MySQL Group Replication

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High Availability Using MySQL Group
ReplicaIon
Mark Swarbrick
MySQL Principle Presales consultant
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Safe Harbor Statement
The following is intended to outline our general product direcIon. It is intended for
informaIon purposes only, and may not be incorporated into any contract. It is not a
commitment to deliver any material, code, or funcIonality, and should not be relied upon
in making purchasing decisions. The development, release, and Iming of any features or
funcIonality described for Oracle’s products remains at the sole discreIon of Oracle.
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Program Agenda

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Program Agenda
Background
MySQL Group ReplicaIon
Architecture
Big Picture
Conclusion
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2
3
4
5
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Background 1

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M S
S
S
S
M
write clients read clients
read clients
write clients
More
reads?
More
slaves!
Read scale-out
Background: What is ReplicaIon Used For?
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C
B
A
C
B
A Crash
C
B
A
B is the
new master
Uh Oh! Whew!
Redundancy as a major building block for high availability: If master crashes, promote
slave to master
Background: What is ReplicaIon Used For?
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MySQL Group ReplicaIon
• What is MySQL Group ReplicaKon?
“Update everywhere replicaIon plugin for MySQL with built-in automaKc distributed
recovery, conflict handling, group membership and distributed agreement.”
• What does the MySQL Group ReplicaKon plugin do for the user?
– Removes the need for handling server fail-over.
– Provides fault tolerance.
– Enables update everywhere setups.
– Automates group reconfiguraIon (handling of crashes, failures, re-connects).
– Provides a highly available replicated database.
– AutomaIc distributed coordinaIon (protects against split-brain and message loss).
– Less admin overhead, means more fun Ime!
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MySQL Group ReplicaIon
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M M M M M
ReplicaKon Group
Clients

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Some Theory Behind It...
• ImplementaIon based in Replicated Database State Machines
– Group CommunicaIon PrimiIves resemble properIes of Databases.
• Deferred update replicaIon: propagate atomically, check conflicts,
eventually apply
– Distributed state machine requires agreed delivery – implies total order;
– DeterminisIc cerIficaIon requires total order delivery.
• Membership Service
– Which servers are parIcipaIng in the replicaIon group at a given moment in Ime?
(associated with a logical Imestamp [ - view idenIfier]).
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MySQL Group ReplicaIon 2
2.1 MulK-Master

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

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

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MulI-Master update everywhere!
• Any two transacIons on different servers can write to the same tuple.
• Conflicts will be detected and dealt with.
– First commiker wins rule.
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M M M M M
UPDATE t1 SET a=2 WHERE a=1 UPDATE t1 SET a=3 WHERE a=1

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

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MySQL Group ReplicaIon 2
2.1
2.2
MulK-Master
AutomaKc distributed server recovery

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AutomaKc distributed server recovery!
• Server that joins the group will automaIcally synchronize with the others.
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M M M M M N
I want to play with you

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AutomaKc distributed server recovery!
• Server that joins the group will automaIcally synchronize with the others.
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M M M M M N
ONLINE
RECOVERING

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AutomaKc distributed server recovery!
• Server that joins the group will automaIcally synchronize with the others.
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M M M M M N
ONLINE

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AutomaKc distributed server recovery!
• If a server leaves the group, the others will automaIcally be informed.
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M M M M M M
My machine needs maintenance
or a system crash happens
Each membership configuraKon
is idenKfied by a logical Kmestamp,
i.e., view_id
view_id: 4

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AutomaKc distributed server recovery!
• If a server leaves the group, the others will automaIcally be informed.
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M M M M M
view_id: 5

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AutomaKc distributed server recovery!
• Server that (re)joins the group will automaIcally synchronize with the
others.
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M M M M M M
RECOVERING -> ONLINE
view_id: 6

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MySQL Group ReplicaIon 2
2.1
2.2
2.3
MulK-Master
AutomaKc distributed server recovery
MySQL/InnoDB look & feel

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MySQL/InnoDB look & feel!
• Load the plugin and start replicaIng.
• Monitor group replicaIon stats though Performance Schema tables.
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mysql> SET GLOBAL group_replication_group_name= "9eb07c6d-5e24-11e5-854b-34028662c0cd";
mysql> START GROUP_REPLICATION;
mysql> SELECT * FROM performance_schema.replication_group_membersG
*************************** 1. row ***************************
CHANNEL_NAME: group_replication_applier
MEMBER_ID: 597dbb72-3e2c-11e4-9d9d-ecf4bb227f3b
MEMBER_HOST: nightfury
MEMBER_PORT: 13000
MEMBER_STATE: ONLINE
*************************** 2. row ***************************
...

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MySQL/InnoDB look & feel!
• Load the plugin and start replicaIng.
• Monitor group replicaIon stats though Performance Schema tables.
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mysql> SELECT * FROM performance_schema.replication_group_member_statsG
*************************** 1. row ***************************
CHANNEL_NAME: group_replication_applier
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

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MySQL/InnoDB look & feel!
• Load the plugin and start replicaIng.
• Monitor group replicaIon stats though Performance Schema tables.
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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
...

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MySQL Group ReplicaIon 2
2.1
2.2
2.3
2.4
MulK-Master
AutomaKc distributed server recovery
MySQL/InnoDB look & feel
Full GTID support

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

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Full GTID support!
• Users can specify the idenIfier for the transacIon.
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M M M M M
INSERT y;
Will have GTID: group_name:1
SET GTID_NEXT= “UUID:50”
INSERT x;

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Full GTID support!
• You can even replicate from a outside server to a group, global idenIfiers
will be preserved.
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M M M M M
Conflicts will be detected!

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MySQL Group ReplicaIon 2
2.1
2.2
2.3
2.4
2.5
MulK-Master
AutomaKc distributed server recovery
MySQL/InnoDB look & feel
Auto-increment configuraKon/handling
Full GTID support

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New distributed agreement and communicaKon engine
MySQL Group ReplicaIon 2
2.1
2.2
2.3
2.4
2.5
2.6
MulK-Master
AutomaKc distributed server recovery
MySQL/InnoDB look & feel
Auto-increment configuraKon/handling
Full GTID support

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New Distributed Agreement and CommunicaIons Engine
• MulIple OS support.
– Linux, but also Windows, OSX, Solaris, FreeBSD…
• No third-party souware required.
• No network mulIcast support required.
– MySQL Group ReplicaIon can now operate on cloud based installaIons on which
mulIcast is disallowed.
• No message size limit.
• No separate process.
– MySQL Group ReplicaIon is now self-contained on the same souware stack.
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Requirements
New distributed agreement and communicaKon engine
Auto-increment configuraKon/handling
Full GTID support
MySQL/InnoDB look & feel
LimitaKons
MySQL Group ReplicaIon 2
2.3
2.4
2.5
2.6
2.7
2.8

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Requirements (by design)
• Support for InnoDB only.
• Primary key is required on every table.
• Requires global transacIon idenIfiers turned on.
• OpImisIc execuIon: transacIons may abort on COMMIT due to conflicts
with concurrent transacIons on other members.
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Requirements
New distributed agreement and communicaKon engine
Auto-increment configuraKon/handling
Full GTID support
MySQL/InnoDB look & feel
LimitaKons
MySQL Group ReplicaIon 2
2.3
2.4
2.5
2.6
2.7
2.8

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LimitaIons
• Concurrent schema changes are not supported.
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Architecture
IntroducKon
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3.1

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MySQL Group ReplicaIon is
• Built on top of proven technology!
– Shares much of MySQL ReplicaIon infrastructure – thence does not feel alien!
– MulI-Master approach to replicaIon.
• Built on reusable components!
– Layered implementaIon approach.
– Interface driven development.
– Decoupled from the server core.
– The plugin registers as listener to server events.
– Reuses the capture procedure from regular replicaIon.
– Provides further decoupling from the communicaIon infrasctructure.
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The Complete Stack
Major Building Blocks
Architecture
IntroducKon
3
3.1
3.2
3.3

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The Complete Stack
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API
ReplicaKon
Plugin
API
MySQL
Server
Performance Schema Tables: Monitoring
MySQL
APIs: Lifecycle / Capture / Applier
InnoDB
ReplicaKon Protocol
Group Com. API
XCom
Network
Plugin
Capture Applier
Conflicts
Handler
Group Comm.
System (Corosync)
Group Com. Engine
Group Com. Binding
Recovery

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Use cases
Use cases
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4.1

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Use Cases
• ElasKc ReplicaKon
– Environments that require a very fluid replicaIon infrastructure, where the number
of servers has to grow or shrink dynamically and with as likle pain as possible.
• Highly Available Shards
– Sharding is a popular approach to achieve write scale-out. Users can use MySQL
Group ReplicaIon to implement highly available shards. Each shard can map into a
ReplicaIon Group.
• AlternaKve to Master-Slave replicaKon
– It may be that a single master server makes it a single point of contenIon. WriIng to
an enIre group may prove more scalable under certain circumstances.
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Use cases
Use cases
4
4.1
4.2 Big Picture

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Dependable and Scalable MySQL Setups
M
App
M M
Orchestrate & Manage
M App M M
Simple Shard
Mapping, State and
Extra metadata.
Control, Coordinate, Provision
...
Monitoring (MEM)
MySQL Router Group ReplicaIon – Shard 1
Group ReplicaIon – Shard N
C, PHP, Perl, ...
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MySQL Router

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Conclusion 5

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Summary
• Cloud Friendly
– Great techonology for deployments where elasIcity is a requirement, such as cloud
based infrastructures.
• Integrated
– With server core through a well defined API.
– With GTIDs, row based replicaIon, performance schema tables.
• Autonomic and OperaKons Friendly
– It is self-healing: no admin overhead for handling server fail-overs.
– Provides fault-tolerance, enables mulI-master update everywhere and a dependable
MySQL service.
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Where to go from here?
• Packages
– hkp://labs.mysql.com
• Blogs from the Engineers (news, technical informaIon, and much more)
– hkp://mysqlhighavailability.com
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