A Generative Programming Approach to Middleware Development

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1 A Generative Programming Approach to Middleware Development Venkita Subramonian and Christopher Gill Washington University, St. Louis OMG Workshop on Distributed Object Computing Real-Time And Embedded Systems, July -7,003

2 Scope of Component Models Component Models for configuring and assembling application level components Weaving of components done based on application characteristics Component configuration isolated from component development Some level of automation Serves reusability of components Component Repository Compose Deployment & Configuration Metadata Deployment & Configuration Mechanism 3 6 Central Data Store System Development Chicago Data Center Component Assembly Middleware Configuration Metadata 6 Flight Scheduling Middleware Bus Flight Scheduling Processing Deploy Business Logic Web Gateway Component Containers Containers 3 5 Middleware Framework Component Server 7 Configuring and deploying an application services end-to-end Composing components into application server components Configuring application component containers Synthesizing application component implementations 5 Synthesizing dynamic QoS provisioning and adaptation logic Synthesizing middleware-specific configurations 7 Synthesizing middleware implementations Field Radar Control Systems Airport Approach Control Real-time Flight Status Bulletin Board Client

3 Need for Finer-level Configuration Component configurations Inter-Component configuration Intra-component configuration Component Implementation infrastructure Mapping of High level component configurations to Low level infrastructure elements Configuration of low-level infrastructure elements involve Selection of various strategies based on high level configurations Validating appropriate combinations of configurations Component Repository Compose Deployment & Configuration Metadata Deployment & Configuration Mechanism 3 6 Central Data Store System Development Chicago Data Center Component Assembly Middleware Configuration Metadata 6 Flight Scheduling Middleware Bus Flight Scheduling Processing Deploy Business Logic Web Gateway Component Containers Containers 3 5 Middleware Framework Component Server 7 Configuring and deploying an application services end-to-end Composing components into application server components Configuring application component containers Synthesizing application component implementations 5 Synthesizing dynamic QoS provisioning and adaptation logic Synthesizing middleware-specific configurations 7 Synthesizing middleware implementations Field Radar Control Systems Airport Approach Control Real-time Flight Status Bulletin Board Client 3

4 Static vs. Dynamic Configuration 0Hz 0Hz 5Hz 5Hz critical 5Hz 0Hz 0Hz non-critical RMS+MLF 0Hz 5Hz 5Hz 0Hz critical 5Hz 0Hz 0Hz non-critical MUF Static configuration chosen at system startup compile-time decisions to improve performance compile-time checks based on system properties known a priori Inference of strategies based on high level configurations Reconfiguration during system mode changes Expensive, but more flexible and dynamic E.g. Factory based configurations Hybrid strategies as a balance between the two

5 Generative Approach as a Solution Generative Programming Focus on families of software systems Concrete system generated based on configuration knowledge Extend Generative programming approach to low-level infrastructure configuration Generate low level configurations from high level configurations automatically Configuration generators For mapping high level to low level configurations For assembling and weaving the right infrastructure elements Configuration Knowledge Generator Concrete Implementation 5

6 C++ Template Meta-Programming Mechanism to embed generators in C++ Completely within the purview of C++ language Metainformation represented using Member traits, Traits classes, Traits templates Compile-time control-flow constructs Template metafunctions E.g. IF, THEN, ELSE, CASE Conditional compilation based on evaluation of typeexpressions Issues Advanced usage of C++ templates Compiler support an issue 6

7 Suppliers Example RT Dispatching Consumers Proxy Filtering Correlation static static laxity Dispatcher Event Channel Proxy Threads are all from dispatcher Timers trigger suppliers Suppliers push to EC Events land in queues Worker threads pull from queues and push to consumers 7

8 RT Dispatching Configuration QoS attributes based on scheduling policy Bundle together all QoS attributes in one descriptor Can we generate the appropriate QoS descriptor? Use a configurator to generate the attributes Scheduling policy as input to generator QoS Descriptor Generator QoS Descriptor Scheduling policy 8

9 Generator for QoS Descriptor enum Disp_Rule_t { RMS, EDF, MLF, MUF, other }; template<disp_rule_t> struct QoSDesc { }; //template specializations template<> struct QoSDesc<RMS> { long period; //fields specific to RMS }; template<> struct QoSDesc<EDF> { long deadline; //fields specific to EDF }; template<> struct QoSDesc<MLF> { //fields specific to MLF }; template <Disp_Rule_t disp_rule> struct QoSDescriptorGenerator { typedef typename CASE<EDF,QoSDesc<EDF>, CASE<RMS,QoSDesc<RMS>, CASE<MLF,QoSDesc<MLF> > > > disp_rule_case_list; typedef typename SWITCH<disp_rule, disp_rule_case_list>::ret QoSDescriptor_; typedef QoSDescriptor_ RET; }; typedef QoSDescriptorGenerator<EDF>::RET QoSDescriptor; 9

10 ORB Infrastructure configuration Strategies based on inference from system properties E.g. Strategy used to wait for replies Wait on connection No interleaved processing of incoming requests No blocking factor Wait on reactive mechanism Interleaved processing of incoming requests Blocking factor needs to be considered Configurator to choose strategy based on system characteristics Other Use-Cases Callback Reactor Callback 6 Reactor Nested Upcall scenario Client Client C 3 wait 3 wait C 5 Deadlock here 5 Deadlock avoided by waiting on reactor Server Servant Reactor Server Reactor Servant 0

11 Related Work RMA using template meta programming RMA schedulability analysis at compile-time within the C++ type system Compile error when utilization bound exceeds the RM utilization bound Rate-Monotonic Analysis in the C++ Typesystem, Deters, Gill and Cytron, presented at RTAS 003 Workshop on Model-Driven Embedded Systems Task-Scheduler Logic Work by John Regehr and Alastair Reid Reasoning about Concurrency in Component-Based Systems Software First order logic for representing system knowledge

12 Conclusions Component models deal with higher level application components Need to map high level specifications to configuration of finer-grained components Extend generative programming to configuration of fine-grained infrastructure Algebraic specification of system behavior Inference of infrastructure configuration strategies by reasoning of system behavior

A QoS-aware CCM for DRE System Development

A QoS-aware CCM for DRE System Development Nanbor Wang Tech-X Corporation 5561 Arapahoe Ave., Suite A Boulder, CO 33 Chris Gill Dept. of Computer Science and Engineering Washington University One Brookings