Adamczewski-Musch, J.

Bellenot, B.

Linev, S.

GSI Repository

THttpServer and JavaScript in ROOT* J. Adamczewski-Musch1, B. Bellenot2, S. Linev1, and the FAIR@GSI project1 1GSI, Darmstadt, Germany, 2CERN, Geneva, SwitzerlandIntroduction The ROOT [1] software framework is widely used in most HEP experiments. ROOT is also often applied for monitoring and control at different stages of data taking and online analysis. Many such online tasks could be solved with web technologies – http protocols for data exchange, and powerful JavaScript/HTML graphics to implement user interfaces. JavaScript ROOT The prominent functionality of JavaScript ROOT (JSROOT) library is the ability to read binary ROOT files and provide interactive ROOT-like graphics in web browsers (Figure 1). Many significant changes and im-provements have been implemented in 2014 compared to original JSRootIO [2] code.   Figure 1: Same canvas, displayed with native ROOT graphics (left) and JSROOT (right)  The I/O part of JSROOT has been organized modular and structurally similar to native ROOT I/O functionality. Most objects stored in binary ROOT files now can be read from the web-browser, using meta-information provided within ROOT files (so-called “streamer-infos”). Several special cases of custom streamers (like TCanvas or TList) are treated in a central place, making it much easier to maintain and extend functionality in the future. It is pos-sible to display and overlay data from different ROOT files in the same browser window. The graphical part of JSROOT code has been fully re-written and decoupled from I/O part of the JSROOT li-brary. The main focus was put on flexibility – now JSROOT graphics can be inserted in any webpage, and one can update graphics interactively. Many new features have been implemented, e.g. context menu, statbox up-date, comfort zooming. JSROOT code, documentation and examples are avail-able online [3] and with ROOT distribution. THttpServer class The new THttpServer class of ROOT implements http protocol by means of embeddable Civetweb [4] server. With simple http requests syntax one could obtain object data from application in different form. (binary, xml, json, png). The TBufferJSON class has been developed to con-vert ROOT objects into JSON (JavaScript Object Nota-tion), which can be directly evaluated in web browsers. The user interface for THttpServer has been imple-mented with JSROOT (Figure 2). One could browse, dis-play, and monitor objects registered to the server. In addi-tion one could execute registered commands (like start/stop analysis or clear histograms) in the server appli-cation. There is also the possibility to perform TTree::Draw() on the server and display results in the browser.   Figure 2. Browser with objects available from httpserv-er.C macro. The objects hierarchy is on the left side, sev-eral displayed objects are on the right. Also tree draw functionality is shown.  Source code, documentation, and several examples for THttpServer are included into the ROOT distribution.  Conclusions and outlook THttpServer together with JSROOT provide a powerful tool set to create ROOT-based online applications. JSROOT functionality is also used to implement web interface for DABC, MBS and Go4 frameworks [5].  References [1] ROOT project homepage http://root.cern.ch [2] B.Bellenot, S.Linev, “ROOT I/O in JavaScript”, Journal of .Physics: Conference Series, vol 513, Pro-ceedings of CHEP 2013, http://iopscience.iop.org/1742-6596/513 [3] JSROOT homepage https://root.cern.ch/js/jsroot.html [4] Civetweb embeddable webserver, project homepage https://github.com/bel2125/civetweb [5] S. Linev, “Web interface in DABC”, GSI scientific report 2013, doi:10.15120/GR-2014-1-FG-CS-12  ___________________________________________  * PSP codes: SFRS 2.4, ILIMA 1.2.2.4, R3B 1.2.5.1.4, 1.2.6.6, 1.2.5.1.2, HADES 1.1.2.4 FG-CS-04 GSI SCIENTIFIC REPORT 2014508 DOI:10.15120/GR-2015-1-FG-CS-04

THttpServer and JavaScript in ROOT

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THttpServer and JavaScript in ROOT

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