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13.5 Deployment Architecture
As the discussions in previous sections
have illustrated, OracleAS Portal lets you combine information from
different sources into a single, server-based interface. But how,
exactly, does OracleAS Portal assemble these pages at runtime? The
workflow is shown in Figure 13-4 and is described in
the following sections.
Figure 13-4. Requesting and receiving a page from OracleAS Portal
13.5.1 Creating Portal Pages at Runtime
When a browser sends a request for a page to
OracleAS Portal, the request is routed to the
Parallel Page Engine (PPE), a Java
servlet. The PPE is responsible for implementing and overseeing the
creation of a single page from the different sources of information
shown on the page.The first step in the process is for the PPE to get the
metadata for the page. The
metadata describes the overall layout of the
page and the portlets used within the page. The PPE builds a
structure to hold the page and its information, as described by the
metadata.Once the metadata is retrieved from the OracleAS Portal Repository,
the PPE sends a request to the provider for each portlet. When the
provider has returned the requested portlet, the PPE adds it to the
structure it has created for the page. Once the entire page has been
assembled, the PPE returns the page to the requester.As you can see from this description, the PPE is central to the
overall runtime operation of an OracleAS Portal site. To ensure
adequate performance, you can have more than one PPE for an OracleAS
Portal site. Each PPE has a default number of fetchers, which request
data from providers. You can increase this number if the performance
of your OracleAS Portal site seems to be suffering from a lack of
fetchers.
13.5.2 Caching
The
earlier
description shows that creating a page involves a number of different
resources. There may be pages or portlets in an OracleAS Portal site
that contain the same content for all users. You can reduce the
overhead of creating these pages by caching the pages at a system
level.You can specify the following types of caching for a page or portlet:Cache page definition at the system level
This approach caches the page metadata once for all users. You can
also set an expiration time for this type of caching.
Cache page definition only
This approach caches the metadata that build the page for each
individual user.
Cache page definition and content for a specified length of time
This approach is helpful for pages that are somewhat dynamic, such as
pages listing current news items.
This caching is implemented through the file system on the Oracle
Application Server server that is running OracleAS Portal, and is
separate from the caching performed by OracleAS Web Cache (described
in Chapter 7). Like other pages, portal pages
can be cached in OracleAS Web Cache as long as they are defined there
as being cacheable. You can set a PPE parameter to prevent OracleAS
Web Cache from caching OracleAS Portal pages if desired.
