We continuously see great interest in MySQL load balancing and HAProxy, so we thought it was about time we organised a live webinar on the topic! Here is the replay of that webinar! As most of you will know, database clusters and load balancing go hand in hand. Once your data is distributed and replicated across multiple database nodes, a load balancing mechanism helps distribute database requests, and gives applications a single database endpoint to connect to. Instance failures or maintenance operations like node additions/removals, reconfigurations or version upgrades can be masked behind a load balancer. This provides an efficient way of isolating changes in the database layer from the rest of the infrastructure. In this webinar, we cover the concepts around the popular open-source HAProxy load balancer, and show you how to use it with your SQL-based database clusters. We also discuss HA strategies for HAProxy with Keepalived and Virtual IP. Agenda: * What is HAProxy? * SQL Load balancing for MySQL * Failure detection using MySQL health checks * High Availability with Keepalived and Virtual IP * Use cases: MySQL Cluster, Galera Cluster and MySQL Replication * Alternative methods: Database drivers with inbuilt cluster support, MySQL proxy, MaxScale, ProxySQL

1. Confidential
Load Balancing with HAProxy and MySQL
!
!
July 9, 2014
Alex Yu
alex@severalnines.com

2. Copyright Severalnines AB
Webinar Housekeeping
!This webinar is being recorded
!A link to the recording & slides will be posted on severalnines.com
!We welcome questions: enter questions into the chat box and we
will respond at the end of the presentation
!Think of something later?
! Email Severalnines at info@severalnines.com
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3. Copyright Severalnines AB
Agenda
!What Is HAProxy?
!SQL Load Balancing with HAProxy
! Failure detection with MySQL
!Fault Tolerance with HAProxy
! Active/Passive setup
!Deployment Scenarios
! MySQL Cluster, Galera Cluster and MySQL Replication
!Load Balancing Alternatives
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4. Copyright Severalnines AB
Why Load Balance?
!Optimising server utilisation
! Queuing and throttling
!Maximise availability
! No SPOF
!Maximise throughput
! Distribute workload across a set of servers
!Scalability
! Site traffic grows
! Add DB servers to provide more throughput
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LB
DB DB DB …

5. !Reliable High Performance TCP/HTTP Load Balancer
! v1.5 stable released June 2014
! Native SSL support, IPv6, full HTTP keepalive, HTTP Compression …
! v1.4 most deployed and stable version, released Feb 2010
! client-side keep alive, TCP speedups, source base stickiness …
! Single Process Event-Driven. Can easily saturate 10Gb link with a single instance
! 108 000 session/s, http://www.haproxy.org/10g.html (2009)
!Reverse Proxy
! load balancing, scaling out, failover (health checks)
!High traffic sites like
! reddit, DISQUS, GitHub, Imgur, StackOverflow/Server Fault, Instagram …
Copyright Severalnines AB
HAProxy?
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6. Copyright Severalnines AB
SQL Load Balancing for MySQL
!Configuration file
! Sections; global, defaults, frontend, backend, listen
! /etc/haproxy/haproxy.cfg
!Global (process wide)
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MySQL
[WSREP]
Galera Replication (Synchronous)
LB
MySQL
[WSREP]
MySQL
[WSREP]
R/W R/W R/W
Client Client Client
global
log 127.0.0.1 local0
pidfile /var/run/haproxy.pid
daemon
user nobody
group nobody
stats socket /tmp/haproxy.socket …
node HAProxy_1
description HAProxy 1
maxconn 40000
spread-checks 3
quiet

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SQL Load Balancing for MySQL (cont.)
!defaults
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MySQL
[WSREP]
Galera Replication (Synchronous)
LB
MySQL
[WSREP]
MySQL
[WSREP]
R/W R/W R/W
Client Client Client
defaults
log global
mode tcp
maxconn 40000
option dontlognull
option tcp-smart-accept
option tcp-smart-connect
option redispatch
retries 3
timeout queue 3500ms
timeout connect 3500ms
timeout client 120s
timeout server 120s

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SQL Load Balancing for MySQL (cont.)
!listen (frontend + backend)
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listen s9s1_33306_defaul_LB
mode tcp
bind *:33306
timeout client 60000ms
timeout server 60000ms
balance leastconn
option httpchk
#option allbackups
default-server port 9200 inter 2s downinter 5s rise 3 fall 2 slowstart 60s maxconn 256
maxqueue 128 weight 100
server db1 10.0.3.70:3306 check
server db2 10.0.3.60:3306 check
server db3 10.0.3.50:3306 check

9. Copyright Severalnines AB
SQL Load Balancing for MySQL (cont.)
!listen (stats ui)
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userlist STATSUSERS
group admin users admin
user admin insecure-password admin
!
listen admin_page 0.0.0.0:9600
mode http
stats enable
stats refresh 60s
stats uri /
acl AuthOkay_ReadOnly http_auth(STATSUSERS)
acl AuthOkay_Admin http_auth_group(STATSUSERS) admin
stats http-request auth realm admin_page unless AuthOkay_ReadOnly

10. Copyright Severalnines AB
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!Session rate
! number of new connections per second
!Sessions
! current number of sessions/connections
!LastChk
! health check
!Wght
! server weight

11. Copyright Severalnines AB
MySQL Health Checks
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!Built-in MySQL health check
! option mysql-check user <username>
! Sends two MySQL packages
! Authentication and Quit
! No errors unless MySQL server is down
!Complete HTTP Request
! option httpchk
! Response: HTTP/1.1 200 OK
! Check Host and/or MySQL server state
! Galera Node State
MySQL
[WSREP]
Galera Replication (Synchronous)
LB
MySQL
[WSREP]
MySQL
[WSREP]
R/W R/W R/W
Client Client Client

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MySQL Health Checks (cont.)
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!Galera Node
! Check 1: Get node state
! SYNCED or DONOR
! Check 2: If Node is a “DONOR”
! Get the SST method
! xtrabackup
! Return “200 OK”
! rsync or mysqldump
! Return “503 Service Unavailable” Galera Node State

13. Copyright Severalnines AB
MySQL Health Checks (cont.)
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!xinetd service
! mysqlchk.sh (shell script)
! spams syslog by default
! log_on_success =
#/etc/xinetd.d/mysqlchk
# default: on
# description: mysqlchk
service mysqlchk
{
flags = REUSE
socket_type = stream
port = 9200
wait = no
user = nobody
server = /usr/local/bin/mysqlchk.sh
log_on_failure += USERID
disable = no
#only_from = 0.0.0.0/0
per_source = UNLIMITED
}

14. Copyright Severalnines AB
Network Tuning
!TCP tuning
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#/etc/sysctl.conf
net.ipv4.ip_nonlocal_bind=1
net.ipv4.tcp_tw_reuse=1 # reuse TIME-WAIT sockets
net.ipv4.ip_local_port_range=1024 65023 # increase max num of ports
net.ipv4.tcp_max_syn_backlog=40000 #Increase the number of outstanding syn requests
net.ipv4.tcp_max_tw_buckets=400000 # Maximal number of timewait sockets
net.ipv4.tcp_max_orphans=60000
net.ipv4.tcp_max_syn_backlog=40000 # TCP SYN Flood Protection
net.ipv4.tcp_synack_retries=3 # TCP SYN Flood Protection
net.core.somaxconn=40000 # burst connection rate
net.ipv4.tcp_fin_timeout=5 # how long to keep sockets in FIN-WAIT-2

15. Copyright Severalnines AB
Fault Tolerance for HAProxy
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Client
HAProxy 1
MySQL MySQL MySQL
IP: 10.10.10.20

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Fault Tolerance for HAProxy (cont.)
!Active/Passive IP failover
! keepalived
! VRRP protocol provides router/IP failover
!VIP, “floating IP”: 10.10.10.10
! net.ipv4.ip_nonlocal_bind=1
!Master - HAProxy 1
! IP: 10.10.10.20
!Backup - HAProxy 2
! IP: 10.10.10.30
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Fault Tolerance for HAProxy (cont.)
!keepalived configuration file
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#/etc/keepalived/keepalived.conf
vrrp_script chk_haproxy {
script "killall -0 haproxy" # verify the pid existence
interval 2 # check every 2 seconds
weight 2 # adjust priority by this weight
}
vrrp_instance VI_1 {
interface eth0
state MASTER
virtual_router_id 51 # ID for this route
priority 101 # 101 on master
# 100 on backup
virtual_ipaddress {
10.10.10.10 # the virtual IP
}
track_script {
chk_haproxy
}
}

18. Copyright Severalnines AB
ClusterControl HAProxy + Keepalived
!Install HAProxy with our admin scripts
! http://www.severalnines.com/blog/using-haproxy-database-clusters
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$ git clone https://github.com/severalnines/s9s-admin.git
$ cd s9s-admin/cluster/
# install haproxy1 on 10.10.10.20 listening on 33306
$ ./s9s_haproxy --install -i 1 -n <ip db1>,<ip db2>,<ip db3> -h10.10.10.20
# install haproxy2 on 10.10.10.30 listening on 33306
$ ./s9s_haproxy --install -i 1 -n <ip db1>,<ip db2>,<ip db3> -h10.10.10.30
# scale out db nodes on haproxy1
$ ./s9s_haproxy --add-node -i 1 -h 10.10.10.20 -n <ip db4>
$ ./s9s_haproxy --add-node -i 1 -h 10.10.10.20 -n <ip db5>
# scale out db nodes on haproxy2
$ ./s9s_haproxy --add-node -i 1 -h 10.10.10.30 -n <ip db4>
$ ./s9s_haproxy --add-node -i 1 -h 10.10.10.30 -n <ip db5>

19. Copyright Severalnines AB
ClusterControl HAProxy + Keepalived (cont.)
!Deployment and configuration automated from ClusterControl
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20. Copyright Severalnines AB
ClusterControl HAProxy + Keepalived (cont.)
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21. Copyright Severalnines AB
Deployment Scenarios
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!MySQL Cluster / NDB Engine
! Active/Active, Shared nothing architecture
! SQL, Data and MGMT Nodes
! HAProxy co-located with MGMT Nodes
! MGMT is a light weight process
! Re-use “idle” servers
! Connections originate from HAProxy server
! Additional latency
! App Server <-> HAProxy <-> SQL Node <-> Data Node
NDB Data
Node
NDB Data
Node
(MGMT)
HAProxy
(MGMT)
HAProxy
SQL Node
MySQL
Server
SQL Node
MySQL
Server

22. Copyright Severalnines AB
Deployment Scenarios (cont.)
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NDB Data
Node
NDB Data
Node
!MySQL Cluster / NDB Engine
! Active/Active, Shared nothing architecture
! SQL, Data and MGMT Nodes
! HAProxy co-located with App servers
! No extra latency
! Extra load on app servers
! Health check loads on SQL nodes from all LBs
! Alt: MySQL Connector/J’s JDBC driver
! jdbc:mysql:loadbalance://host-1,host-2,…host-n/database?
loadBalanceBlacklistTimeout=5000
! Config changes propagate to all app servers
(App)
HAProxy
(App)
HAProxy
SQL Node
MySQL
Server
SQL Node
MySQL
Server

23. Copyright Severalnines AB
Deployment Scenarios (cont.)
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NDB Data
Node
NDB Data
Node
!MySQL Cluster / NDB Engine
! Active/Active, Shared nothing architecture
! SQL, Data and MGMT Nodes
! HAProxy co-located with SQL nodes
! No extra latency
! Extra load on SQL nodes
! Do not use JDBC load balancing
! VIP
(App) (App)
SQL Node
MySQL
Server
SQL Node
MySQL
Server
HAProxy HAProxy
…

24. Copyright Severalnines AB
Deployment Scenarios (cont.)
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MySQL Slave
MySQL
Master
!MySQL Replication Master/Slave
! 1 Master for Writes
! N Slaves for Reads
! Separate front and backends configs for Master and Slaves
!ex: backend configuration for Slaves
HAProxy
MySQL Slave
MySQL Slave
Writes
Reads
frontend front_reads
mode tcp
bind 192.168.100.110:3316
default_backend cluster_reads
backend cluster_reads
mode tcp
balance roundrobin
server Slave1 10.10.10.30:3306 check
server Slave2 10.10.10.40:3306 check

25. Copyright Severalnines AB
Deployment Scenarios (cont.)
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!Galera Cluster
! Synchronous Replication, Read & Write to any Node
! Cluster wide optimistic locking
! Higher probability for “deadlocks”
! Pessimistic locking on the Node
MySQL
[WSREP]
Galera Replication (Synchronous)
LB
MySQL
[WSREP]
MySQL
[WSREP]
R/W R/W R/W
Client Client Client

26. Copyright Severalnines AB
Deployment Scenarios (cont.)
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!Galera Cluster
! Synchronous Replication, Read & Write to all Nodes
! Cluster wide optimistic locking
! Higher probability for “deadlocks”
! Pessimistic locking on the Node
MySQL
[WSREP]
Galera Replication (Synchronous)
LB
MySQL
[WSREP]
MySQL
[WSREP]
R/W R/W R/W
Client Client Client

27. Copyright Severalnines AB
Deployment Scenarios (cont.)
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MySQL
[WSREP]
Galera Replication (Synchronous)
LB
MySQL
[WSREP]
MySQL
[WSREP]
R/W R/W R/W
Client Client Client
listen s9s1_33307_LB1
bind *:33307
mode tcp
timeout client 60000ms
timeout server 60000ms
balance leastconn
option httpchk
default-server port 9200 inter 2s <…>
server db1 10.0.3.70:3306 check
server db2 10.0.3.60:3306 check backup
server db3 10.0.3.50:3306 check backup
!Handle “dead locks”
! Write to only one Node - Use HAProxy
! Expect deadlocks and make sure applications
handles it properly. Retry the transaction.
! wsrep_retry_autocommit=1
! Changes to the App code to minimise data hotspots.

28. Copyright Severalnines AB
Alternatives
!MySQL’s Connector/J JDBC driver
!jdbc:mysql:loadbalance://host-1,host-2,…
!PHP mysqlnd
! http://www.php.net/manual/en/intro.mysqlnd-ms.php
!Oracle’s MySQL Proxy 0.84
! http://dev.mysql.com/downloads/mysql-proxy/
!SkySQL’s MaxScale 1.0.0. beta
! https://github.com/skysql/MaxScale
!ProxySQL
! https://github.com/renecannao/proxysql
!Pen 0.24.0
! http://morestuff.siag.nu/category/pen/
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29. Copyright Severalnines AB
Thank You!
!Tutorial – MySQL Load Balancing with HAProxy
! http://www.severalnines.com/resources/clustercontrol-mysql-haproxy-load-
balancing-tutorial
!Severalnines Blog
! www.severalnines.com/blog
!s9s-admin tools
! https://github.com/severalnines/s9s-admin
!More Questions? Contact us at:
! info@severalnines.com
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