什么是“客户” Hadoop / HDFS究竟意味着什么？ [英] What does "Client" exactly mean for Hadoop / HDFS?
问题描述
我理解它背后的一般概念，但我想要更多的澄清以及对客户是什么的清晰定义。
例如，如果我只是在终端上编写hdfs命令，它仍然是一个客户端吗？
基本文件系统客户端 hdfs dfs 用于连接到Hadoop文件系统，执行基本的文件相关任务。它使用ClientProtocol与NameNode守护程序进行通信，并直接连接到DataNode以读取/写入块数据。
要在HDFS上执行管理任务，有 hdfs dfsadmin 。对于HA相关任务， hdfs haadmin 。
有类似的客户可用于执行 YARN 相关任务。
这些客户端可以在安装了Hadoop的节点上使用各自的CLI命令进行调用，并且具有连接到Hadoop文件系统所需的必要配置和库。这些节点通常称为Hadoop客户端。
例如，如果我只是在终端上写一个hdfs命令，它是
还是一个客户端吗？
从技术上讲，是。如果您可以使用 hdfs 命令访问FS，则节点具有Hadoop客户端所需的配置和库。
PS： API也可用于以编程方式创建这些客户端。
I understand the general concept behind it, but I would like more clarification and a clear-cut definition of what a "client" is.
For example, if I just write an hdfs command on the Terminal, is it still a "client" ?
Client in Hadoop refers to the Interface used to communicate with the Hadoop Filesystem. There are different type of Clients available with Hadoop to perform different tasks.
The basic filesystem client hdfs dfs is used to connect to a Hadoop Filesystem and perform basic file related tasks. It uses the ClientProtocol to communicate with a NameNode daemon, and connects directly to DataNodes to read/write block data.
To perform administrative tasks on HDFS, there is hdfs dfsadmin. For HA related tasks, hdfs haadmin.
There are similar clients available for performing YARN related tasks.
These Clients can be invoked using their respective CLI commands from a node where Hadoop is installed and has the necessary configurations and libraries required to connect to a Hadoop Filesystem. Such nodes are often referred as Hadoop Clients.
For example, if I just write an hdfs command on the Terminal, is it still a "client" ?
Technically, Yes. If you are able to access the FS using the hdfs command, then the node has the configurations and libraries required to be a Hadoop Client.
PS: APIs are also available to create these Clients programmatically.
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