Programmer Group

Last blog shared mapreduce's programming ideas. In this section, the blogger will take his friends to understand the principle of wordcount program and the details of code implementation / operation. Through this section, we can have a general understanding of map reduce program. In fact, map and reduce programs in hadoop are only two of them. ...

I. how to compare the consistency of two strings in java 1. You can't use double equal signs to compare whether two strings are equal. You should use the equals method to compare, for example   package com.bjpowernode.java_learning; ​ public class D57_1_ { public static void main(String[] args){ String s1 = new String("ABC"); St ...

1.HBase installation configuration, using independent zookeeper 2. Modify environment variables:The first machine is planned to be master, the second machine is RegionServer, and then start RegionServer on the first machineMake a cluster1 master2 RegionServer Execute vi /etc/profile on the machine, and add the following:export HBASE_HOME=/usr/ ...

7-18 merging of two ordered linked list sequences (20 minutes) Given two non descending list sequences S1 and S2, the design function constructs a new non descending list S3 after the combination of S1 and S2. Input format: The input is divided into two lines. Each line gives a non descending sequence composed of several pos ...

Machine distribution hadoop1 192.168.56121 hadoop2 192.168.56122 hadoop3 192.168.56123 Preparing the installation package jdk-7u71-linux-x64.tar.gz zookeeper-3.4.9.tar.gz hadoop-2.9.2.tar.gz Upload the installation package to the / usr/local directory of three machines and extract it Configure hosts echo "192.168.56.121 hadoop1" >> /etc/ ...

1. Review 1. Differences between Classes and Objects 2.UML(uniform makeup language) 3. Method areas store static variables, constants (static final modifications) 4. Stored objects in heap memory 5. Stack Storage Variables 6.this() can be used to construct the first line of the method 7.static static statement blocks (static statement blocks ar ...

date 20191125 MondayInstall Python 3.7.3 environment on linux 6.5Because our mac environment is:(base) majihuideMacBook-Pro:~ majihui$ python -VPython 3.7.3 Next, install Python 3.7.3 on my local test environment[root@templatec6 ~]# cat /etc/redhat-release CentOS release 6.5 (Final)linux centos6.5 and centos7 are available on linux, the compi ...

The second keyword in cluster fault tolerance is Router, which means routing in Chinese The front-end routing is different from the back-end routing, but the idea is basically the same In view of the fact that many technical articles have a criticism, that is, they only talk about concepts, but not application scenarios. In fact, Router has i ...

Use the health api to view the health of the es cluster The usage of the health api is as follows: curl 'http://localhost:9200/_cluster/health' There is a core field status in the return value of health api. Status has three values: green, yellow, red. They represent three states of the cluster: the primary partition and the replica have been ...

Record a series of errors after modifying the size of sga once After modifying the sga size of oracle, we encountered a series of errors. 00844 and 00851 error reporting SQL> startup; ORA-00844: Parameter not taking MEMORY_TARGET into account ORA-00851: SGA_MAX_SIZE 2147483648 cannot be set to more than MEM SQL> 01078 error reporting SQ ...