Transactional Caching of Application Data using Recent Snapshots - - PowerPoint PPT Presentation

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May 09, 2023 206 likes •362 views

Transactional Caching of Application Data using Recent Snapshots Dan R. K. Ports Austin T. Clements Irene Y. Zhang Samuel Madden Barbara Liskov MIT CSAIL How to improve performance of DB-driven web site? Distributed in-memory caching ( e.g.

SLIDE 1

Transactional Caching

f Application Data

using Recent Snapshots

Dan R. K. Ports Austin T. Clements Irene Y. Zhang Samuel Madden Barbara Liskov MIT CSAIL

SLIDE 2

How to improve performance

f DB-driven web site?

Distributed in-memory caching (e.g. memcached)

SLIDE 3

Distributed In-Memory Caching

Application Database

SLIDE 4

Distributed In-Memory Caching

Application Database Cache

SLIDE 5

in-memory DHT;

very lightweight

stores application
bjects

(not part of DB)

Distributed In-Memory Caching

Application Database Cache

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Databases work hard to provide transactional consistency. Existing application caches violate these guarantees!

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Consistency Properties

ur goal:

consistency: all accesses to cache and database in a transaction see the same snapshot

Can’t guarantee both without blocking! usual goal:

freshness: cache is up-to-date with database

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Consistency Properties

ur goal:

consistency: all accesses to cache and database in a transaction see the same snapshot

Can’t guarantee both without blocking! usual goal:

freshness: cache is up-to-date with database

SLIDE 9

Embracing Staleness

Run r/o transactions on previous snapshots – avoids blocking – improves cache utilization Safe: stale data is already everywhere! Allow application control over staleness

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TxCache Anatomy

Application Database TxCache Library Cache

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TxCache Anatomy

Cache is a versioned DHT,

tagged by validity interval

Application Database TxCache Library Cache

K1 K2 time

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TxCache Anatomy

Cache is a versioned DHT,

tagged by validity interval

Database returns validity

interval with each query

Application Database TxCache Library Cache SELECT * FROM users… [...result...] VALID FROM t=50 TO t=53

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TxCache Anatomy

Cache is a versioned DHT,

tagged by validity interval

Database returns validity

interval with each query

Library assigns timestamp

to each transaction

Uses timestamp to request

data from cache & DB

Application Database TxCache Library Cache

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