advanced distributed software architectures and technology group adsat 1 microsoft middleware...

1Advanced Distributed Software Architectures and Technology group

ADSaT

Microsoft Middleware Technology

Paul GreenfieldADSaTCSIRO


ADSaT

COM, MTS & COM+

• An evolving component technology– Components not objects– Designed for practical code re-use– COM for local components– DCOM for remote components– MTS for transactional components– COM+ integrating and extending MTS– ActiveX and OLE for adding confusion


ADSaT

COM

• Just one Component Object Model• Language-neutral, binary model

– Use any language to write components• VB, C++, Java, Delphi, C, Perl, …

– Call from any language, inc. scripts• Components are …

– Reusable software building blocks– Defined, contracted, stable behaviour


ADSaT

COM Interfaces• Components implement interfaces

– Interfaces define behaviour– Components have multiple interfaces– Clients only access interfaces

• Not objects and no access to internals

– Interfaces are immutable• Should be defined once and never changed• Give stability in distributed systems

– Polymorphism through interfaces• No class inheritance in COM itself


ADSaT

Component Example

• Kangaroo component class• Supports Hopping and Eating

behaviour

CKangaroo

IHop

IEat

IUnknown Dim BigHopper as IHopDim BigEater as IEatSet BigHopper = new CKangarooSet BigEater = BigRedBigHopper.Hop “over log”

BigEater.Graze “grass”


ADSaT

COM Run-time

• COM objects can be in …– A library (DLL) ‘in-process server’ – A separate program ‘out-of-process’

• Objects accessed through stubs and proxies

Client process

Out-of-process server In-process server


ADSaT

Distributed COM• Took COM into distributed computing

– Exactly the same programming model– Components can be remote

Client process

Out-of-process server In-process server

Remote server


ADSaT

COM/DCOM Practicalities• How does a client find a server?

– Through the registry on the client• Registry set up when client app installed

– No ‘name server’ … until COM+

• Are there really libraries of COM components that can be re-used?– Office, Visio, SAP, ActiveX controls, …

• Much additional flexibility– And subsequent (seeming)

complexity…


ADSaT

Building COM Code

• Good tool support – MS C++ with MFC/ATL, VB, J++,

Delphi, …– Templates, wizards and run-times– Compilers know about components

and their interfaces


ADSaT

Moving from the Desktop

• Addressing the enterprise market– Challenging mainframes and UNIX– Addressing questions of availability,

scalability, integrity, security– Keep ease of programming and admin

• Build enterprise apps in VB?• Avoid need for complex tuning and admin

• Response was MTS – Brought transactions to COM


ADSaT

MS Application Model

• Windows DNA– Three tier architecture– Client layer

• Web based using scripting (ASP)• Traditional client applications

– Business logic layer• Transactional business components

– Data access layer• Components enforce data integrity


ADSaT

Application LayersOrder

component

Customer component

Payment component

Order component

Goods component

Stock component

Delivery component

MTS

DCOM/COM

Web server Scripted

Web pages

Business Logic Layer

Data Access Layer

Client Access Layer

User interface

app

Print invoicesPrint ship requests

Background processes


ADSaT

MTS and Transactions

• MTS added transactions to COM– Simple programming model

• Write code as if it was all that was running on the system

• COM/MTS will ensure isolation• Minimal coding changes needed

– add commit/abort

– Full ACID properties• Using XA-compliant databases etc• Full support for distributed transactions


ADSaT

MTS Programming• Encourages stateless programming

– Methods are complete business transactions

– Transaction starts when method called and ends when it returns

– No state left on server after method returns, except in databases…

• Other models possible– Client controlled transactions – Stateful objects


ADSaT

MTS and Server Objects

• MTS deletes server objects when transaction commits – Client still thinks it has a server object– Server object created anew if needed

• ‘Just-in-time activation’ • Makes it impossible to keep state in

server objects and so violate ACID properties

– Reduces resource usage on server– Server objects recycled in COM+


ADSaT

MTS Architecture• Application ‘packages’

– Collection of libraries (DLLs)– Each package has its own server

process• Multiple threads within each process• Failing application code isolated• Can also run application code ‘in-line’

– Method calls run on threads• No tuning parameters• Low overhead• No binding from client to thread


ADSaT

MTS Architecture

MTS Process

Application Packages

Clients


ADSaT

MTS Administration


ADSaT

MTS Security

• COM security based on NT security– ACLs on components, interfaces, …– Based on users and groups

• MTS has role-based security– Rights assigned to ‘roles’

• ‘manager’, ‘clerk’, ‘teller’, …• Access to interfaces, packages, …• Separates security policy from admin

– Roles assigned to users and groups


ADSaT

MTS Performance

• Stateless transactional applications – Minimal server resources used

• Database connection pooling– ODBC and OLE DB

• Method calls run on any thread– Minimal waiting unlike some OTMs– No tuning or rebinding needed


ADSaT

MTS Performance

• Stock on-line application– Both application and SQL/Server

database running on Dell 2x 400MHz Pentium II with 512MB

– Application coded in … • C++ (ODBC), Visual Basic (ADO), J++ (ADO)

– Two versions• Using Keytable (heavy database locking)• Using Identity (avoids contention on Keytable)


ADSaT

C++ Sample

STDMETHODIMP CStocks::UpdateAccount(long subAccNo, long sCredit)

{ HRESULT hr = S_OK; SubscriberAccount sub ;

hr = sub.Update(subAccNo, sCredit) ;

if (m_spObjectContext) if FAILED(hr)

m_spObjectContext->SetAbort();else m_spObjectContext->SetComplete();

return hr;}


ADSaT

C++ SampleHRESULT SubscriberAccount::Update(long pAccNo, long pCredit) { HRESULT hr; SQLHENV henv = NULL; SQLHDBC hdbc = NULL; SQLHSTMT hstmt= NULL;

hr = GetSQLHandles(henv, hdbc, hstmt); if (FAILED(hr)) return hr; // ODBC handle allocations failed

RETCODE retCode; SDWORD cbNumLen = 0, cbNTS = SQL_NTS ; SQLCHAR stmt [MAX_STMT_LEN] ;

sprintf ((CHAR *) stmt, "UPDATE SUBACCOUNT SET SUB_CREDIT = %ld WHERE SUB_ACCNO = %ld", pCredit, pAccNo ); retCode = SQLExecDirect ( hstmt, stmt, SQL_NTS ) ; if (retCode != SQL_SUCCESS && retCode != SQL_SUCCESS_WITH_INFO) return error("SubAccount Update", henv, hdbc, hstmt);

ReleaseSQLHandles(henv, hdbc, hstmt); return S_OK;}


ADSaT

VB SamplePublic Sub update(pAccNo As Long, pCredit As Long) On Error GoTo ErrorHandler Dim conn As New ADODB.Connection Dim cmd As New ADODB.Command conn.Open DSNString Set cmd.ActiveConnection = conn cmd.CommandText = "update SubAccount set sub_credit=" &

_ pCredit & " where sub_accno=" & pAccNo cmd.Execute conn.Close Set conn = Nothing GetObjectContext.SetComplete Exit Sub ErrorHandler: . . . . . . . . Err.Raise Err.Number, , Err.Description GetObjectContext.SetAbort

End Sub


ADSaT

MTS PerformanceMTS Stock Throughput

0

50

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150

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300

0 100 200 300 400 500 600

Client threads

TP

S

C++ Keytable

C++ Identity

VB Keytable

VB Identity


ADSaT

MTS Performance• How many clients can be supported?

– 2 second average response time– No wait time between requests– Application and database on same box

VB Keytable 200 clients

VB Identity 300 clients

C++ Keytable 350 clients

C++ Identity 500 clients


ADSaT

MTS Response TimesMTS Local Response Times

0

500

1000

1500

2000

2500

3000

3500

4000

4500

1 5 10 20 50 100 200 400 600 800 1000

Client threads

Res

po

nse

tim

e (m

s)

Buy

Create Account

Get Holding

QueryID

QueryCode

Sell

Update


ADSaT

MTS Performance

• Performance limited by processor• Run with remote database

– Doubles available processor power– Needs 100M LAN

• Results for C++ and Identity– 800 clients with 2 sec response time– 430tps


ADSaT

MTS Performance MTS Remote Response Time

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3500

4000

4500

1 5 10 20 50 100 200 400 600 800 1000

Client threads

Res

po

nse

tim

e (m

s)

Buy

Create Account

Get Holding

QueryID

QueryCode

Sell

Update


ADSaT

MTS Scalability• Good up to the capacity of the box

– $20,000 of hardware will support 800 concurrent clients – thousands of users

• But what if we want to support tens of thousands of very active users?– Bigger boxes – scale up

• Commodity 8x servers, Itanium, GHz chips• Proprietary SMP boxes – Unisys, Sequent,..

– More boxes – scale out• Share workload over many servers


ADSaT

Scale Out

• Stateless, transactional applications– No binding between clients and servers– Transactions can go to any server

• Need load balancing support to share workload over available servers– Web server-based– Write-your-own– COM+ load balancing coming soon

• Moved to Windows 2000 Application Server


ADSaT

Integration

• Integrating with non-COM/MTS code– COMTI for full integration with CICS

servers – Support for CICS clients expected– Bridges between COM, CORBA, EJB,

…


ADSaT

Sample System

Customercomponent

Paymentcomponent

Ordercomponent

Goodscomponent

Stockcomponent

Deliverycomponent

DCOM/COM

MTS

Databaseserver

Applicationserver

Warehousemanager

Printinvoices

Webserver

Webserver

Local clientworkstations

Internet/Intranet

Remote warehousesScripted

Webpages

Central Office

Userclientapps

Remote sales offices

Router

Remote sites

HTTP

ORPC

ORPC/MQ

Userclientapps

CICSinterface

Externalcompany

accountingsystem


ADSaT

COM+

• The Windows 2000 version of COM– Features of MTS folded back into

mainstream COM and extended– COM GUI administration tool– Asynchronous method calls– Load balancing– Publish-subscribe events– Compensating resource manager– Object pooling– Performance improvements


ADSaT

COM+ Administration


ADSaT

COM+ Features

• Asynchronous methods– Client can call method and continue– Method call turned in queued message– Uses MSMQ (Microsoft Message Queue)

• Compensating Resource Managers– Allow use of non-transactional

resources within a transaction– Write code to back out changes

• Called if transaction aborts


ADSaT

COM+ Features

• Publish/Subscribe– Event-based programming model– Publish events and subscribers notified

• Use of Windows 2000 features– Reduced use of registry– Use of Active directory to find servers– Use of standard Windows Installer


ADSaT

COM+ Load Balancing

• Scale-out by spreading workload over multiple computer systems– Router knows what servers are

available and how busy they are– Client calls router to find a server– Client gets component reference

and calls methods as normal– Router only involved at component

creation time• no overhead on calls


ADSaT

COM+ Component Load Balancing

Client

Client

Client

Response time tracker

RouterCreate object

Call object’s methods

Pass request to server

Create object and pass back reference

COM + CLB balancing load across multiple systems


ADSaT

COM+ Performance

• Object Pooling– Server-side objects are pooled and

recycled on activation• Lowers cost of object creation/activation

• Dynamic thread pool – Adjusts no. of server threads with load

• Faster but still evaluating how much– Good improvements so far– Tests hitting limits on database server

• Expect improvements with Win2K db server


ADSaT

COM+ PerformanceMTS and COM+ Throughput

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0 200 400 600 800 1000 1200

Client threads

MTS localMTS remoteCOM+ localCOM+ remoteCOM+ cp localCOM+ cp remote


ADSaT

COM+ Performance

Calculated response times

0

500

1000

1500

2000

2500

3000

3500

4000

4500

0 200 400 600 800 1000 1200

Client threads

Resp

on

se t

ime (

ms)

MTS local

MTS remote

COM+ local

COM+ remote

COM+ cp local

COM+ cp remote


ADSaT

COM+ Performance


ADSaT

COM+ Performance

• Ported application MTS -> COM+– Reduced application processor

usage– 300tps, 600 users with local db– 400tps, 800 users with remote db

• Object pooling– Pool objects rather than connections– 400tps, 800 users with local db– 450tps, 900 users with remote db


ADSaT

TPCC Performance?

• TPCC figures for Windows 2000, COM+ and SQL/Server 2000– Top 2 places on TPCC performance list

• 227,000 TPMC – 96 processors - $19/tpmc• 152,000 TPMC – 64 processors - $19/tpmc• ‘shared nothing’ partitioned database

– Then UNIX boxes• About 135,000 TPMC at $50 - $100+

/tpmc


ADSaT

MTS and COM+

• Microsoft’s transactional middleware – Good tool integration for ease of use

• C++, VB, Java – coding, debugging

– Performance good and getting better– Very scalable for the right applications

• Scale-up limited compared to UNIX?• Scale-out requires right architectures

– Good value for money…• Comes as part of NT and Windows 2000

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