Alireza Angabini Advanced DB class Dr. M.Rahgozar Fall 88.

Alireza Angabini

Advanced DB classDr. M.Rahgozar

Fall 88

Introduction

PNUTS Overview

Functionality

Architecture

Applications

Experimental Results

Conclusion

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Main requirements of Web Apps

Scalability

Response Time and Geographic Scope

High Availability & Fault Tolerance

Relaxed Consistency Guarantees

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PNUTS is

Massively parallel

Geographically distributed database system

Designed Yahoo!

Used by their web application

Shared between several applications

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Data Model & Features

Fault Tolerance

Pub-Sub Message System

Hosting

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Data & Query Model

Consistency Model

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Simplified relational data model

Organizes data into tables of records with attributes

Allows arbitrary structure inside a record – “blob”

Schema are flexible

New attribute is added without halting query or update

activity

Allow to have empty attribute in the record

Query language

Supports selection and projection in single table

Updates & deletes with primary key only

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Hide the complexity of replication

Considered between general serializability & eventual consistency

Per-record timeline consistency “All replica of given record apply all updates to the record

in the same order”

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Support range of API calls with different

levels of consistency

Read-any

Read-critical(required_version)

Read-latest

Write

Test-and-set-write(required_version)

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Data tables are horizontally partitioned into groups of records called tablets

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Ordered table

Primary-key space of a table is divided into

intervals

Each interval corresponds to one tablet

The router stores interval mapping

For a given PMK, binary search is used to find

the tablet

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Hash-organized tablen-bit hash function H(), 0 ≤ H() < 2n [0... 2n) is divided into intervals Each interval corresponds to single tabletTo map a key to a tablet,

1. Hash the key2. Search set of interval using binary search

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The system uses asynchronous

replication

To ensure low-latency updates

Yahoo! Message Broker (YMB)

Used for replication & logging because:

1. Multiple steps are applied before committed

to DB

2. YMB is designed for wide-area replication

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Recovery from failure (3 Steps)

1. the tablet controller requests a copy from the source tablet3. the source tablet is copied to the destination region2. “checkpoint message” is published to YMB

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User Database

Social Applications

Content Meta-Data

Listings Management

Session Data

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Three PNUTS regions 2 west coast, 1 east coast 5 storage units, 2 message brokers, 1 router West: Dual 2.8 GHz Xeon, 4GB RAM, 6 disk RAID 5 array East: Quad 2.13 GHz Xeon, 4GB RAM, 1 SATA disk

Workload 1200-3600 requests/second 0-50% writes 80% locality

Storage engine for hash table “Yahoo! propriety disk-based hashtable”

Storage engine for ordered tables MySQL using InnoDB

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The coming experiments showThe impact of several factors on the

average latency for request

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Rich database functionality and low

latency at massive scale.

Tradeoffs between functionality,

performance and scalability.

Choose asynchronous replication to

ensure low write latency.

Delivers the data management as

hosted service

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B. Cooper, R. Ramakrishnan, U. Srivastava, A. Silberstein, P.

Bohannon, H. Jacobsen, N. Puz, D. Weaver, and R. Yerneni,

"PNUTS: Yahoo!'s hosted data serving platform," Proceedings of

the VLDB Endowment archive, vol. 1, 2008, p. 1277–1288.

Technical report, Raghu Ramakrishnan, Yahoo! Research and Platform Engineering Team

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Thanks For Your AttentionThanks For Your Attention

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