Replication featuresinmysql5.7andbeyond osi-final

Copyright © 2015, Oracle and/or its affiliates. All rights reserved. |Friday, November 20, 2015 OSI - Bangalore
An Overview of the New Replication
Features in MySQL 5.7 and Beyond
Sujatha Sivakumar (sujatha.sivakumar@oracle.com)
Software Engineer, MySQL Server Sustaining Team

Copyright © 2015, Oracle and/or its affiliates. All rights reserved. |
Safe Harbor Statement
The following is intended to outline our general product direction. It is intended for
information purposes only, and may not be incorporated into any contract. It is not a
commitment to deliver any material, code, or functionality, and should not be relied upon
in making purchasing decisions. The development, release, and timing of any features or
functionality described for Oracle’s products remains at the sole discretion of Oracle.
Friday, November 20, 2015 OSI - Bangalore

Program Agenda

Program Agenda
Background
Celebrating MySQL 5.7 Replication
The New Replication Features in MySQL 5.7
Development Sneak Peek
Roadmap
Summary
1
2
3
4
5
6

Celebrating MySQL 5.7 Replication
GA ready!
1

Thank You!
• After two and half years baking the team is very happy to share the
outcome with you!
– We did it for you!
• Thank you for being part of it!
• Enjoy MySQL 5.7, in particular the replication features! ;)

Background2

Background: Replication Components
Friday, November 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
OSI - Bangalore

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 transaction 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
OSI - Bangalore

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
3
3.1
OSI - Bangalore

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
OSI - Bangalore

• 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)
OSI - Bangalore

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
OSI - Bangalore

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)
OSI - Bangalore

Online Reconfiguration of Replication Receiver/Applier
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
OSI - Bangalore

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!
OSI - Bangalore

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.
OSI - Bangalore

• 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;
OSI - Bangalore

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
OSI - Bangalore
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
OSI - Bangalore

mysql> select * from performance_schema.replication_applier_status_by_workerG
*************************** 1. row ***************************
CHANNEL_NAME:
WORKER_ID: 1
THREAD_ID: 35
SERVICE_STATE: ON
LAST_SEEN_TRANSACTION: 4ba0eb86-63c3-11e4-92ba-28b2bd168d07:2368
LAST_ERROR_NUMBER: 0
LAST_ERROR_MESSAGE:
LAST_ERROR_TIMESTAMP: 0000-00-00 00:00:00
*************************** 2. row ***************************
CHANNEL_NAME:
WORKER_ID: 2
THREAD_ID: 36
SERVICE_STATE: ON
LAST_SEEN_TRANSACTION: 4ba0eb86-63c3-11e4-92ba-28b2bd168d07:2367
LAST_ERROR_NUMBER: 0
LAST_ERROR_MESSAGE:
LAST_ERROR_TIMESTAMP: 0000-00-00 00:00:00
2 rows in set (0,00 sec)
OSI - Bangalore

Usability / Online
Performance
3
3.1
3.2
OSI - Bangalore

Improved Applier Throughput – Locking-based Parallelism
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
OSI - Bangalore

Single Threaded Apply 8 Threads Applier 24 Threads Applier 48 Threads Applier 96 Threads Applier
0%
50%
100%
150%
200%
250%
Fast and Scalable Multi-threaded Replication Applier
(statement-based replication, durable settings, SSD storage)
Slaveapplytime
(SysbenchRWonthemasterwith96threads=100%)
10X
OSI - Bangalore

• Leverage parallelization information from master execution:
– Concurrent transactions, which have not blocked each other on the master, are
marked as non-contending in the binary log.
• Meanwhile, at the slave:
– Non-contending transactions are scheduled in parallel;
– Concurrent transactions commit independently, thus no waiting involved.

• T2 is scheduled to execute
together with T1.
• T3 is scheduled to execute
as soon as T1 finishes.
T1
T2
T3
Time
Commit Finishes
Last Lock Acquired
Concurrent Execution History
on the Master
Execution
Commit
T1 and T2 execute in
parallel on the slave.
T2 and T3 execute in
parallel on the slave.
OSI - Bangalore

• Supports statement-based or row-based formats.
• Scheduling policy controlled through:
– logical_clock - means schedule based on the locking interval timestamps.
– database - the scheduling policy from 5.6 (concurrency control done per database).
• Work to improve slave scalability continues, does not stop here.
mysql> SET slave_parallel_type= [logical_clock|database]
OSI - Bangalore

Improved User Threads-Sender Threads Synchronization
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
OSI - Bangalore

Improved User Threads-Sender Threads Synchronization
• Concurrent reads by the sender thread with ongoing writes from user
threads.
– Sender thread does not block user sessions more than necessary.
– Higher throughput for both sender threads and user sessions.
Sender Thread Reads Binary Log User Thread Writes to Binary Log
Sender Thread Reads Binary Log
User Thread Writes to Binary Log
pre 5.7.2
5.7.2+
OSI - Bangalore

Faster Sender Thread
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
OSI - Bangalore

• Send buffer is not allocated and freed every time an event is sent.
• When sender threads require larger send buffer - buffer grows as needed.
• When buffer is larger than needed - buffer shrinks dynamically.
• Together with the sender thread enhancements released on MySQL 5.7.2:
– increases master scalability;
– reduces resource consumption (CPU);
– Master, with dump threads attached, copes better with peak loads.
OSI - Bangalore

• Ad hoc microbenchmark using
mysqlslap
• 1M queries, concurrency=200,
commit=1
• N slaves attached (fake slaves using
remote mysqlbinlogs)
• 48 cores HT / 512 GB RAM / HDD
0
2000
4000
6000
8000
10000
12000
14000
16000
0 1 5 10 20 30 40 50 100
QpS
Number of Connected Sender Threads
Master’s Throughput
MySQL 5.6.16 MySQL 5.7.4
OSI - Bangalore

Faster Semi-sync Replication – ACK Receiver Thread
Insert...
Insert...
B
binary log
Insert...
relay log
Insert...
A
binary log
Client
ACK
Receiver
thread
Receiver
thread
Applier
Threads
Receiver
Meta-data
Update
Applier
Meta-data
Update
Network
Sender
thread
OSI - Bangalore

Faster Semi-sync Replication – ACK Receiver Thread
• Consecutive transactions do not block each other while waiting for ACKs
– Transaction t1 and t2 are sent immediately to the slave by the sender thread
– ACKs are received only by a special thread
– Transaction t2 does not include t1 round trip in its semi-sync overall latency
• Thread starts when semi-sync is activated
• Thread stops when semi-sync is deactivated
mysql> SET GLOBAL rpl_semi_sync_master_enabled= ON
mysql> SET GLOBAL rpl_semi_sync_master_enabled= OFF
OSI - Bangalore

Faster Semi-sync: Durability over the Network
Orange bar percentage shows the throughput gain (orange) when compared to the corresponding
blue bar. Blue and stacked bars show throughput ratio computed against the best blue bar.

Usability / Online
Performance
Dependability
3
3.1
3.2
3.3
OSI - Bangalore

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
OSI - Bangalore

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

• 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]
OSI - Bangalore

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
OSI - Bangalore

• 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
OSI - Bangalore

• 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
OSI - Bangalore
ACK

Usability / Online
Performance
Dependability
Flexibility
3
3.1
3.2
3.3
3.4
OSI - Bangalore

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
OSI - Bangalore

• 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)
OSI - Bangalore

• 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 do not get an automatic GTID assigned.
• 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.
OSI - Bangalore

• A server (slave) can replicate from multiple sources (masters).
• Multiple channels (channel: receiver thread, relay logs, 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 coordinator.
– replication_applier_status_by_worker shows multiple entries, multiple entries per
channel
– 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
3
3.1
3.2
3.3
3.4
3.5
OSI - Bangalore

“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. Useful for tracking GTID session state and enabler for session consistency.
• Support for XA transactions when the binary log is enabled.
• Change in the defaults. E.g., binlog_format=ROW and sync_binlog=1.
• Options to fine tune the binary log group commit procedure.

Usability / Online
Performance
Dependability
Flexibility
Misc
Other Components Working with Replication
3
3.1
3.2
3.3
3.4
3.5
OSI - Bangalore
3.6

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
MySQL
Fabric
GA

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).
M
Router
App
M M
MySQL
Fabric
NEW
GA

Development Sneak Peek4

MySQL Group Replication Plugin
M M M M M
Replication Group
• Multi-master update everywhere
• Automatic group membership
management and failure detection.
• No need for server fail-over.
• Automatic reconfiguration.
• No single point of failure.
• Shared-nothing state machine
replication.
• InnoDB compliant. Off-the-shelf
hardware friendly.
OSI - Bangalore

• Great technology for deployments where elasticity is a requirement, such
as cloud based infrastructures.
– Integrated with the server core through a well defined API.
– It is integrated with GTIDs, row based replication.
– It is integrated with performance schema tables.
– It is elastic and self-healing: adding or removing servers does not need human
intervention.

• Strong development cycles and continuous community engagement
through regular and frequent releases on labs.mysql.com.
2014-Sep-29
Labs release: 0.2.0
2015-Apr-06
Labs release: 0.3.0
2014-Aug-06
Labs release: 0.4.0
2015-Sep-14
Labs release: 0.5.0
Introduces standalone plugin,
with its own release cycle!
2015-Oct-26
Labs release: 0.6.0
Multi-platform, No need for
Corosync.

• With MySQL Group Replication for 5.7.9 we introduce a new group
communication engine.
– Corosync is not needed anymore.
– All pieces are integrated and is now easier to build, install and use.
– Plugin now builds on multiple platforms: Linux, Solaris, FreeBSD, OSX and Windows.
– Cloud friendly transport – TCP transport.

Roadmap5

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, more online operations
• MySQL Replication Performance
– Continue to improve replication stream multi-threaded (slave) applier
– Continue to improve replication stream pipeline performance and efficiency

Summary6

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

Other Interesting Presentations From Us …
• Topic: Optimizer Enhancements and JSON Support in MySQL 5.7
 Time: 12:30 to 1.15 PM
 Speaker: Sree Harsha
• Topic: State of the Dolphin
 Time: 2.15 to 3.00 PM
 Speaker: Sanjay Manwani
• Topic: Security and Performance – out of the box in MySQL 5.7
 Time: 3:15 to 4:00 PM
 Speaker: Nitin Mehta and Mayank Prasad

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