Transcript .NET Application Design Considerations Mark Sapossnek CS 594

.NET Application
Design Considerations
Mark Sapossnek
CS 594
Computer Science Department
Metropolitan College
Boston University
Prerequisites
 This module assumes that you understand the
fundamentals of:
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Object-oriented programming
C#
ADO.NET
ASP.NET
Web Services
.NET Framework Class Library
Learning Objectives
 Understand how to design a .NET application
 Understand key design considerations on the
following topics:
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Scalability
Performance
Availability
Security
Agenda
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Design Model and Process
.NET System Architecture
.NET Design Patterns
Security
Scalability
Availability
Design Model and Process
 Microsoft Enterprise Services Framework
Services-Based Application Design Model
 Design Process
 Design Principles
Design Model and Process
Microsoft Enterprise Services Framework
(ESF)
Microsoft Readiness
Framework (MRF)
Microsoft Solutions
Framework (MSF)
Microsoft Operations
Framework (MOF)
Enterprise
Architecture
Design Model and Process
Microsoft Solutions Framework
Team Model
Process Model
Features
Application Model
Design Model and Process
MSF Process Model
Release
Scope
Complete/
First Use
Vision/Scope
Approved
Project Plan
Approved
Design Model and Process
Services-Based Application Model
Application 1
Application 2
User Services
Can be implemented
as Web Services
Business Services
Data Services
Design Model and Process
MSF Design Process Overview
Conceptual
Logical
Scenarios
Physical
Objects and Services,
UI, Logical DB
Components,
UI, Physical DB
http://
Design Model and Process
Conceptual Design
Conceptual
Logical
Scenarios
Physical
Objects and Services,
UI, Logical DB
Components,
UI, Physical DB
http://
The goal of conceptual design is to understand what the users do
and to identify business needs. The output is scenarios or use cases.
Design Model and Process
Logical Design
Conceptual
Logical
Scenarios
Physical
Objects and Services,
UI, Logical DB
Components,
UI, Physical DB
http://
The goal of logical design is to lay out the
structure of the solution and the
communication among elements.
The output is a set of objects and services,
high-level user interface design,
and logical database design.
Design Model and Process
Conceptual
Physical Design
Physical
Conceptual
Logical
Scenarios
Objects and Services,
UI, Logical DB
Components,
UI, Physical DB
http://
The goal of physical design is to apply real-world technology constraints to the logical
model, including implementation and performance considerations. The output is a set of
components, UI design for a particular platform, and physical database design.
Design Model and Process
Design Principles
 Understand and solve the business problem
 Communicate effectively with users and project teams
 Design based on a modular approach
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Consistent
Distributable (Web-centric)
Implementation language-independent
Flexible
Reusable
Reliable
 Balance innovation and discipline through each iteration
 Pay attention to the Enterprise Architecture and
Infrastructure
Design Model and Process
Design Principles
 Object Stereotypes
Entity
Service (Control)
Boundary (Interface)
 Design Patterns
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E.g. Factory, Singleton, Proxy, Flyweight, Iterator,
Façade, Memento, Adaptor
Agenda
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Design Model and Process
.NET System Architecture
.NET Design Patterns
Security
Scalability
Availability
.NET System Architecture
Distributed System Architecture
Rendering engine
Input/Output
Presentation logic
I/O Processing
Business logic
Data logic
Data engine
Everything Else
Data Management
Database
.NET System Architecture
Windows DNA Application Architecture
Rendering engine
HTML 3.2 Browser
Presentation logic
IIS/ASP (.asp)
Business logic
Data logic
Data logic
Data engine
COM Components
SQL Server Database
.NET System Architecture
2-Tier Application Architecture
Rendering engine
Presentation logic
Business logic
Data logic
Data logic
Data engine
VB or PowerBuilder
Application
SQL Server Database
.NET System Architecture
.NET Application Architecture
Rendering engine
HTML 3.2 Browser
Presentation logic
IIS/ASP (.aspx, .ascx)
Business logic
Data logic
Data logic
Data engine
.NET Assemblies
Web
Services
SQL Server Database
.NET System Architecture
Web Service Architecture
Rendering engine
Presentation logic
Business logic
Data logic
Data logic
Data engine
SOAP Clients
Web Service (.asmx)
.NET Assemblies
SQL Server Database
.NET System Architecture
Web Services Application Model
Partner
Web Service
Web Services
Internet + XML
Partner
Web Service
YourCompany.com
Application
Business
Logic
Tier
Data Access and
Storage Tier
Other
Applications
Agenda
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Design Model and Process
.NET System Architecture
.NET Design Patterns
Security
Scalability
Availability
.NET Design Patterns
 Samples
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IBuySpy (http://www.ibuyspy.com/)
MSDN Sample: Duwamish 7.0
MSDN Sample: Fitch & Mather Stocks 7.0
 Using Uniform Modeling Language (UML)
 Discuss design patterns of each sample
application
.NET Design Patterns
IBuySpy Portal Sample
.NET Design Patterns
IBuySpy Design Patterns
 Clean code/HTML content separation using
server controls
 Pages that are constructed from
dynamically-loaded User Controls
 Configurable output caching of portal page
regions
 Modular site layout defined by XML configuration
file
.NET Design Patterns
IBuySpy Design Patterns
 XML serialization that maps XML config file to
custom config classes
 Cached config settings automatically reloaded
when file changes
 Role-based security to control user access to
portal content
.NET Design Patterns
Duwamish Sample Application
.NET Design Patterns
Duwamish Activity Diagram
.NET Design Patterns
Duwamish Sequence Diagram
.NET Design Patterns
Duwamish Design Patterns
 Move processing to the data rather than moving
data to the processing
 Pass all data back to the client in a method call
 Minimize the time that a database resource is
locked
 Use Binary/HTTP for remoting
.NET Design Patterns
Duwamish Design Patterns
 Use ASP.NET within its Web layer and utilize the
ASP.NET caching features
 Publish a single XML Web service named
CatalogService to expose its book catalog
search functions to the Internet
.NET Design Patterns
Fitch & Mather 7.0 Sample
 A port of the MSDN Fitch & Mather 2000 sample
to .NET technologies
 Not a complete deployable application
 Focus on
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Performance
Technology porting issues from the Windows DNA
architecture to the .NET Framework
Legacy integration and interoperability
Real-life deployment scenarios in a distributed
computing environment.
.NET Design Patterns
Fitch & Mather 7.0 Architecture
.NET Design Patterns
Fitch & Mather 7.0 Activity Diagram
.NET Design Patterns
Fitch & Mather 7.0 - Transactions
 Transaction Composability
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Transactions are composed
by a transaction root object
from individual transactional
or nontransactional objects
Transaction root objects are
located at a layer above the
data access layer
No objects in data access
layer marked for requiring
new transaction
Objects that perform write
operation must at least
support transactions
.NET Design Patterns
Fitch & Mather 7.0 - Security
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Use forms authentication with the combination of forms
and role-based security
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Show login page and verify user credentials on access to
restricted resources
Issue an authentication cookie as means of re-acquiring user
identity at a later stage.
Based on the user’s identity/roles, replace the principal object
on the current thread to reflect the identity of the user.
In the application OnAuthenticateRequest event handler of
Global.asax, automatically replace the principal on the
thread every time authentication happens.
On BLL and DAL components, place code segments into the
constructor of each class to verify the identity of the user and
whether they are authenticated. Throw an exception if they
are not.
.NET Design Patterns
UML Models
Agenda
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Design Model and Process
.NET System Architecture
.NET Design Patterns
Security
Scalability
Availability
Security
Overview
 Security is APAIN:
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Authentication
Privacy
Authorization
Integrity
Nonrepudiation
Who‘s there?
No eavesdroppers
What are you allowed to do?
Did the data get changed?
Keep your promises
 As always: understand the requirements
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E.g. Search vs. bank account vs. news
Do you just need personalization?
Security
Questions to Ask
 Authentication
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How does the user provide their credentials?
Where are credentials stored?
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Temporary or persistent
Security
Authentication Approaches
 IIS/Windows
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Basic, Digest, NTLM, Kerberos, Certificates
 ASP.NET
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Windows
Forms-based (cookie) authentication
Microsoft Passport authentication
Custom authentication
Security
Forms-Based Authentication
 Easy to implement
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ASP.NET provides redirection
Custom Login UI (no popup dialogs)
Custom credential verification
Custom application roles
Support for advanced usage
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Application defined data
Control over cookie lifetime, paths
Security
Authorization Strategies
 ASP.NET
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Windows Security & ACLs
URL Authorization
Custom Authorization
 All applications
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Declarative Method Authorization
Explicit Authorization
Agenda
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Design Model and Process
.NET System Architecture
.NET Design Patterns
Security
Scalability
Availability
Scalability
How Do You Handle Success?
…
Scalability
Approach 1 – Scale Up
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 SMP:
Symmetric
MultiProcessor
 Can only get so big
 Expensive
Scalability
Approach 2 – Scale Out
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 Less expensive, though more to manage
 Symmetric (load balancing) or asymmetric
(partitioning)
Scalability
Approach 3 – Partition Database
 Scale out with database
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 Scale up database
 Partition database
Scalability
Design for Scalability
 Design a stateless application if possible
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Use a database for state management
Run on a cluster of Web servers
Use caching or offline content generation
Partition the database tier or the Web tier
Use stored procedures
Use transactions intelligently
Use asynchronous programming techniques
Benchmark your application – performance
measurement and tuning
Scalability
Use a Database for State Management
 Design your Web application to run on a cluster
of Web servers
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Shared nothing, stateless
 This means you must manage user session
state somewhere other than the Web server
 Use a database
Scalability
Single Stateless Application Server
 A single stateless server running your
application code
Application
Code
Scalability
Multiple Identical Stateless
Application Servers
 The application code is cloned across a set of
identical servers
Application
Code
Application
Code
Application
Code
Scalability
Load Balancing
Each server has at least two
network cards: one card for
receiving requests that are
coming in from the Internet,
passing through a fire wall
open on port 80 for HTTP
and 443 for HTTPS (SSL),
and a second card for
communicating with backend servers such as
database servers. Often
there is a third card to traffic
the NLB heartbeat. Each
Web server is running NLB,
which provides dynamic load
balancing.
Internet
Firewall
Public Network
NLB
NLB
NLB
Application
Code
Application
Code
Application
Code
Admin Network
Private Network
Scalability
State Management
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Use a database to persist state
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Use a Session GUID to identify a user within the
application
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Membership, session state, shopping cart, etc.
A GUID is a 128-bit identifier guaranteed to be unique
Use a cookie, hidden variable, or the query string
to pass the Session GUID from server cluster to
browser and back
Do not fear the performance overhead of the
database
Scalability
State Management Architecture
•The database is accessed over
the private network.
•The database is clustered for
failover.
Public Network
Admin Network
NLB
NLB
NLB
Application
Code
Application
Code
Application
Code
•As page requests arrive on a Web
server, the user’s unique session
GUID is used as a key into the
database to retrieve their session
Private Network
state.
•Session state could be their
registration properties, or the status
of a shopping cart, or the
information they filled out on a
previous HTML form.
Database
Cluster
Scalability
Using ASP.NET Caching
 Output caching
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Serves rendered result of a page from cache
Big performance win: cached pages are as fast as static pages
 Cache API
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Enables arbitrary objects to be cached
Can be a big performance win
 Cache XML/XSL in the Web tier
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Cut down on DB hits
Internationalize your site
Expose your data to partners via Web Services
Scalability
Partition the Database Tier
 Functional
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Each functional area of the site gets its own DB
This allows you control over how you deploy into the
production environment
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Dedicated hardware to certain functions
Class of hardware per function
 Table
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Takes some planning
SQL Server 2000 makes this easier than ever before
Huge scale opportunity for large tables
Scalability
Partition the Database Tier
 Load balance read-only databases
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Read-only databases can be IP-load balanced, just
like Web servers
You could load balance your product catalog, for
example
Scalability
Partition the Web Tier
 Just like database functional partitioning, you
can dedicate clusters to application functions
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WWW.mydomain.com is handled by one cluster
SEARCH.mydomain.com is handled by another
cluster
You can also create clusters of clusters
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Use DNS Round Robin to distribute traffic across multiple
load balanced clusters that serve one function
Scalability
Partition the Web Tier
 Use DNS Host names or hardware solutions to
distribute traffic to dedicated clusters
 Once you have a stateless application, this is
how you achieve huge scale
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Scalability throttling with inexpensive hardware
Scalability
Recommended Architecture
REGISTRATION.mydomain.com
Public Network
DNS Host
Names can be
used to direct
traffic to
functional
clusters.
Public Network
NLB
NLB
NLB
NLB
NLB
NLB
App
Code
App
Code
App
Code
App
Code
App
Code
App
Code
Private Network
Databases are
partitioned by
function.
WWW.mydomain.com
Private Network
Database
Cluster
Database
Cluster
Scalability
Benefits of Partitioning
 More control over traffic flow through the
application
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Users who are searching or registering are moved off
of the WWW cluster to keep the response time of the
WWW cluster snappy
 Application and server tuning can be different for
each function
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Search servers may have more memory, more CPUs
than the servers handling WWW
Scalability
Benefits of Partitioning
 Different content management techniques can be used
on different functions
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WWW may be primarily static content or dynamically generated
offline. WWW may use XML and XSL for high performance UI
formatting and internationalization
Registration requires real-time database access and custom
code
 Administration of the clusters can be handled separately
 Database partitioning gives you scale-out capabilities at
the database tier
Scalability
Using Stored Procedures
 There is a real performance benefit to stored
procedures
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Compiled code in the database
 DBA can tune stored procedures
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Can’t tune embedded SQL
 Good separation (API) between table structure
and application code
 Tradeoff is database portability
Scalability
Using Transactions Intelligently
 Transactions are powerful but they do have overhead
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Use them intelligently
 Not every COM component ‘requires’ a transaction
 Design your components with your transactions in mind
 Be aware of the transactional semantics of the
underlying database
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Long-lived locks in the DB will kill application performance
Look for blocking and deadlocks when testing
Scalability
Using Messaging
 Use store and forward where applicable
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Can provide a high degree of scalability by
decoupling the user experience from the backend
processing
 MSMQ
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Underlying messaging technology on Windows
 COM+ Queued Components
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Combines ease of COM programming with MSMQ
 Tradeoffs
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Manual implementation of 2 phase commit semantics
(Compensating Transactions)
Scalability
Performance Tuning
 Performance Tuning is the process by which you
measure individual operations on your site
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Still a bit of a black art
Need to measure for detail but analyze with a holistic view of the
system
Database performance is key; focus there first
 Know your tools
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PerfMon
WAST
SQL Server Profiler
SQL Server Index Tuning Wizard
SQL Server Query Analyzer
Scalability
Framework/CLR Best Practices
 Enable Web Garden: run applications in
multiple worker processes (with processor
affinity)
 Use Early Binding: Late Binding requires work at
runtime
 “Pre-JIT” to start up faster (available in beta 2)
 Make chunky and not chatty calls
 Implement Dispose method on the object that
cleans up your resources and release the
reference (set to null) once you are done
Scalability
Framework/CLR Best Practices
 Use value type for small data
 Do not cache strings or arrays length: Strings
are immutable
 For best inlining performance
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Minimize the use of virtual methods
Use sealed types if possible
Scalability
ASP.NET Best Practices
 Disable “ViewState” if you are not doing Postback
 Disable session state for all pages or Web Methods that
don’t require/need session data
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Set to “readonly” if you read but do not update session state
 Design pages around these ASP.NET built-in caching
features
 Always use System.Data.SqlClient for SQL Server
Access
 Use DataReaders for ASP.NET data access
Scalability
ASP.NET Best Practices
 Avoid apartment threaded COM components
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Migrate apartment threaded components to .NET
Alternatively, enable the <%@ AspCompat=“true” %> directive
for pages that utilize apartment COM objects
Always generate early-bound managed wrappers for COM
components (avoid late bound hit)
 Recommend UI Logic in ASP.NET Pages
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Business and data logic in re-usable components
User Controls for UI reuse
 Recommend web pages & components run in same
process
 Leverage web services only for application to application
communication (not intra application)
Agenda
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Design Model and Process
.NET System Architecture
.NET Design Patterns
Security
Scalability
Availability
Availability
What Is High Availability?
 The question you must ask yourself is:
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How much downtime can my organization afford
without losing productivity, profits, sales, etc.?
 It is a combination of people, process, AND
technology
Availability
High Availability Is Not …
 Only a technology solution
 A scalability solution
Availability
How Much Availability Do I Need?
 Understand the business need
 Five nines (99.999% uptime) is 5 minutes of
downtime per year
 Formulas for downtime:
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% Uptime/year = (8760 - # of total hours down per
year)/8760
% Uptime/month = ((24 * # of days in the month) - #
of total hours down in that calendar month)/(24 * # of
days in the month)
% Uptime/week = (168 - # of total hours down in that
week)/168
Availability
How Do I Achieve High Availability?
 It’s deceptively simple …
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Plan and prepare
Deploy systems to create redundancy – this is the key
to high availability from a technology standpoint
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Use more than one method – avoid a single point of failure
Test, test, test
Monitor on a continuous basis
Availability
Basic Questions To Ask
 Who is the end user? What do they expect in
terms of availability and performance?
 What type of activity is going to be done within
the database (i.e. OLTP, DSS, etc.)?
 Are there any budget considerations?
 How much will not having HA hurt the business?
Calculate how much downtime will actually cost.
Availability
SQL Server 2000 HA Technology
 Failover Clustering
 Log Shipping
 Replication
Availability
SQL Failover Clustering
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Feature of SQL Server 2000 Enterprise Edition
Not a scalability solution
Automatic failover
Always the method to lead with
Requires specialized hardware solutions
Availability
Log Shipping
 New feature of SQL Server 2000 Enterprise
Edition
 Concept has been in use for a long time
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Transaction logs from a primary database are applied
to a secondary database
 Great primary or secondary method even if you
can’t afford failover clustering
Availability
Replication
 Not the traditional method of High Availability –
technology has been around for a long time
 Sometimes better than log shipping for
transactional consistency
 Easy to replicate read-only data
 Possibly more complex, additional resources
 Uses for replication
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Reporting, read-only data, possibly updates
Partitioned data
Availability
NLB
 NLB = Network Load Balancing service
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Formerly known as Windows Load Balancing Service
(WLBS)
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Formerly known as Convoy
 Generally used for scalability
 Can be used with databases to give some
degree of High Availability
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Front end switch for log shipping role change
Warm standby server
Protect Analysis Services
Availability
Design For High Availability
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Involve your programmers from the start
Use versioning
Use source control for all code – including SQL
Take implementation into account – build
programs with clean installs and uninstalls
 Use the right technology
Availability
Design For High Availability
 Establish development, testing, staging
environments, plus one that is an exact code
copy of production (with current production data)
 Take into account downtime, and how you will
handle it – don’t leave it to IT
 Read-only data should be cached if possible to
speed up application performance
Availability
Design For High Availability
 Resolve any application issues that directly
affect SQL Server
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Locking/blocking
Optimized queries/indexing schemes
No ad hoc queries (If possible)
Ensure no memory leaks or bad code will make an
extended stored procedure unstable and cause
availability problems
Make sure statistics are up to date
Availability
Improved Availability with ASP.NET
 ASP.NET has been designed with assumption
that failures will occur on systems
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Designing for failure reduced fragility
 Detects/recovers from common problems
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Access violations, memory leaks, deadlocks
 Preemptive cycling of applications
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Time- and request-based settings
 Net Result: Users should never think that an
ASP.NET application is down or unavailable
Conclusion
 Follow design process
 Understand the architecture and design
trade-offs
 Study design patterns of other .NET applications
 Build security into the overall design
 Chose appropriate design patterns for scalability
and availability
Resources
 Microsoft Solutions Framework
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http://www.microsoft.com/business/micro
soft/mcs/msf.asp
 Microsoft Operations Framework
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http://www.microsoft.com/business/micro
soft/mcs/mof.asp
 General .NET information
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http://msdn.microsoft.com/net
 .NET Framework SDK