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Asbury Hadoop Overview


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Slides from Hadoop workshop on 3/8/2014

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Asbury Hadoop Overview

  1. 1. Overview, HDFS and Map/Reduce Hadoop Workshop 1
  2. 2. - SW Engineer who has worked as designer / developer on NOSQL (Mongo, Cassandra, Hadoop) - Consultant – HBO, ACS, ACXIOM (GM), AT&T - Specialize in SW Development, architecture and training - Currently working with Cassandra, Storm, Kafka, Node.js and MongoDB - Hadoop Workshop 2
  3. 3. • Intros, Agenda and software • Hadoop Overview, Ecosystem and Use Cases • HDFS – hadoop distributed file system • Map/Reduce – how to create and use • Hadoop Streaming and Pig • A little bit about the supporting cast, the Hadoop Eco- System Hadoop Workshop 3
  4. 4. What is you experience and interests with Big Data, NoSql, Hadoop and Software Development? Hadoop Workshop 4
  5. 5. • Cloudera Quickstart VM content/cloudera-docs/DemoVMs/Cloudera-QuickStart- VM/cloudera_quickstart_vm.html We are using Cloudera, there is also HortonWorks, MapR, Apache Hadoop and multitide of other players. Hadoop Workshop 5
  6. 6. • The reason for products like Hadoop is the emergence of Big Data. • Big Data is not new, but is more common now, we are more capable of collecting. • Big Data is not just about size. It is also frequency of delivery and the unstructured nature. • RDMS was about structure and definition. It fails in handling data requirements in many cases. Hadoop Workshop 6
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  9. 9. • Not Only SQL. Doesn‟t mean “No” SQL • Category of products developed to handle big data demands. • Built to handle distributed architecture • Take advantage of large clusters of commodity hardware • There are trade-offs, live with CAP Theroem Hadoop Workshop 9
  10. 10. • Hadoop itself is not a NoSQL product • Hbase, which is part of Hadoop eco-system is a NoSQL product. • Hadoop is a computing framework (a lot more to come) and typically runs on a cluster of machines • NoSQL products example Cassandra, MongoDB, Riak, CouchDB and Hbase. Hadoop Workshop 10
  11. 11. Where does the name come from? The name my kid gave a stuffed yellow elephant. Short, relatively easy to spell and pronounce, meaningless, and not used elsewhere: those are my naming criteria. Kids are good at generating such. Googol is a kid’s term. • This is from Doug Cutting, inventor of Hadoop (also of Lucene the search engine and Nutch (along with Mike Cafarella) which a web crawler and various other items). Hadoop was created to process data created by Nutch. Hadoop Workshop 11
  12. 12. • Hadoop is an open source framework for processing large amounts of data in batch. • Designed from the ground up to scale out as you add hardware. • Hadoop Core has three main components: • Commons • HDFS • MapReduce Hadoop Workshop 12
  13. 13. • The first is called Commons and contains (as the name implied) common functionality. • In addition Hadoop has its own file system called HDFS that is made to be fault tolerant and supplies the cornerstone to let it run on commodity hardware. • The final component making up the Hadoop system is called MapReduce and it implements the model that allows processing the data in a parallel manner. Hadoop Workshop 13
  14. 14. • Hadoop Distributed File System (aka HDFS, or Hadoop DFS) • Runs on top of regular OS file system, typically Linux ext3 • Fixed-size blocks (64MB by default) that are replicated • Write once, read many; optimized for streaming in and out Hadoop Workshop 14
  15. 15. • Responsible for running a job in parallel on many servers • Handles re-trying a task that fails • Validating complete results • Jobs consist of special “map” and “reduce” operations Hadoop Workshop 15
  16. 16. • Has one “master” server - high quality, beefy box. • NameNode process - manages file system • JobTracker process - manages tasks • Has multiple “slave” servers - commodity hardware. • DataNode process - manages file system blocks on local drives • TaskTracker process - runs tasks on server • Uses high speed network between all servers Hadoop Workshop 16
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  18. 18. • Hadoop is a lot more than HDFS and MapReduce. • There is an large (and ever growing) Eco-System built up around Hadoop. • These are for making MapReduce less complex, Montoring and Job Control, Adding Persistence systems and adding Real-Time capabilities. Hadoop Workshop 18
  19. 19. • Avro A serialization system for efficient, cross-language RPC and persistent data storage. • Mahout Machine Learning System • Pig High Level query langiage (PigLatin) that creates map reduce jobs. • Hive A distributed data warehouse. Hive manages data stored in HDFS and provides a query language based on SQL (and which is translated by the runtime engine to MapReduce jobs) for querying the data. Hadoop Workshop 19
  20. 20. • HBase A distributed, column-oriented database. HBase uses HDFS for its underlying storage, and supports both batch-style computations using MapReduce and point queries (random reads). • ZooKeeper A distributed, highly available coordination service. ZooKeeper provides primitives such as distributed locks that can be used for building distributed applications. • Sqoop A tool for efficient bulk transfer of data between structured data stores (such as relational databases) and HDFS. • Oozie A service for running and scheduling workflows of Hadoop jobs (including Map- Reduce, Pig, Hive, and Sqoop jobs). Hadoop Workshop 20
  21. 21. • A new MapReduce runtime, called MapReduce 2, implemented on a new system called YARN (Yet Another Resource Negotiator), which is a general resource management system for running distributed applications. MR2 replaces the “classic” runtime in previous releases. • HDFS federation, which partitions the HDFS namespace across multiple namenodes to support clusters with very large numbers of files. • HDFS high-availability, which removes the namenode as a single point of failure by supporting standby namenodes for failover. Hadoop Workshop 21
  22. 22. • YARN was added in Hadoop 2 • It is a resource-management platform responsible for managing compute resources in clusters and using them for scheduling of users' applications • YARN can run applications that do not follow the MapReduce model, unlike the original MapReduce model (MR1) • YARN provides the daemons and APIs necessary to develop generic distributed applications of any kind, handles and schedules resource requests (such as memory and CPU) from such applications, and supervises their execution Hadoop Workshop 22
  23. 23. Any questions on the Hadoop Overview? Hadoop Workshop 23
  24. 24. • Hadoop Distributed File System • Single Name Node and a Cluster of Datanodes • Stores large files (+ GB) across nodes • Reliability is through replication, default value is 3. Hadoop Workshop 24
  25. 25. • Master and in Hadoop 1 is a SPOF. • In Hadoop 2 added failover to prevent the SPOF aspect • Contains • Directory Tree of all the files • Keeps track of where all the data resides across the cluster • For really large clusters, tracking these files becomes an issue, Hadoop 2 added NameNode Federation to fix that. Hadoop Workshop 25
  26. 26. • http://localhost:50070/ • Can view information on namenode, blocks and view logs. Hadoop Workshop 26
  27. 27. • Files stored on HDFS are chunked and stored as blocks on DataNode • Manages storage attached to the nodes that they run on. • Data never flows through NameNode, only DataNodes Hadoop Workshop 27
  28. 28. • Typically file system blocks are a few kilobytes. • HDFS uses block size typically 64MB or 128MB. • The large size minimizes the cost of seeking data. • Blocks do not need to be on the same cluster. So large files in HDFS often span multiple clusters • >hadoop fsck / -files -blocks Hadoop Workshop 28
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  31. 31. • You can interact with HDFS from command line by use of “hadoop fs” • >hadoop fs –help • >hadoop fs -ls / Hadoop Workshop 31
  32. 32. • Get some data • • • • Save to /tmp/gutenberg local Hadoop Workshop 32
  33. 33. • hadoop fs -mkdir /tmp • hadoop fs -mkdir /tmp/gutenberg • hadoop fs -copyFromLocal /tmp/gutenberg/* /tmp/gutenberg Check it: hadoop fs -ls /tmp/gutenberg/ Or http://localhost:50075/ Hadoop Workshop 33
  34. 34. • Let‟s rename them hadoop fs -mv /tmp/gutenberg/pg20417.txt /tmp/gutenberg/pg20417.txt.bak hadoop fs -mv /tmp/gutenberg/pg4300.txt /tmp/gutenberg/pg4300.txt.bak hadoop fs -mv /tmp/gutenberg/pg5000.txt /tmp/gutenberg/pg5000.txt.bak • Then hadoop fs -copyToLocal /tmp/gutenberg/*.bak /tmp/gutenberg • And again ls /tmp/gutenberg Hadoop Workshop 34
  35. 35. • Quite simple, like normal Java File I/O • General write to FileSystem abstract class, can use DistributedFileSystem • Simple way to read and write to file system is using For example: InputStream in = new URL("hdfs://host/path").openStream(); Hadoop Workshop 35
  36. 36. • Listing Files • Getting Status • Copying to HDFS • Copying from HDFS • Viewing Hadoop Workshop 36
  37. 37. Any questions on HDFS? Hadoop Workshop 37
  38. 38. • Splits Processing Into Steps • Mapper • Reducer • These are by nature easily parallized and can take advantage of available hardware. Hadoop Workshop 38
  39. 39. • Key Value Pair: two pieces of data, exchanged between the Map and Reduce phases. Also sometimes called a TUPLE • Map: The „map‟ function in the MapReduce algorithm user defined converts each input Key Value Pair to 0...n output Key Value Pairs • Reduce: The „reduce‟ function in the MapReduce algorithm user defined converts each input Key + all Values to 0...n output Key Value Pairs • Group: A built-in operation that happens between Map and Reduce ensures each Key passed to Reduce includes all Values Hadoop Workshop 39
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  41. 41. • Map translates input to keys and values to new keys and values • System Groups each unique key with all its values • Reduce translates the values of each unique key to new keys and values Hadoop Workshop 41
  42. 42. • Let‟s look at the combining english to foreign language translations Hadoop Workshop 42
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  44. 44. • Is a single point of failure • Determines # Mapper Tasks from file splits via InputFormat • Uses predefined value for # Reducer Tasks • Client applications use JobClient to submit jobs and query status • Command line use hadoop job <commands> • Web status console use http://jobtracker-server:50030/ Hadoop Workshop 44
  45. 45. • Spawns each Task as a new child JVM • Max # mapper and reducer tasks set independently • Can pass child JVM opts via • Can re-use JVM to avoid overhead of task initialization Hadoop Workshop 45
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  47. 47. • MRUnit‟s MapDriver or ReduceDriver are the key class • Configure which mapper under test • The input value, • The expected output key • The expected output value Hadoop Workshop 47
  48. 48. • Testing A Mapper • Testing A Reducer Hadoop Workshop 48
  49. 49. • Not for quick jobs • Scripts / R programs are often better • Doesn‟t work well with a lot of small files in HDFS • Don‟t have that real – time aspect (see Apache Storm) • Don‟t let people tell you Hadoop is the answer for everything • Hive * Pig are good alternative (espcially for SQL speakers) Hadoop Workshop 49
  50. 50. • Questions? • Contact Me Hadoop Workshop 50