MACROMEDIA COLDFUSION MX-CLUSTERCATS Instrukcja Użytkownika Pobierz pdf (Strona 23)

Successful scalability implementations 13

Successful scalability implementations

Achieving scalable web servers is not a trivial task. There are various solutions from which

to pick, setup and configuration tasks to understand and perform, and many delicate

dependencies between related but heterogeneous technologies. This section describes

some of the major issues affecting successful scalability implementations:

• “Designing and coding scalable applications” on page 13

• “Avoiding common bottlenecks” on page 16

• “DNS effects on website performance and availability” on page 17

• “Load testing your web applications” on page 20

Designing and coding scalable applications

Application architects must create designs that are inherently flexible by relying on open

standards that don’t restrict the application’s construction and implementation to

vendor-specific interfaces and tools. Similarly, web developers that construct the designed

application must be aware that they can significantly impact the application’s scalability

in the way in which they write their code, build their SQL queries, invoke thread

management, access databases, and partition the application.

This section discusses the following topics to consider when designing and building a

web application:

• “Application session and state management” on page 13

• “Database locking and concurrency issues” on page 14

• “Application partitioning” on page 15

Application session and state management

As you create web applications, you will probably create specific variables that you intend

to carry across multiple interactions between a user’s browser and a site’s web server(s).

Using client variables that are stored in a shared state repository, or session variables that

are stored in memory of a specific server, are popular approaches for accomplishing this

task. The latter approach, however, introduces a significant challenge for a website that is

supported by multiple servers. When a user has begun a session and variables are stored

on a specific server, the user must return to that server for the life of the session to

maintain correct state information.

An example that illustrates this concept is an e-commerce application that uses shopping

carts. With this type of application, as a customer accumulates items in a cart, there must

be a mechanism to ensure that the user can see the items as they are added. One approach

is to store these items in session variables on a specific web server. However, if you use this

approach, there must also be a way to ensure that the user always returns to the same

server for the life of the session. ClusterCATS automatically handles this challenge for

you.

Another approach to solving this problem is to store client variables in a back-end

common state repository. This approach enables all web servers in a cluster to access

variables in a common, shared back-end data store, such as a database. However, this

approach can potentially affect your site’s performance.

1 2 ... 18 19 20 21 22 23 24 25 26 27 28 ... 155 156

Brak uwag

MACROMEDIA COLDFUSION MX-CLUSTERCATS Instrukcja Użytkownika Strona 23