rootjs: node.js bindings for root 6 - theo beffart, maximilian

1 2016-10-10 Marek Szuba et al.

Steinbuch Centre for Computing (SCC)

RootJS: Node.js Bindings for ROOT 6Theo Beffart, Maximilian Früh, Christoph Haas, Sachin Rajgopal,Jonas Schwabe, Christoph Wolff, Marek Szuba

KIT – The Research University in the Helmholtz Association www.kit.edu

Background


ROOT — scientific software framework from CERNde facto standard tool in particle physicswritten mainly in C++essentially a library of classesintegrated C++ interpreter based on LLVM (ROOT 6)bindings exist for Python, R, Ruby, …

Node.js — high-performance runtime environment for Web applicationsuser code in JavaScriptinternals in C++ — Google V8 enginenon-blocking, asynchronous I/Opopular in modern large-scale systems

Web applications in high-energy physicsnumerous — e.g. data browsers, quality assurance, …back-end processing with ROOT frequently desired

Project Overview


RootJS: Node.js bindings for ROOT 6JavaScript access to all ROOT classesinject, JIT-compile and execute C++ macrosdynamically updated stateasynchronous

Native Node.js module written in C++System requirements:

OS supporting ROOT 6tested under Linux, Mac OS X

Node.js 4–6v4 LTS recommended

Use-case Examples


Live event viewerImportant for monitoring, basic QATypically, standalone ROOT applicationLimited portability:

needs ROOT and dependencies installedrequires access to data source

Alternative — modern Web application:back-end processing: ROOT, close to detectorfront-end anywhere in the worldonly require a Web browser

Analytics in Web applicationsTake advantage of ROOT in machine learning,statistical analysis, linear algebra, …Gain access to XRootD, PROOF etc.

Related WorkJavaScript ROOT


JSROOTWeb clientreimplementationfeature set limited by design:

ROOT graphicsbasic file inputTHttpServer interface

RootJSstandalone, or Web serverwrapperall features of ROOT 6

Highly complementary!Example: Web application with RootJS back-end and JSROOT front-end.

Related WorkJupyter Notebook


ROOT in JupyterWeb client and serversophisticated interactiveinterfacenot meant for scripting/batchlimited access to third-partylibraries

but: Python 2 kernel +PyROOT + …

RootJSstandalone, or Web serverno interactive interface (yet)aimed at scripted/batchprocessingfull access to the Node.jsecosystem

Some overlapDifferent context — interactive vs scriptedJupyter + Javascript kernel + RootJS + …

Design Overview


RTTICLING | CINT

Basic architecture requirements:dynamic object creation and encapsulationnon-blocking function calls via callbacks

Fundamental language differencesdifferent type systems (dynamic vs static)a functional languageclassless objects, prototype functions

“Need an adapter”software design patternhelp incompatible interfaces work together

Environment:V8 API — object exposure and callback handlingROOT RTTI interface — class, namespace, global andmember variable information

Fulfilment of Requirements


provide async call contextbefore forwarding to RTTI API

initcallbackhandling

function calls object access object creation

forward constructor calls

encapsulate construcedobjects for exposure

recursively seek & expose

classes and namespaces

direct access to C++ objects in memory via corresponding proxyobject

JavaScript object

Proxy object

C++ object

entry point for client

interactions with ROOT

Core Architecture


initcallbackhandling

function calls object access object creation

FunctionProxyFactory

+ fromArgs()

FunctionProxy

+ call()

ObjectProxy

+ readValue()

+ writeValue()

ObjectProxyFactory

+ createCapsule()

ObjectProxy

- address

TemplateFactory

+ createTmplt()

Core Architecture


CallbackHandler

+ onAccess()

Proxy

- address

ObjectProxy

+ read() / write()

FunctionProxy

+ call()

ObjectProxyFactory

+ createCapsule()

NodeHandler

+ exposeROOT()

PrimitiveProxy

TemplateFactory

+ createTmplt()

FunctionProxyFactory

+ fromArgs()

Non-blocking Execution


Killer feature of Node.jsRootJS: can add a callback to any exposed functionAsynchronous workersWorker–V8 message passing using libuv

integrates well with Node.jsno need to actively wait for threadsbased on signals — non-blocking, no waste of CPU time

Installation and Invocation


We are on npmjs.com — easy!npm install rootjsRequirements: Node.js, npm, C++ compiler, ROOT 6, libuv headersLoaded the standard Node.js way:var root = require('rootjs');All ROOT variables and classes now accessible through rootNeed more libraries? No problem:root.loadlibrary("libMathCore.so"); // load it...root.ROOT.Math.Pi(); // ...and use it!Callback example:root.TFile.Open("foo.root", function (fin) {

fin.ls();});

Infrastructure


Source-code repository: Gitprimary: GitHubmirror: CERN GitLabcurrently: ≈4000 lines of code

Issue tracker: GitHubContinuous integration: CERN Jenkins

integration testscode coverageDoxygen documentationcurrently: 90 tests, 76 % line coverage


THANK YOU

https://github.com/rootjs/rootjshttps://www.npmjs.com/package/rootjs

rootjs: node.js bindings for root 6 - theo beffart, maximilian

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