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From Jianqiu Lu <l...@yahoo-inc.com>
Subject question on a state change scenario
Date Wed, 18 Jun 2014 02:05:00 GMT
Hi team,
  First I want to thanks all for this great software.
  I am using helix for our storage system. In our system we have 3 states  read , weak read
and offline. The state transactions are  read-> <- weak read-> <-offline, very
similar to the master/slave example. But the difference is that we need participate to control
its status , which means a participate can decide what is itself's  current ideal state. If
a participate find he can’t follow write speed(we use a queue to do write , participate
consumes message from this queue), then it can change its state from read to weak read.  Is
there a proper way to do this state change from participate side? I looked into Helix java
doc and found in HelixAdmin there is a method “rebalance” seems can achieve my goal, but
my scenario is only need to change one server’s state,“rebalance” seems too over. Or
does this a Helix fit scenario?
  The other solution I thought about is using zookeeper  to manage read and weak read states,
and helix only maintain the online offline state. Once I get an online server from helix ,
then I will look up into zookeeper to find out what is the current read state of this server(maybe
push mode from zookeeper is more proper).  In this solution we don’t need to change helix
ideal state from participate side, but this seems like mix helix and zookeeper to maintain
state machine together.  Could you please give me some advise on my thoughts?


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