PADME Conductor Library

A library to simplify the interactions with the Personal Health Train (PHT) and its Stations.

Connection Parameters

When working with the Stations you typically want to retrieve the information of how to connect to the database first. This can be done with the get_environment_vars function, by passing the variable keys which need to be retrieved.

env = pc.get_environment_vars(
    [
        "DATA_SOURCE_USERNAME",
        "DATA_SOURCE_HOST",
        "DATA_SOURCE_PASSWORD",
        "DATA_SOURCE_PORT",
        "STATION_NAME",
    ]
)

Database Plugins

The next step would be to use the connection parameters and query the database of the Station. For that, we first instantiate a database plugin for the appropriate database type.

SQL

sql = SqlPlugin(
    db_name="patientdb",
    user=env["DATA_SOURCE_USERNAME"],
    password=env["DATA_SOURCE_PASSWORD"],
    host=env["DATA_SOURCE_HOST"],
    port=env["DATA_SOURCE_PORT"],
)

FHIR

fhir_plugin = FHIRClient(f"http://192.168.0.1:8080/fhir")

Querying Databases

With the database plugin, we can query the data from the Station. For that, we pass a default Query object and the current station name to the query function.

result = pc.query(
    Query("SELECT * FROM patients WHERE age >= 50", sql_plugin))

If the queries for each station differ, you can pass a list of queries and the current station name instead:

result = pc.query(
    [
        Query("SELECT * FROM patients WHERE age >= 50", sql, "Klee"),
        Query("SELECT * FROM patient_info WHERE age >= 50", sql, "Bruegel"),
    ],
    env["STATION_NAME"],
)

Executing the Analysis

You can now design your analysis with the libraries and frameworks you like. This analysis can be e.g. a Machine Learning model, you set up and train, or an analysis that collects statistical data.

To execute the analysis we then pass the analysis function to the execute_analysis function, with all the parameters your function expects.

def my_analysis(query_result):
    res = len(query_result)
    pc.log(f"found {res} patients")
    return res

res = pc.execute_analysis(my_analysis, result)

Saving the Results

We can then save the results from our analysis in the Train file system. To simplify this Train interaction we provide the save function.

You can separate the saved results, either by each run, each station, or not separate them. The append parameter defines whether the content should be appended to the file or not.

save_string = f"The result is {res}"
pc.save(save_string, "result.txt", separate_by=Separation.STATION, append=True)

Retrieving Previous Results

To retrieve the previous results, like a previous state of a machine learning model, you can use the retrieve_prev_result function.

If you have separated your results when saving, you also need to provide the separation strategy when retrieving.

prev = pc.retrieve_prev_result("result.txt", separate_by=Separation.STATION)

Logging

You can use the log functions to log simultaneously to stdout/stderr and a log file in the Train file system. We also provide the ability to add custom tags to a log function with the extra parameter.

pc.log("hello world", extra={"tags": ["cpu_consumption"]})

pc.log_debug("hello world")
pc.log_info("hello world")
pc.log_warning("hello world")
pc.log_error("hello world")
pc.log_critical("hello world")

Simple example

This is a simple example Train-analysis showing the concepts described above.

import padme_conductor as pc
from padme_conductor import Query, Separation
from padme_conductor.Plugins.SQL import SqlPlugin

env = pc.get_environment_vars(
    [
        "DATA_SOURCE_USERNAME",
        "DATA_SOURCE_HOST",
        "DATA_SOURCE_PASSWORD",
        "DATA_SOURCE_PORT",
        "STATION_NAME",
    ]
)

sql = SqlPlugin(
    db_name="patientdb",
    user=env["DATA_SOURCE_USERNAME"],
    password=env["DATA_SOURCE_PASSWORD"],
    host=env["DATA_SOURCE_HOST"],
    port=env["DATA_SOURCE_PORT"],
)

result = pc.query(
    [
        Query("SELECT * FROM patients WHERE age >= 50", sql, "Klee"),
        Query("SELECT * FROM patient_info WHERE age >= 50", sql, "Bruegel"),
    ],
    env["STATION_NAME"],
)


def analysis(query_result):
    res = len(query_result)
    pc.log(f"found {res} patients")
    return res


res = pc.execute_analysis(analysis, result)
prev = pc.retrieve_prev_result("result.txt", separate_by=Separation.STATION)
pc.log(prev, extra={"tags": ["cpu_consumption"]})


# Write to file
save_string = env["STATION_NAME"] + ":" + str(res) + "\n"
pc.save(save_string, "result.txt", separate_by=Separation.STATION)