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
January 28, 2015
Alex Yu
alex@severalnines.com

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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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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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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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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 60s
timeout server 60s
balance leastconn
option httpchk
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

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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

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!Session rate
! number of new connections per second
!Sessions
! current number of sessions/connections
!LastChk
! health check
!Wght
! server weight

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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

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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
}

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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

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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”: 10.10.0.10
! 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 {
10.10.0.10 # the virtual IP
}
track_script {
chk_haproxy
}
}

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ClusterControl HAProxy + Keepalived (cont.)
!Deployment and configuration automated from ClusterControl
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ClusterControl HAProxy + Keepalived (cont.)
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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

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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

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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

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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
! Ex: sequence table, “hotspot” tables
! Write to one node, Read/Write split
! Application: Retry deadlock errors
MySQL
[WSREP]
Galera Replication (Synchronous)
LB
MySQL
[WSREP]
MySQL
[WSREP]
R/W R/W R/W
Client Client Client

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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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Thank You!
!Tutorial – MySQL Load Balancing with HAProxy
! http://www.severalnines.com/resources/clustercontrol-mysql-haproxy-load-
balancing-tutorial
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! www.severalnines.com/blog
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