http://lucene.472066.n3.nabble.com/Reg-Too-many-fetch-failures-Error-td4037975.html
http://www.slideshare.net/cloudera/hadoop-troubleshooting-101-kate-ting-cloudera
http://lucene.472066.n3.nabble.com/Reg-Too-many-fetch-failures-Error-td4037975.html
As you may be aware this means the reduces are unable to fetch intermediate data from TaskTrackers that ran map tasks – you can try:
* increasing tasktracker.http.threads so there are more threads to handle fetch requests from reduces.
* decreasing mapreduce.reduce.parallel.copies : so fewer copy / fetches are performed in parallel
It could also be due to a temporary DNS issue.
cdh3u4：
TaskTracker里面：
workerThreads = conf.getInt("tasktracker.http.threads", 40);
ReduceTask里面：
this.numCopiers = conf.getInt("mapred.reduce.parallel.copies", 5);
http://lucene.472066.n3.nabble.com/Error-Too-Many-Fetch-Failures-td3990324.html
$ cat /proc/sys/net/core/somaxconn
1024
$ ulimit -n
131072
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