MySQL Group Replication

Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |Sunday,March 20, 2016 FOSSASIA'2016 -Singapore
Enhanced High Availability using
MySQL Group Replication
Manish Kumar (manish.4.kumar@oracle.com)
Senior Member Technical Staf
1

Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
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2Sunday,March 20, 2016 FOSSASIA'2016 -Singapore

Program Agenda
Sunday,March 20, 2016 FOSSASIA'2016 -Singapore

Program Agenda
The Theory
How things work!
How to Use
Conclusion
1
2
3
4

The theory1

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?

C
B
A
C
B
ACrashCrash
C
B
A
B is the
new master
Uh Oh! Whew!
Redundancy: If master crashes, promote slave to master
Background: What is Replication Used For?

8
M M M M M
Replication Group
Clients

• What is MySQL Group Replication?
“Multi-master update everywhere replication plugin for MySQL with built-in
automatic distributed recovery, conflict detection and group
membership.”
• What does the MySQL Group Replication plugin do for the user?
– Removes the need for handling server fail-over.
– Provides fault tolerance.
– Enables update everywhere setups.
– Automates group reconfiguration (handling of crashes, failures, re-connects)
Provides a highly available replicated database.

Use Cases
• Elastic Replication
– Environments that require a very fluid replication infrastructure, where the
number of servers has to grow or shrink dynamically and with as little pain as
possible.
• Highly Available Shards
– Sharding is a popular approach to achieve write scale-out. Users can use
MySQL Group Replication to implement highly available shards. Each shard
can map into a Replication Group.
• Alternative to Master-Slave replication
– It may be that a single master server makes it a single point of contention.
Writing to an entire group may prove more scalable under certain
circumstances.

The theory behind it...
• Implementation based in Replicated Database State Machines
– Group Communication Primitives resenble properties of Databases
– Distributed systems meet Databases: Pedone, Guerraoui and Schiper paper
• Deferred update replication: before committing locally we certify in all
nodes
– In order to implement it one needs Atomic Broadcast
– Necessary to avoid inconsistent Certification outcome. Endured by Atomic
Broadcast:minimum requirement for DBSM.
• Membership Service
– Group Members: It allows one to know in a moment in time all the members that
are participating in the protocol, associated with a logical identifier (view id)
– View Synchrony: Ensure that messages from past views are all delivered before a
new view is installed.

How things work!2

Lets add a node to an existing group: Setup
• Create a user for distributed recovery
• Server needs to be started with the correct configuration:
13
./bin/mysqld --no-defaults --basedir=. --datadir=<DATADIR_LOCATION> –P <PORT>
--socket=mysqld<ID>.sock --log-bin=master-bin --server-id=<ID>
--gtid-mode=on --enforce-gtid-consistency --log-slave-updates
--binlog-checksum=NONE --binlog-format=row
--master-info-repository=TABLE --relay-log-info-repository=TABLE
--transaction-write-set-extraction=MURMUR32
--plugin-dir=lib/plugin --plugin-load=group_replication.so
./bin/mysqld --no-defaults --basedir=. --datadir=<DATADIR_LOCATION> –P <PORT>
--socket=mysqld<ID>.sock --log-bin=master-bin --server-id=<ID>
--gtid-mode=on --enforce-gtid-consistency --log-slave-updates
--binlog-checksum=NONE --binlog-format=row
--master-info-repository=TABLE --relay-log-info-repository=TABLE
--transaction-write-set-extraction=MURMUR32
--plugin-dir=lib/plugin --plugin-load=group_replication.so
./bin/mysql -uroot -h 127.0.0.1 -P 13001 -p --prompt='server1>'

server1>
CREATE USER 'rpl_user'@'%' IDENTIFIED BY 'rpl_pass';
GRANT REPLICATION SLAVE ON *.* TO rpl_user@'%';
./bin/mysql -uroot -h 127.0.0.1 -P 13001 -p --prompt='server1>'

server1>
CREATE USER 'rpl_user'@'%' IDENTIFIED BY 'rpl_pass';
GRANT REPLICATION SLAVE ON *.* TO rpl_user@'%';

Lets add a node to a group : Setup (2)
• Now lets configure the replication user for recovery...
• ...and the communication backbone
14
SET GLOBAL group_replication_recovery_user='rpl_user';
SET GLOBAL group_replication_recovery_password='rpl_pass';
SET GLOBAL group_replication_recovery_user='rpl_user';
SET GLOBAL group_replication_recovery_password='rpl_pass';
SET GLOBAL group_replication_group_name= <valid UUID>;
SET GLOBAL group_replication_local_address=<this node address:port for the
communication backbone>;
SET GLOBAL group_replication_peer_addresses= <comma-separated list of all other
nodes in the group>;
SET GLOBAL group_replication_bootstrap_group= 0;
SET GLOBAL group_replication_group_name= <valid UUID>;
SET GLOBAL group_replication_local_address=<this node address:port for the
communication backbone>;
SET GLOBAL group_replication_peer_addresses= <comma-separated list of all other
nodes in the group>;
SET GLOBAL group_replication_bootstrap_group= 0;

Start me up!
• Server that joins the group will automatically synchronize with the
others.
• It will retrieve the difference from its data to the data of the group members
• Hint: provision the new node with data before joining an existing group
15
M M M M M N
I want to play with you
START GROUP REPLICATION;
ONLINE

Start me up! (2)
16
M M M M M N
ONLINE
RECOVERING
SELECT * FROM performance_schema.replication_group_membersG
M M M M M N
ONLINE

Well, I need to go now...
• If a server leaves the group, the others will automatically be informed.
17
M M M M M M
My machine needs maintenance
or a system crash happens
Each membership configuration
is identified by a view_id
view_id: 4
STOP GROUP REPLICATION;

The world keeps spinning until...
• If a server leaves the group, the others will automatically be informed.
• Server that (re)joins the group will automatically synchronize with the
others.
18
M M M M M
view_id: 5
M M M M M M
RECOVERING -> ONLINE
view_id: 6

How to use3

Multi-Master update everywhere!
• Any two transactions on different servers can write to the same tuple.
• Conflicts will be detected and dealt with.
– First committer wins rule.
20
M M M M M
UPDATE t1 SET a=4 WHERE a=2UPDATE t1 SET a=3 WHERE a=1
OKOK
M M M M M
UPDATE t1 SET a=2 WHERE a=1UPDATE t1 SET a=3 WHERE a=1
OK

Full GTID support!
• All group members share the same UUID, the group name.
21
M M M M M
INSERT y;
Will have GTID: group_name:2
INSERT x;
Will have GTID: group_name:1

Management
• Monitor group replication stats though Performance Schema tables.
22
mysql> SELECT * FROM
performance_schema.replication_connection_statusG
*************************** 1. row ***************************
CHANNEL_NAME: group_replication_applier
GROUP_NAME: 8a94f357-aab4-11df-86ab-c80aa9429563
SOURCE_UUID: 8a94f357-aab4-11df-86ab-c80aa9429563
THREAD_ID: NULL
SERVICE_STATE: ON
...
mysql> SELECT * FROM
performance_schema.replication_connection_statusG
*************************** 1. row ***************************
GROUP_NAME: 8a94f357-aab4-11df-86ab-c80aa9429563
SOURCE_UUID: 8a94f357-aab4-11df-86ab-c80aa9429563
THREAD_ID: NULL
SERVICE_STATE: ON
...
mysql> SELECT * FROM performance_schema.replication_group_member_statsG
*************************** 1. row ***************************
VIEW_ID: 1428497631:3
MEMBER_ID: e38fdea8-dded-11e4-b211-e8b1fc3848de
COUNT_TRANSACTIONS_IN_QUEUE: 0
COUNT_TRANSACTIONS_CHECKED: 12
COUNT_CONFLICTS_DETECTED: 5
COUNT_TRANSACTIONS_VALIDATING: 6
TRANSACTIONS_COMMITTED_ALL_MEMBERS: 8a84f397-aaa4-18df-89ab-
c70aa9823561:1-7
LAST_CONFLICT_FREE_TRANSACTION: 8a84f397-aaa4-18df-89ab-c70aa9823561:7
mysql> SELECT * FROM performance_schema.replication_group_member_statsG
*************************** 1. row ***************************
VIEW_ID: 1428497631:3
MEMBER_ID: e38fdea8-dded-11e4-b211-e8b1fc3848de
COUNT_TRANSACTIONS_IN_QUEUE: 0
COUNT_TRANSACTIONS_CHECKED: 12
COUNT_CONFLICTS_DETECTED: 5
COUNT_TRANSACTIONS_VALIDATING: 6
TRANSACTIONS_COMMITTED_ALL_MEMBERS: 8a84f397-aaa4-18df-89ab-
c70aa9823561:1-7
LAST_CONFLICT_FREE_TRANSACTION: 8a84f397-aaa4-18df-89ab-c70aa9823561:7
mysql> SELECT * FROM performance_schema.replication_group_membersG
*************************** 1. row ***************************
MEMBER_ID: 597dbb72-3e2c-11e4-9d9d-ecf4bb227f3b
MEMBER_HOST: nightfury
MEMBER_PORT: 13000
MEMBER_STATE: ONLINE
*************************** 2. row ***************************
...
mysql> SELECT * FROM performance_schema.replication_group_membersG
*************************** 1. row ***************************
MEMBER_ID: 597dbb72-3e2c-11e4-9d9d-ecf4bb227f3b
MEMBER_HOST: nightfury
MEMBER_PORT: 13000
MEMBER_STATE: ONLINE
*************************** 2. row ***************************
...

Conclusion4

Summary
• Cloud Friendly
– Great technology for deployments where elasticity is a requirement, such as cloud
based infrastructures.
• Integrated
– With server core through a well defined API.
– With GTIDs, row based replication, performance schema tables.
• Autonomic and Operations Friendly
– It is self-healing: no administrative overhead for handling server fail-overs.
– Provides fault-tolerance, enables multi-master update everywhere and a
dependable MySQL service.
• Lab releases provide a sneak peek at what is coming - a new replication plugin and
exciting new infrastructure: MySQL Group Replication and MySQL Router.

• Strong development cycles and continuous community
engagement through regular lab releases.
Releases
25
2014-Apr-06
Labs release: 0.3.0
2014-Aug-06
Labs release: 0.4.0
2015-Sep-14
Labs release: 0.5.0
Introduces new
communication engine!
2015-Oct-22
Labs release: 0.6.0
2016-Jan-13
Labs release: 0.7.0
WINDOWS SUPPORT

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

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