In preparation for LHC Run 3 starting spring 2021, the ALICE Experiment at CERN LHC is undergoing a major upgrade, which includes a new computing system called O² (Online-Offline). To ensure the efficient operation of the upgraded experiment along with its newly designed computing system, a reliable, high performance and automated experiment control system is being developed with the goal of managing all O² synchronous processing software, and of handling the data taking activity by interacting with the detectors, the trigger system and the LHC.
The ALICE Experiment Control System (AliECS) is a distributed system based on state of the art cluster management and microservices which have recently emerged in the distributed computing ecosystem. AliECS is being built from scratch in Go and takes advantage of Apache Mesos for its cluster resource management capabilities, with the goal of controlling tens of thousands of processes over hundreds of nodes. It includes a distributed state machine, hierarchical configuration facilities with Consul as key-value store, a Git-based workflow template system and both command-line and graphical user interfaces. Thanks to its novel design and fresh technical foundation, AliECS aims to deliver unprecedented operational flexibility, performance, reliability and data taking efficiency.
For ALICE O², 2020 is a year of intense system integration activity. As part of this collective effort, it is necessary to improve the workflow configuration import capabilities of AliECS.
A workflow template is a file (YAML) which describes a set of data-driven processes to run and control throughout the O²/FLP cluster at LHC Point 2. For developers of processing software, the high level interface is called DPL (O² Data Processing Layer). This component is able to generate dumps of data-driven workflows (i.e. files describing a set of processes to run and how they talk to each other), which currently cannot directly be imported into AliECS. Besides DPL dumps, it would also be interesting to be able to import other experiment-agnostic workflow descriptions for use in the ALICE O²/FLP farm.
Furthermore, while AliECS defines its own workflow template input format, this format has been extended over time and isn’t subject to a formal schema. It would be very useful to be able to validate this kind of configuration input against a schema, both in AliECS and in a future DPL to AliECS workflow converter tool.
While the files in question describe ALICE O²-specific configuration structures, the student does not need to be familiar with experiment-specific concepts and most of the code produced by the student need not be experiment-specific. Even so, the tasks listed below provide ample opportunity for creative solutions to real world challenges in large physics experiment data acquisition.
The completed work would become an essential software component of ALICE experiment operations at the LHC, starting 2021.
Full-featured workflow configuration import and validation facilities.
Integration of said facilities into AliECS, documentation, tests.
Optionally other additional configuration import interfaces can be considered, such as Web UI or graphical terminal, or other configuration input related improvements.