升级ambari、HDP版本（ambari2.1升级到2.4、HDP2.3升级到2.5）

官方升级版本说明
http://docs.hortonworks.com/HDPDocuments/Ambari-2.4.0.1/bk_ambari-installation/content/determine_stack_compatibility.html

官方升级步骤
http://docs.hortonworks.com/HDPDocuments/Ambari-2.4.0.1/bk_ambari-upgrade/content/preparing_to_upgrade_ambari.html

官方HDP问题搜索
https://community.hortonworks.com/answers/index.html

Upgrade Ambari

一、升级前准备

Preparing to Upgrade

确认版本
Be sure to review the Release Notes for this Ambari release for Known Issues and Behavioral Changes.

拥有root权限
You must have root, administrative, or root-equivalent authorization on the Ambari server host and all servers in the cluster.

备份ambari数据库
You must backup the Ambari Server database.

备份好ambari.properties配置文件
You must make a safe copy of the Ambari Server configuration file found at /etc/ambari-server/conf/ambari.properties.


二、停止服务、下载新的ambari.repo

关闭Ambari Metrics
If you are running Ambari Metrics service in your cluster, stop the service. From Ambari Web, browse to Services > Ambari Metrics and select Stop from the Service Actions menu.
    
停止ambari-server
Stop the Ambari Server. On the host running Ambari Server:
    ambari-server stop

停止ambari-agent
Stop all Ambari Agents. On each host in your cluster running an Ambari Agent:
    ambari-agent stop

获取新的ambari.repo
Fetch the new Ambari repo and replace the old repository file with the new repository file on all hosts in your cluster.

wget -nv http://public-repo-1.hortonworks.com/ambari/centos6/2.x/updates/2.4.0.1/ambari.repo -O /etc/yum.repos.d/ambari.repo

三、升级操作
Upgrade Ambari Server. On the host running Ambari Server:

    yum clean all
    yum info ambari-server

在ambari节点更新ambari-server
In the info output, visually validate that there is an available version containing "2.4"
    yum upgrade ambari-server

显示如下成功：
Updated:
   ambari-server.x86_64 0:2.4.0.1-1      
Complete!

在所有节点更新ambari-agent
Upgrade all Ambari Agents. On each host in your cluster running an Ambari Agent:
    yum upgrade ambari-agent

显示如下成功：
Updated:
  ambari-agent.x86_64 0:2.4.0.1-1                                                         

Complete!

查看ambari-agent
After the upgrade process completes, check each host to make sure the new files have been installed:
rpm -qa | grep ambari-agent

升级ambari-server
Upgrade Ambari Server database schema. On the host running Ambari Server:
ambari-server upgrade

[root@testserver2 yum.repos.d]# ambari-server upgrade
Using python  /usr/bin/python
Upgrading ambari-server
Updating properties in ambari.properties ...
WARNING: Can not find ambari.properties.rpmsave file from previous version, skipping import of settings
INFO: Can not find ambari-env.sh.rpmsave file from previous version, skipping restore of environment settings. ambari-env.sh may not include any user customization.
Fixing database objects owner
Ambari Server configured for Embedded Postgres. Confirm you have made a backup of the Ambari Server database [y/n] (y)?
Upgrading database schema
Adjusting ambari-server permissions and ownership...
Ambari Server 'upgrade' completed successfully.

启动ambari-server
Start the Ambari Server. On the host running Ambari Server:
ambari-server start

[root@testserver2 yum.repos.d]# ambari-server start
Using python  /usr/bin/python
Starting ambari-server
Ambari Server running with administrator privileges.
Organizing resource files at /var/lib/ambari-server/resources...
Ambari database consistency check started...
No errors were found.
Ambari database consistency check finished
Server PID at: /var/run/ambari-server/ambari-server.pid
Server out at: /var/log/ambari-server/ambari-server.out
Server log at: /var/log/ambari-server/ambari-server.log
Waiting for server start....................
Ambari Server 'start' completed successfully.

所有节点启动ambari-agent
Start all Ambari Agents. On each host in your cluster running an Ambari Agent:
ambari-agent start

登录ambari管理界面，查看版本，升级成功。

打开管理界面后出现图中内容，使用’ctrl+shift+R’刷新下就好了。

四、增加新版本HDP

浏览Ambari Web > Admin > Stack and Versions.

点击Versions标签，你将看到已经安装的HDP版本

如果看不到已经安装(Current)的版本, 说明客户端没有更新完。

Admin > Manager Ambari > 左侧Versions
点击右上角的按钮Register Version，添加新的hdp版本。

8. 点击Install Packages就能够将hadoop升级到该HDP版本了。

安装后点击upgrade，有两种升级模式，一种是保持服务运行升级，另一种是停止服务升级，后者升级更快些

点击Checks查看警告信息，需要检查TEZ服务，进入TEZ服务，选择“”run service check“”

提示是否升级

选择i have performed the clients will retry on their above. 之后proceed

开始升级，我选择的是停止服务升级，过程中会自动stop服务，有时候需要retry

最后确认是否完成升级，升级后无法回退到旧版本。

HDP2.5已经为当前版本

在添加新服务的时候已经是新版本组件了

看了下hdfs中的数据还在

总结：

对于生产环境hadoop集群升级，绝对是个重量级工作，一定要有敬畏之心，以上升级步骤虽然看着不复杂，也很顺利的完成，我是在测试环境上进行的，没有一点心理负担，

如果是生产环境，不仅需要停止服务，如果在过程中出现问题，后果肯定无法想象，新版本组件也需要在升级前进行测试，业务是否可以运行正常，需要大量的测试实践工作，建议如果真要升级hadoop集群，还是考虑异地备份重要数据，避免数据丢失，比起数据丢失的风险，多买几台服务器进行数据备份，不算什么的，总之不到万不得已，轻易不要升级集群。