────────┤
│ broker.id                 │ 1001       │ The broker id for this server. If unset, a unique broker id will be g │ broker  │ int     │ -1        │                │ high         │ read-only     │
│                           │            │ enerated.To avoid conflicts between zookeeper generated broker id's a │         │         │           │                │              │               │
│                           │            │ nd user configured broker id's, generated broker ids start from reser │         │         │           │                │              │               │
│                           │            │ ved.broker.max.id + 1.                                                │         │         │           │                │              │               │
├───────────────────────────┼────────────┼───────────────────────────────────────────────────────────────────────┼─────────┼─────────┼───────────┼────────────────┼──────────────┼───────────────┤
│ auto.create.topics.enable │ false      │ Enable auto creation of topic on the server                           │ broker  │ boolean │ true      │                │ high         │ read-only     │
├───────────────────────────┼────────────┼───────────────────────────────────────────────────────────────────────┼─────────┼─────────┼───────────┼────────────────┼──────────────┼───────────────┤
│ background.threads        │ 10         │ The number of threads to use for various background processing tasks  │ broker  │ int     │ 10        │ [1,...]        │ high         │ cluster-wide  │
╘═══════════════════════════╧════════════╧═══════════════════════════════════════════════════════════════════════╧═════════╧═════════╧═══════════╧════════════════╧══════════════╧═══════════════╛

kafkacfg overrides

The overrides command will only display and enrich the configuration tunables with non-default values, to help you understand in what way your kafka configuration was tuned:

$ kafkacfg overrides -k 3.4 test.properties | jtbl
name                       override    description                                                                                     scope    type     default    valid_values    importance    update_mode
-------------------------  ----------  ----------------------------------------------------------------------------------------------  -------  -------  ---------  --------------  ------------  -------------
num.io.threads             10          The number of threads that the server uses for processing requests, which may include disk I/O  broker   int      8          [1,...]         high          cluster-wide
auto.create.topics.enable  false       Enable auto creation of topic on the server                                                     broker   boolean  true                       high          read-only

kafkacfg filter

The filter command allows you to filter the kafka configuration tunables with a custom query, while enriching the filter results with the usual metadata and potential override value.

$ kafkacfg filter --query name=replica.fetch.min.bytes -k 1.1 | jtbl
name                     override    description                                                                                           scope    type      default  valid_values    importance    update_mode
-----------------------  ----------  ----------------------------------------------------------------------------------------------------  -------  ------  ---------  --------------  ------------  -------------
replica.fetch.min.bytes              Minimum bytes expected for each fetch response. If not enough bytes, wait up to replicaMaxWaitTimeMs  broker   int             1                  high          read-only

You can also compose filter predicates and even use * for a glob match:

$ kafkacfg filter --query "name=replica.*.bytes;importance=high" -k 3.4 | jtbl
╒═════════════════════════════════════╤════════════╤═══════════════════════════════════════════════════╤═════════╤════════╤══════════════════════╤════════════════╤══════════════╤═══════════════╕
│ name                                │ override   │ description                                       │ scope   │ type   │ default              │ valid_values   │ importance   │ update_mode   │
╞═════════════════════════════════════╪════════════╪═══════════════════════════════════════════════════╪═════════╪════════╪══════════════════════╪════════════════╪══════════════╪═══════════════╡
│ replica.fetch.min.bytes             │            │ Minimum bytes expected for each fetch response. I │ broker  │ int    │ 1                    │                │ high         │ read-only     │
│                                     │            │ f not enough bytes, wait up to replica.fetch.wait │         │        │                      │                │              │               │
│                                     │            │ .max.ms (broker config).                          │         │        │                      │                │              │               │
├─────────────────────────────────────┼────────────┼───────────────────────────────────────────────────┼─────────┼────────┼──────────────────────┼────────────────┼──────────────┼───────────────┤
│ replica.socket.receive.buffer.bytes │            │ The socket receive buffer for network requests    │ broker  │ int    │ 65536 (64 kibibytes) │                │ high         │ read-only     │
╘═════════════════════════════════════╧════════════╧═══════════════════════════════════════════════════╧═════════╧════════╧══════════════════════╧════════════════╧══════════════╧═══════════════╛

kafkacfg recommends

The recommends command emits sourced configuration recommendation based on broker attributes (number of CPUs, number of disks, etc).

Note: These are suggestions more than absolute thruths. We encourage you to read the sources, test the configuration values and make your own mind.

$ kafkacfg recommends -k 3.4 --broker-num-cpus 24 --broker-num-disks 12 server.properties
Recommendation 1: set num.io.threads == 12 (num_disks)
* https://strimzi.io/blog/2021/06/08/broker-tuning/

Recommendation 2: set replica.fetch.min.bytes == 512
* https://azure.microsoft.com/en-us/blog/processing-trillions-of-events-per-day-with-apache-kafka-on-azure/

Recommendation 3: set socket.receive.buffer.bytes == 512
* https://azure.microsoft.com/en-us/blog/processing-trillions-of-events-per-day-with-apache-kafka-on-azure/
* https://strimzi.io/blog/2021/06/08/broker-tuning/

Recommendation 4: set socket.send.buffer.bytes == 1048576
* https://azure.microsoft.com/en-us/blog/processing-trillions-of-events-per-day-with-apache-kafka-on-azure/
* https://strimzi.io/blog/2021/06/08/broker-tuning/

Recommendation 5: set replica.socket.receive.buffer.bytes == 1048576
* https://azure.microsoft.com/en-us/blog/processing-trillions-of-events-per-day-with-apache-kafka-on-azure/