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Percona XtraDB 集群内部 http://www.ossez.com/forum.php?mod=viewthread&tid=26859&fromuid=426 (出处: OSSEZ)
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Percona XtraDB Cluster in a Nutshell
Frédéric DescampsSeppo Jaakola
Percona Live UK (London) 2012
www.percona.com
Who are we ?Frédéric Descamps
@lefredPercona Consultanthttp://about.me/lefreddevops believerManaging MySQL since
3.23 (as far as I remember)
Seppo Jaakola
@codershipFounder of Codership
www.percona.com
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 urlshttp://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: rootpassword: vagrant
ssh -p 2221 [email protected] (node1)ssh -p 2222 [email protected] (node2)ssh -p 2223 [email protected] (node3)
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The production
● We have a script that simulate our production load
while truedo pluk.py sleep 5done
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The production
● We have a script that simulate our production load
while truedo pluk.py sleep 5done
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/mysqluser=mysqllog_error=node2-error.logbinlog_format=ROW
innodb_log_file_size=64Minnodb_locks_unsafe_for_binlog=1innodb_autoinc_lock_mode=2
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Configure PXC (2)
wsrep_cluster_name=pluk2k12wsrep_cluster_address=gcomm://192.168.70.1,192.168.70.2,192.168.70.3wsrep_node_name=node2wsrep_node_address=192.168.70.2
wsrep_provider=/usr/lib64/libgalera_smm.sowsrep_sst_method=rsyncwsrep_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 LiveMySQL 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/
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