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The four tiers are browser, network, servers, and databases:
► Browser
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AJAX applications, by definition, perform work (to some extent) on the client side, inside
the browser. All typical client work, such as building the user interface (UI), is done on the
client side, which differentiates these applications from classical web applications, where
only the rendering of HTML is done in the browser. Optimizing the browser and client
system are key to delivering excellent performance (as described in 2.4.2, “Use a
high-performing browser” on page 18 through 2.4.5, “Use modern desktop hardware” on
page 18).
Network
In contrast to static web pages, AJAX applications load the content of a page dynamically
as needed, instead of loading the complete page immediately. Instead of one or several
requests with significant payloads, AJAX applications often send many requests with
smaller payloads. Therefore, delays in the network can have significantly affect response
times because they add time to each message. Ultimately, network delays can add up to
the most significant factor for the overall page-response time.
Figure 2-1 on page 16 is simplified because the network also plays a role in
communications between the servers and the databases and even between servers in a
clustered setup. However, because of the nature of AJAX applications, the first point to
analyze for delays is generally between the browser and the servers.
Servers
The server infrastructure is responsible for handling the requests from the clients that are
attached to it, running business applications (processes, state machines, web services,
and other applications) and integrating back-end services. The configuration of this
infrastructure heavily depends on the chosen topology.
The following servers play an important role for Business Process Manager solutions:
– HTTP server
An HTTP server is not part of all topologies. However, for environments that aim to
serve thousands of users, an HTTP server is indispensable. Both static and dynamic
requests from clients come to the HTTP server. This server can cache and then send
the static (cached) content back to the client and route dynamic requests to the
WebSphere Process Server REST API. Furthermore, an HTTP server can provide
load balancing and support high-availability scenarios.
– Business Process Manager V8.0 servers (Process Server or Process Center)
Business Process Manager V8.0 servers execute various business logic (such as
BPEL and BPMN business processes), querying task lists, creating and claiming tasks,
and other functions. In addition, the Process Center executes authoring requests
initiated by the Process Designer.
Databases
There are multiple relevant databases depending on the client that is used (Process
Designer, Process Portal, or Business Space). Each of these databases must be properly
configured and tuned to support the anticipated load.
Use a network with low latency and high bandwidth. Each Business Process Manager client
uses multiple HTTP requests per user action, so minimizing the network delay per request is
crucial. Network bandwidth is also crucial because some HTTP requests return a significant
amount of data. Where possible, use a dedicated network that is both high-speed and
high-bandwidth (1 Gb or faster) for connectivity between Business Process Manager clients
and servers.
Chapter 2. Architecture best practices 17