mapper-generic

Generic Singer mapper for overriding with a lightweight script.

Built with the Meltano Singer SDK.

Capabilities

• stream-maps

Settings

Setting	Required	Default	Description
code_path	False	None	A path to the python file that contains your custom mapper code. The module should contain a Mapper class with optional overrides for map_schema_message, map_record_message, map_state_message, and map_activate_version_message. If none of those methods are overridden in your custom script then the mapper will do nothing and pass all message to the target.
stream_maps	False	None	Config object for stream maps capability. For more information check out Stream Maps.
stream_map_config	False	None	User-defined config values to be used within map expressions.

A full list of supported settings and capabilities is available by running: mapper-generic --about

Supported Python Versions

• 3.8
• 3.9
• 3.10
• 3.11

Usage

This mapper is meant to be versatile and lightweight so users can install it and do simple transformations of their data without having to build a new standalone mapper or add functionality into the Meltano SDK.

To use the mapper you configure it to reference a script using the code_path setting. The script should contain code similar to the following so the mapper can access it properly. The code below only overrides the map_record_message to make some minor adjustments to the data.

import typing as t

from singer_sdk._singerlib.messages import (
    Message,
)

class Mapper():

    def map_record_message(self, message_dict: dict) -> t.Iterable[Message]:
        page_content = message_dict["record"]["page_content"]
        text_nl = " ".join(page_content.split("\n"))
        text_spaces = " ".join(text_nl.split())
        message_dict["record"]["page_content"] = text_spaces
        return message_dict

Currently the mapper expects a Mapper class in the script and allows you to override each of the 4 methods provided:

• map_record_message
• map_schema_message
• map_state_message
• map_activate_version_message

Usually map_state_message and map_activate_version_message shouldn't need to be overridden and map_schema_message should only be, and is required to be, overridden if the records structure is changed i.e. a property is added, removed, renamed.

Additional Dependencies

If you're running this mapper with Meltano you can add additional dependencies to the pip_url so that they're accessible to your mapper script.

  - name: mapper-generic
    namespace: mapper_generic
    pip_url: git+https://github.com/pnadolny13/mapper-generic.git <MY_EXTRA_DEPENDENCY>

Accepted Config Options

A full list of supported settings and capabilities for this mapper is available by running:

mapper-generic --about

Configure using environment variables

This Singer mapper will automatically import any environment variables within the working directory's .env if the --config=ENV is provided, such that config values will be considered if a matching environment variable is set either in the terminal context or in the .env file.

Usage

You can easily run mapper-generic by itself or in a pipeline using Meltano.

Executing the Mapper Directly

mapper-generic --version
mapper-generic --help

Developer Resources

Follow these instructions to contribute to this project.

Initialize your Development Environment

pipx install poetry
poetry install

Create and Run Tests

Create tests within the tests subfolder and then run:

poetry run pytest

You can also test the mapper-generic CLI interface directly using poetry run:

poetry run mapper-generic --help

Testing with Meltano

Note: This mapper will work in any Singer environment and does not require Meltano. Examples here are for convenience and to streamline end-to-end orchestration scenarios.

Next, install Meltano (if you haven't already) and any needed plugins:

# Install meltano
pipx install meltano
# Initialize meltano within this directory
cd mapper-generic
meltano install

Now you can test and orchestrate using Meltano:

# Run a test `run` pipeline:
meltano run tap-smoke-test mapper-generic target-jsonl

SDK Dev Guide

See the dev guide for more instructions on how to use the SDK to develop your own taps, targets, and mappers.