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Wiki  |   SVN  |   Apache Hadoop   | Last Published: 2016-10-02  | Version: 2.6.5

General

• Overview
• Single Node Setup
• Cluster Setup
• Hadoop Commands Reference
• FileSystem Shell
• Hadoop Compatibility
• FileSystem Specification

Common

• CLI Mini Cluster
• Native Libraries
• Superusers
• Secure Mode
• Service Level Authorization
• HTTP Authentication
• Hadoop KMS
• Tracing

HDFS

• HDFS User Guide
• HDFS Commands Reference
• High Availability With QJM
• High Availability With NFS
• Federation
• ViewFs Guide
• HDFS Snapshots
• HDFS Architecture
• Edits Viewer
• Image Viewer
• Permissions and HDFS
• Quotas and HDFS
• HFTP
• C API libhdfs
• WebHDFS REST API
• HttpFS Gateway
• Short Circuit Local Reads
• Centralized Cache Management
• HDFS NFS Gateway
• HDFS Rolling Upgrade
• Extended Attributes
• Transparent Encryption
• HDFS Support for Multihoming
• Archival Storage, SSD & Memory

MapReduce

• MapReduce Tutorial
• MapReduce Commands Reference
• Compatibilty between Hadoop 1.x and Hadoop 2.x
• Encrypted Shuffle
• Pluggable Shuffle/Sort
• Distributed Cache Deploy
• Hadoop Streaming
• Hadoop Archives
• DistCp

MapReduce REST APIs

• MR Application Master
• MR History Server

YARN

• YARN Architecture
• Capacity Scheduler
• Fair Scheduler
• ResourceManager Restart
• ResourceManager HA
• Web Application Proxy
• YARN Timeline Server
• Writing YARN Applications
• YARN Commands
• Scheduler Load Simulator
• NodeManager Restart
• DockerContainerExecutor

YARN REST APIs

• Introduction
• Resource Manager
• Node Manager

Auth

• Overview
• Examples
• Configuration
• Building

Reference

• Release Notes
• API docs
• Common CHANGES.txt
• HDFS CHANGES.txt
• MapReduce CHANGES.txt
• YARN CHANGES.txt
• Metrics

Configuration

• core-default.xml
• hdfs-default.xml
• mapred-default.xml
• yarn-default.xml
• Deprecated Properties

• Hadoop MapReduce Next Generation - Cluster Setup
  • Purpose
  • Prerequisites
  • Installation
  • Running Hadoop in Non-Secure Mode
    • Configuring Environment of Hadoop Daemons
    • Configuring the Hadoop Daemons in Non-Secure Mode
  • Hadoop Rack Awareness
  • Monitoring Health of NodeManagers
  • Slaves file
  • Logging
  • Operating the Hadoop Cluster
    • Hadoop Startup
    • Hadoop Shutdown
  • Operating the Hadoop Cluster
    • Hadoop Startup
    • Hadoop Shutdown
  • Web Interfaces

Hadoop MapReduce Next Generation - Cluster Setup

Purpose

This document describes how to install, configure and manage non-trivial Hadoop clusters ranging from a few nodes to extremely large clusters with thousands of nodes.

To play with Hadoop, you may first want to install it on a single machine (see Single Node Setup).

Prerequisites

Download a stable version of Hadoop from Apache mirrors.

Installation

Installing a Hadoop cluster typically involves unpacking the software on all the machines in the cluster or installing RPMs.

Typically one machine in the cluster is designated as the NameNode and another machine the as ResourceManager, exclusively. These are the masters.

The rest of the machines in the cluster act as both DataNode and NodeManager. These are the slaves.

Running Hadoop in Non-Secure Mode

The following sections describe how to configure a Hadoop cluster.

Configuration Files

Hadoop configuration is driven by two types of important configuration files:

• Read-only default configuration - core-default.xml, hdfs-default.xml, yarn-default.xml and mapred-default.xml.
• Site-specific configuration - conf/core-site.xml, conf/hdfs-site.xml, conf/yarn-site.xml and conf/mapred-site.xml.

Additionally, you can control the Hadoop scripts found in the bin/ directory of the distribution, by setting site-specific values via the conf/hadoop-env.sh and yarn-env.sh.

Site Configuration

To configure the Hadoop cluster you will need to configure the environment in which the Hadoop daemons execute as well as the configuration parameters for the Hadoop daemons.

The Hadoop daemons are NameNode/DataNode and ResourceManager/NodeManager.

Configuring Environment of Hadoop Daemons

Administrators should use the conf/hadoop-env.sh and conf/yarn-env.sh script to do site-specific customization of the Hadoop daemons' process environment.

At the very least you should specify the JAVA_HOME so that it is correctly defined on each remote node.

In most cases you should also specify HADOOP_PID_DIR and HADOOP_SECURE_DN_PID_DIR to point to directories that can only be written to by the users that are going to run the hadoop daemons. Otherwise there is the potential for a symlink attack.

Administrators can configure individual daemons using the configuration options shown below in the table:

Daemon	Environment Variable
NameNode	HADOOP_NAMENODE_OPTS
DataNode	HADOOP_DATANODE_OPTS
Secondary NameNode	HADOOP_SECONDARYNAMENODE_OPTS
ResourceManager	YARN_RESOURCEMANAGER_OPTS
NodeManager	YARN_NODEMANAGER_OPTS
WebAppProxy	YARN_PROXYSERVER_OPTS
Map Reduce Job History Server	HADOOP_JOB_HISTORYSERVER_OPTS

For example, To configure Namenode to use parallelGC, the following statement should be added in hadoop-env.sh :

  export HADOOP_NAMENODE_OPTS="-XX:+UseParallelGC ${HADOOP_NAMENODE_OPTS}"

Other useful configuration parameters that you can customize include:

• HADOOP_LOG_DIR / YARN_LOG_DIR - The directory where the daemons' log files are stored. They are automatically created if they don't exist.
• HADOOP_HEAPSIZE / YARN_HEAPSIZE - The maximum amount of heapsize to use, in MB e.g. if the varibale is set to 1000 the heap will be set to 1000MB. This is used to configure the heap size for the daemon. By default, the value is 1000. If you want to configure the values separately for each deamon you can use.

  Daemon	Environment Variable
  ResourceManager	YARN_RESOURCEMANAGER_HEAPSIZE
  NodeManager	YARN_NODEMANAGER_HEAPSIZE
  WebAppProxy	YARN_PROXYSERVER_HEAPSIZE
  Map Reduce Job History Server	HADOOP_JOB_HISTORYSERVER_HEAPSIZE

Configuring the Hadoop Daemons in Non-Secure Mode

This section deals with important parameters to be specified in the given configuration files:

• conf/core-site.xml

  Parameter	Value	Notes
  fs.defaultFS	NameNode URI	hdfs://host:port/
  io.file.buffer.size	131072	Size of read/write buffer used in SequenceFiles.

• conf/hdfs-site.xml
  • Configurations for NameNode:

    Parameter	Value	Notes
    dfs.namenode.name.dir	Path on the local filesystem where the NameNode stores the namespace and transactions logs persistently.	If this is a comma-delimited list of directories then the name table is replicated in all of the directories, for redundancy.
    dfs.namenode.hosts / dfs.namenode.hosts.exclude	List of permitted/excluded DataNodes.	If necessary, use these files to control the list of allowable datanodes.
    dfs.blocksize	268435456	HDFS blocksize of 256MB for large file-systems.
    dfs.namenode.handler.count	100	More NameNode server threads to handle RPCs from large number of DataNodes.

  • Configurations for DataNode:

    Parameter	Value	Notes
    dfs.datanode.data.dir	Comma separated list of paths on the local filesystem of a DataNode where it should store its blocks.	If this is a comma-delimited list of directories, then data will be stored in all named directories, typically on different devices.

• conf/yarn-site.xml
  • Configurations for ResourceManager and NodeManager:

    Parameter	Value	Notes
    yarn.acl.enable	true / false	Enable ACLs? Defaults to false.
    yarn.admin.acl	Admin ACL	ACL to set admins on the cluster. ACLs are of for comma-separated-usersspacecomma-separated-groups. Defaults to special value of * which means anyone. Special value of just space means no one has access.
    yarn.log-aggregation-enable	false	Configuration to enable or disable log aggregation

  • Configurations for ResourceManager:

    Parameter	Value	Notes
    yarn.resourcemanager.address	ResourceManager host:port for clients to submit jobs.	host:port  If set, overrides the hostname set in yarn.resourcemanager.hostname.
    yarn.resourcemanager.scheduler.address	ResourceManager host:port for ApplicationMasters to talk to Scheduler to obtain resources.	host:port  If set, overrides the hostname set in yarn.resourcemanager.hostname.
    yarn.resourcemanager.resource-tracker.address	ResourceManager host:port for NodeManagers.	host:port  If set, overrides the hostname set in yarn.resourcemanager.hostname.
    yarn.resourcemanager.admin.address	ResourceManager host:port for administrative commands.	host:port  If set, overrides the hostname set in yarn.resourcemanager.hostname.
    yarn.resourcemanager.webapp.address	ResourceManager web-ui host:port.	host:port  If set, overrides the hostname set in yarn.resourcemanager.hostname.
    yarn.resourcemanager.hostname	ResourceManager host.	host  Single hostname that can be set in place of setting all yarn.resourcemanager*address resources. Results in default ports for ResourceManager components.
    yarn.resourcemanager.scheduler.class	ResourceManager Scheduler class.	CapacityScheduler (recommended), FairScheduler (also recommended), or FifoScheduler
    yarn.scheduler.minimum-allocation-mb	Minimum limit of memory to allocate to each container request at the Resource Manager.	In MBs
    yarn.scheduler.maximum-allocation-mb	Maximum limit of memory to allocate to each container request at the Resource Manager.	In MBs
    yarn.resourcemanager.nodes.include-path / yarn.resourcemanager.nodes.exclude-path	List of permitted/excluded NodeManagers.	If necessary, use these files to control the list of allowable NodeManagers.

  • Configurations for NodeManager:

    Parameter	Value	Notes
    yarn.nodemanager.resource.memory-mb	Resource i.e. available physical memory, in MB, for given NodeManager	Defines total available resources on the NodeManager to be made available to running containers
    yarn.nodemanager.vmem-pmem-ratio	Maximum ratio by which virtual memory usage of tasks may exceed physical memory	The virtual memory usage of each task may exceed its physical memory limit by this ratio. The total amount of virtual memory used by tasks on the NodeManager may exceed its physical memory usage by this ratio.
    yarn.nodemanager.local-dirs	Comma-separated list of paths on the local filesystem where intermediate data is written.	Multiple paths help spread disk i/o.
    yarn.nodemanager.log-dirs	Comma-separated list of paths on the local filesystem where logs are written.	Multiple paths help spread disk i/o.
    yarn.nodemanager.log.retain-seconds	10800	Default time (in seconds) to retain log files on the NodeManager Only applicable if log-aggregation is disabled.
    yarn.nodemanager.remote-app-log-dir	/logs	HDFS directory where the application logs are moved on application completion. Need to set appropriate permissions. Only applicable if log-aggregation is enabled.
    yarn.nodemanager.remote-app-log-dir-suffix	logs	Suffix appended to the remote log dir. Logs will be aggregated to ${yarn.nodemanager.remote-app-log-dir}/${user}/${thisParam} Only applicable if log-aggregation is enabled.
    yarn.nodemanager.aux-services	mapreduce_shuffle	Shuffle service that needs to be set for Map Reduce applications.

  • Configurations for History Server (Needs to be moved elsewhere):

    Parameter	Value	Notes
    yarn.log-aggregation.retain-seconds	-1	How long to keep aggregation logs before deleting them. -1 disables. Be careful, set this too small and you will spam the name node.
    yarn.log-aggregation.retain-check-interval-seconds	-1	Time between checks for aggregated log retention. If set to 0 or a negative value then the value is computed as one-tenth of the aggregated log retention time. Be careful, set this too small and you will spam the name node.

• conf/mapred-site.xml
  • Configurations for MapReduce Applications:

    Parameter	Value	Notes
    mapreduce.framework.name	yarn	Execution framework set to Hadoop YARN.
    mapreduce.map.memory.mb	1536	Larger resource limit for maps.
    mapreduce.map.java.opts	-Xmx1024M	Larger heap-size for child jvms of maps.
    mapreduce.reduce.memory.mb	3072	Larger resource limit for reduces.
    mapreduce.reduce.java.opts	-Xmx2560M	Larger heap-size for child jvms of reduces.
    mapreduce.task.io.sort.mb	512	Higher memory-limit while sorting data for efficiency.
    mapreduce.task.io.sort.factor	100	More streams merged at once while sorting files.
    mapreduce.reduce.shuffle.parallelcopies	50	Higher number of parallel copies run by reduces to fetch outputs from very large number of maps.

  • Configurations for MapReduce JobHistory Server:

    Parameter	Value	Notes
    mapreduce.jobhistory.address	MapReduce JobHistory Server host:port	Default port is 10020.
    mapreduce.jobhistory.webapp.address	MapReduce JobHistory Server Web UI host:port	Default port is 19888.
    mapreduce.jobhistory.intermediate-done-dir	/mr-history/tmp	Directory where history files are written by MapReduce jobs.
    mapreduce.jobhistory.done-dir	/mr-history/done	Directory where history files are managed by the MR JobHistory Server.

Hadoop Rack Awareness

The HDFS and the YARN components are rack-aware.

The NameNode and the ResourceManager obtains the rack information of the slaves in the cluster by invoking an API resolve in an administrator configured module.

The API resolves the DNS name (also IP address) to a rack id.

The site-specific module to use can be configured using the configuration item topology.node.switch.mapping.impl. The default implementation of the same runs a script/command configured using topology.script.file.name. If topology.script.file.name is not set, the rack id /default-rack is returned for any passed IP address.

Monitoring Health of NodeManagers

Hadoop provides a mechanism by which administrators can configure the NodeManager to run an administrator supplied script periodically to determine if a node is healthy or not.

Administrators can determine if the node is in a healthy state by performing any checks of their choice in the script. If the script detects the node to be in an unhealthy state, it must print a line to standard output beginning with the string ERROR. The NodeManager spawns the script periodically and checks its output. If the script's output contains the string ERROR, as described above, the node's status is reported as unhealthy and the node is black-listed by the ResourceManager. No further tasks will be assigned to this node. However, the NodeManager continues to run the script, so that if the node becomes healthy again, it will be removed from the blacklisted nodes on the ResourceManager automatically. The node's health along with the output of the script, if it is unhealthy, is available to the administrator in the ResourceManager web interface. The time since the node was healthy is also displayed on the web interface.

The following parameters can be used to control the node health monitoring script in conf/yarn-site.xml.

Parameter	Value	Notes
yarn.nodemanager.health-checker.script.path	Node health script	Script to check for node's health status.
yarn.nodemanager.health-checker.script.opts	Node health script options	Options for script to check for node's health status.
yarn.nodemanager.health-checker.script.interval-ms	Node health script interval	Time interval for running health script.
yarn.nodemanager.health-checker.script.timeout-ms	Node health script timeout interval	Timeout for health script execution.

The health checker script is not supposed to give ERROR if only some of the local disks become bad. NodeManager has the ability to periodically check the health of the local disks (specifically checks nodemanager-local-dirs and nodemanager-log-dirs) and after reaching the threshold of number of bad directories based on the value set for the config property yarn.nodemanager.disk-health-checker.min-healthy-disks, the whole node is marked unhealthy and this info is sent to resource manager also. The boot disk is either raided or a failure in the boot disk is identified by the health checker script.

Slaves file

Typically you choose one machine in the cluster to act as the NameNode and one machine as to act as the ResourceManager, exclusively. The rest of the machines act as both a DataNode and NodeManager and are referred to as slaves.

List all slave hostnames or IP addresses in your conf/slaves file, one per line.

Logging

Hadoop uses the Apache log4j via the Apache Commons Logging framework for logging. Edit the conf/log4j.properties file to customize the Hadoop daemons' logging configuration (log-formats and so on).

Operating the Hadoop Cluster

Once all the necessary configuration is complete, distribute the files to the HADOOP_CONF_DIR directory on all the machines.

Hadoop Startup

To start a Hadoop cluster you will need to start both the HDFS and YARN cluster.

Format a new distributed filesystem:

$ $HADOOP_PREFIX/bin/hdfs namenode -format <cluster_name>

Start the HDFS with the following command, run on the designated NameNode:

$ $HADOOP_PREFIX/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR --script hdfs start namenode

Run a script to start DataNodes on all slaves:

$ $HADOOP_PREFIX/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR --script hdfs start datanode

Start the YARN with the following command, run on the designated ResourceManager:

$ $HADOOP_YARN_HOME/sbin/yarn-daemon.sh --config $HADOOP_CONF_DIR start resourcemanager

Run a script to start NodeManagers on all slaves:

$ $HADOOP_YARN_HOME/sbin/yarn-daemon.sh --config $HADOOP_CONF_DIR start nodemanager

Start a standalone WebAppProxy server. If multiple servers are used with load balancing it should be run on each of them:

$ $HADOOP_YARN_HOME/sbin/yarn-daemon.sh start proxyserver --config $HADOOP_CONF_DIR

Start the MapReduce JobHistory Server with the following command, run on the designated server:

$ $HADOOP_PREFIX/sbin/mr-jobhistory-daemon.sh start historyserver --config $HADOOP_CONF_DIR

Hadoop Shutdown

Stop the NameNode with the following command, run on the designated NameNode:

$ $HADOOP_PREFIX/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR --script hdfs stop namenode

Run a script to stop DataNodes on all slaves:

$ $HADOOP_PREFIX/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR --script hdfs stop datanode

Stop the ResourceManager with the following command, run on the designated ResourceManager:

$ $HADOOP_YARN_HOME/sbin/yarn-daemon.sh --config $HADOOP_CONF_DIR stop resourcemanager

Run a script to stop NodeManagers on all slaves:

$ $HADOOP_YARN_HOME/sbin/yarn-daemon.sh --config $HADOOP_CONF_DIR stop nodemanager

Stop the WebAppProxy server. If multiple servers are used with load balancing it should be run on each of them:

$ $HADOOP_YARN_HOME/sbin/yarn-daemon.sh stop proxyserver --config $HADOOP_CONF_DIR

Stop the MapReduce JobHistory Server with the following command, run on the designated server:

$ $HADOOP_PREFIX/sbin/mr-jobhistory-daemon.sh stop historyserver --config $HADOOP_CONF_DIR

Operating the Hadoop Cluster

Once all the necessary configuration is complete, distribute the files to the HADOOP_CONF_DIR directory on all the machines.

This section also describes the various Unix users who should be starting the various components and uses the same Unix accounts and groups used previously:

Hadoop Startup

To start a Hadoop cluster you will need to start both the HDFS and YARN cluster.

Format a new distributed filesystem as hdfs:

[hdfs]$ $HADOOP_PREFIX/bin/hdfs namenode -format <cluster_name>

Start the HDFS with the following command, run on the designated NameNode as hdfs:

[hdfs]$ $HADOOP_PREFIX/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR --script hdfs start namenode

Run a script to start DataNodes on all slaves as root with a special environment variable HADOOP_SECURE_DN_USER set to hdfs:

[root]$ HADOOP_SECURE_DN_USER=hdfs $HADOOP_PREFIX/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR --script hdfs start datanode

Start the YARN with the following command, run on the designated ResourceManager as yarn:

[yarn]$ $HADOOP_YARN_HOME/sbin/yarn-daemon.sh --config $HADOOP_CONF_DIR start resourcemanager

Run a script to start NodeManagers on all slaves as yarn:

[yarn]$ $HADOOP_YARN_HOME/sbin/yarn-daemon.sh --config $HADOOP_CONF_DIR start nodemanager

Start a standalone WebAppProxy server. Run on the WebAppProxy server as yarn. If multiple servers are used with load balancing it should be run on each of them:

[yarn]$ $HADOOP_YARN_HOME/bin/yarn start proxyserver --config $HADOOP_CONF_DIR

Start the MapReduce JobHistory Server with the following command, run on the designated server as mapred:

[mapred]$ $HADOOP_PREFIX/sbin/mr-jobhistory-daemon.sh start historyserver --config $HADOOP_CONF_DIR

Hadoop Shutdown

Stop the NameNode with the following command, run on the designated NameNode as hdfs:

[hdfs]$ $HADOOP_PREFIX/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR --script hdfs stop namenode

Run a script to stop DataNodes on all slaves as root:

[root]$ $HADOOP_PREFIX/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR --script hdfs stop datanode

Stop the ResourceManager with the following command, run on the designated ResourceManager as yarn:

[yarn]$ $HADOOP_YARN_HOME/sbin/yarn-daemon.sh --config $HADOOP_CONF_DIR stop resourcemanager

Run a script to stop NodeManagers on all slaves as yarn:

[yarn]$ $HADOOP_YARN_HOME/sbin/yarn-daemon.sh --config $HADOOP_CONF_DIR stop nodemanager

Stop the WebAppProxy server. Run on the WebAppProxy server as yarn. If multiple servers are used with load balancing it should be run on each of them:

[yarn]$ $HADOOP_YARN_HOME/bin/yarn stop proxyserver --config $HADOOP_CONF_DIR

Stop the MapReduce JobHistory Server with the following command, run on the designated server as mapred:

[mapred]$ $HADOOP_PREFIX/sbin/mr-jobhistory-daemon.sh stop historyserver --config $HADOOP_CONF_DIR

Web Interfaces

Once the Hadoop cluster is up and running check the web-ui of the components as described below:

Daemon	Web Interface	Notes
NameNode	http://nn_host:port/	Default HTTP port is 50070.
ResourceManager	http://rm_host:port/	Default HTTP port is 8088.
MapReduce JobHistory Server	http://jhs_host:port/	Default HTTP port is 19888.