Random things I work on

From Mehdi Abaakouk (sileht)

Galera and puppetlabs mysql module

Recently I have tested mysql galera on debian, here a quick description of the installation of galera with the puppetlabs-mysql This will allow to use galera for all applications that setup mysql with this module.

Start by add the percona repository of mysql galera

class mygalera_klass{

$local_ip = $ipaddress_eth0

# apt repository
apt::source { "galera_percona_repo":
    location          => "http://repo.percona.com/apt/"
    release           => "squeeze",
    repos             => "percona",
    key               => "CD2EFD2A"
    include_src       => false,

We define what is the initial galera node and what are the other nodes in the galera ring:

$galera_nextserver = {
    "galera1.lan" => "",  # replace the empty string by $ipaddress_galera3 when all nodes are correclty setup
    "galera2.lan" => "$ipaddress_galera1",
    "galera3.lan" => "$ipaddress_galera2",
$galera_master = "galera1.lan"

Note: This part can be sexiest if puppetdb is used

Setup the mysql server class, it allow to change the package name of the mysql database

# mysql definifition
class { 'mysql::server':
  package_name => "percona-xtradb-cluster-server-5.5",
  config_hash => {
    bind_address  => $local_ip,
    root_password => "myrootpassword"
  require => Apt::Source["galera_percona_repo"]

Ensure some mandatory packages for galera are installed

        "percona-xtrabackup"] :
  ensure => latest,
  require => Apt::Source["galera_percona_repo"]

If the node is the initial master node, we create one user for the clustercheck user used by some percona script for load balancing purpose, and a other one the debian-sys-maint user to make the debian script happy

if $fqdn == $galera_master {
    database_user { "clustercheckuser@localhost":
      ensure => "present",
      password_hash => mysql_password("clustercheckpassword!"), # can not change password in clustercheck script
      provider      => 'mysql',
      require => File["/root/.my.cnf"] # why this is require ?
    database_user { "debian-sys-maint@localhost":
      ensure => "present",
      password_hash => mysql_password("debiansysmaint_password!"),
      provider  => "mysql",
      require => File["/root/.my.cnf"] # why this is require ?

The debian-sys-maint password should be the same on all nodes, so update it in debian cnf files

# set the same debian_sys_maint password
    command => "/bin/sed -i 's/^password.*/password = debiansysmaint_password!/g' /etc/mysql/debian.cnf",
    unless => "/bin/grep -qFx 'password = debiansysmaint_password!' /etc/mysql/debian.cnf",
    require => Package["mysql-server"]

Next, configure the http service of percona package to monitor the cluster health (useful for load balancers and nagios)

service{"xinetd": hasstatus => false }
    command => "/bin/echo mysqlchk 9200/tcp >> /etc/services",
    unless => "/bin/grep -qFx 'mysqlchk 9200/tcp' /etc/services",
    notify => Service["xinetd"],
# fix the broken link provided by the percona package
    ensure => "link",
    target => "/usr/bin/clustercheck",

Note: percona provide a simple script to control the health of the cluster
The output of the script look like this and it is used with a percona xinetd (/etc/xinetd.d/mysqlchk) to provide the cluster status via the HTTP protocol

# /usr/bin/clustercheck 
HTTP/1.1 200 OK
Content-Type: text/plain

Percona XtraDB Cluster Node is synced.

And to finish the mysql configuration for galera:

# for galera
    settings => inline_template('
# mandatory for galera
# galera configuration
wsrep_cluster_address="gcomm://<%= galera_nextserver[fqdn] %>"
wsrep_sst_auth=root:mymysqlrootpassword %>
wsrep_node_address="<%= local_ip %>"
wsrep_node_incoming_address="<%= local_ip %>"

# this value here are used by /usr/bin/innobackupex
# and wsrep_sst_xtrabackup take only one configuration file and use the last one
# (/etc/mysql/my.cnf is not used)
datadir = /var/lib/mysql
tmpdir = /tmp
#innodb_flush_method             = O_DIRECT
#innodb_log_buffer_size          = 32M
#innodb_log_file_size            = 256M
#innodb_log_files_in_group       = 2


Note: the user in “wsrep_sst_auth” should be allowed to replicate the whole database, here root, it seems safe because only the connection on localhost is used by galera

Some snippet of code for the load balancer if puppetlabs-haproxy module is used:

# On a galera node:
    listening_service => "galera_cluster",
    server_names      => $::hostname,
    ipaddresses       => $local_ip,
    ports             => '3306',
    options           => inline_template("check inter 2000 rise 2 fall 5 port 9200 <% if @hostname != @galera_master -%>backup<% end %>")

# On a haproxy node:
haproxy::listen { 'galera_cluster':
    ipaddress => $haproxy_local_net_ip,
    ports     => 3306,
    options   => {
        'mode' => 'tcp',
        'balance' => 'roundrobin',
        'option' => ["tcpka", "tcplog", "httpchk"],

Some check

after applied the puppet configuration, the status of the galera can be checked with:

# mysql mysql -e 'show status'  | grep wsrep
wsrep_local_state_uuid  c3271751-4091-11e2-0800-8f9f852b5de4
wsrep_protocol_version  4
wsrep_last_committed    1159
wsrep_replicated    0
wsrep_replicated_bytes  0
wsrep_received  7
wsrep_received_bytes    995
wsrep_local_commits 0
wsrep_local_cert_failures   0
wsrep_local_bf_aborts   0
wsrep_local_replays 0
wsrep_local_send_queue  0
wsrep_local_send_queue_avg  0.000000
wsrep_local_recv_queue  0
wsrep_local_recv_queue_avg  0.000000
wsrep_flow_control_paused   0.000000
wsrep_flow_control_sent 0
wsrep_flow_control_recv 0
wsrep_cert_deps_distance    0.000000
wsrep_apply_oooe    0.000000
wsrep_apply_oool    0.000000
wsrep_apply_window  0.000000
wsrep_commit_oooe   0.000000
wsrep_commit_oool   0.000000
wsrep_commit_window 0.000000
wsrep_local_state   4
wsrep_local_state_comment   Synced (6)
wsrep_cert_index_size   0
wsrep_causal_reads  0
wsrep_cluster_conf_id   4
wsrep_cluster_size  3
wsrep_cluster_state_uuid    c3271751-4091-11e2-0800-8f9f852b5de4
wsrep_cluster_status    Primary
wsrep_connected ON
wsrep_local_index   1
wsrep_provider_name Galera
wsrep_provider_vendor   Codership Oy <info@codership.com>
wsrep_provider_version  2.2(r115)
wsrep_ready ON

Some interesting field are wsrep_local_state for the node status, wsrep_local_state_uuid for the last uuid commited on this node

# nc localhost 9200
HTTP/1.1 200 OK
Content-Type: text/plain

Percona XtraDB Cluster Node is synced.

The http service seems work fine, too :)

This two checks should be done on all nodes