MySQL Replication Options - Percona · MySQL Replication Options. 2 Few Words About Percona Your Partner in MySQL and MongoDB Success 100% Open Source Software “No Lock in Required”

Peter Zaitsev, CEO, Percona

Moscow MySQL User Meetup Moscow,Russia

MySQL Replication Options

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Few Words About Percona

Your Partner in MySQL and MongoDB Success

100% Open Source Software

“No Lock in Required” Solutions

and Services

We work with MySQL, MariaDB, MongoDB,

Amazon RDS and Aurora

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In This Presentation

Why Replication ?

How to think about Replication

Overview of what MySQL Has to Offer

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Replication

Having Multiple Copies of the data, updated with

changes

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Why Replication

Availability Scalability

Performance

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Availability

Service Stays up when component

fails

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Availability via Redundancy

Have more than one system

Works well for stateless systems

Is not enough for databases

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Availability via Replication

Redundant Computing Resource

Paired with Replicated Data

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Component Failure

Node Failures • Total Crash • Process Crash • Stall/Unresponsive • Consistency Issues

Network Failures • Single Port Failures • Partitions • Complicated Failures

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Scalability

Scales Reads

Does not Scale Writes very well

Data Distribution is needed for scaling writes

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Performance

Reduce response time by maintaining replica closer to

user

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Talking about

Full Database Replication • System of Record

Partial Database Replication Can be used as • Cache • Synchronization of Client Data

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Where Replication Happens

Storage Level

Database Level

Application Level

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Storage Level Replication

Replication RAID

Typically provides cold standby

Simple choice which works with many systems

Amazon Aurora – Smart Storage

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Database level

Most Flexible

Most Common

Hot/Warm Spare

Some can do Active-Active

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Application Level

Hard to get right

Rarely used, even more so used right

Partial Replication/Syncronization

Smart conflict resolution

Cross Vendor Redundancy

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Replication Properties

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Number of Writable Nodes

Single Writer (Master)

Write Anywhere (Multi Master)

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Single Master

All writes go to the single node

One way replication stream

Simple

No Conflicts

Replication aware Application or Connector

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Multiple Active Masters

Can write to multiple masters

Replication is multi-directional

More Complicated

Possibility of Conflicts

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Sync or Async

Synchronous Replication

Asynchronous Replication

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Data “Persisted” on Target Server

Guarantees No Data Loss if Source server fails

Conflicts can be easily prevented

Expensive

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What “Persisted” means ?

In Memory • Assumes power loss of both servers

does not happen

On Disk • Handles Total Loss of Master and

Power loss on the Slave

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Asynchronous Replication

Anything not Synchronous

Many different variants exist!

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Asynchronous Properties

Commit on Master • What happens with

Persistence ? • What happens with

Visibility ?

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Persistence

Uncommitted Data on Master

Committed Data on Master

Date in Slave’s memory

Data on Slave’s Disk (log)

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Visibility

Results be visible by concurrent sessions before acknowledgement • Phantom Reads

Results can’t be visible by concurrent sessions • No Phantom Reads

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Conflits

No Conflict Handling

Conflict Detection

Conflict Resolution

Conflict Prevention

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Acknowledgements

Applies both to Sync and Some Async

How many node have successfully replicated data ?

All ?

One ?

Majority ?

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Level of Control

Global Control vs Database Control

Control by Writer vs Reader

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Number of Replicas

On (2 nodes)

Two or more (3+ nodes)

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2 nodes

Basic Redundancy

Need Help with Failure detection and Split Brain

No Redundancy in case of node maintainance

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3+ Nodes

Much better Redundancy

Quorum based failure handling works out of the box

Can do node maintenance without redundancy loss

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Failure Detection and Promotion

Built-In

Handled by External Tools

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Replica Provisioning

Manual

Automatic

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Gotchas

Distributed systems are complicated. All products have their own gotchas.


MySQL Replication

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“Classic” MySQL Replication

Fully Asynchronous

No Failure Detection and Promotion

Manual Provisioning

Can run Multi-Master

No Conflict Handling

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Semi-Sync Replication 5.6

Wait for one of the slaves to ack update before response to client

Commits too soon on the Master

“Phantom Reads” / Possible loss of visible changes

Can switch to asynchronous mode

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Semi-Sync Replication 5.7

Commits on the Master only after slave acknowledges

Update invisible to other clients until slave acknowledges

Can be Configured to have MySQL 5.6 behavior

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Making MySQL Replication Better

MHA

MySQL Failover

PRM


Percona XtraDB Cluster and “Galera”

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Percona XtraDB ClusterVirtually Synchronous Replication

Well known Innodb Storage Engine

All Reads are Local

Parallel Replication

Write to any node behavior

Built in Node Provisioning and HA

Works great in the Cloud !

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PXC vs Galera

Galera • Is replication

technology/library • Compare to Linux

Kernel

Percona XtraDB Cluster • Percona Server • Enabling Enhancements • Galera Library • Provisioning Tools • HA and Load Balancing • Integrated together and

Tested • Compare to Linux

Distribution

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PXC Data Architecture

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Architecture Concepts

All Nodes Have Full copy of Data

Every Node is Equal

No Central Management

No SPOF

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Understanding Cluster

The cluster can be seen as a meeting !

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PXC (Galera cluster) is a meeting

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PXC (Galera cluster) is a meeting 55

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New meeting !

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Cluster Reads

Reads are always Local

Stale Reads can be allowed or disallowed

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Cluster Writes

Write on one node or Write Anywhere

Certification Based Replication

Communication on Commit only

Asynchronous Application

Parallel Replication

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Transaction Commit Flow

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Loss of connectivity

Quorum 61

Network Problem

Does not accept Reads & Writes

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Automatic Node Provisioning

writes

writeswrites

new node joining

data is copied via SST or IST

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Automatic Node Provisioning

writes

writeswrites

new node joiningwhen ready

writes

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Dedicated shared HAProxy application server 1 application server 2 application server 3

PXC node 1 PXC node 2 PXC node 3

HA PROXY

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HAProxy on application sideapplication server 1 application server 2 application server 3

PXC node 1 PXC node 2 PXC node 3

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HA PROXY HA PROXY HA PROXY

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Scaling Writes ?

Shard over PXC Cluster rather than MySQL Replicas

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Thinks To Keep in MindUse Innodb storage engine

Primary Key on all tables

Avoid Large write transactions (changing many rows)

Plan Data size for SST time correctly

Hot Rows

Optimistic Locking

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MySQL Group Replication

Similar to Galera

Currently in Development

Better integrated with MySQL

No Automated provisioning (yet)

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MySQL Cluster

Mostly In Memory Storage


Pessimistic Locking

Conflict Detection with Async Replication

Niche Use Only

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New Developments

MySQL Fabric

MySQL Router

MariaDB Max Scale

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Percona Live 2016 call for papers is Open

Call for Papers Open until November 29, 2015

MySQL, MongoDB, NoSQL, Data in The Cloud

Anything to make Data Happy!

http://bit.ly/PL16Call

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Peter Zaitsev [email protected]

P.S We’re Hiring http://bit.ly/PerconaJobs

Thank You!

mailto:[email protected]

MySQL Replication Options - Percona · MySQL Replication Options. 2 Few Words About Percona Your Partner in MySQL and MongoDB Success 100% Open Source Software “No Lock in Required”

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