It is the mapper which will push the o/p to the respective reducer as soon as it completes.
The no of reducers are known at the beginning itself. The mapper as it process the input split, generate the o/p of for each reducer (if the mapper o/p key is eligible for the reducer). The reducer will wait till the completion of all map tasks to start it processing. On 12/22/14, [email protected] <[email protected]> wrote: > Could some one help me on this question? thanks. > > > > [email protected] > > 发件人： Todd > 发送时间： 2014-12-21 21:59 > 收件人： [email protected] > 主题： Question about shuffle/merge/sort phrase > Hi, Hadoopers, > I got a question about shuffle/sort/merge phrase related.. > My understanding is that shuffle is used to transfer the mapper > output(key/value pairs) from mapper node to reducer node, and merge phrase > is used to merge all the mapper output from all mapper nodes, and sort > phrase is used to sort the key/value pair by key, > Then my question, whose responsibility is it that brings each key with all > its values together (The reducer's input is a key and an iterative values). > > > Thanks. >
