TriHUG November HCatalog Talk by Alan Gates

HCatalogTable Management for HadoopAlan F. Gates

Motivation: Data Sharing is Hard This is analyst Joe, he usesThis is programmer Bob, he Hive to build reports anduses Pig to crunch data. answer ad-hoc queries. Joe, I need today’s data OkPhoto Credit: totalAldo via Flickr Hmm, is it done yet? Where is it? What format did you use to store it today? Is it compressed? And can you help me load it into Hive, I can never remember all the parameters I have to pass that alter table command. Dude, we need HCatalog

More Motivation: Each tool requires its ownTranslator Pig Hive Map Reduce Hive HCatLoader HCatSerDe RCFile Custom HCatInputFormat Custom Columnar Custom Columnar Input Input Loader SerDe SerDe Loader Format Format HCatalog RCFile Custom StorageDriver StorageDriver Custom RCFile Format

End User Exampleraw = load „/rawevents/20100819/data‟ using MyLoader() as (ts:long, user:chararray, url:chararray);botless = filter raw by NotABot(user);…store output into „/processedevents/20100819/data‟;Processedevents consumers must be manually informed by producer that data isavailable, or poll on HDFS (= bad for the NameNode)raw = load „rawevents‟ using HCatLoader();botless = filter raw by date = „20100819‟ and NotABot(user);…store output into „processedevents‟ using HCatStorage(“date=20100819”);Processedevents consumers will be notified by HCatalog data is available and canthen start their jobs

Command Line for DDL• Uses Hive SQL• Create, drop, alter table• CREATE TABLE employee ( emp_id INT, emp_name STRING, emp_start_date STRING, emp_gender STRING) PARTITIONED BY ( emp_country STRING, emp_state STRING) STORED AS RCFILE tblproperties( hcat.isd=RCFileInputDriver, hcat.osd=RCFileOutputDriver);

Manages Data Format and Schema Changes• Allows columns to be appended to tables in new partitions − no need to change existing data − fields not present in old data will be read as null − must do „alter table add column‟ first• Allows storage format changes − no need to change existing data, HCatalog will handle reading each partition in the appropriate format − all new partitions will be written in current format

Security• Uses underlying storage permissions to determine authorization − Currently only works with HDFS based storage − If user can read from the HDFS directory, then he can read the table − If user can write to the HDFS directory, then he can write to the table − If the user can write to the database level directory, he can create and drop tables − Allows users to define which group to create table as so table access can be controlled by Unix group• Authentication done via kerberos

Metadata Architecture HCatLoader HCatStorage HTTP HCatInputFormat HCatOutputFormat CLI Notification Hive metadata interface Thrift server RDBMS = Current HCatalog = Hive = Future HCatalog

Storage Architecture HCatLoader HCatStorage HCatInputFormat HCatOutputFormat Input Output StorageDriver StorageDriver HDFS HBase

Project Status• HCatalog was accepted to the Apache Incubator last March• 0.2 released in October, includes: − Read/write from Pig − Read/write from MapReduce − Read/write from Hive − StorageDrivers for RCFile − Notification via JMS when data is available − Store to multiple partitions simultaneously − Import/Export tools

HCatalog 0.3• Plan to release mid-December• Adds a Binary type (to Hive and HCatalog)• Storage drivers for JSON and text• Improved integration with Hive for custom storage formats• Web services interface

Future Plans• Support for HBase and other data sources for storage• RCFile compression improvements• High Availability for Thrift server• Data management interfaces for archivers, cleaners, etc.• Additional metadata storage: − statistics − lineage/provenance − user tags

Get Involved• incubator.apache.org/hcatalog• Join the mailing lists − User list: hcatalog-user@incubator.apache.org − Dev list: hcatalog-dev@incubator.apache.org

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TriHUG November HCatalog Talk by Alan Gates

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