Hadoop Elephant Safari 010- using Eclipse to view Hadoop source code sinomThis is what I'm using. hadoop-1.1.2.tar.gz , this file can be downloaded at the following address:Official Address: http://archive.apache.org/dist/hadoop/core/hadoop-1.1.2/1. Unzip the
Reprint Please specify source: http://blog.csdn.net/l1028386804/article/details/51538611
The following warning message appears when you configure Hadoop to start:
WARN util. nativecodeloader:unable to load Native-hadoop library for your platform ... using Builtin-java classes where applicableThe question is where. Some people say that this is the pre-compiled Hadoop
Build a Hadoop development environment for Fedora 20
1. configuration information:
Operating System: fedora 20X86
Eclipse version: eclipse-jee-helios-SR2-linux-gtk.tar.gz (preferably use Galileo or Helios, otherwise there may be compatibility issues)
Hadoop version: hadoop-1.1.2.tar.gz
Ant: apache-ant-1.9.3-bin.tar.gz
2. Compile the
First, ready to run the required jar package1) Avro-1.7.4.jar2) Commons-cli-1.2.jar3) Commons-codec-1.4.jar4) Commons-collections-3.2.1.jar5) Commons-compress-1.4.1.jar6) Commons-configuration-1.6.jar7) Commons-io-2.4.jar8) Commons-lang-2.6.jar9) Commons-logging-1.2.jar) Commons-math3-3.1.1.jarOne) Commons-net-3.1.jarCurator-client-2.7.1.jar)Curator-recipes-2.7.1.jar)Gson-2.2.4.jar)Guava-20.0.jar)Hadoop-annotations-2.8.0.jar)
When Hadoop was started today, it was discovered that Datanode could not boot, and the following errors were found in the View log: Java.io.ioexception:file/opt/hadoop/tmp/mapred/system/jobtracker.info could only is replicated to 0 nodes, instead o F 1 at Org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getAdditionalBlock (fsnamesystem.java:1271) at Org.apache.hadoop.hdfs.server.namenode.NameNode.addBl
This morning, I helped a new person remotely build a hadoop cluster (1. in versions X or earlier than 0.22), I am deeply touched. Here I will write down the simplest Apache hadoop construction method and provide help to new users. I will try my best to explain it in detail. Click here to view the avatorhadoop construction steps.
1. Environment preparation:
1 ). machine preparation: the target machine must b
What is hadoop?
Before doing something, the first step is to know what, then why, and finally how ). However, after many years of project development, many developers get used to how first, then what, and finally why. This will only make them impetuous, at the same time, technologies are often misused in unsuitable scenarios.
The core designs in the hadoop framework are mapreduce and HDFS. The idea of mapre
Hadoop FS: The widest range of users can operate any file system.
Hadoop DFS and HDFs dfs: only HDFs file system related (including operations with local FS) can be manipulated, the former has been deprecated, generally using the latter.
The following reference from StackOverflow
Following are the three commands which appears same but have minute differences Hadoop
job failed to run
Delete temp directory
The
setuptask
Task initializes
without any action. It was originally necessary to create the Side-effect file in the temp directory, but it was created when it was used (create on demand)
needstaskcommit
returns True if Side-effect file exists
committask
task successfully run complete
commit results, move Side-effect file to ${mapred.out.dir} directory
Run Hadoop WordCount. jar in Linux.
Run Hadoop WordCount in Linux
Enter the shortcut key of Ubuntu terminal: ctrl + Alt + t
Hadoop launch command: start-all.sh
The normal execution results are as follows:
Hadoop @ HADOOP :~ $ Start-all.sh
Warning: $ HADOOP_HOME is deprecate
Now that namenode and datanode1 are available, add the node datanode2 first step: Modify the Host Name of the node to be added hadoop @ datanode1 :~ $ Vimetchostnamedatanode2 Step 2: Modify the host file hadoop @ datanode1 :~ $ Vimetchosts192.168.8.4datanode2127.0.0.1localhost127.0
Now that namenode and datanode1 are available, add the node datanode2 first step: Modify the Host Name of the node to be added
Once Hadoop is installed, you will often be prompted with a warning:
WARN util. nativecodeloader:unable to load Native-hadoop library for your platform ...
Using Builtin-java classes where applicableSearched a lot of articles, all say is related to the system bit number, I use CentOS 6.5 64-bit operating system.
The first two days in the Docker image to find a step to solve the problem, the pro tried
(1) First create Java projectSelect File->new->java Project on the Eclipse menu.and is named UploadFile.(2) Add the necessary Hadoop jar packagesRight-click the JRE System Library and select Configure build path under Build path.Then select Add External Jars. Add the jar package and all the jar packages under Lib to your extracted Hadoop source directory.All jar packages in the Lib directory.(3) Join the Up
This article has agreed:Dn:datanodeTt:tasktrackerNn:namenodeSnn:secondry NameNodeJt:jobtrackerThis article describes the communication protocol between the Hadoop nodes and the client.Hadoop communication is based on RPC, a detailed introduction to RPC you can refer to "Hadoop RPC mechanism introduce Avro into the Hadoop RPC mechanism"Communication between nodes
This article will go on to the wordcount example in the previous article to abstract the simplest process and explore how the System Scheduling works in the mapreduce operation process.
Scenario 1: Separate data from operations
Wordcount is the hadoop helloworld program. It counts the number of times each word appears. The process is as follows:
Now I will describe this process in text.
1. The client submits a job and sends mapreduce programs and dat
Exception Analysis
1. "cocould only be replicated to 0 nodes, instead of 1" Exception
(1) exception description
The configuration above is correct and the following steps have been completed:
[Root @ localhost hadoop-0.20.0] # bin/hadoop namenode-format
[Root @ localhost hadoop-0.20.0] # bin/start-all.sh
At this time, we can see that the five processes jobtracke
Hadoop datanode node time-out settingDatanode process death or network failure caused datanode not to communicate with Namenode,Namenode will not immediately determine the node as death, after a period of time, this period is temporarily known as the timeout length.The default timeout period for HDFs is 10 minutes + 30 seconds. If the definition time-out is timeout, the time-out is calculated as:Timeout = 2 * heartbeat.recheck.interval + ten * dfs.hea
This section mainly analyzes the principles and processes of mapreduce.
Complete release directory of "cloud computing distributed Big Data hadoop hands-on"
Cloud computing distributed Big Data practical technology hadoop exchange group:312494188Cloud computing practices will be released in the group every day. welcome to join us!
You must at least know the following points about mapreduce:
1. map
1. Concept2. ReferencesImprove the MapReduce job Efficiency Note II of Hadoop (use combiner as much as possible): Http://sishuo (k). com/forum/blogpost/list/5829.htmlHadoop Learning notes -8.combiner and custom Combiner:http://www.tuicool.com/articles/qazujavHadoop in-depth learning: combiner:http://blog.csdn.net/cnbird2008/article/details/23788233(mean Scene) 0Hadoop using combiner to improve Map/reduce program efficiency: http://blog.csdn.net/jokes0
from the Agent cannot be received.请确保主机的名称已正确配置。请确保端口 7182 可在 Cloudera Manager Server 上访问(检查防火墙规则)。请确保正在添加的主机上的端口 9000 和 9001 空闲。检查正在添加的主机上 /var/log/cloudera-scm-agent/ 中的代理日志(某些日志可在安装详细信息中找到)。Could not find config file/var/run/cloudera-scm-agent/supervisor/supervisord.confThe solution to this error is:After we have modified our/etc/hosts file, we have to restart the service cloudera-scm-agentService Cloudera-scm-agent Restart8. Cannot be displayed after installing cm9, 7180 interface cannot op
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