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From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Update of "ZooKeeper/Tao" by PatrickHunt
Date Wed, 23 Jul 2008 22:13:02 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Hadoop Wiki" for change notification.

The following page has been changed by PatrickHunt:
http://wiki.apache.org/hadoop/ZooKeeper/Tao

New page:
= The Tao of ZooKeeper =

!ZooKeepers are dedicated to the animals they are in charge of as well as the people that
visit those animals. They are guided by a code, until now known only to those of their craft,
that keep the both the animals and their visitors safe.

 * '''!ZooKeepers keep order''' - There are schedules to be kept, procedures that need to
be followed. Total order is needed for changes to avoid confusion among !ZooKeepers; however,
individual !ZooKeepers may answer questions from memory unless explicitly asked not to. Even
these answers are consistent with the total ordering of changes to procedures or policies.
 * '''!ZooKeepers are reliable''' - The Zoo is a dangerous place. Changes agreed upon by ZooKeeper
survive even the deaths of individual !ZooKeepers. If a ZooKeeper is asked to make a change
that it can't make a durability guarantee for, it will inform the requester of a problem.
 * '''!ZooKeepers are efficient''' - !ZooKeepers have a big job and Zoos are getting larger
everyday. They do their jobs efficiently without flair. They let visitors and animals have
the bells and whistles and focus on their jobs.
 * '''!ZooKeepers are timely''' - There are time constraints that !ZooKeepers have: animals
must be fed on schedule, visitors have questions, fences mended, etc. If feeding the elephant
took 5 mins yesterday, it better take 5 mins today.
 * '''!ZooKeepers avoid contention''' - !ZooKeepers don't want animals and visitors to get
angry at each other, so they never make an animal or a visitor they are currently helping
wait on another visitor or animal. (For example, a ZooKeeper if one guest on a tour requests
to visit the elephants first and later another guest asks to visit the pigs, a ZooKeeper should
never check with the first guest before responding to the second. The first guest could have
fallen asleep or may take a while to decide. Ancient !ZooKeepers wasted a lot of time trying
to satisfy a request by consulting others. So, in this example, the ZooKeeper will simply
announce to the first guest that "the plans have changed, we are seeing the pigs".)
 * '''!ZooKeepers are ambition free''' - !ZooKeepers consider their job to be a great honor
and have dedicated their lives to it. Sometimes they are presented with ways to enhance their
careers, doing some mail delivery on the side or serving as an event announcer, but they know
that such things will distract them from their important role of keeping the Zoo safe and
organized.

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