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.

Note

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"
}

If any certificate or key path is simply the name of the file, it is assumed to be in the same directory as the auth file itself. For example if the path to the auth file is /some/dir/kt-auth.json then a "client-certificate": "kt-test.crt" will be qualified to /some/dir/kt-test.crt.

TLS one-way

Required fields:

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

Optional fields:

• ca-certificate: Path to your CA certificate

Example:

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

Other modes

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