tkati-core 0.2.0

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tkati-core

For now we assume that each node gets one input and produces one output in a form of kafka stream.

Settings

General form of settings is:

[input.topic]
# definition of input stream:
# - broker
# - topic name
# - message schema
# - message format = "json" / "arrow-batch"

[input.consumer]
# parameters local to this consumer
# - group_id
# - batch_size
# - batch_timeout_sec
# - auto_offset_reset

[output.topic]
# definition of output stream
# - broker
# - topic name
# - message schema
# - message format = "json" / "arrow-batch"
# - key_column (optional) = column to use as the Kafka message key

[...]
# settings specific to node function

Usage

Constructing a consumer from settings

Use KafkaArrowConsumer.from_input_settings to construct a consumer directly from KafkaInputSettings — no need to manually map fields to Confluent Kafka config keys.

from tkati_core.settings import TomlBaseSettings, KafkaInputSettings
from tkati_core.consumer import KafkaArrowConsumer

class AppSettings(TomlBaseSettings):
    input: KafkaInputSettings
    # ...

settings = AppSettings()
consumer = KafkaArrowConsumer.from_input_settings(settings.input)

# Read a batch
table = consumer.read_to_pyarrow(
    aggregation_interval_seconds=settings.input.consumer.batch_timeout_sec,
    max_events_to_aggregate=settings.input.consumer.batch_size,
)
consumer.commit()

The factory method sets enable.auto.commit=False — offsets must be committed explicitly via consumer.commit().

Constructing a producer from settings

Use KafkaArrowProducer.from_output_settings to construct a producer directly from KafkaOutputSettings. It accepts PyArrow tables or record batches and handles serialization according to the topic's format setting.

from tkati_core.settings import TomlBaseSettings, KafkaOutputSettings
from tkati_core.producer import KafkaArrowProducer

class AppSettings(TomlBaseSettings):
    output: KafkaOutputSettings
    # ...

settings = AppSettings()
producer = KafkaArrowProducer.from_output_settings(settings.output)

# Produce a PyArrow table (one message per row for "json" format)
producer.produce(table)
producer.flush()
producer.close()  # flushes and releases resources

Formats — controlled by output.topic.format in settings.toml:

• "json" (default): each row becomes a separate Kafka message serialized with orjson.
• "arrow-batch": the entire table is serialized as a single Arrow IPC stream message.

Message keys — controlled by output.topic.key_column in settings.toml:

[output.topic]
broker = "localhost:9092"
name = "my-output-topic"
key_column = "customer_id"   # column whose value becomes the Kafka message key

key_column is optional. When omitted (or None), messages are produced without a key. When set, the value of that column for each row is used as the Kafka message key (JSON format only — ignored for "arrow-batch"). This determines which Kafka partition each message is routed to.