Download - TriHUG November HCatalog Talk by Alan Gates
HCatalogTable Management for HadoopAlan F. Gates
Motivation: Data Sharing is Hard
Photo Credit: totalAldo via Flickr
This is programmer Bob, he uses Pig to crunch data.
This is analyst Joe, he uses Hive to build reports and answer ad-hoc queries.
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.
Ok
Joe, I need today’s data
Dude, we need HCatalog
More Motivation: Each tool requires its own Translator
Pig Hive Map Reduce
RCFile Custom Format
CustomLoader
HiveColumnarLoader
RCFileInputFormat
CustomInputFormat
ColumnarSerDe
CustomSerDe
HCatalog
HCatLoader HCatSerDe HCatInputFormat
RCFileStorageDriver
CustomStorageDriver
End User Example
raw = 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 is available, 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 can then 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 RCFILEtblproperties('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
Thrift server
Hive metadata interface
HCatInputFormat HCatOutputFormat
HCatLoader HCatStorage
RDBMS
CLI
= Hive
= Current HCatalog
Notification
= Future HCatalog
HTTP
Storage Architecture
HCatInputFormat HCatOutputFormat
HCatLoader HCatStorage
InputStorageDriver
HDFS
OutputStorageDriver
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: [email protected] −Dev list: [email protected]
Questions?
