The Online Monitoring API for the DIALOG Library of the COMPASS Experiment

Ondřej Šubrt,Dmytro Levit,Vladimir Frolov,Martin Bodlák,Miroslav Virius,Vladimίr Jarý,Josef Nový,Antonίn Květoň,Stefan Huber,Jan Tomsa,Matouš Jandek,Dominik Steffen,A Forti,O Smirnova,P Hristov,M Litmaath,L Betev

doi:10.1051/epjconf/201921401020

Abstract

Modern experiments demand a powerful and efficient Data Acquisition System (DAQ). The intelligent, FPGA-based Data Acquisition System (iFDAQ) of the COMPASS experiment at CERN is composed of many processes communicating between each other. The DIALOG library covers a communication mechanism between processes and establishes a communication layer to each of them. It has been introduced to the iFDAQ in the Run 2016 and improved significantly the stability of the system. The paper presents the online monitoring API for the DIALOG library. Communication between processes is challenging from a synchronization, reliability and robustness point of view. Online monitoring tools of the communication between processes are capable to reveal communication problems to be fixed in future. The debugging purpose has been crucial during introduction period to the iFDAQ. On the other hand, based on the measurement of communication between processes, the proper load balancing of processes among machines can improve the stability of the system. The online monitoring API offers a general approach for the implementation of many monitoring tools with different purposes. In the paper, it is discussed its fundamental concept, integration to a new monitoring tool and a few examples of monitoring tools are given.

Highlights

The Common Muon and Proton Apparatus for Structure and Spectroscopy (COMPASS) [1, 2] is a multipurpose experiment at the Super Proton Synchrotron (SPS) in the CERN’s North Area
The communication layer of iFDAQ is based on the DIALOG library since 2016 and this integration improved the stability of iFDAQ significantly
The DIALOG library is a new communication library for iFDAQ of the COMPASS experiment at CERN. It is responsible for basically all communications inside the iFDAQ, in this environment it makes available around 100 services provided by 30 servers

Summary

Introduction

The Common Muon and Proton Apparatus for Structure and Spectroscopy (COMPASS) [1, 2] is a multipurpose experiment at the Super Proton Synchrotron (SPS) in the CERN’s North Area. The paper presents the online monitoring API for the DIALOG library In complex softwares, such as the iFDAQ, having tens of processes communicating with each other, the. Current COMPASS DAQ system – the intelligent, FPGA-based Data Acquisition System (iFDAQ) [4,5,6] – is new and was designed in 2014 to improve its scalability, reliability, and performance; the process of event building is executed completely in hardware and the number of readout computers was reduced to only four (up to eight in full setup). The iFDAQ enables configuration and control of hardware, monitors data taking, controls data flow, logs information and monitors errors and messages from the system This is ensured by six main processes [6, 11]: Master, Slave-control, Slave-readout, Runcontrol GUI, MessageLogger and MessageBrowser. The MessageLogger receives informative and error messages from other processes and the MessageBrowser enables access to these messages

DIALOG Library

The DIALOG Online Monitoring API

The DIALOG POST Daemon

The DIALOG WebSockets Daemon

Conclusion