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SEAL Framework & Services

The SEAL Framework allows LCG developers to write portable and modular code across all LCG projects. It provides handy abstractions for modeling software systems and incorporates the best ideas from existing systems.

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SEAL Framework & Services

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  1. LCG AA Internal Review 20 October, 2003 Radovan Chytracek / CERN on behalf of SEAL team SEALFramework & Services

  2. Motivation • Allow LCG developers and users to write portable and modular code across all LCG projects • Provide developers with handy abstractions for modeling software systems • Learn from mistakes in the past and come with software component system which gets the best ideas which work well in existing systems 20 October 2003 SEAL Review - Framework & Services R. Chytracek/CERN 2

  3. Requirements • There are simply too many to list here • Too many parties and interests involved • Very often controversial between two parties • Inspired by technologies in HEP and outside • Gaudi, Iguana, J2EE, Qt, COM, .NET, Python • Basic requirements: • KISS, flexible, type-safe, fast(if possible) • Features: • contextual composition, type-safe lookup, abstract interface support, plug-ins friendly 20 October 2003 SEAL Review - Framework & Services R. Chytracek/CERN 3

  4. Requirements (2) • Encourage well-known communication protocols • call-backs, signals/slots,, observer-notification • Encourage simple services • direct use, targeted interfaces • configurable components via state/contextinstead of a->b->c->d style of navigation • Aim at lightweight framework, simple, repeatable usage pattern • common wiring, not a lot imposed on experiment framework • Component model must fit needs of majority and must be easily adopted by the rest

  5. How we did it • Baseline taken from Iguana component system • Re-design followed to make it independent • The design we agreed was first prototyped in Python • Focus on functionality & component collaboration apects • 2 quick independent C++ prototypes followed • The first goal to achieve the Python prototype look-alike • The second to achieve minimal amount of code needed to build and use components in a C++ application • Internal review of the prototypes • Benchmark, C++ implementations comparison, identifying performance bottle-necks and points of inflexibility

  6. ComponentFactory ComponentLoader RefCounted Component Context Service MyComponent MyService Component Model • Designed as hierarchy of bases classes to support the component model • Each Component lives in a Context • Contexts form their own hierarchy • Support for component look-up • If not in local context, look in parent • A Service provides its own local Context • Components of a Service live in the scope defined by its own Context • User classes inherit from Component or Service • Plug-in functionality for free * 1 1 * 20 October 2003 SEAL Review - Framework & Services R. Chytracek/CERN 6

  7. Application C1 C1 C2 C1 C5 C1 Svc1 Svc2 C3 C1 C4 C1 C1 C6 C7 C1 Svc1 C7 C1 Context Hierarchy • Any Component may attempt to locate another Component in the running application (collaboration network) • By “type” or by “key” • If the not found in the current context, the parent context is searched recursively Context Component Service 20 October 2003 SEAL Review - Framework & Services R. Chytracek/CERN 7

  8. #include "SealKernel/Component.h“ class MyComponent : public seal::Component{ DECLARE_SEAL_COMPONENT; public: MyComponent (seal::Context* context); MyComponent (seal::Context* context, const std::string & label); // implicit copy constructor // implicit assignment operator // implicit destructor //.....component member functions.. void doSomething(); }; MyComponent.h Component Model: How-To (1) 20 October 2003 SEAL Review - Framework & Services R. Chytracek/CERN 8

  9. #include "MyComponent.h“ #include <iostream> DEFINE_SEAL_COMPONENT (MyComponent, "seal/example/MyComponent"); MyComponent::MyComponent (seal::Context* context) : Component (context, classContextKey ()){} MyComponent::MyComponent (seal::Context* context, const std::string & label) : Component (context, label){} // member function implementations void MyComponent::doSomething() { std::cout << "MyComponent: Hello World ! " << std::endl; } MyComponent.cpp #include "MyComponent.h“ #include "SealKernel/ComponentFactory.h“ #include "PluginManager/ModuleDef.h“ DEFINE_SEAL_MODULE (); DEFINE_SEAL_PLUGIN (seal::ComponentFactory, MyComponent, MyComponent::classContextLabel ()); Module.cpp Component Model: How-To (2) 20 October 2003 SEAL Review - Framework & Services R. Chytracek/CERN 9

  10. #include “SealKernel/ComponentLoader.h” #include “MyComponent.h” Handle<MyComponent> handle = component<MyComponent>(); handle->doSomething(); OtherComponent.cpp Look-up by type #include “SealKernel/ComponentLoader.h” #include “MyComponent.h” Handle<MyComponent> handle = component<MyComponent>( “seal/example/MyComponent2” ); handle->doSomething(); OtherComponent1.cpp Look-up by key Component Model: How-To (3) 20 October 2003 SEAL Review - Framework & Services R. Chytracek/CERN 10

  11. IFace.h class IFace { public: virtual void ifaceCall(void)=0; virtual ~Iface(){} }; IFaceComponent.cpp class IFaceComponent : public IFace, public Component {public: DECLARE_SEAL_COMPONENT; IFaceComponent( Context* c ) : Component( c, IFaceComponent::classContextKey() ) {} IFaceComponent( Context* c, const ContextKey& key ) : Component( c, key ) {} IFaceComponent( Context* c, conststd::string& key ) : Component( c, key ) {} virtual ~IFaceComponent() {}public: // IFace implementationvirtual void ifaceCall(void);};DEFINE_SEAL_COMPONENT(IFaceComponent,"seal/example/IFaceComponent")void IFaceComponent::ifaceCall(void) { MessageStream optimist( this, "Optimistic" ); optimist << "I live!" << flush;} Using abstract interface Main.cpp #include "IFace.h"intmain(){ Application theApp; Handle<ComponentLoader> loader = theApp.context()->component<ComponentLoader>(); loader->load("seal/example/IFaceComponent");IHandle<IFace> ifacehandle = theApp.context()->query<IFace>("seal/example/IFaceComponent");if( ifacehandle ) ifacehandle->ifaceCall();return 0;} Component Model: How-To (4) 20 October 2003 SEAL Review - Framework & Services R. Chytracek/CERN 11

  12. Basic Framework Services • The first set of Basic Services came with the new Component Model • Application • Defines the top level Context • Possibility to set the initial set of Components to be loaded in the application • Message Service • Message composition, filtering and reporting • Closely related to MessageStream • Configuration Service • Management of Component properties and loading configurations • Multiple backends foreseen: • Gaudi style options, .INI style, CMS style, XML, ... 20 October 2003 SEAL Review - Framework & Services R. Chytracek/CERN 12

  13. Future development • New Services • Whiteboard service • Design started and discussed with the interested experiments • Waiting for feedback from experiments • Implementation plan similar to that of component model • DictionaryService - loading of dictionary libraries on-demand • Design and prototyping in progress • More ConfigurationService back-ends • Get feedback (from experiments + POOL+…) about Component model and Framework services • Corrections and re-designs are foreseen and possible 20 October 2003 SEAL Review - Framework & Services R. Chytracek/CERN 13

  14. Summary • Component model & basic services came with SEAL 1.0.0 • Combining existing designs into a “common” one is not trivial • Base classes to support the model provided • First set of basic Framework services • Ready to be used (tested) by experiments frameworks, however: • POOL is waiting for the component model to stabilize • LHCb may jump on it after POOL integration in Gaudi is O.K. • CMS similar attitude as LHCb, going for minimalist approach • ATLAS not there yet 20 October 2003 SEAL Review - Framework & Services R. Chytracek/CERN 14

  15. int main(int,char**) { Application theApp; //----Get Loader Handle<ComponentLoader> loader = theApp.component<ComponentLoader>(); //----Instantiate the plug-in loader->load("SEAL/Kernel/Test/Loadable"); //----Get a handle to it Handle<Loadable> loadable = theApp.component<Loadable>(); } main.cpp Application • Establishes the “top” Context • But, it can be inserted in an exiting Context • Instantiates a basic number of Components (or Services) useful to all applications • ComponentLoaded (interface to Plug-in manager) • PropertyManager (application level configuration parameters) • MessageService • ConfigurationService 20 October 2003 SEAL Review - Framework & Services R. Chytracek/CERN 15

  16. #include “SealKernel/MessageStream.h” MessageStream info( this,”MyName”, MSG::INFO); info << “Hello world” << flush; MessageStream log( this, “OtherName”); log(MSG::ERROR) << “This is an error” << flush; OtherComponent.cpp MyName INFO Hello World OtherName ERROR This is an error output Message Service • The user instantiates a MessageStream to compose messages. It reports to the MessageService when message is completed • MessageService dispatches and filters all messages of the application 20 October 2003 SEAL Review - Framework & Services R. Chytracek/CERN 16

  17. Component.cpp struct callObj { operator()(const Propertybase&) {…} }; int m_int; Property<double> m_double(“double”, 0.0,”descr”, callObj); propertyManager()->declareProperty(“int”, m_int, 0, “descr”); propertyManager()->declareProperty(m_double); Configuration Service • A Component may declare its own Properties • Templated Property instances (any type with a stream operator<<) • References to data members (any type with a stream operator<<) • Possibility to associate “callback” update function • Properties have a “name” (scoped) and a “description” • The PropertyCatalogue is the repository of all properties of the application • It is filled from the “configuration file” (Gaudi JobOptions format currently) 20 October 2003 SEAL Review - Framework & Services R. Chytracek/CERN 17

  18. ? Mapping from labels to keys to objects A a 0 TopContext B b 1 f e g b d 8 a c next h 6 7 0 1 2 3 4 5 C c 2 1 3 5 7 0 2 4 6 A B H D d 3 E e 4 0 1 2 3 4 5 Child Context 1 0 1 2 3 Child Context 2 F f 5 F D G g 6 H h 7 Handle Context::query(“key”) { return m_vec[ ContextKey::m_keys[“key”] ] } Single Context Look-up object model ContextKey 20 October 2003 SEAL Review - Framework & Services R. Chytracek/CERN 18

  19. SEAL Team (credits) • Christian Arnault (Dictionary) • Radovan Chytracek (Foundation, Framework) • Jacek Generowicz (Scripting, Framework, Documentation) • Fred James (MathLibs) • Wim Lavrijsen (Scripting) • Massimo Marino (Foundation, Framework, Scripting) • Pere Mato (Framework, Dictionary, Scripting) • Lorenzo Moneta (Foundation, Framework) • Stefan Roiser (Dictionary) • RD Schaffer (Dictionary) • Lassi Tuura (Foundation, Framework, Infrastructure) • Matthias Winkler (MathLibs) • Zhen Xie (Dictionary) 20 October 2003 SEAL Review - Framework & Services R. Chytracek/CERN 19

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