MySQL Tech Tour 2015 - 5.7 Replication

Copyright © 2015, Oracle and/or its affiliates. All rights reserved. |Tuesday, October 20, 2015 Oracle Confidential – Restricted
MySQL 5.7 Replication Update
1
The Latest and Greatest MySQL 5.7 Replication Features and More!

Copyright © 2015, Oracle and/or its affiliates. All rights reserved. |
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Tuesday, October 20, 2015 Oracle Confidential – Restricted 2

Program Agenda
Tuesday, October 20, 2015 Oracle Confidential – Restricted

Program Agenda
Background
Replication Features in MySQL 5.7
News From The Lab!
The Road Ahead!
Conclusion
1
2
3
4
5

Background1

Background: Replication Components
Tuesday, October 20, 2015
Insert...
Insert...
B
binary log
Insert...
relay log
Insert...
A
binary log
Client
Sender
thread
Receiver
thread
Applier
Threads
Receiver
Meta-data
Update
Applier
Meta-data
Update
Network
Oracle Confidential – Restricted 6

Background: Replication Components
• Binary Log
– File based logical log that records the changes on the master.
– Statement or Row based format (may be intermixed).
– Each transactions is split into groups of events.
– Control events: Rotate, Format Description, Gtid, ...
Layout of a
Binary Log File
BEGIN ...E1 E2 COMMIT BEGIN ...E1 E2 COMMIT

M S
S
S
S
M
write clients read clients
read clients
write clients
More
reads?
More
slaves!
Read scale-out
Background: What is Replication Used For?

M M?
write clients write clients
More
writes?
More
Masters?
M?
M?
MySQL Fabric helps sharding your data with MySQL...
What about write scale-out?

C
B
A
C
B
ACrash
C
B
A
B is the
new master
Uh Oh! Whew!
Redundancy: If master crashes, promote slave to master

M
S
write clients
business intelligent client applications
reporting client applications
big queries client applications
On-line Backup and Reporting

CB
BA
AC
Image from
www.ginkgomaps.com

Usability / Online
2
2.1
Oracle Confidential – Restricted

Online Reconfiguration of Global Transaction Identifiers
Insert...
Insert...
B
binary log
Insert...
relay log
Insert...
A
binary log
Client
Sender
thread
Receiver
thread
Applier
Threads
Receiver
Meta-data
Update
Applier
Meta-data
Update
Network

• The procedure is online.
– Both reads and writes are allowed while global transaction identifiers are being
turned on or off in the entire replication cluster.
• No need to synchronize servers, ever.
• No need to restart servers.
• No need to change replication topology.
– Works in arbitrary topologies.
• Should anything happen in the middle of the procedure, you can always roll
back.

• Over simplified procedure to turn on global transaction identifiers:
• Details: http://dev.mysql.com/doc/refman/5.7/en/replication-mode-
change-online-enable-gtids.html
1) SET @@GLOBAL.GTID_MODE = OFF_PERMISSIVE; (on every server)
2) SET @@GLOBAL.GTID_MODE = ON_PERMISSIVE; (on every server)
3) wait for a bit longer than your replication lag
4) SET @@GLOBAL.GTID_MODE = ON; (on every server)

Online Reconfiguration of Replication Filters
Insert...
Insert...
B
binary log
Insert...
relay log
Insert...
A
binary log
Client
Sender
thread
Receiver
thread
Applier
Threads
Receiver
Meta-data
Update
Applier
Meta-data
Update
Network

Online Reconfiguration of Replication Filters
• Change Slave's Replication Filters dynamically.
– No need to stop and restart the slave server for setting new replication filtering rules.
– All slave filters are supported.
– Values can be input in various character sets.
mysql> CHANGE REPLICATION FILTER REPLICATE_DO_DB= (db1, db2)

Online Switch/Fail-over to a new Master
Insert...
Insert...
B
binary log
Insert...
relay log
Insert...
A
binary log
Client
Sender
thread
Receiver
thread
Applier
Threads
Receiver
Meta-data
Update
Applier
Meta-data
Update
Network

Change master from A to B without stopping the applier threads.
C
B
A
C
B
ACrash
C
B
A
B is the
new master
Uh Oh! Whew!

Change master from A to B without stopping the applier threads.
C
B
A
C
B
ACrash
C
B
A
Uh Oh! Whew!
DBA did not need C to stop applying its
relay log to change C's master from A to B.

• Enables more online operations during fail-over:
• Stopping, changing master and restarting the receiver thread are all done
while the applier thread is running.
• Change applier properties while the receiver thread is working:
mysql> STOP SLAVE IO_THREAD;
mysql> CHANGE MASTER TO MASTER_HOST='master2', …;
mysql> START SLAVE IO_THREAD;
mysql> STOP SLAVE SQL_THREAD;
mysql> CHANGE MASTER TO MASTER_DELAY=3600, …;
mysql> START SLAVE SQL_THREAD;

Improved Replication Monitoring
Insert...
Insert...
B
binary log
Insert...
relay log
Insert...
A
binary log
Client
Sender
thread
Receiver
thread
Applier
Threads
Receiver
Meta-data
Update
Applier
Meta-data
Update
Network
DBA

• Monitoring through SQL.
• Logically unrelated information into different places.
• Extensible, can be adapted to new features.
• More accurate and consistent identifier names.
• Master-slave, Multi-source, Group Replication support.
Performance Schema Replication Tables

Connection
Configuration
Connection
Status
Applier
Configuration
Applier
Status
(Slave) Receiver and Applier Status
Applier / Coordinator
Status
Workers
Status

Usability / Online
Performance
2
2.1
2.2

Usability / Online
Performance
Dependability
2
2.1
2.2
2.3

Loss-less Semi-sync Replication
Insert...
Insert...
B
binary log
Insert...
relay log
Insert...
A
binary log
Client
Sender
thread
Receiver
thread
Applier
Threads
Receiver
Meta-data
Update
Applier
Meta-data
Update
Network

Master
Slave
T1: INSERT INTO t1 VALUES (1000)
ACK
Time
T2: SELECT * FROM t1; empty set
execute prepare binlog
relay log
commitexecute

• Master waits for slave's ACK before committing (as opposed to: master
waits for slave's ACK after committing).
– Therefore, concurrent transactions do not see changes while this transaction waits for
ack.
• Should a master fail, then any transaction that it may have externalized is
also persisted on a slave.
• User can choose between the original semi-sync behavior and the new
one.
mysql> SET rpl_semi_sync_master_wait_point= [AFTER_SYNC|AFTER_COMMIT]

Semi-sync Replication – Wait for Multiple ACKs
Insert...
Insert...
B
binary log
Insert...
relay log
Insert...
A
binary log
Client
Sender
thread
Receiver
thread
Applier
Threads
Receiver
Meta-data
Update
Applier
Meta-data
Update
Network

• Master does not commit transaction until it receives N ACKs from N slaves.
• Dynamically settable:
mysql> SET GLOBAL rpl_semi_sync_master_wait_for_slave_count= N

• Master does not commit transaction until it receives N ACKs from N slaves.
• Dynamically settable:
mysql> SET GLOBAL rpl_semi_sync_master_wait_for_slave_count= N
Master
Slave 2
T1: COMMIT
ACK
Slave 1
ACK
T1: COMMIT
succeeds
mysql> SET GLOBAL rpl_semi_sync_master_wait_for_slave_count= 2
Slave 3
Time
relay log
relay log
relay log
ACK

Usability / Online
Performance
Dependability
Flexibility
2
2.1
2.2
2.3
2.4

Storing Global Transaction Identifiers in a Table
Insert...
B
Insert...
relay log
Insert...
A
binary log
Client
Sender
thread
Receiver
thread
Applier
Threads
Receiver
Meta-data
Update
Applier
Meta-data
Update
Network

• Slaves can use GTIDs with binary logs disabled.
– Slaves that are never candidates to become a master can still use GTIDs for auto
positioning.
Use Cases

• GTIDs are saved into a mysql system table (range-compressed).
• GTIDs are inserted into the table as transactions commit.
• A compression thread runs periodically and compresses the table into
ranges.
– New global variable controls the period: gtid_executed_compression_period.
Mechanics
CREATE TABLE gtid_executed(
source_uuid CHAR(36) NOT NULL,
interval_start BIGINT NOT NULL,
interval_end BIGINT NOT NULL,
PRIMARY KEY(source_uuid, interval_start)
);
mysql> SET GLOBAL gtid_executed_compression_period= N;(N – number of transactions)

• Binary Log Enabled
– Store GTID in binary log (transactionally).
– Copy GTID set to table on binary log rotation.
• Binary Log Disabled
– Store GTID in table (transactionally).
– New transactions are not assigned a GTID.
• Always store GTIDs transactionally.
Mechanics

Multi-Source Replication
S
M M Slave can have more than one master.M M
The need for gathering data in a central server:
• Integrated backup;
• Complex queries for analytics purposes;
• Data HUB for inter-cluster replication.

• A server (slave) can replicate from multiple sources (masters).
• Multiple channels (channel: connection thread, relay log, applier threads)
that can be stopped started individually.
• Integrated with Multi-threaded Slave.
– Each channel has its own multi-threaded applier set of threads.
• Integrated with the new P_S tables.
– replication_applier_status_by_coordinator shows multiple entries, one per
channel/source applier.
– replication_connection_status shows multiple entries, one per connection to
different sources.

• Integrated with GTIDs.
• Integrated with crash-safe tables.
– Progress state is stored in these tables for recoverability purposes.
• Virtually no limit on the number of sources (capped to 256, but can be
changed if server binary is rebuilt).
• Able to manage each source separately.

Usability / Online
Performance
Dependability
Flexibility
Misc
2
2.1
2.2
2.3
2.4
2.4

“Smaller”, yet interesting, enhancements!
• Multi-threaded applier is able to retry failed transactions.
• Option to make the Multi-threaded applier preserve commit order.
• SSL options for mysqlbinlog tool.
• Rewrite DB rules for the mysqlbinlog tool.
• Function to wait for transactions to be applied, regardless of the replication stream
they come from.
• Options to track global transaction identifiers in the return packet of the mysql
protocol.
• Support for XA transactions when the binary log is enabled.
• Change in the defaults. E.g., binlog_format=ROW and sync_binlog=1.

MySQL Router
• Motivation
– The need for transparent integration with Fabric.
• No need to upgrade existing connectors.
• Use Fabric with connectors that do not support it (e.g.,
PHP, Ruby, Perl, C).
– The need for read-write and read-only automatic
routing.
• Do not need to know which server is the master.
• Transparent fail-over support for a new master.
• End Result
– Generic and versatile framework: MySQL Router.
NEW
M
Router
App
M M
Fabric
45

MySQL Router
• Highlights
– High Performance
– Plugin Driven Architecture
– Simple to setup, configure and deploy.
• Features
– Connection routing and simple load balancing.
– Seamless fail-over based on Fabric HA Groups.
– Fail-over without Fabric (needs 3rd party tool to
handle fail-over itself).
– reducing conflicts when deployed together with
Group Replication.
M
Router
App
M M
Fabric
NEW
46

The Road Ahead!4

What is Next?
• MySQL Group Replication
– Rapid releases.
– Improve performance, stability and usability.
• MySQL Replication Usability
– Instrument even more replication and extend replication P_S tables
– Simpler administrative commands
• MySQL Replication Performance
– Continue to improve multi-threaded (slave) applier
– Continue to improve semi-sync
• Orchestration and MySQL Router inter-operability

Focus
MySQL
Replication
Performance High Availability
Ease of Use Integration
Recoverability
Automation of Fail-over
and crash recovery
Configurability
GTIDs
HPC optimizations
MySQL
Router
Integration
More
Modularization
Pluggability
Modernization
Of Replication
Interfaces
MySQL
Fabric
Integration
Multi-threaded Applier
Address Contention
Points
MySQL
Group Replication
Leverage
Consensus
Further
P_S Instrumentation
Simplify UI

Summary7

Summary
• Replication feature set in MySQL 5.7 shows many improvements:
– Semi-sync is more flexible and faster.
– Less contention on the binary log.
– Slave is faster and provides an inter-transaction parallelization scheme.
– More online reconfiguration: Global Transaction Identifiers, filters, configuration.
– Improved monitoring.
– Even more flexible replication with multi-source enabling new deployment scenarios.
– Enhancements all over: transaction retries, sequential commits, XA support, new
replication functions, security.
• Lab releases provide a sneak peek at what is coming - a new replication plugin and
exciting new infrastructure: MySQL Group Replication and MySQL Router.

Where to go from here?
• Packages
– http://dev.mysql.com
– http://labs.mysql.com
• Reference Documentation
– http://dev.mysql.com/doc/#manual
• Blogs from the Engineers (news, quirks, technical information and much
more)
– http://mysqlhighavailability.com

MySQL Tech Tour 2015 - 5.7 Replication

MySQL Tech Tour 2015 - 5.7 Replication

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