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Ryan Rawson |
at Mar 21, 2011 at 11:32 pm
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it would make sense to avoid moving regions, so therefore the more
recently a region was moved, the less likely we should move it.
you could imagine a hypothetical perfect 'region move cost' function
that might look like:
F(r) = timeSinceMoved(r) + size(r) + loadAvg(r)
The functions should probably be normalized to [0,1], so the range of
F would be [0,3] with 3 == 'dont move' and 0 == 'move first'.
The goal is to minimize all the F(r[i]) in the moves.
-ryan
On Mon, Mar 21, 2011 at 4:26 PM, Jonathan Gray wrote:Also, using more stable measures of request count will help, such as 30 minute rolling averages.
-----Original Message-----
From: Jonathan Gray
Sent: Monday, March 21, 2011 4:23 PM
To:
[email protected]Subject: RE: gauging cost of region movement
This is an interesting direction, and definitely file a JIRA as this could be an
additional metric in the future, but it's not exactly what I had in mind.
One of the hardest parts of load balancing based on request count and other
dynamic/transient measures is that you can get some pretty pathological
conditions where you are always moving stuff around.
To guard against it, I think we'll need to move to more of a cost-based
algorithm that is taking not just the difference in request counts into account
but also a baseline "cost" of moving a region. The cost difference in load
between two unbalanced servers would have to outweigh the cost
associated with moving a region. As you say, looking at the number of live
operations to a given region could contribute to the cost of moving that
region, but the best measure for that is probably just looking at request
count (it's all requests that incur a cost, not just active scanners).
JG
-----Original Message-----
From: Ted Yu
Sent: Monday, March 21, 2011 3:44 PM
To:
[email protected]Subject: gauging cost of region movement
Can we add a counter for the number of InternalScanner's to HRegion ?
We decrement this counter when close() is called.
Such counter can be used to gauge the cost of moving the underlying region.
Cheers
