MySQL Replication Basics -Ohio Linux Fest 2016

MySQL Replication Basics
Ohio Linux Fest 2016
Dave Stokes
david.stokes@oracle.com
@stokes
slideshare.net/davidmstokes
1

Safe Harbor 2
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.

Quick MySQL Catch Up
21 Years Old
MySQL has been part of
Oracle’s family of databases for
six years.
MySQL 8
MySQl 5.7 is the current release
but the next version will be
MySQL 8. Big feature is real
time data dictionary
Group Replication
Active master-master
replication.
JSON
A new native JSON datatype to
store documents in a column of
a table
Document Store
Programmers not know SQL
but need a database? X Devapi
allows them to use RDMS from
language of choice
Encryption
Use Oracle Key Vault to encrypt
your data at rest.
3

Replication
Past
Present
Future
4

Basic Premise Behind
Replication
1. Copy all the data off one server and on to another.
2. Setup Replication.
3. Log any changes on the first server to a log file, apply that
logfile to the second server.
5

Imagine Your Data as a Painting:
Make copy of Mona Lisa
6

Make copy of changes to Mona Lisa
7

Keep making copy of changes to Mona Lisa
8

Architecture
Binary Log on master
Slave Attaches
I/O Thread Grabs Data
Data copied to slave
Applier thread changes slave’s data
9

Graphic overview of replication
10

But what are we
replicating?
11

Replicating changes to tables and data
SBR: When using statement-based binary logging, the
master writes SQL statements to the binary log.
Replication of the master to the slave works by
executing the SQL statements on the slave. This is
called statement-based replication (often abbreviated
as SBR), which corresponds to the standard MySQL
statement-based binary logging format. Replication
capabilities in MySQL version 5.1.4 and earlier used
this format exclusively.
Structured Query Language (SQL)
RBR: When using row-based logging, the master
writes events to the binary log that indicate how
individual table rows are changed. Replication of the
master to the slave works by copying the events
representing the changes to the table rows to the
slave. This is called row-based replication (often
abbreviated as RBR).
The Delta
12

OrBoth
MBR: You can also configure MySQL to use a mix of both
statement-based and row-based logging, depending on which is
most appropriate for the change to be logged. This is called
mixed-format logging. When using mixed-format logging, a
statement-based log is used by default. Depending on certain
statements, and also the storage engine being used, the log is
automatically switched to row-based in particular cases.
Replication using the mixed format is often referred to as
mixed-based replication or mixed-format replication.
13

Notes for the future
With MySQL.5.6 RBR started sending over only the
primary key and the changed data (not sending
unchanged data) which can drastically cut the amount
of data sent to slave servers. This can be huge!!
Many future products will work better with RBR as it
more deterministic. So plan accordingly.
14

Threading
Before 5.6 MySQL Replication is SINGLE threaded – Airline
boarding example
MySQL 5.6 is multi-threaded at the database level
MySQL 5.7 is multi-threaded at the table level
15

Async and Semi Synchronous
Semi Synchronous replication -- a commit
performed on the master blocks before
returning to the session that performed the
transaction until at least one slave
acknowledges that it has received and
logged the events for the transaction (Note
not written to table, just recorded for
future).
Asynchronous replication -- slave servers
retrieve data, master unaware of slave’s
consumption.
17

Common - Read / Write Split
20

Multi-source Replication -- MySQL 5.7
21

Group Replcation -- Labs.MySQL.Com for evaluation
22

Multi-Master
Lots of folks want TWO active
masters and this can be done but
not recommended, You need to
have a sharp crew and plan for
conflicts.
Not generally recommended
before Group Replication
23

Multi-Master
MySQL Cluster
You can run active-active
master-master with MySQL
Cluster, even between data
centers.
This can be very expensive and
MySQl Cluster is not a full
featured version of the MySQL
Server.
24

Galera Cluster
Layer separate from MySQL that is
mainly for high availability (not high
performance).
Claims to have snapshot isolation on
transactions but watch out for ‘first
committer wins’ and prepare for
rollbacks.
Not low latency
25

How to setup
MySQL
Replication
26

Two types of
replication
w/ & w/o
GTIDs
A global transaction identifier (GTID) is a unique
identifier created and associated with each
transaction committed on the server of origin
(master). This identifier is unique not only to the
server on which it originated, but is unique across
all servers in a given replication setup. There is a
1-to-1 mapping between all transactions and all
GTIDs.
3E11FA47-71CA-11E1-9E33-C80AA9429562:1-5
Note the 1-5 is a group of
transactions
27

Binlog & ID
Enable Binary Log on
Master, Unique ID
number
Create
User
Create user for
replication
Binlog
Offset
Get Master’s Binary
Log coordinates
Snapshot
Snapshot data, copy
onto slave
SLAVE
running
CHANGE MASTER
command and START
SLAVE
Before GTIDs (MySQL 5.5 and before) 28

Enable Binary Log & Unique ID on Master
Edit my.cnf file
[mysqld]
log-bin=mysql-bin
server-id=1
29

Create replication user
mysql> CREATE USER 'repl'@'%.mydomain.com' IDENTIFIED BY
'slavepass';
mysql> GRANT REPLICATION SLAVE ON *.* TO
'repl'@'%.mydomain.com';
30

Unlock tables mysql> UNLOCK TABLES;
32

Config
slave &
load data
No config thee slave
server. Remember
server-id must be
unique
[mysqld]
server-id=2
shell> mysql -h master
< fulldb.dump
33

Change Master & Start Slave
mysql> CHANGE MASTER TO
-> MASTER_HOST='master_host_name',
-> MASTER_USER='replication_user_name',
-> MASTER_PASSWORD='replication_password',
-> MASTER_LOG_FILE='recorded_log_file_name',
-> MASTER_LOG_POS=recorded_log_position;
mysql> START SLAVE;
34

Read only
Sync both servers by
setting to read if
replication is already
running
Stop
Servers
Stop both servers
Restart
w/GTIDs
Restart both servers
with GTIDs enabled
Change
master
Instruct the slave to use the
master as the replication
data source and to use
auto-positioning, and then
start the slave.
Read Only
off
Remove read only
With GTIDs (MySQL 5.6 and later) 35

Replication Setup
with GTIDs
mysql> SET @@global.read_only = ON;
mysql>mysqladmin -uusername -p
shutdown
shell> mysqld --gtid-mode=ON
--enforce-gtid-consistency &
mysql> CHANGE MASTER TO
> MASTER_HOST = host,
> MASTER_PORT = port,
> MASTER_USER = user,
> MASTER_PASSWORD = password,
> MASTER_AUTO_POSITION = 1;
mysql> START SLAVE;
36

Finished!
(Almost)
David.Stokes@oracle.com
@stoker
slideshare.net/davidmstokes
37
Hard to get a lot of info in in
such a short time. Please get
details from the MySQL Manual

30 Minutes!!!
30 Minutes! Can’t Cover all of MySQL Replication in 30 minutes!!!!! 38

https://github.com/datacharmer
Giuseppe Maxia has lot of great code
for getting used to replication -- see
~/mysql-replication-sample
39
Great Place
to Find
examples &
MySQL
Sandbox

MySQL
Utilities
FREE Scripts written in Python, used with MySQL
Workbench or stand alone
1. Copy, diff databases
2. Disk usage, grants, copy users
3. Search for processed and kill ‘em
4. Setup replication and failover
40

Mysqlrplcheck -- check replication setup
shell> mysqlrplcheck --master=root@host1:3310 --slave=root@host2:3311
# master on host1: ... connected.
# slave on host2: ... connected.
Test Description Status
------------------------------------------------------------------------
Checking for binary logging on master [pass]
Are there binlog exceptions? [pass]
Replication user exists? [pass]
Checking server_id values [pass]
Is slave connected to master? [pass]
Check master information file [pass]
Checking InnoDB compatibility [pass]
Checking storage engines compatibility [pass]
Checking lower_case_table_names settings [pass]
Checking slave delay (seconds behind master) [pass]
# ...done.
41

Mysqlrplcheck -- replication checker
shell> mysqlrplsync --master=user:pass@localhost:3310
--slaves=rpl:pass@localhost:3311,rpl:pass@localhost:3312
#
# GTID differences between Master and Slaves:
# - Slave 'localhost@3311' is 15 transactions behind Master.
# - Slave 'localhost@3312' is 12 transactions behind Master.
#
# Checking data consistency.
#
# Using Master 'localhost@3310' as base server for comparison.
# Checking 'test_rplsync_db' database...
# - Checking 't0' table data...
# [OK] `test_rplsync_db`.`t0` checksum for server 'localhost@3311'.
# - Checking 't1' table data...
# Checking 'test_db' database... 42

Mysqlslavetrx -- skip bad transactions
shell> mysqlslavetrx --gtid-set=af6b22ee-7b0b-11e4-aa8d-606720440b68:7-9
--slaves=user:pass@localhost:3311,user:pass@localhost:3312
WARNING: Using a password on the command line interface can be insecure.
#
# GTID set to be skipped for each server:
# - localhost@3311: af6b22ee-7b0b-11e4-aa8d-606720440b68:7-9
# - localhost@3312: af6b22ee-7b0b-11e4-aa8d-606720440b68:7-9
#
# Injecting empty transactions for 'localhost:3311'...
# Injecting empty transactions for 'localhost:3312'...
#
#...done.
43

MySQL Replication Basics -Ohio Linux Fest 2016

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MySQL Replication Basics -Ohio Linux Fest 2016