servicex-transformer 0.3.1rc3

ServiceX Data Transformer for HEP Data

ServiceX_transformer Library

Library of common classes for building serviceX transformers.

Minimum Requiremnts

Works with Python version 2.7 and above

Download from PyPi

To use this library:

pip install servicex-transformer

Standard Command Line Arguments

This library provides a subclass of ArgParse for standardizing commnand line arguments for all transformer implementations.

Available arguments are:

Transformed Result Output

Command line arguments determine a destination for the results as well as an output format.

• Kafka - Streaming system. Write messages formatted as Arrow tables. The chunks parameter determines how many events are included in each message.
• Object Store - Each transformed file is written as an object to an S3 compatible object store. The only currently supported output file format is parquet. The objects are stored in a bucket named after the transformation request ID.

Command Line Reference

Option	Description	Default
--brokerlist BROKERLIST	List of Kafka broker to connect to if streaming is selected	servicex-kafka-0.slateci.net:19092, servicex-kafka-1.slateci.net:19092, servicex-kafka-2.slateci.net:19092"
--topic TOPIC	Kafka topic to publish arrays to	servicex
--chunks CHUNKS	Number of events to include in each message. If ommitted, it will compute a best guess based on heuristics and max message size	None
--tree TREE	Root Tree to extract data from. Only valid for uproot transformer	Events
--path PATH	Path to single Root file to transform. Any file path readable by xrootd
--limit LIMIT	Max number of events to process
--result-destination DEST	Where to send the results: kafka or object-store, output-dir	kafka
--output-dir	Local directory where the result will be written. Use this to run standalone without other serviceX infrastructure	None
--result-format	Binary format for the results: arrow, parquet, or root-file	arrow
--max-message-size	Maximum size for any message in Megabytes	14.5 Mb
--rabbit-uri URI	RabbitMQ Connection URI	host.docker.internal
--request-id GUID	ID associated with this transformation request. Used as RabbitMQ Topic Name as well as object-store bucket	servicex

Running Tests

Validation of the code logic is performed using pytest and pytest-mock. Unit test fixtures are in test directories inside each package.

The tests are instrumented with code coverage reporting via codecov. The travis job has a the codecov upload token set as an environment variable which is passed into the docker container so the report can be uploaded upon successful conclusion of the tests.

Coding Standards

To make it easier for multiple people to work on the codebase, we enforce PEP8 standards, verified by flake8. The community has found that the 80 character limit is a bit awkward, so we have a local config setting the max_line_length to 99.