WordCount schematic
Partition in-depth analysis of Hadoop: http://blog.csdn.net/yhyr_ycy/article/details/51988218
Sort custom sorting of Hadoop: http://blog.csdn.net/l1028386804/article/details/46288107
Hadoop之Combiner: https://www.cnblogs.com/edisonchou/p/4297786.html
Zookeeper principle: http://blog.csdn.net/xlgen157387/article/details/53572760
Why must the number of nodes configured in zookeeper be an odd number?
Zookeeper has such a feature: as long as more than half of the machines in the cluster are working normally, the entire cluster is available to the outside world. That is to say, if there are 2 zookeepers, then as long as there is 1 dead zookeeper, it cannot be used, because 1 is not more than half, so the death tolerance of 2 zookeepers is 0; similarly, if there are 3 zookeepers, one dies , there are still 2 normal ones, more than half, so the tolerance of 3 zookeepers is 1; similarly, you can list a few more: 2->0;3->1;4->1;5->2; 6->2 will find a rule, the tolerance of 2n and 2n-1 is the same, both are n-1, so in order to be more efficient, why add that unnecessary zookeeper.