Percona XtraDB 集群内部 http://www.ossez.com/forum.php?mod=viewthread&tid=26859&fromuid=426 (出处: OSSEZ)

1. Percona XtraDB Cluster
in a Nutshell
Frédéric Descamps
Seppo Jaakola
Percona Live UK (London) 2012

2. www.percona.com
Who are we ?
Frédéric Descamps
@lefred
Percona Consultant
http://about.me/lefred
devops believer
Managing MySQL since
3.23 (as far as I
remember)
Seppo Jaakola
@codership
Founder of Codership

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Agenda
● What is Percona XtraDB Cluster (in few
words)
● Hands on !

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What is PXC ?
+
=

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To remember
Important urls
http://www.codership.com/wiki/doku.php?id=galera_parameters
http://www.codership.com/wiki/doku.php?id=mysql_options_0.8

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Present
● Currently we have one node (production)
running Percona Server

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Future
● We want to have a 3 nodes PXC
● We want to have a smooth migration with
minimum downtime

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The Plan
● Configure PXC on node2 and node3
● Take a backup of node1
● Restore the backup on node2
● Play with the 2 nodes cluster
● Setup the current production server as
3rd node

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Connect to your servers
● Test the connection (ssh) to all your
servers (node1, node2 and node3)
login: root
password: vagrant
ssh -p 2221 root@127.0.0.1 (node1)
ssh -p 2222 root@127.0.0.1 (node2)
ssh -p 2223 root@127.0.0.1 (node3)

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The production
● We have a script that simulate our
production load
while true
do
pluk.py
sleep 5
done

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The production
● We have a script that simulate our
production load
while true
do
pluk.py
sleep 5
done
Run the script (pluk.py) once on node1

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Install PXC
● On node2 and node3, install Percona-
XtraDB-Cluster-Server
● You should use yum (or apt)
● We will use rpm as the files are already
downloaded in /usr/local/rpms

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Configure PXC
[mysql]
prompt="node2 mysql> "
[mysqld]
datadir=/var/lib/mysql
user=mysql
log_error=node2-error.log
binlog_format=ROW
innodb_log_file_size=64M
innodb_locks_unsafe_for_binlog=1
innodb_autoinc_lock_mode=2

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Configure PXC (2)
wsrep_cluster_name=pluk2k12
wsrep_cluster_address=gcomm://192.
168.70.1,192.168.70.2,192.168.70.3
wsrep_node_name=node2
wsrep_node_address=192.168.70.2
wsrep_provider=/usr/lib64/libgalera_smm.so
wsrep_sst_method=rsync
wsrep_slave_threads=4

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To remember
● Disable selinux
● wsrep_cluster_address now supports multiple
entries, wsrep_urls in [mysqld_safe] is
deprecated
● SST method is defined in my.cnf
● when wsrep_node_address is used we can omit
wsrep_sst_receive_address,
wsrep_node_incoming_address and ist.
recv_addr

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Let's have a look...
● Check MySQL error log, what do we see?
● Check variables and status related to PXC
○ SHOW GLOBAL VARIABLES LIKE
'wsrep%';
○ SHOW GLOBAL STATUS LIKE 'wsrep%';
● Play with the cluster (follow instructor)

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To remember
● wsrep = 'Write Set Replicator'
● Settings are available with SHOW GLOBAL VARIABLES
LIKE 'wsrep%';
● Status counters available with SHOW GLOBAL STATUS
LIKE 'wsrep%';
● Are important to check cluster status:
○ wsrep_local_state_comment
○ wsrep_cluster_size
○ wsrep_cluster_status
○ wsrep_connected
○ wsrep_ready

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What about State Snapshot
Transfer (SST)
● SST = full copy of cluster data to a
specific node (from DONOR to JOINER)
● wsrep_sst_donor
● Multiple SST methods:
○ skip
○ rsync
○ mysqldump
○ xtrabackup

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What about State Snapshot
Transfer (SST)
● SST = full copy of cluster data to a
specific node (from DONOR to JOINER)
● wsrep_sst_donor
● Multiple SST methods:
○ skip
○ rsync
○ mysqldump
○ xtrabackup
Test all SST methods

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What about State Snapshot
Transfer (SST)
● SST = full copy of cluster data to a
specific node (from DONOR to JOINER)
● wsrep_sst_donor
● Multiple SST methods:
○ skip
○ rsync
○ mysqldump
○ xtrabackup
No problem
with
mysldump ?

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To remember
● SST methods are not all the same.
● You can specify a donor per node
● Xtrabackup doesn't freeze the donor for the complete
SST period
● Xtrabackup requires authentication parameter

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Loadbalancer
● Let's configure a loadbalancer to connect
to our cluster
○ HA proxy (needs clustercheck)
○ glb
Install and configure glb on node2

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Loadbalancer - glb
glbd --daemon --threads 6
--control 127.0.0.1:4444
192.168.70.2:3307
192.168.70.2:3306
192.168.70.3:3306

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Quorum and split brain
● PXC checks for Quorum to avoid split
brain situation

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Quorum and split brain
● PXC checks for Quorum to avoid split
brain situation
stop the communication between node2 and
node3

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Quorum and split brain
● BAD solution :-(
wsrep_provider_options = “pc.
ignore_quorum = true”
● and the GOOD solution.... next slide !

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Quorum and split brain (2)
● Galera Arbitration Daemon (garbd)

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Quorum and split brain (2)
● Galera Arbitration Daemon (garbd)
run garbd on node1
Test the following :
● Stop mysql on node3: what's happening ?
● Stop garbd on node1: what's happening ?
● Start garbd on node1 and mysql on node3, block communication
between node2 and node3, what's happening this time ?
● Block communication between node1 and node3: what's happening ?

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To remember
● 3 nodes is the minimum recommended !
● odd numbers of nodes are always better
● you can use a "fake" node (garbd) even to replicate
through it !

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Incremental State Transfer
(IST)
● Used to avoid full SST (using gcache)
● gcache.size can be specified using
wsrep_provider_options
● Now works even after a crash if the state
is consistent

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Incremental State Transfer
(IST)
● Used to avoid full SST (using gcache)
● gcache.size can be specified using
wsrep_provider_options
● Now works even after a crash if the state
is consistent
stop mysql on node3, run pluk.py on
node2, restart node3

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Production Migration
● Backup the production server and restore
the production on node2
● Run pluk.py on node1

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Production Migration (2)
● Start node3
● Run pluk.py on node1
● Start the async replication of node1 to
node2
● What about node3 ?
● Run pluk.py on node1

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Production Migration (2)

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Production Migration (3)
● Configure pluk.py to connect to the
loadbalancer
● Run pluk.py
● Scratch data on node1 and install PXC
● Configure PXC on node1
● Start the cluster on node1 (SST should be
done with node3)
● Run pluk.py and check data on all
nodes

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Production Migration (3)

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Production Migration (4)

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Online Schema Changes
● Total Order Isolation (TOI)
● Rolling Schema Upgrade (RSU)
wsrep_OSU_method
● pt-online-schema-change

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Online Schema Changes (2)
● Create a large table to modify
CREATE database pluk; use pluk;
CREATE TABLE `actor` (
`actor_id` int unsigned NOT NULL AUTO_INCREMENT PRIMARY KEY,
`first_name` varchar(45) NOT NULL,
`last_name` varchar(45) NOT NULL,
`last_update` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON
UPDATE CURRENT_TIMESTAMP) ENGINE=InnoDB;
INSERT INTO actor (first_name, last_name) SELECT REPEAT('a',
45), REPEAT('b', 45) FROM dual;
INSERT INTO actor (first_name, last_name) SELECT REPEAT('a',
45), REPEAT('b', 45) FROM actor;
repeat this step
until it takes 10
sec+

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Online Schema Changes (3)
● Use all three methods while running
pluk.py against your new database and
add each time a new column
● Check pluk.py output

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Thank you !
Visit:
http://www.percona.com/live/london-2012/

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Annual Percona Live
MySQL Conference and Expo
The Hyatt Regency Hotel, Santa Clara, CA
April 22nd-25th, 2013
Registration
and
Call for Papers
are Open!
Visit:
http://www.percona.com/live/mysql-conference-2013/