[GitHub] couchdb-couch-replicator pull request: Add jittered delay during r...

[nickva]

Github user nickva commented on the pull request:

    
https://github.com/apache/couchdb-couch-replicator/pull/37#issuecomment-217233800
  
    @janl @kxepal 
    
    Here is a poor man's cluster graph. From local dev cluster, single source 
to 500 targets replications. Data on ramdisk. The time window show 20-30 
seconds after the source is deleted.
    
    
![no_jitter](https://cloud.githubusercontent.com/assets/211822/15052501/0542e8b8-12cc-11e6-8aec-73e83ef8478a.png)
    
    With no jitter code, scheduler utilization shoots close 100% in shorter 
period of time, same thing with io usage. Then after all replications sleep 
they'll have another spike like that when they wake up together.
    
    
![with_jitter](https://cloud.githubusercontent.com/assets/211822/15052507/09f6e648-12cc-11e6-9227-53d5cd70e133.png)
    
    With jitter, scheduler utilization stays around 50, load is spread more 
uniformly. Same story with IO.



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