GoodData FlexFun

The GoodData FlexFun package is a GoodData Flight Server-compatible extension that provides a framework for hosting custom pluggable functions called FlexFuns. These can be used to act as a dataset for GoodData FlightRPC data sources.

What is a FlexFun?

In essence, FlexFun is a class that provides a set of methods that can be called by the GoodData Cloud when data is requested from the corresponding FlightRPC data source dataset.

Each FlexFun provides a name used to identify the FlexFun in the GoodData Cloud. FlexFuns can provide a set of metadata that can further influence when and how they are called by GoodData Cloud. They also provide a schema (defined in terms of pyarrow.Schema) that describes the shape of data that the FlexFun can provide. Finally, they provide a set of methods that can be called to provide data in response to queries:

• call - called to provide data in response to a query
• cancel - called to cancel a query if GoodData Cloud decides to stop requesting data (e.g. if there is a timeout)
• on_load - called when the FlexFun is created before any call or cancel methods are called

Getting Started using the FlexFun Template

The easiest way to get started writing FlexFuns is to use the template repository. It provides a simple example of a FlexFun that can be used as a starting point for your own FlexFun with all the necessary infrastructure in place. It also has a README that explains how to get started with the template and some general tips on how to write FlexFuns.

Getting started using the FlexFun package directly

Install the package alongside the gooddata-flight-server using pip:

pip install gooddata-flight-server gooddata-flexfun

Next, update the GoodData Flight Server configuration to load the FlexFun methods.

[flexfun]

# specify one or more modules that contain your FlexFun implementations
#
functions = [
    "flexfun.your_function"
]

Then when running the GoodData Flight Server, use the --methods-provider option to load the FlexFun methods. For example:

#!/bin/bash

SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )"
SERVER_CMD="${SCRIPT_DIR}/.venv/bin/gooddata-flight-server"

export PYTHONPATH="${SCRIPT_DIR}/src"
export CONFIG_ENV="${1:-dev}"

$SERVER_CMD start \
              --methods-provider gooddata_flexfun \
              --config \
                config/${CONFIG_ENV}.server.toml \
                config/flexfun.config.toml \
              --logging-config config/default.logging.ini \
              --dev-log

This will start the GoodData Flight Server with the FlexFun methods loaded.