MySQL

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MySQL
For
Linux
Sysadmins
Morgan
Tocker
MySQL
Community
Manager
August,
2014

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Safe
Harbor
Statement
The
following
is
intended
to
outline
our
general
product
direction.
It
is
intended
for
information
purposes
only,
and
may
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be
incorporated
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contract.
It
is
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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
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Oracle’s
products
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4
Program
Agenda
Introduction
MySQL
Architecture
Backup
&
Replication
Performance
&
Capacity
Planning
1
2
3
4

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The
Career
Path
to
DBA
• Start
as
a
Developer
• Start
as
a
Sysadmin
• Train
to
be
a
DBA
5
Usually either #1 or #2.
I started as a Developer
}

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Non
Exhaustive
List
of
Duties
• Backup
• Replication
• Patching
&
Upgrades
• Performance
and
Capacity
Planning
• Coaching
&
Mentoring
• Fighting
Fires
6

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Program
Agenda
Introduction
MySQL
Architecture
Backup
&
Replication
Performance
&
Capacity
Planning
1
2
3
4
2
1

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About
MySQL
• Version
numbers
are
misleading:
• 5.5
to
5.6
was
the
biggest
upgrade
in
history
• 5.6.xx
• Micro-­‐release
approximately
every
2
months.
• Fixes
bugs
and
security
vulnerabilities.
8

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About
MySQL
(cont.)
• 5.7.xx
• Current
focus
of
development.
• Release
cycle
is
2-­‐3
years.
• 5.5
and
5.6
are
under
active
support.
9

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Storage
Engines
in
MySQL
• InnoDB
(default)
• MyISAM
(previous
default)
• NDB
Cluster
• Other
11

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Memory
Usage
• Databases
like
to
allocate
large
amounts
of
memory
for
caches
• Better
to
run
with
smaller
caches
than
swap
• Kind
of
works
as
“double
buffering”
of
operating
system
caches
12

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MySQL
Server
• Single
process
of
mysqld
• Supervisor
process
is
mysqld_safe
• Each
new
MySQL
connection
consumes
a
thread
• With
the
server
maintaining
a
small
thread
cache
13

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Transaction
System
StorageCaching
SYS_TABLES
ibdata1
space0
Page Cache
A.ibd
B.ibd
C.ibd
IBUF_HEADER
IBUF_TREE
TRX_SYS
FIRST_RSEG
DICT_HDR
Data Dict.
SYS_COLUMNS
SYS_INDEXES
SYS_FIELDS
Block 1 (64 pages)
Block 2 (64 pages)
iblogfile0 iblogfile1 iblogfile2
Tables with
file_per_tableDoublewrite Buffer
BufferPool
Data Dictionary Cache
Adaptive Hash Indexes
Buffer Pool LRU
Additional Mem Pool
Log Buffer
LogGroup
Buffer Pool Flush List
In Memory
On Diskhttps://github.com/jeremycole/innodb_diagrams

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InnoDBTransaction
System
StorageCaching
SYS_TABLES
ibdata1
space0
Page Cache
A.ibd
B.ibd
C.ibd
IBUF_HEADER
IBUF_TREE
TRX_SYS
FIRST_RSEG
DICT_HDR
Data Dict.
SYS_COLUMNS
SYS_INDEXES
SYS_FIELDS
Block 1 (64 pages)
Block 2 (64 pages)
iblogfile0 iblogfile1 iblogfile2
Tables with
file_per_tableDoublewrite Buffer
BufferPool Data Dictionary Cache
Adaptive Hash Indexes
Buffer Pool LRU
Additional Mem Pool
Log Buffer LogGroup
Buffer Pool Flush List
SELECT * FROM a
WHERE id = 10;
mysqld
Not Found
Query
-­‐
Non
Cached

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InnoDBTransaction
System
StorageCaching
SYS_TABLES
ibdata1
space0
Page Cache
A.ibd
B.ibd
C.ibd
IBUF_HEADER
IBUF_TREE
TRX_SYS
FIRST_RSEG
DICT_HDR
Data Dict.
SYS_COLUMNS
SYS_INDEXES
SYS_FIELDS
Block 1 (64 pages)
Block 2 (64 pages)
iblogfile0 iblogfile1 iblogfile2
Tables with
file_per_tableDoublewrite Buffer
BufferPool Data Dictionary Cache
Adaptive Hash Indexes
Buffer Pool LRU
Additional Mem Pool
Log Buffer LogGroup
Buffer Pool Flush List
SELECT * FROM a
WHERE id = 10;
mysqld
Query
-­‐
Cached

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Update
Query
in
a
Transaction
(simplified)
InnoDB
Transaction
System
StorageCaching
SYS_TABLES
ibdata1
space0
Page Cache
A.ibd
B.ibd
C.ibd
IBUF_HEADER
IBUF_TREE
TRX_SYS
FIRST_RSEG
DICT_HDR
Data Dict.
SYS_COLUMNS
SYS_INDEXES
SYS_FIELDS
Block 1 (64 pages)
Block 2 (64 pages)
iblogfile0 iblogfile1 iblogfile2
Tables with
file_per_tableDoublewrite Buffer
BufferPool
Data Dictionary Cache
Adaptive Hash Indexes
Buffer Pool LRU
Additional Mem Pool
Log Buffer
LogGroup
Buffer Pool Flush List
UPDATE a SET col1 =
‘new’ WHERE id = 10;
mysqld
commit;

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Log
Files
• Provide
recovery.
• Only
written
to
in
regular
operation.
• Read
only
required
if
there
is
a
crash.
• Are
rewritten
over-­‐and-­‐over
again.
• Think
of
it
like
a
tank
tread.
18

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19
Program
Agenda
Introduction
MySQL
Architecture
Backup
&
Replication
Performance
&
Capacity
Planning
1
2
3
4
1
3

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Backup
(Theory)
• Cold
• Warm
• Hot
20

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Backup
Consistency
• Must
represent
a
single
point
in
time
21

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| 22
customerid name
1 Acorn Enterprises
2 First National Squirrel Bank
3 Squirrels 5000 Inc
invoiceid customerid ...
1 1 # Acorn Enterprises
2 1 # Acorn Enterprises
3 3 # Squirrels 5000 Inc
customer
invoice
itemid invoiceid Description Amount
1 1 1 hrs Professional
Services
$10
2 2 Acorn Parts $12.50
3 2 5 hrs Professional
Services
$50
4 3 Delivery Fee $17.50
5 3 Replacement
Acorn
$20
invoice_item

23. Copyright
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| 23
customerid name
1 Acorn Enterprises
2 First National Squirrel Bank
3 Squirrels 5000 Inc
invoiceid customerid ...
1 1 # Acorn Enterprises
2 1 # Acorn Enterprises
3 3 # Squirrels 5000 Inc
customer
invoice
itemid invoiceid Description Amount
1 1 1 hrs Professional
Services
$10
2 2 Acorn Parts $12.50
3 2 5 hrs Professional
Services
$50
4 3 Delivery Fee $17.50
5 3 Replacement
Acorn
$20
invoice_item

24. Copyright
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2014
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| 24
customerid name
1 Acorn Enterprises
2 First National Squirrel Bank
3 Squirrels 5000 Inc
invoiceid customerid ...
1 1 # Acorn Enterprises
2 1 # Acorn Enterprises
3 3 # Squirrels 5000 Inc
customer
invoice
itemid invoiceid Description Amount
1 1 1 hrs Professional
Services
$10
2 2 Acorn Parts $12.50
3 2 5 hrs Professional
Services
$50
4 3 Delivery Fee $17.50
5 3 Replacement
Acorn
$20
invoice_item

25. Copyright
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2014
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| 25
customerid name
1 Acorn Enterprises
2 First National Squirrel Bank
3 Squirrels 5000 Inc
4 Savvy Squirrel Global
invoiceid customerid ...
1 1 # Acorn Enterprises
2 1 # Acorn Enterprises
3 3 # Squirrels 5000 Inc
4 4 # Savvy Squirrels
customer
invoice
itemid invoiceid Description Amount
1 1 1 hrs Professional
Services
$10
2 2 Acorn Parts $12.50
3 2 5 hrs Professional
Services
$50
4 3 Delivery Fee $17.50
5 3 Replacement
Acorn
$20
6 4 Premium Acorn $999
invoice_item

26. Copyright
©
2014
Oracle
and/or
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rights
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| 26
customerid name
1 Acorn Enterprises
2 First National Squirrel Bank
3 Squirrels 5000 Inc
4 Savvy Squirrel Global
invoiceid customerid ...
1 1 # Acorn Enterprises
2 1 # Acorn Enterprises
3 3 # Squirrels 5000 Inc
4 4 # Savvy Squirrels
customer
invoice
itemid invoiceid Description Amount
1 1 1 hrs Professional
Services
$10
2 2 Acorn Parts $12.50
3 2 5 hrs Professional
Services
$50
4 3 Delivery Fee $17.50
5 3 Replacement
Acorn
$20
6 4 Premium Acorn $999
invoice_item

27. Copyright
©
2014
Oracle
and/or
its
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rights
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| 27
customerid name
1 Acorn Enterprises
2 First National Squirrel Bank
3 Squirrels 5000 Inc
4 Savvy Squirrel Global
invoiceid customerid ...
1 1 # Acorn Enterprises
2 1 # Acorn Enterprises
3 3 # Squirrels 5000 Inc
4 4 # Savvy Squirrels
customer
invoice
itemid invoiceid Description Amount
1 1 1 hrs Professional
Services
$10
2 2 Acorn Parts $12.50
3 2 5 hrs Professional
Services
$50
4 3 Delivery Fee $17.50
5 3 Replacement
Acorn
$20
6 4 Premium Acorn $999
invoice_item

28. Copyright
©
2014
Oracle
and/or
its
affiliates.
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rights
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| 28
customerid name
1 Acorn Enterprises
2 First National Squirrel Bank
3 Squirrels 5000 Inc
4 Savvy Squirrel Global
invoiceid customerid ...
1 1 # Acorn Enterprises
2 1 # Acorn Enterprises
3 3 # Squirrels 5000 Inc
4 4 # Savvy Squirrels
customer
invoice
itemid invoiceid Description Amount
1 1 1 hrs Professional
Services
$10
2 2 Acorn Parts $12.50
3 2 5 hrs Professional
Services
$50
4 3 Delivery Fee $17.50
5 3 Replacement
Acorn
$20
6 4 Premium Acorn $999
invoice_item

29. Copyright
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Backup
Methods
• mysqldump
• Is
warm
by
default.
Can
safely
be
set
hot
if
all
InnoDB.
• Logical
backup.
Slow
to
recover.
• Snapshot
Based
-­‐
i.e.
LVM
snapshot.
• Consistent
+
Hot
• May
have
higher
impact
during
snapshot
phase.
• Best
used
with
a
script
like
mylvmbackup.
29

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Backup
Methods
(cont.)
• MySQL
Enterprise
Backup
• Commercial
Tool
• Hot
with
InnoDB.
Warm
for
MyISAM
phase
• Low
Impact
30

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How
to
Decide?
• MTTR
of
logical
backups
is
much
higher.
• Most
failures
are
accidents
(either
by
DBA
or
user).
• “I
accidentally
updated
the
phone
number
of
the
wrong
customer!”
31

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Replication
• Built
in
to
MySQL
• Easy
to
setup
and
get
running
• Uses
same
port
3306
• Most
deployments
will
use
Replication
32

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Replication
Options
• Row
Format
• Statement
Based
(default)
• Row
Based
• Global
Transaction
IDs
• Semi-­‐Synchronous
• Time
delayed
33

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Program
Agenda
Introduction
MySQL
Architecture
Backup
&
Replication
Performance
&
Capacity
Planning
1
2
3
4
1
4

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Quality
of
Service
• Often
better
to
let
one
too
demanding
user
go
unserviced
than
all
users
go
unserviced
• Statement
Timeout
coming
to
MySQL
5.7.
35

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Quality
of
Service
(cont.)
• Replication
Slaves,
Hadoop
very
useful.
• Important
to
Optimize
for
Response
Time
(user
facing)
before
sub
optimizing
for
background
tasks.
36

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Configuration
Most
important
settings
• innodb_buffer_pool_size
-­‐
50-­‐80%
of
memory
• innodb_log_file_size
-­‐
up
to
4G
quite
safe
37

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Configuration
Also
Useful
• innodb_flush_method
• innodb_flush_neighbors
• innodb_io_capacity
and
innodb_lru_scan_depth
• Explained
here:
• http://www.tocker.ca/2013/09/17/what-­‐to-­‐tune-­‐in-­‐
mysql-­‐56-­‐after-­‐installation.html
38

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How
much
can
you
expect
from
config?
Versus
other
optimizations
• Optimizing
Queries
is
critical
to
performance
• SQL
is
hard
• Easy
to
write
• Hard
to
sight
check
for
performance
39

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How
to
find
slow
queries?
• Pro-­‐active:
• Design
or
review
all
schema
and
queries.
• Re-­‐active:
• Find
worst
offenders
and
suggest
improvements
to
development
staff.
40

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Realistic
Compromise
• Query
and
index
usage
changes
over
time
• You
have
to
have
tools
in
place
to
find
slow
SQL
• We
release
MySQL
Enterprise
Monitor
for
this
purpose
41

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Hardware
Choices
• Frequently
memory
is
under-­‐provisioned
• http://rhaas.blogspot.ca/2014/08/memory-­‐
matters.html
(PostgreSQL)
• http://www.tocker.ca/2013/05/10/twice-­‐as-­‐much-­‐
ram-­‐does-­‐not-­‐equal-­‐twice-­‐as-­‐fast.html
(Me;
MySQL)
42

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Hardware
Choices
(cont.)
• SSD
transition
is
real
• But
still
better
to
buy
more
memory
first
• Database
need
to
write
for
persistence.
Heavier
IO
requirements
than
any
other
tier
43

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Hardware
Choices
(cont.)
• More
CPUs
can
mean
more
consistent
performance
• Some
level
of
scale
up
+
scale
out
is
best:
• http://www.tocker.ca/2014/04/22/five-­‐reasons-­‐why-­‐
vertical-­‐scalability-­‐matters.html
44

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|
Non
Exhaustive
List
of
Duties
• Backup
• Replication
• Patching
&
Upgrades
• Performance
and
Capacity
Planning
• Coaching
&
Mentoring
• Fighting
Fires
45

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46