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2 COM and .NET Com ponent Services Dedication Foreword Preface Scope of This Book Som e Assum pt ions About t he Reader Definit ions and Text Convent ions Ot her COM+ Books and References How to Contact Us Acknowledgm ent s 1. COM+ Com ponent Services 1.1 COM+ Com ponent Ser vices 1.2 The Com ponent Services Explorer 1.3 Hello COM+ 1.4 COM+ Configured Com ponent s 1.5 Applicat ions, DLLs, and Com ponent s 1.6 Configur ing COM+ Applications 1.7 Debugging COM+ Applicat ions 1.8 Deploying COM+ Applications 1.9 Sum m ary 2. COM+ Cont ext 2.1 Encapsulat ion via Marshaling in COM 2.2 Encapsulat ion via I nt ercept ion in COM+ 2.3 The Cont ext Object 2.4 The Call Obj ect 2.5 Cross- Cont ext Manual Marshaling 2.6 Sum m ary 3. COM+ I nst ance Managem ent 3.1 Client Types 3.2 I nstance Managem ent and Scaling 3.3 Obj ect Pooling 3.4 Just - in-Tim e Act ivation 3.5 Com bining JITA wit h Obj ect Pooling 3.6 Obj ect Const ruct or String 3.7 COM+ I nst ance Managem ent Pitfalls 4. COM+ Transactions 4.1 Transact ion Basics 4.2 Transact ion Properties 4.3 Transact ion Scenarios 4.4 COM+ Transact ions Archit ecture 4.5 Configur ing Transact ions 4.6 Vot ing on a Transaction 4.7 Transact ional Obj ect Life Cycle 4.8 Designing Transact ional Com ponent s 4.9 Nont ransactional Clients 4.10 Transact ions and Obj ect Pooling 4.11 Com pensating Transactions 4.12 Transact ion Execut ion Tim e 3 4.13 Tracing Transact ions 4.14 I n-Doubt Transactions 4.15 Transact ion St atist ics 4.16 COM+ Transactions Pitfalls 5. COM+ Concurr ency Model 5.1 Obj ect - Oriented Program m ing and Multiple Threads 5.2 Apart m ent s: The Classic COM Solution 5.3 Act ivities: The COM+ I nnovat ion 5.4 COM+ Configuration Set t ings 5.5 Act ivities and JITA 5.6 Act ivities and Transact ions 5.7 Tracing Act ivit ies 5.8 The Neutral Threaded Apart m ent 5.9 Sum m ary 6. Program m ing t he COM+ Catalog 6.1 Why Program the Cat alog? 6.2 The Cat alog Progr am ming Model 6.3 Catalog St ruct ur e 6.4 I nt eract ing w it h t he Catalog 6.5 Features of COMAdm inCat alog 6.6 The COM+ Catalog and Transact ions 6.7 Sum m ary 7. COM+ Securit y 7.1 The Need for Securit y 7.2 Basic Securit y Term s 7.3 Role- Based Securit y 7.4 Securing a Server Applicat ion 7.5 Securing a Library Applicat ion 7.6 Program matic Role- Based Security 7.7 Security Boundaries 7.8 Advanced COM+ Securit y 7.9 COM+ Securit y Pit falls 7.10 Sum m ary 8. COM+ Queued Com ponent s 8.1 Major Benefits of Queued Com ponent s 8.2 Queued Com ponent s Archit ect ure 8.3 Com ponent Services Explorer Configurat ion 8.4 I nvoking Queued Com ponents on the Client Side 8.5 Designing Queued Com ponent I nt erfaces 8.6 Receiving Out put from a Queued Com ponent 8.7 Queued Com ponent Error Handling 8.8 Queued Com ponent s and Transact ions 8.9 Synchronous Versus Asynchronous Com ponent s 8.10 Queued Com ponents Security 8.11 Queued Com ponents Pit falls 8.12 Sum m ary 9. COM+ Event Service 9.1 Classic COM Event s 9.2 COM+ Event Model 9.3 The Event Class 9.4 Subscript ion Types 9.5 Delivering Event s 4 9.6 Event Filtering 9.7 Distribut ed COM+ Event s 9.8 Asynchronous Event s 9.9 COM+ Event s and Transact ions 9.10 COM+ Events and Securit y 9.11 COM+ Events Lim it ation 9.12 Sum m ary 10. .NET Serviced Com ponent s 10.1 Developing Serviced Com ponent s 10.2 .NET Assem blies and COM+ Applications 10.3 Regist ering Assem blies 10.4 Configur ing Serviced Com ponents 10.5 Applicat ion Activat ion Type 10.6 The Descript ion At t ribute 10.7 Accessing t he COM+ Cont ext 10.8 COM+ Cont ext At t ributes 10.9 COM+ Object Pooling 10.10 COM+ Just - in-Tim e Act ivat ion 10.11 COM+ Const ruct or St r ing 10.12 COM+ Transact ions 10.13 COM+ Synchronization 10.14 Program m ing t he COM+ Cat alog 10.15 COM+ Security 10.16 COM+ Queued Com ponents 10.17 COM+ Loosely Coupled Events 10.18 Sum mary A. The COM+ Logbook A.1 Logbook Requirem ent s A.2 Log File Exam ple A.3 Using the Logbook A.4 Configuring t he Logbook A.5 How Does t he Logbook Work? A.6 Sum mary B. COM+ 1.5 B.1 I m proved User I nterface Usabilit y B.2 Legacy Applications and Com ponent s B.3 Disabling Applications and Com ponent s B.4 Pausing Applicat ions B.5 Service Activat ion Type B.6 I m proved Queuing Support B.7 Application Pooling and Recycling B.8 Application Dum p B.9 Application Partitioning B.10 Aliasing Com ponent s B.11 Configurable Transact ion I solat ion Level B.12 I m proved Cont ext Act ivat ion Set t ing B.13 Private Com ponent s B.14 Web Serv ices in COM+ 1.5 B.15 Sum m ary C. I nt roduction to .NET C.1 .NET Program m ing Languages C.2 Packaging .NET Com ponent s: Assem blies C.3 Developing .NET Com ponent s 5 C.4 Writing .NET Client - Side Code C.5 .NET as a Com ponent Technology C.6 Com posing Assem blies Colophon 6 Dedicat ion To m y wife, Dana 7 Forew ord I first ran into COM+ back in 1996. I n those days, I was working as a Com m on Obj ect Request Broker Architect ure ( CORBA) consultant and was fresh out of I BM, where I had been heav ily involved in I BM’s original CORBA im plem entat ion. CORBA was the first of the archit ect ures that we m ight describe today as Dist ribut ed Com ponent archit ect ures, which set the stage for both COM/ DCOM in the Microsoft space and RMI / I I OP in t he Java space. Back t hen, I was int erest ed in a particularly knot ty problem related to distributed com ponent archit ect ures. System s built wit h such architectures had a characteristic perform ance pattern. They could handle large num bers of t ransact ions, as long as t hose transact ions originated from a sm all num ber of client s. So, for exam ple, 5,000 transact ions per m inute divided between 5 clients worked fine. But when those sam e 5,000 transactions per m inut e were split am ong 1,000 client s, each processing 5 t ransact ions per m inut e, t he system s choked. This was odd, I t hought. Why should 5 clients, each processing 1,000 transactions per m inut e, be fundam ent ally different than 1,000 client s, each processing 5 t ransact ions per m inut e? What is the difference bet ween the first 5,000 tr ansactions per m inut e and the second? Dist ributed com ponent archit ect ures, as they existed in 1996, dict at ed a one- to- one relationship bet ween client s and com ponent inst ances. The business logic of such architect ures is in the com ponent instances. And it is the business logic that makes transact ional request s of transactional resources, such as t he dat abase. In order t o m ake transact ional requests, the com ponent inst ances require expensive resources, such as database connections. We run out of steam ( i.e., t ransact ional throughput ) when one of two t hings happen: we overload the syst em wit h transact ional request s or we run out of resources ( e.g., database connections) . Clearly, going from 5 client s, each m ak ing 1,000 transactional request s per m inute, t o 1,000 clients, each making 5 transact ional request s per m inute, has no overall im pact on t he t ransact ional throughput. Therefore, the reason why our distribut ed com ponent system s m ust be dying is t hat we ar e running out of resources. So the answer to getting lot s of client s on a distributed com ponent architecture is not going to com e from increased capability of the back- end transact ional resources ( e.g., databases) . I t will have to com e from som et hing else- som et hing that allows resource sharing. This, t hen, is the problem I worked on back in 1996. How do you 8 get several clients t o share resources in a distributed com ponent architecture? The solut ion to this problem cam e from an unex pect ed source. I was asked to write a book on COM and DCOM. I knew very litt le about COM and DCOM back t hen. As I looked over t he COM/ DCOM white papers on t he Microsoft web site, I quickly recognized it as a typical dist ribut ed com ponent archit ect ure and predicted the sam e throughput problem s I had seen in other distributed com ponent system s. As I browsed through the whit e papers, I not iced an obscure bet a product called Microsoft Transact ion Server ( MTS) . At first, I dism issed MTS as an API used to manage dist ribut ed t ransactions. But as I read m ore about MTS, I realized that it had litt le to do with transact ions. I nst ead, it at tacked a m uch m ore interesting problem : how to share resources am ong clients. I n a nut shell, MTS addressed the very problem that had so vexed the existing dist ribut ed com ponent system s-how to support a large num ber of low- transact ion generat ing clients! I did eventually w rit e that book, as well as m any articles on the im portance of the ideas int roduced by MTS. Many of t hese articles appear ed in m y ObjectWat ch newslet ter (available at www.obj ectwatch.com ), a newslet ter t hat has, over t im e, becom e influential in its space. Back in 1996, I predicted t hat MTS would be a hist orically im portant product- one t hat w ould redefine approaches to scalabilit y in dist ribut ed com ponent system s. I n fact , t hat prediction has com e true. Today, every infrast ructure designed to support high scalability in distributed com ponent system s is based directly on the ideas, algorithm s, and principals first introduced by MTS in 1996. Enterprise JavaBeans, for exam ple, the Jav a scalabilit y infrastruct ure, is alm ost a direct copy of MTS. But what does this have t o do with COM+ , you may ask. I t t urns out that COM+ and MTS are one and the sam e. Microsoft, never known for its m arketing savvy, decided to wait unt il cust om ers finally got used to t he nam e MTS ( itself a m isleading nam e), and then it pulled a fast one- it switched the nam e! And not just any nam e, but one t hat would be as confusing as possible! So they renam ed MTS as COM+ . Naturally, cust om ers assum ed that COM+ was the next release of COM. I n fact , COM+ was t he next release of MTS. Now Microsoft has announced .NET. Once again, the brilliant Microsoft m ark et ing organization has left m any custom ers confused. I s COM+ now dead? Far from it —.NET is a series of int er esting new features, none of which replace COM+ . COM+ is st ill the scalable infrastruct ure that supports resource sharing and deals with the m yriad of issues (such as security and transaction boundary 9 m anagem ent) that are so closely relat ed t o resource sharing and so crucial t o dist ributed applicat ions. So whether you are rushing into Microsoft ’s new .NET t echnology platform or taking a wait and see att it ude, if you need to put a lot of clients around your system , you need to understand COM+ . Therefore, this book is very tim ely. COM+ is going to be with us for a long time. I ts nam e m ay change again, j ust to confuse the innocent; but the ideas, algorit hm s, and principals will not . COM+ , under whatever nam e, is here to stay! Roger Sessions, CEO, Object Watch, I nc. Publisher, Obj ect Watch newslet ter ( www.objectwatch.com ) Author, COM+ and the Bat tle for t he Middle Tier Austin, Texas 10 Preface This book discusses COM+ com ponent services. Each service is covered in it s own chapter, and each chapter discusses a sim ilar range of issues: the problem the serv ice addresses, possible solutions t o t hat problem , an in- depth description of the COM+ solution, tradeoffs, design, and im plem entation guidelines, tips, and known pitfalls. I have tried t o provide useful design inform ation and lessons I learned while applying COM+ . I also descr ibe COM+ helper classes and ut ilities I developed that will enhance your productivit y significantly . ( The COM+ Events helper object s and t he COM+ Logbook are prim e ex am ples.) This book focuses on the "how to"— that is, it provides practical inform at ion. You should read the chapt ers in order, since m ost chapt ers rely on inform ation discussed in t he preceding chapters. The book also aim s to explain COM+ step by step. A soft ware engineer already fam iliar with COM who wants to know what COM+ is and how to use it can read this book and st art developing COM+ applications im m ediately. Scope of Th is Book Here is a brief sum mary of the chapters and appendixes in this book: • Chapter 1 introduces t he Com ponent Services Explorer and basic COM+ term inology. This chapter deliberately holds your hand as you develop your first " Hello World" COM+ com ponent. Subsequent chapters do m uch less handholding and assum e y ou are fam iliar with the COM+ environment . I f you already have experience wit h basic COM+ developm ent, feel free to skip t his chapt er. • Chapter 2 dem ystifies the COM+ context by presenting it as the key mechanism for providing com ponent services using call int erception. Generally , you need not be concerned with cont ext s at all. However, t he COM+ context underlies the way COM+ services are im plem ented. • Chapter 3 describes t wo scalability- enabling m echanism s t hat COM+ provides for a m odern ent erprise application: obj ect pooling and Just- in- Tim e Act iv at ion ( JITA) . The discussion of inst ance m anagem ent, and especially JI TA, is independent of transact ions. Early COM+ docum entat ion and books t ended t o couple inst ance m anagem ent and transactions. However, I found that not only can you use instance m anagem ent independent ly of t ransact ions, but it is easier to explain it that [...]... an in- proc com ponent is im port ed t o COM+ , it is called a configured com ponent t o em phasize t he fact t hat m uch com ponent funct ionalit y and behav ior is act ually configured and adm inist er ed out side t he com ponent A classic COM com ponent ( be it in- pr oc or local) t hat has not been im port ed int o COM+ is called a nonconfigur ed com ponent Configured and nonconfigur ed com ponent... refer t o t he COM+ com ponent services When we speak of COM+ com ponent s, we refer t o COM com ponent s configured t o run under t hose services Howev er, as y ou will see, a COM+ applicat ion m ay consist of eit her COM or NET com ponent s ( see COM+ : The Migrat ion Pat h t o NET) Her e is a quick sum m ar y of t he m ost im port ant serv ices prov ided by COM+ : Adm inist r at ion Tools and serv ices... window: Com put ers My Com put er COM+ Applicat ions Ev ery icon in t he COM+ Applicat ions folder represent s a COM+ applicat ion Each COM+ applicat ion cont ains COM+ com ponent s Com ponent s m ust be explicit ly im port ed int o t he Com ponent Ser vices Explor er t o t ak e advant age of COM+ serv ices The Com ponent Serv ices Explorer offers a hier archical approach t o m anaging COM+ serv ices and. .. erpr ise applicat ions You will also creat e, debug, and deploy a sim ple COM+ " Hello Wor ld" applicat ion, using a t r adit ional COM com ponent and learning about COM+ applicat ion t y pes and configured com ponent s as y ou do so 17 1 1 COM+ Com pon e n t Ser vice s Com ponent s need runt im e services t o work The original COM runt im e support ed com ponent s locat ed on t he sam e m achine, t y... program m ers and adm inist rat ors t o configure and m anage com ponent s and com ponent - based applicat ions The m ost im por t ant t ool is t he Microsoft Managem ent Console Com ponent Serv ices Ex plorer COM+ also prov ides a st andard locat ion, t he COM+ Cat alog, for st oring configur at ion infor m at ion The Com ponent Services Explorer is explained in t he following sect ion The COM+ Cat alog... oft en COM- based, code base and t he developer sk ills needed t o m aint ain it Unless com panies hav e a com pelling reason t o m ove t o NET or a r easonable m igr at ion pat h, t hey post pone or avoid m ak ing t he change However, because COM and NET com ponent s can coexist in t he sam e COM+ applicat ion, com panies can cont inue t o build COM com ponent s t oday , adding NET ser viced com ponent... fort hcom ing changes 1 2 Th e Com pone n t Ser vice s Ex plor e r COM+ com ponent s and applicat ions ar e m anaged t hrough t he Com ponent Services Explorer ( form erly known as t he COM+ Explorer) The Com ponent Serv ices Explorer is a Microsoft Managem ent Console snap- in and is available on ev ery Windows 2000 m achine To fir e up t he Com ponent Ser vices Explor er, go t o t he St art m enu and. .. Obj ect Model ( COM) has been t he st andard for com ponent s t hat r un on Windows m achines, including Windows 9x and Me client s and Windows NT and 2000 server s The COM m odel is well docum ent ed by t he Microsoft Com ponent Obj ect Model Specificat ion Tools such as Visual C+ + and Visual Basic m ake it easy t o cr eat e COM com ponent s, and scor es of book s, t raining classes, and art icles... classic COM com ponent All COM+ com ponent s st ar t t heir life as classic COM com ponent s, developed wit h such t ools as ATL, MFC, or Visual Basic 6.0 2 Cr eat e a new COM+ applicat ion t o host t he com ponent 3 Add t he com ponent t o t he applicat ion 4 Writ e a client and t est t he com ponent The r est of t his chapt er uses t his " Hello COM+ " exam ple t o dem onst r at e v arious COM+ feat... ill regist er it for you As y ou will see lat er, COM+ m aint ains it s own com ponent s regist r at ion and configurat ion reposit ory 1 3 2 Cr e a t in g a COM + Applica t ion Open t he Com ponent Ser vices Explorer and expand My Com put er COM+ Applicat ions folder Right - click t he COM+ Applicat ions folder and select New Applicat ion from t he pop- up cont ext m enu This st ep br ings up t he Applicat . Internet. Collectively, the services that support COM and .NET com ponent- based applications are known as the COM+ com ponent services, or sim ply as COM+ . The Evolut ion of COM + Services COM. 1. COM+ Com ponent Services 1.1 COM+ Com ponent Ser vices 1.2 The Com ponent Services Explorer 1.3 Hello COM+ 1.4 COM+ Configured Com ponent s 1.5 Applicat ions, DLLs, and Com ponent. of MTS and DCOM by fusing t hem into a new com prehensive component services suit e. Microsoft added yet m ore services, including obj ect pooling, queued com ponents, and events, and m ade