replic8 - Replication in MySQL 8

The Eighth Generation of MySQL Replication
Sven Sandberg
(sven.sandberg@oracle.com)
MySQL Replication Core Team Lead
replic8

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there’s no deb8:
it’s never too l8
to replic8
with version 8

Overview
Background: (Group) Replication
8.0: Performance
8.0: Monitoring
8.0: Operations
More!

MySQL Group Replication
Traditional database
●
Many clients
●
One server
server
clients

server
A
server
B
server
C
clients
Group Replication
●
Many clients
●
Many servers
●
Read scalability
●
Write everywhere*
●
Elastic,
Highly available
●
Agreement on:
●
Members
●
Message delivery
●
State updates

server
A
server
B
W WW
server
C
R RR R RR
clients
Group Replication
●
Many clients
●
Many servers
●
Read scalability
●
Write everywhere*
●
Elastic,
Highly available
●
Agreement on:
●
Members
●
Message delivery
●
State updates

server
A
server
B
W RW
server
C
R W RW
clients
WR
Group Replication
●
Many clients
●
Many servers
●
Read scalability
●
Write everywhere*
●
Elastic,
Highly available
●
Agreement on:
●
Members
●
Message delivery
●
State updates
Limitations apply!
https://dev.mysql.com/doc/refman/8.0/en/group-replication-limitations.html

server
A
server
B
W RW
server
C
R W RW
clients
server
D
WR
Group Replication
●
Many clients
●
Many servers
●
Read scalability
●
Write everywhere*
●
Elastic,
Highly available
●
Agreement on:
●
Members
●
Message delivery
●
State updates

server
A
server
B
W RW
server
C
WR R W RW
clients
server
D
server
E
Group Replication
●
Many clients
●
Many servers
●
Read scalability
●
Write everywhere*
●
Elastic,
Highly available
●
Agreement on:
●
Members
●
Message delivery
●
State updates

server
A
server
B
W RW
server
C
R WR W RW
clients
server
D
server
E
Group Replication
●
Many clients
●
Many servers
●
Read scalability
●
Write everywhere*
●
Elastic,
Highly available
●
Agreement on:
●
Members
●
Message delivery
●
State updates

server
A
server
B
W RW
server
C
R WR W RW
clients
server
E
Group Replication
●
Many clients
●
Many servers
●
Read scalability
●
Write everywhere*
●
Elastic,
Highly available
●
Agreement on:
●
Members
●
Message delivery
●
State updates

server
A
server
B
W RW
server
C
R WR W RW
clients
Group Replication
●
Many clients
●
Many servers
●
Read scalability
●
Write everywhere*
●
Elastic,
Highly available
●
Agreement on:
●
Members
●
Message delivery
●
State updates

server
A
server
B
W RW
server
C
R WR W RW
clients
We are 3:
A, B, C!
We are 3:
A, B, C!
We are 3:
A, B, C!
Group Replication
●
Many clients
●
Many servers
●
Read scalability
●
Write everywhere*
●
Elastic,
Highly available
●
Agreement on:
●
Members
●
Message delivery
●
State updates

server
A
server
B
W RW
server
C
R WR W RW
clients
Group Replication
●
Many clients
●
Many servers
●
Read scalability
●
Write everywhere*
●
Elastic,
Highly available
●
Agreement on:
●
Members
●
Message delivery
●
State updates

server
A
server
B
W RW R WR W RW
clients
You and me:
A and B!
You and me:
A and B!
Group Replication
●
Many clients
●
Many servers
●
Read scalability
●
Write everywhere*
●
Elastic,
Highly available
●
Agreement on:
●
Members
●
Message delivery
●
State updates

server
A
server
B
W RW R WR W RW
clients
Group Replication
●
Many clients
●
Many servers
●
Read scalability
●
Write everywhere*
●
Elastic,
Highly available
●
Agreement on:
●
Members
●
Message delivery
●
State updates
B B
A A
All receive in
same order

server
A
server
B
W RW R WR W RW
clients
Group Replication
●
Many clients
●
Many servers
●
Read scalability
●
Write everywhere*
●
Elastic,
Highly available
●
Agreement on:
●
Members
●
Message delivery
●
State updates
Table
row 1
row 2
row 3
Queue
insert row 4
Table
row 1
row 2
Queue
insert row 3
insert row 4

Group Replication
●
Many clients
●
Many servers
●
Read scalability
●
Write everywhere*
●
Elastic,
Highly available
●
Agreement on:
●
Members
●
Message delivery
●
State updates
Summary:
GR in 8 is gr8

MySQL Async Replication

MySQL Async Replication
Example: Async replication between geo-distributed groups

Replication Architecture: Applier Pipeline
Replica
Relay
Log
Worker
Queues
Worker
Threads
Coordinator
Thread
Receiver
Thread
network

Replica
Relay
Log
Worker
Queues
Worker
Threads
Coordinator
Thread
Receiver
Thread
network

Overview
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

 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
less than primary
more than primary

 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:
server
A
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
Relay
Log
Worker
Queues
Worker
Threads
Coordinator
Thread
Receiver
Thread
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(...))

Overview
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

8.0 Monitoring: Lag
between:
machine Bmachine B
B C D
machine Amachine A
A

8.0 Monitoring: Lag
between:
machine Bmachine B
B C D
machine Amachine A
A
original
commit
timestamp
immediate
commit
timestamp

8.0 Monitoring: Lag
between:
machine Bmachine B
B C D
machine Amachine A
A
original
commit
timestamp
immediate
commit
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)

8.0 Monitoring: Lag
between:
machine Bmachine B
B C D
machine Amachine A
A
original
commit
timestamp
immediate
commit
timestamp
This transaction’s latency vs last hop:
SELECT LAST_APPLIED_TRANSACTION_END_APPLY_TIMESTAMP -
LAST_APPLIED_TRANSACTION_IMMEDIATE_COMMIT_TIMESTAMP
WHERE LAST_APPLIED_TRANSACTION_END_APPLY_TIMESTAMP =
MAX(LAST_APPLIED_TRANSACTION_END_APPLY_TIMESTAMP)

8.0 Monitoring: Lag
between:
machine Bmachine B
B C D
machine Amachine A
A
original
commit
timestamp
immediate
commit
timestamp
These transactions’ latencies vs last hop:
SELECT APPLYING_TRANSACTION_START_APPLY_TIMESTAMP –
APPLYING_TRANSACTION_IMMEDIATE_COMMIT_TIMESTAMP

8.0 Monitoring: Lag
between:
machine Bmachine B
B C D
machine Amachine A
A
original
commit
timestamp
immediate
commit
timestamp
SELECT LAST_PROCESSED_TRANSACTION_END_BUFFER_TIMESTAMP –
LAST_PROCESSED_TRANSACTION_IMMEDIATE_COMMIT_TIMESTAMP
replication_applier_status_by_coordinator

8.0 Monitoring: Lag
between:
machine Bmachine B
B C D
machine Amachine A
A
original
commit
timestamp
immediate
commit
timestamp
SELECT PROCESSING_TRANSACTION_END_BUFFER_TIMESTAMP –
PROCESSING_TRANSACTION_IMMEDIATE_COMMIT_TIMESTAMP
replication_applier_status_by_coordinator

8.0 Monitoring: Lag
between:
machine Bmachine B
B C D
machine Amachine A
A
original
commit
timestamp
immediate
commit
timestamp
SELECT LAST_QUEUED_TRANSACTION_END_QUEUE_TIMESTAMP –
LAST_QUEUED_TRANSACTION_IMMEDIATE_COMMIT_TIMESTAMP
replication_connection_status

8.0 Monitoring: Lag
between:
machine Bmachine B
B C D
machine Amachine A
A
original
commit
timestamp
immediate
commit
timestamp
SELECT QUEUEING_TRANSACTION_END_QUEUE_TIMESTAMP –
QUEUEING_TRANSACTION_IMMEDIATE_COMMIT_TIMESTAMP
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_members
MEMBER_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
B
5.7.21
A
5.7.20
C
8.0.3

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

Overview
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
--replicate-ignore-
table=db.users
only users
users bio groups posts com-
ments
Different filters on
two channels

8.0 Operations: Set Next Primary
BA 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
BA 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
BA C D
W WW

BA C D
Locally on A:
STOP GROUP REPLICATION
W WW
1. Disallow new writes
2. Wait for ongoing writes
3. Leave group

BA C D
Locally on A:
W WW
3. Leave group

W WW
BA C D
Locally on A:
3. Leave group

Overview
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 * 2
Daniel
Daniël * 2
Laurynas * 5
Ovais
Tsubasa * 2
Yura

“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
 Contempl8
http://mysqlhighavailability.com
 Cooper8
https://bugs.mysql.com

Thank You!& cu l8r, m8s

replic8 - Replication in MySQL 8

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