This setting is
disabled by default and is intended for sites where Internet connectivity is
patchy or those who wish to continue providing some pages to users even in the
event of a temporary loss of connectivity.
There are several
stages in configuring this option, and before beginning you should visit the HTTP Proxy
Configuration page and ensure that you increase the size of your proxy on
disc to a suitably large setting, for example 100000 Megabytes (or 100G).
Having pre-sized
your cache to a suitable amount you need to upload a list of web sites (URLS)
that you wish to cache. The easiest way
to do this is to create a text file.
Each site should be on a separate line.
You may include the http:// part of the URL or not, as the system will
assume the HTTP protocol if you do not tell it otherwise. You should include the www portion if it
normally forms part of the URL of the site.
The options for uploading the Cache Prefetch URL, or downloading it so
that you can modify it, are shown in figure 4.18.
Figure 4.18 Prefetch List Upload or Download options
Notice how you can,
having uploaded your list, run the prefetcher immediately rather than waiting
for the periodic run to occur. However,
most sites using this facility will want the prefetcher to run automatically on
a periodic basis and you can set those using the radio buttons, as shown in
fugure 4.19
Figure 4.19 Set the prefetch refresh period
You now need to
choose how deeply you wish to recurse the web sites you have selected for
prefetching. Figure 4.20 shows the
options in the drop down list.
Figure 4.20 selecting the depth to traverse
As you can see from
the drop down list (and read in the rubrics) we do not recommend that you go
deeper than 3 levels from the root of your selected sites. Doing so can lead to you holding vast amounts
in the cache, possibly even more than you have configured it for.
Finally, you can
choose whether or not to activate the Offline Watchdog. If you do enable it, the CensorNet will try
and serve pages even if it detects that your connection to the Internet is
down. The way it determines this is to
ping an external machine (somewhere outside of your network). We recommend that you ask your ISP for the IP
address of one of their Name Servers and use that. Figure 4.21 shows the Watchdog configuration
section.
Figure 4.21 Offline Watchdog configuration
As the rubric in
this section warns you, pages that are generated dynamically are unlikely to be
served well by the Offline Watchdog, they may not even have been cached. However, static pages will normally be
available when you are offline.
Finally, to write
these settings away, you can press the button at the bottom of the page. If you dont want to wait until the automatic
run the first time you configure this, you can press the button at the top of
the page to activate the prefetcher now.
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