replic8 - Replication in MySQL 8

The Eighth Generation of MySQL Replication

Sven Sandberg ([email protected])MySQL Replication Core Team Lead

replic8

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there’s no deb8:it’s never too l8to replic8with version 8


OverviewBackground: (Group) Replication

8.0: Performance

8.0: Monitoring

8.0: Operations

More!


MySQL Group ReplicationTraditional database● Many clients● One server

server

clients


MySQL Group Replication

serverA

serverB

serverC

clientsGroup Replication● Many clients● Many servers● Read scalability● Write everywhere*● Elastic,

Highly available● Agreement on:

● Members● Message delivery● State updates



serverA

serverB

W WW

serverC

R RR R RRclients

Group Replication● Many clients● Many servers● Read scalability● Write everywhere*● Elastic,





serverA

serverB

W RW

serverC

R W RWclients

WR




Limitations apply!https://dev.mysql.com/doc/refman/8.0/en/group-replication-limitations.html



serverA

serverB

W RW

serverC

R W RWclients

serverD

WR






serverA

serverB

W RW

serverC

WR R W RWclients

serverD

serverE






serverA

serverB

W RW

serverC

R WR W RWclients

serverD

serverE






serverA

serverB

W RW

serverC

R WR W RWclients

serverE






serverA

serverB

W RW

serverC

R WR W RWclients






serverA

serverB

W RW

serverC

R WR W RWclients

We are 3:A, B, C!

We are 3:A, B, C!

We are 3:A, B, C!






serverA

serverB

W RW

serverC

R WR W RWclients






serverA

serverB

W RW R WR W RWclients

You and me:A and B!

You and me:A and B!






serverA

serverB





B B A A

All receive insame order



serverA

serverB





Tablerow 1row 2row 3

Queue

insert row 4

Tablerow 1row 2

Queue

insert row 3insert row 4


MySQL Group ReplicationGroup Replication● Many clients● Many servers● Read scalability● Write everywhere*● Elastic,



Summary:

GR in 8 is gr8


MySQL Async Replication


MySQL Async Replication

Example: Async replication between geo-distributed groups


Replication Architecture: Applier Pipeline

Replica

RelayLog

WorkerQueues

WorkerThreads

Coordinator Thread

ReceiverThread

network



Replica

RelayLog

WorkerQueues

WorkerThreads

Coordinator Thread

ReceiverThread

network



8.0: Performance

8.0: Monitoring

8.0: Operations

More!


8.0 Performance: Writeset Parallelization Replica can apply more transactions in parallel

– Able to keep worker threads busy– Can now use the full potential of the applier pipeline


8.0 Performance: Writeset Parallelization 5.6: parallelize transactions that modify different databases

parallel isolated isolated isolated

5.7: parallelize transactions that committed together

parallel parallel

8.0: parallelize transactions that modify disjoint sets of rows

always >= 3 transactions applying in parallel in this example

db1 db2 db3 db3 db3 db3

row 1 row 2,3 row 4 row 1,5 row 6 row 4

Typical parallelism:close to primary

Typical parallelism:less than primary

Typical parallelism:more than primary


8.0 Performance: Writeset Parallelization To enable:primary> SET binlog_transaction_dependency_tracking = WRITESET;replica> SET slave_parallel_workers = 4, slave_parallel_type = LOGICAL_CLOCK, slave_preserve_commit_order = 1;

Note: slave_preserve_commit_order = 1:– Apply in parallel, commit in order– Preserves application constraints between transactions:

serverA

Constraint: “trx1 must commit before trx2”w trx1, trx2


8.0 Performance: Applier Pipeline Parallelize reads and writes to relay log

Performance for free

Replica

RelayLog

WorkerQueues

WorkerThreads

Coordinator Thread

ReceiverThread

network

trx1

trx1


8.0 Performance: Efficient JSON Replication Document store / NOSQL is now efficient! UPDATE t SET j = JSON_REPLACE(j, “$[0].x.y[8]”, 7);

Replicate only the modified part Huge saving for small changes in big documents

JSON document

modified part


8.0 Performance: Efficient JSON Replication Enable:

SET GLOBAL binlog_row_image = MINIMAL, binlog_row_value_options = PARTIAL_JSON;

JSON_SET, JSON_REPLACE, JSON_REMOVE– And also composition: JSON_SET(JSON_REMOVE(...))



8.0: Performance

8.0: Monitoring

8.0: Operations

More!


machine Cmachine C machine Dmachine D

8.0 Monitoring: Lag Difference in server states,

measured in microseconds between commits,between:

– Replica and primary– Hops in topology– Stages of applier

machine Bmachine B

B C D

machine Amachine A

A






machine Bmachine B

B C D

machine Amachine A

A






machine Bmachine B

B C D

machine Amachine A

Aoriginalcommit

timestamp

immediatecommit

timestamp






machine Bmachine B

B C D

machine Amachine A

Aoriginalcommit

timestamp

immediatecommit

timestamp

This transaction’s latency vs primary:

SELECT LAST_APPLIED_TRANSACTION_END_APPLY_TIMESTAMP - LAST_APPLIED_TRANSACTION_ORIGINAL_COMMIT_TIMESTAMP FROM performance_schema. replication_applier_status_by_worker WHERE LAST_APPLIED_TRANSACTION_END_APPLY_TIMESTAMP = MAX(LAST_APPLIED_TRANSACTION_END_APPLY_TIMESTAMP)






machine Bmachine B

B C D

machine Amachine A

Aoriginalcommit

timestamp

immediatecommit

timestamp

This transaction’s latency vs last hop:

SELECT LAST_APPLIED_TRANSACTION_END_APPLY_TIMESTAMP - LAST_APPLIED_TRANSACTION_IMMEDIATE_COMMIT_TIMESTAMP FROM performance_schema. replication_applier_status_by_worker WHERE LAST_APPLIED_TRANSACTION_END_APPLY_TIMESTAMP = MAX(LAST_APPLIED_TRANSACTION_END_APPLY_TIMESTAMP)






machine Bmachine B

B C D

machine Amachine A

Aoriginalcommit

timestamp

immediatecommit

timestamp

These transactions’ latencies vs last hop:

SELECT APPLYING_TRANSACTION_START_APPLY_TIMESTAMP – APPLYING_TRANSACTION_IMMEDIATE_COMMIT_TIMESTAMP FROM performance_schema. replication_applier_status_by_worker






machine Bmachine B

B C D

machine Amachine A

Aoriginalcommit

timestamp

immediatecommit

timestamp


SELECT LAST_PROCESSED_TRANSACTION_END_BUFFER_TIMESTAMP – LAST_PROCESSED_TRANSACTION_IMMEDIATE_COMMIT_TIMESTAMP FROM performance_schema. replication_applier_status_by_coordinator






machine Bmachine B

B C D

machine Amachine A

Aoriginalcommit

timestamp

immediatecommit

timestamp


SELECT PROCESSING_TRANSACTION_END_BUFFER_TIMESTAMP – PROCESSING_TRANSACTION_IMMEDIATE_COMMIT_TIMESTAMP FROM performance_schema. replication_applier_status_by_coordinator






machine Bmachine B

B C D

machine Amachine A

Aoriginalcommit

timestamp

immediatecommit

timestamp


SELECT LAST_QUEUED_TRANSACTION_END_QUEUE_TIMESTAMP – LAST_QUEUED_TRANSACTION_IMMEDIATE_COMMIT_TIMESTAMP FROM performance_schema. replication_connection_status






machine Bmachine B

B C D

machine Amachine A

Aoriginalcommit

timestamp

immediatecommit

timestamp


SELECT QUEUEING_TRANSACTION_END_QUEUE_TIMESTAMP – QUEUEING_TRANSACTION_IMMEDIATE_COMMIT_TIMESTAMP FROM performance_schema. replication_connection_status


8.0 Monitoring: Group Members Who are in this group?

– server_uuid, host, port, MySQL version Who is the primary? Online status of each node

mysql> SELECT … FROM performance_schema.replication_group_membersMEMBER_ID MEMBER_HOST MEMBER_PORT MEMBER_STATE MEMBER_ROLE MEMBER_VERSION<uuid-A> murkla 3306 ONLINE PRIMARY 5.7.20<uuid-B> kremla 3306 ONLINE SECONDARY 5.7.21<uuid-C> kantarell 3306 UNREACHABLE SECONDARY 8.0.3

New in 8.0

B5.7.21

A5.7.20

C8.0.3


8.0 Monitoring: Group Member Statistics Statistics used to diagnose group members

– Conflict ratio of the group– Conflict ratio of each member (multi-primary)– Is any member falling behind on certification or applying?

Table performance_schema.replication_group_member_stats:counts of transactions, by member:

– Positively/negatively certified transactions of any origin– Positively/negatively certified transactions from the node– Transactions waiting to be certified– Certified transactions waiting to be applied



8.0: Performance

8.0: Monitoring

8.0: Operations

More!


8.0 Operations: Multi-source Filters

Users Posts

Aggr-egate

users bio groups posts com-ments

users

No filter

-

-replic

ate-ignore

-

ta

ble=db.users

only users

users bio groups posts com-ments

Different filters ontwo channels


8.0 Operations: Set Next Primary

B

A

C

W WW

SET group_replication_member_weight = [0-100]

Dw=25 w=20

R RR R RR R RR

w=10w=15


W WW


B

A

Cw=15

Dw=10 w=25 w=20

R RR R RR R RR




B

C

Dw=10 w=25 w=20

? ? ?

W WW R RR R RR R RR





B

C

Dw=10 w=25 w=20

? ? ?

W WW R RR R RR R RR

25 is the biggest→ C is new primary



B

C

Dw=10 w=25 w=20

W WW R RR R RR R RR



8.0 Operations: No Writes After Leaving Group

B

A

C

D

W WW



B

A

C

D

Locally on A:

STOP GROUP REPLICATION

W WW

1. Disallow new writes2. Wait for ongoing writes3. Leave group



B

A

C

D

Locally on A:

STOP GROUP REPLICATION

W WW



W WW


B

A

C

D

Locally on A:STOP GROUP REPLICATION




8.0: Performance

8.0: Monitoring

8.0: Operations

More!


More!Global performance: Flow control tuning (throttle writes to sustain replicas)

Usability: Better default configuration Monitoring: Monitor replication even when disk full Monitoring: Currently applying query, even for row-based replication Recoverability: Recover DDL after crash Interoperability: Metadata in binary log (full type information for DML) Interoperability: Transaction byte-length in binary log Operations: GTID support for restoring backup on non-empty server Operations: Specify binary log file number after RESET MASTER Operations: Specify how long binary log files are kept, with second precision Operations: Group Replication support for SAVEPOINT Debugging: Group Replication: message bus logging Maintenance: Removed 4.x/5.0 compatibility code


Contributions! Thank you:

Davi * 2DanielDaniël * 2Laurynas * 5OvaisTsubasa * 2Yura


“I can’t w8 to replic8 with version 8” Evalu8

https://dev.mysql.com/downloads/mysql Educ8

http://dev.mysql.com/doc/refman/8.0/en/group-replication.html http://dev.mysql.com/doc/refman/8.0/en/replication.html

Contempl8http://mysqlhighavailability.com

Cooper8https://bugs.mysql.com


Thank You!& cu l8r, m8s

replic8 - Replication in MySQL 8

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