MapReduce | 清华大数据作业MapReduce处理几百个G的JSON数据

 by   datamaning Java Version: Current License: No License

kandi X-RAY | MapReduce Summary

kandi X-RAY | MapReduce Summary

MapReduce is a Java library. MapReduce has no bugs, it has no vulnerabilities and it has low support. However MapReduce build file is not available. You can download it from GitHub.


            kandi-support Support

              MapReduce has a low active ecosystem.
              It has 32 star(s) with 21 fork(s). There are 3 watchers for this library.
              It had no major release in the last 6 months.
              MapReduce has no issues reported. There are no pull requests.
              It has a neutral sentiment in the developer community.
              The latest version of MapReduce is current.

            kandi-Quality Quality

              MapReduce has 0 bugs and 0 code smells.

            kandi-Security Security

              MapReduce has no vulnerabilities reported, and its dependent libraries have no vulnerabilities reported.
              MapReduce code analysis shows 0 unresolved vulnerabilities.
              There are 0 security hotspots that need review.

            kandi-License License

              MapReduce does not have a standard license declared.
              Check the repository for any license declaration and review the terms closely.
              Without a license, all rights are reserved, and you cannot use the library in your applications.

            kandi-Reuse Reuse

              MapReduce releases are not available. You will need to build from source code and install.
              MapReduce has no build file. You will be need to create the build yourself to build the component from source.
              Installation instructions are not available. Examples and code snippets are available.
              MapReduce saves you 60 person hours of effort in developing the same functionality from scratch.
              It has 156 lines of code, 7 functions and 2 files.
              It has low code complexity. Code complexity directly impacts maintainability of the code.

            Top functions reviewed by kandi - BETA

            kandi has reviewed MapReduce and discovered the below as its top functions. This is intended to give you an instant insight into MapReduce implemented functionality, and help decide if they suit your requirements.
            • Main entry point
            Get all kandi verified functions for this library.

            MapReduce Key Features

            No Key Features are available at this moment for MapReduce.

            MapReduce Examples and Code Snippets

            No Code Snippets are available at this moment for MapReduce.

            Community Discussions


            Import org.apache statement cannot be resolved in GCP Shell
            Asked 2021-Jun-10 at 21:48

            I had used the below command in GCP Shell terminal to create a project wordcount



            Answered 2021-Jun-10 at 21:48

            I'd suggest finding an archetype for creating MapReduce applications, otherwise, you need to add hadoop-client as a dependency in your pom.xml



            Map-reduce functional outline
            Asked 2021-Jun-02 at 02:15

            Note: this is more a basic programming question and nothing about the Hadoop or Map/Reduce methods of "big data processing".

            Let's take a sequence (1 2 3 4 5):

            To map it to some function, let's say square, I can do something like:



            Answered 2021-Jun-02 at 02:15

            To give you the intuition, we need to step away (briefly) from a concrete implementation in code. MapReduce (and I'm not just talking about a particular implementation) is about the shape of the problem.

            Say we have a linear data structure (list, array, whatever) of xs, and we have a transform function we want to apply to each of them, and we have an aggregation function that can be represented as repeated application of an associative pairwise combination:



            How to use apache-dolphinscheduler's queue?
            Asked 2021-May-22 at 14:50

            I am confused about the apache-dolphinscheduler's queue, as in user-guide, the queue is used for spark、mapreduce. But I want to use python code product seeds to queue and another python code in workers pull seeds from queue and run tasks. Can you tell me whether dolphinscheduler can handle it or I must use another tools, such as Redis? Thanks.



            Answered 2021-May-22 at 14:50

            as what you said, you need to use another tools. the queue designed to choose corresponding queue which exists in hadoop yarn cluster.



            Weird behaviour in MapReduce, values get overwritten
            Asked 2021-May-20 at 12:08

            I've been trying to implement the TfIdf algorithm using MapReduce in Hadoop. My TFIDF takes place in 4 steps (I call them MR1, MR2, MR3, MR4). Here are my input/outputs:

            MR1: (offset, line) ==(Map)==> (word|file, 1) ==(Reduce)==> (word|file, n)

            MR2: (word|file, n) ==(Map)==> (file, word|n) ==(Reduce)==> (word|file, n|N)

            MR3: (word|file, n|N) ==(Map)==> (word, file|n|N|1) ==(Reduce)==> (word|file, n|N|M)

            MR4: (word|file, n|N|M) ==(Map)==> (word|file, n/N log D/M)

            Where n = number of (word, file) distinct pairs, N = number of words in each file, M = number of documents where each word appear, D = number of documents.

            As of the MR1 phase, I'm getting the correct output, for example: hello|hdfs://..... 2

            For the MR2 phase, I expect: hello|hdfs://....... 2|192 but I'm getting 2|hello|hdfs://...... 192|192

            I'm pretty sure my code is correct, every time I try to add a string to my "value" in the reduce phase to see what's going on, the same string gets "teleported" in the key part.

            Example: gg|word|hdfs://.... gg|192

            Here is my MR1 code:



            Answered 2021-May-20 at 12:08

            It's the Combiner's fault. You are specifying in the driver class that you want to use MR2Reducer both as a Combiner and a Reducer in the following commands:



            ZK hbase replication node grows exponentially though hbase datas properly replication for peers
            Asked 2021-May-17 at 14:27

            In the hbase-1.4.10, I have enabled replication for all tables and configured the peer_id. the list_peers provide the below result:



            Answered 2021-May-17 at 14:27

            The above issue has been already filed under the below issue.


            Upgrading to 1.4.11 fixed the zknode grows exponetially



            timeout with couchdb mapReduce when database is huge
            Asked 2021-May-13 at 14:18


            • Apache CouchDB v. 3.1.1
            • about 5 GB of twitter data have been dumped in partitions

            Map reduce function that I have written:



            Answered 2021-May-13 at 14:18

            So, I thought of answering my own question, after realizing my mistake. The answer to this is simple. It just needed more time, as the indexing takes a lot of time. you can see the metadata to see the db data being indexed.



            Apache Oozie throws ClassNotFoundException (org.apache.hadoop.conf.Configuration) during startup
            Asked 2021-May-09 at 23:25

            I built the Apache Oozie 5.2.1 from the source code in my MacOS and currently having trouble running it. The ClassNotFoundException indicates a missing class org.apache.hadoop.conf.Configuration but it is available in both libext/ and the Hadoop file system.

            I followed the 1st approach given here to copy Hadoop libraries to Oozie binary distro.

            I downloaded Hadoop 2.6.0 distro and copied all the jars to libext before running Oozie in addition to other configs, etc as specified in the following blog.


            This is how I installed Hadoop in MacOS. Hadoop 2.6.0 is working fine.

            This looks pretty basic issue but could not find why the jar/class in libext is not loaded.

            • OS: MacOS 10.14.6 (Mojave)
            • JAVA: 1.8.0_191
            • Hadoop: 2.6.0 (running in the Mac)


            Answered 2021-May-09 at 23:25

            I was able to sort the above issue and few other ClassNotFoundException by copying the following jar files from extlib to lib. Both folder are in oozie_install/oozie-5.2.1.

            • libext/hadoop-common-2.6.0.jar
            • libext/commons-configuration-1.6.jar
            • libext/hadoop-mapreduce-client-core-2.6.0.jar
            • libext/hadoop-hdfs-2.6.0.jar

            While I am not sure how many more jars need to be moved from libext to lib while I try to run an example workflow/job in oozie. This fix brought up Oozie web site at http://localhost:11000/oozie/

            I am also not sure why Oozie doesn't load the libraries in the libext/ folder.



            How to declare in scala a default param in a method of an implicit class
            Asked 2021-May-07 at 11:16

            In order to use infix notation, I have the following example of scala code.



            Answered 2021-May-07 at 11:16

            No, because default arguments are only used if argument list is provided



            Function is not recognized in map reduce command, mongoDB (javascript)
            Asked 2021-May-06 at 02:43

            I have some problems with a map reduce I tried to do in MongoDB. A function I defined seems to not be visible in the reduce function. This is my code:



            Answered 2021-May-06 at 02:43

            The function was defined in the locally running javascript instance, not the server.

            In order for that function to be callable from the server you will need to either predefine it there or include the definition inside the reduce function.

            But don't do that.

            From the reduce function documentation:

            The reduce function should not access the database, even to perform read operations.

            Look at using aggregation with a $lookup stage instead.



            spark submit java.lang.IllegalArgumentException: Can not create a Path from an empty string
            Asked 2021-May-04 at 06:03

            i am getting this error when i do spark submit. java.lang.IllegalArgumentException: Can not create a Path from an empty string i am using spark version 2.4.7 hadoop version 3.3.0 intellji ide jdk 8 first i was getting class not found error which i solved now i am getting this error Is it because of the dataset or something else. link to dataset




            Answered 2021-May-04 at 06:03

            It just seems as output_dir variable contains incorrect path:


            Community Discussions, Code Snippets contain sources that include Stack Exchange Network


            No vulnerabilities reported

            Install MapReduce

            You can download it from GitHub.
            You can use MapReduce like any standard Java library. Please include the the jar files in your classpath. You can also use any IDE and you can run and debug the MapReduce component as you would do with any other Java program. Best practice is to use a build tool that supports dependency management such as Maven or Gradle. For Maven installation, please refer For Gradle installation, please refer .


            For any new features, suggestions and bugs create an issue on GitHub. If you have any questions check and ask questions on community page Stack Overflow .
            Find more information at:

            Find, review, and download reusable Libraries, Code Snippets, Cloud APIs from over 650 million Knowledge Items

            Find more libraries
          • HTTPS


          • CLI

            gh repo clone datamaning/MapReduce

          • sshUrl


          • Stay Updated

            Subscribe to our newsletter for trending solutions and developer bootcamps

            Agree to Sign up and Terms & Conditions

            Share this Page

            share link

            Consider Popular Java Libraries


            by CyC2018


            by Snailclimb


            by MisterBooo


            by spring-projects

            Try Top Libraries by datamaning


            by datamaningHTML


            by datamaningPython


            by datamaningPython


            by datamaningJavaScript


            by datamaningPython