kt - a Kafka tool that likes JSON

Some reasons why you might be interested:

• Consume messages on specific partitions between specific offsets.
• Display topic information (e.g., with partition offset and leader info).
• Modify consumer group offsets (e.g., resetting or manually setting offsets per topic and per partition).
• JSON output for easy consumption with tools like kp or jq.
• JSON input to facilitate automation via tools like jsonify.
• Configure brokers, topic, Kafka version and authentication via environment variables KT_BROKERS, KT_TOPIC, KT_KAFKA_VERSION and KT_AUTH.
• Fast start up time.
• No buffering of output.
• Binary keys and payloads can be passed and presented in base64 or hex encoding.
• Support for TLS authentication.
• Basic cluster admin functions: Create & delete topics.

I'm not using kt actively myself anymore, so if you think it's lacking some feature - please let me know by creating an issue!

Examples

Read details about topics that match a regex

$ kt topic -filter news -partitions
{
  "name": "actor-news",
  "partitions": [
    {
      "id": 0,
      "oldest": 0,
      "newest": 0
    }
  ]
}

Produce messages

$ echo 'Alice wins Oscar' | kt produce -topic actor-news -literal
{
  "count": 1,
  "partition": 0,
  "startOffset": 0
}
$ echo 'Bob wins Oscar' | kt produce -topic actor-news -literal
{
  "count": 1,
  "partition": 0,
  "startOffset": 0
}
$ for i in {6..9} ; do echo Bourne sequel $i in production. | kt produce -topic actor-news -literal ;done
{
  "count": 1,
  "partition": 0,
  "startOffset": 1
}
{
  "count": 1,
  "partition": 0,
  "startOffset": 2
}
{
  "count": 1,
  "partition": 0,
  "startOffset": 3
}
{
  "count": 1,
  "partition": 0,
  "startOffset": 4
}

Or pass in JSON object to control key, value and partition

$ echo '{"value": "Terminator terminated", "key": "Arni", "partition": 0}' | kt produce -topic actor-news
{
  "count": 1,
  "partition": 0,
  "startOffset": 5
}

Read messages at specific offsets on specific partitions

$ kt consume -topic actor-news -offsets 0=1:2
{
  "partition": 0,
  "offset": 1,
  "key": "",
  "value": "Bourne sequel 6 in production.",
  "timestamp": "1970-01-01T00:59:59.999+01:00"
}
{
  "partition": 0,
  "offset": 2,
  "key": "",
  "value": "Bourne sequel 7 in production.",
  "timestamp": "1970-01-01T00:59:59.999+01:00"
}

Follow a topic, starting relative to newest offset

$ kt consume -topic actor-news -offsets all=newest-1:
{
  "partition": 0,
  "offset": 4,
  "key": "",
  "value": "Bourne sequel 9 in production.",
  "timestamp": "1970-01-01T00:59:59.999+01:00"
}
{
  "partition": 0,
  "offset": 5,
  "key": "Arni",
  "value": "Terminator terminated",
  "timestamp": "1970-01-01T00:59:59.999+01:00"
}
^Creceived interrupt - shutting down
shutting down partition consumer for partition 0

View offsets for a given consumer group

$ kt group -group enews -topic actor-news -partitions 0
found 1 groups
found 1 topics
{
  "name": "enews",
  "topic": "actor-news",
  "offsets": [
    {
      "partition": 0,
      "offset": 6,
      "lag": 0
    }
  ]
}

Change consumer group offset

$ kt group -group enews -topic actor-news -partitions 0 -reset 1
found 1 groups
found 1 topics
{
  "name": "enews",
  "topic": "actor-news",
  "offsets": [
    {
      "partition": 0,
      "offset": 1,
      "lag": 5
    }
  ]
}
$ kt group -group enews -topic actor-news -partitions 0
found 1 groups
found 1 topics
{
  "name": "enews",
  "topic": "actor-news",
  "offsets": [
    {
      "partition": 0,
      "offset": 1,
      "lag": 5
    }
  ]
}

Create and delete a topic

$ kt admin -createtopic morenews -topicdetail <(jsonify =NumPartitions 1 =ReplicationFactor 1)
$ kt topic -filter news
{
  "name": "morenews"
}
$ kt admin -deletetopic morenews
$ kt topic -filter news

Change broker address via environment variable

$ export KT_BROKERS=brokers.kafka:9092
$ kt <command> <option>

Installation

You can download kt via the Releases section.

Alternatively, the usual way via the go tool, for example:

$ go install github.com/fgeller/kt/v14@latest

Or via Homebrew on OSX:

$ brew tap fgeller/tap
$ brew install kt

Docker

@Paxa maintains an image to run kt in a Docker environment - thanks!

For more information: https://github.com/Paxa/kt

Usage:

$ kt -help
kt is a tool for Kafka.

Usage:

        kt command [arguments]

The commands are:

        consume        consume messages.
        produce        produce messages.
        topic          topic information.
        group          consumer group information and modification.
        admin          basic cluster administration.

Use "kt [command] -help" for for information about the command.

Authentication:

Authentication with Kafka can be configured via a JSON file.
You can set the file name via an "-auth" flag to each command or
set it via the environment variable KT_AUTH.

Authentication / Encryption

Authentication configuration is possibly via a JSON file. You indicate the mode of authentication you need and provide additional information as required for your mode. You pass the path to your configuration file via the -auth flag to each command individually, or set it via the environment variable KT_AUTH.

TLS

Required fields:

• mode: This needs to be set to TLS
• client-certificate: Path to your certificate
• client-certificate-key: Path to your certificate key
• ca-certificate: Path to your CA certificate

Example for an authorization configuration that is used for the system tests:

{
    "mode": "TLS",
    "client-certificate": "test-secrets/kt-test.crt",
    "client-certificate-key": "test-secrets/kt-test.key",
    "ca-certificate": "test-secrets/snakeoil-ca-1.crt"
}

TLS one-way

Required fields:

• mode: This needs to be set to TLS-1way

Example:

{
    "mode": "TLS-1way",
}

Other modes

Please create an issue with details for the mode that you need.