CockroachDB設計與實現(xiàn)PT課件

CockroachDB

設計與實現(xiàn)1數(shù)據(jù)庫的演化SQL時代：MySql,

PostgreSQLNoSQL:

MongoDB,

redis,

HBase…NewSQL:

Google

F1,

FoundationDB,CockroachDB2WhyTransaction

+

Scale3Google的歷程2004:

BigTableeventually

consistent

NoSQL2006:

Megastore

(on

top

of

BigTable)

transactional,

slow,

complex2010:

remove

sharding

mysql2012:

Spanner

(+F1

on

top

of

it)

semi-relational,

fully

linearizable4歷史上的努力cobar:

just

sharding.

Simplevitess:

from

youtube.

Complex還有無數(shù)各大公司造的輪子….No

distributed

transaction

!!!!!!!5CockroachDB●

Cockroach

is

CP

in

CAP●

“A”vailable

not

same

as

“H”ighly

“A”

vailable678事務原理●

Variation

of

two

phase

commit●

Txn

writes

stored

as

MVCC

“intents”●

Txn

table

has

a

single

key

/

txn○

Stores

txn

status,

timestamp,

priority○

Modified

by

concurrent

txns

-

first

writerwins○

The

single

source

of

truth●

2nd

phase

more

efficient

--

1

write●

Intents

resolved

after

commit9Txn

table在哪里？●

也作為kv存在某個range里面，具體由

txn.Key決定10●●●●

LinearizabilitySerializable

for

all

casesTemporal

reverse?Client

decision:

perf

/

correctnessMax

Timestamp

○

Passed

to

order

causal

txns●

Commit

wait

○

Always

waiting

means

true

linearizability

○

More

accurate

clocks

=

less

wait11選擇讀時間戳Spanner:

TrueTime

always

readscommitted

valueCockroach:Doesn’t

wait

on

writesSometimes

waits

on

readsFor

txn,

choose

Tstart,

TmaxIf

read

encounters

timestamp

in

“uncertainty”window,

restart

read-only

txnShrinking

window

means

max

wait

is

clockskew12Uncertainty●

---------ts--------------txn.MaxTs----------->●

剪頭指向的絕對時間方向13關(guān)于

存儲引擎●

重用已有的成果，不是整個系統(tǒng)的重點●

rocksdb

已經(jīng)足夠快了●

設計上考慮支持多種存儲