Implement active self-updating online hosts cache

[GoogleCodeExporter]

Now online cache updates only while processing user query.
This may be useful to have self-updating online status cache -- this improves 
speed of results 
presentations => usability and happiness of users.

Implementation:
For example separate thread based on TimerTask iterate through the cache and 
update outdated 
items.
This leads to aggressive behavior of the punksearch regarding to remote hosts 
which may be 
bad. So feature should be disabled by default.

Possible system property names:
#whatever use active(aggressive, self-updating) online cache
org.punksearch.online.cache.active=true|false
# timeout to self-update (only outdated items to be updated)
org.punksearch.online.cache.active.timeout=number (in sec, by default same as 
cache.timeout)

Original issue reported on code.google.com by ysol...@gmail.com on 22 Aug 2008 at 11:29

[GoogleCodeExporter]

ping may be enough, no need to make a socket connection
should be configurable as well

Original comment by ysol...@gmail.com on 22 Aug 2008 at 11:31

[GoogleCodeExporter]

Original comment by ysol...@gmail.com on 28 Aug 2008 at 8:35

• Added labels: Milestone-Release1.0