2023-01-14

Kedro Hooks

Hooks

Hooks are a mechanism for adding sub-processes to the main execution of Kedro, and the timing for firing Hooks is selected from the following main execution timings.

  • after_catalog_created
  • before_node_run
  • after_node_run
  • on_node_error
  • before_pipeline_run
  • after_pipeline_run
  • on_pipeline_error
  • before_dataset_loaded
  • after_dataset_loaded
  • before_dataset_saved
  • after_dataset_saved
  • after_context_created

The above is named by the rule <before/after>_<noun>_<past_participle>. For example, before_node_run means that the Hook is run before the Node is executed.

How to use Hooks

Follow the steps below to set up Hooks.

  1. Define Hooks in src/<project_name>/hooks.py
  2. Update HOOKS in src/<project_name>/settings.py

In src/<project_name>/hooks.py, use the @hook_impl decorator to declare the execution of the Hook. The following code declares the Hook to run at after_data_catalog_created timing, that is, after the DataCatalog has been created.

src/<project_name>/hooks.py
import logging

from kedro.framework.hooks import hook_impl
from kedro.io import DataCatalog


class DataCatalogHooks:
    @property
    def _logger(self):
        return logging.getLogger(self.__class__.__name__)

    @hook_impl
    def after_catalog_created(self, catalog: DataCatalog) -> None:
        self._logger.info(catalog.list())

Update src/<project_name>/settings.py as follows to set up the Hook.

src/<project_name>/settings.py
 `from <project_name>.hooks import ProjectHooks, DataCatalogHooks

-  HOOKS = (ProjectHooks(),)
+ `HOOKS = (ProjectHooks(), DataCatalogHooks())

Hooks examples

Tracking memory consumption

You can use memory-profiler to track memory consumption.

$ pip install memory_profiler
src/<project_name>/hooks.py
from memory_profiler import memory_usage
import logging


def _normalise_mem_usage(mem_usage):
    # memory_profiler < 0.56.0 returns list instead of float
    return mem_usage[0] if isinstance(mem_usage, (list, tuple)) else mem_usage


class MemoryProfilingHooks:
    def __init__(self):
        self._mem_usage = {}

    @property
    def _logger(self):
        return logging.getLogger(self.__class__.__name__)

    @hook_impl
    def before_dataset_loaded(self, dataset_name: str) -> None:
        before_mem_usage = memory_usage(
            -1,
            interval=0.1,
            max_usage=True,
            retval=True,
            include_children=True,
        )
        before_mem_usage = _normalise_mem_usage(before_mem_usage)
        self._mem_usage[dataset_name] = before_mem_usage


    @hook_impl
    def after_dataset_loaded(self, dataset_name: str) -> None:
        after_mem_usage = memory_usage(
            -1,
            interval=0.1,
            max_usage=True,
            retval=True,
            include_children=True,
        )
        # memory_profiler < 0.56.0 returns list instead of float
        after_mem_usage = _normalise_mem_usage(after_mem_usage)

        self._logger.info(
            "Loading %s consumed %2.2fMiB memory",
            dataset_name,
            after_mem_usage - self._mem_usage[dataset_name],
        )

Edit HOOKS in src/<project_name>/settings.py as follows.

src/<project_name>/settings.py
-  HOOKS = (ProjectHooks(),)
+  HOOKS = (MemoryProfilingHooks(),)

Running kedro run will output a log of memory consumption.

$ kedro run

$ 2021-10-05 12:02:34,946 - kedro.io.data_catalog - INFO - Loading data from `shuttles` (ExcelDataSet)...
2021-10-05 12:02:43,358 - MemoryProfilingHooks - INFO - Loading shuttles consumed 82.67MiB memory
2021-10-05 12:02:43,358 - kedro.pipeline.node - INFO - Running node: preprocess_shuttles_node: preprocess_shuttles([shuttles]) -> [preprocessed_shuttles]
2021-10-05 12:02:43,440 - kedro.io.data_catalog - INFO - Saving data to `preprocessed_shuttles` (MemoryDataSet)...
2021-10-05 12:02:43,446 - kedro.runner.sequential_runner - INFO - Completed 1 out of 2 tasks
2021-10-05 12:02:43,559 - kedro.io.data_catalog - INFO - Loading data from `companies` (CSVDataSet)...
2021-10-05 12:02:43,727 - MemoryProfilingHooks - INFO - Loading companies consumed 4.16MiB memory

Data validation

You can use Great Expectations to validate inputs and outputs.

$ pip install great-expectations
src/<project_name>/hooks.py
from typing import Any, Dict

from kedro.framework.hooks import hook_impl
from kedro.io import DataCatalog

import great_expectations as ge


class DataValidationHooks:

    # Map expectation to dataset
    DATASET_EXPECTATION_MAPPING = {
        "companies": "raw_companies_dataset_expectation",
        "preprocessed_companies": "preprocessed_companies_dataset_expectation",
    }

    @hook_impl
    def before_node_run(
        self, catalog: DataCatalog, inputs: Dict[str, Any], session_id: str
    ) -> None:
        """Validate inputs data to a node based on using great expectation
        if an expectation suite is defined in ``DATASET_EXPECTATION_MAPPING``.
        """
        self._run_validation(catalog, inputs, session_id)

    @hook_impl
    def after_node_run(
        self, catalog: DataCatalog, outputs: Dict[str, Any], session_id: str
    ) -> None:
        """Validate outputs data from a node based on using great expectation
        if an expectation suite is defined in ``DATASET_EXPECTATION_MAPPING``.
        """
        self._run_validation(catalog, outputs, session_id)

    def _run_validation(
        self, catalog: DataCatalog, data: Dict[str, Any], session_id: str
    ):
        for dataset_name, dataset_value in data.items():
            if dataset_name not in self.DATASET_EXPECTATION_MAPPING:
                continue

            dataset = catalog._get_dataset(dataset_name)
            dataset_path = str(dataset._filepath)
            expectation_suite = self.DATASET_EXPECTATION_MAPPING[dataset_name]

            expectation_context = ge.data_context.DataContext()
            batch = expectation_context.get_batch(
                {"path": dataset_path, "datasource": "files_datasource"},
                expectation_suite,
            )
            expectation_context.run_validation_operator(
                "action_list_operator",
                assets_to_validate=[batch],
                session_id=session_id,
            )

Edit HOOKS in src/<project_name>/settings.py as follows.

src/iris/settings.py
-  HOOKS = (ProjectHooks(),)
+  HOOKS = (DataValidationHooks(),)

Metrics tracking

You can use MLflow to plant metrics tracking.

$ pip install mlflow
src/<project_name>/hooks.py
from typing import Any, Dict

import mlflow
import mlflow.sklearn
from kedro.framework.hooks import hook_impl
from kedro.pipeline.node import Node


class ModelTrackingHooks:
    """Namespace for grouping all model-tracking hooks with MLflow together."""

    @hook_impl
    def before_pipeline_run(self, run_params: Dict[str, Any]) -> None:
        """Hook implementation to start an MLflow run
        with the session_id of the Kedro pipeline run.
        """
        mlflow.start_run(run_name=run_params["session_id"])
        mlflow.log_params(run_params)

    @hook_impl
    def after_node_run(
        self, node: Node, outputs: Dict[str, Any], inputs: Dict[str, Any]
    ) -> None:
        """Hook implementation to add model tracking after some node runs.
        In this example, we will:
        * Log the parameters after the data splitting node runs.
        * Log the model after the model training node runs.
        * Log the model's metrics after the model evaluating node runs.
        """
        if node._func_name == "split_data":
            mlflow.log_params(
                {"split_data_ratio": inputs["params:example_test_data_ratio"]}
            )

        elif node._func_name == "train_model":
            model = outputs["example_model"]
            mlflow.sklearn.log_model(model, "model")
            mlflow.log_params(inputs["parameters"])

    @hook_impl
    def after_pipeline_run(self) -> None:
        """Hook implementation to end the MLflow run
        after the Kedro pipeline finishes.
        """
        mlflow.end_run()

Edit HOOKS in src/<project_name>/settings.py as follows.

src/<project_name>/settings.py
-  HOOKS = (ProjectHooks(),)
+  HOOKS = (ModelTrackingHooks(),)

References

https://kedro.readthedocs.io/en/stable/hooks/introduction.html
https://kedro.readthedocs.io/en/stable/kedro.framework.hooks.html

Ryusei Kakujo

researchgatelinkedingithub

Focusing on data science for mobility

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