kandi X-RAY | MapReduce Summary
kandi X-RAY | MapReduce Summary
Top functions reviewed by kandi - BETA
- Main entry point
MapReduce Key Features
MapReduce Examples and Code Snippets
Trending Discussions on MapReduce
I had used the below command in GCP Shell terminal to create a project wordcount...
ANSWERAnswered 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
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:
ANSWERAnswered 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:
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....
ANSWERAnswered 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.
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:
(offset, line) ==(Map)==> (word|file, 1) ==(Reduce)==> (word|file, n)
(word|file, n) ==(Map)==> (file, word|n) ==(Reduce)==> (word|file, n|N)
(word|file, n|N) ==(Map)==> (word, file|n|N|1) ==(Reduce)==> (word|file, n|N|M)
(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:
For the MR2 phase, I expect:
hello|hdfs://....... 2|192 but I'm getting
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.
Here is my MR1 code:...
ANSWERAnswered 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:
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:...
ANSWERAnswered 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
- Apache CouchDB v. 3.1.1
- about 5 GB of twitter data have been dumped in partitions
Map reduce function that I have written:...
ANSWERAnswered 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.
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. https://oozie.apache.org/docs/5.2.1/DG_QuickStart.html
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. http://zhongyaonan.com/hadoop-tutorial/setting-up-hadoop-2-6-on-mac-osx-yosemite.html
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)
ANSWERAnswered 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.
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.
In order to use infix notation, I have the following example of scala code....
ANSWERAnswered 2021-May-07 at 11:16
No, because default arguments are only used if argument list is provided
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:...
ANSWERAnswered 2021-May-06 at 02:43
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.
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. https://www.kaggle.com/datasnaek/youtube-new?select=INvideos.csv link to dataset
ANSWERAnswered 2021-May-04 at 06:03
It just seems as
output_dir variable contains incorrect path:
No vulnerabilities reported
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 maven.apache.org. For Gradle installation, please refer gradle.org .
Reuse Trending Solutions
Subscribe to our newsletter for trending solutions and developer bootcamps
Share this Page