1.1 Synopsis
In this part, we will explain how to create a load-balancer withnginxfor a lot of OpenERPservers.The
load-balancing
and the
multi-process
mode of OpenERPonly work with gunicorn.And in this case, the cron are not launched by the system.
1.2 Nginx
Nginx is a free, open-source, high-performance HTTP server and reverse proxyYou can copy/paste the code in
/etc/nginx/sites-enabled/
with a filenameYou will find the documentation about the upstream keyword at
http://wiki.nginx.org/HttpUpstreamModule
upstream openerp_servers{ server openerp-server1.back.local max_fails=3 fail_timeout=30s; server openerp-server2.back.local max_fails=3 fail_timeout=30s; server openerp-server3.back.local max_fails=3 fail_timeout=30s;} serfver { listen 80; server_name openerp.example.com; rewrite ^ https://$server_name$request_uri?permanent;} server { listen 443; server_name openerp.example.com; access_log /var/log/nginx/openerp.example.com-access.log; error_log /var/log/nginx/openerp.example.com-error.log debug; ssl on; ssl_certificate /etc/nginx/ssl/server.crt; ssl_certificate_key /etc/nginx/ssl/server.key; ssl_session_timeout 5m; ssl_protocols SSLv3 TLSv1; ssl_ciphers ALL:!ADH:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv3:+EXP; ssl_prefer_server_ciphers on; location /{ proxy_pass http://openerp_servers; proxy_set_header Host$http_host; proxy_set_header X-Real-IP$remote_addr; proxy_set_header X-Forwarded-For$proxy_add_x_forwarded_for;}}
1.3 Gunicorn
Gunicornis a Python WSGI HTTP Server for UNIX.
We will use it for the multi-process mode of OpenERP.On the OpenERP servers, just install gunicorn via apt-get
# apt-get install python-gunicorn
1.4 OpenERP
You should configure OpenERP with the gunicorn mode.In the directory of the server, you can execute gunicorn with the following command
cd/home/openerp/servergunicorn openerp:wsgi.proxied.application -c gunicorn.conf.py
2.1 PostgreSQL
2.1.1 Synopsis
PostgreSQLis a free and open source database server.In this documentation, we will use PostgreSQL 9.x because this is the first release with theStreaming Replication.In PostgreSQL, there are two kind of replication.•
Warm Standby
It’s a simple replication without any access.•
Hot Standby
, in this mode, you can connect to the database but only in read access.We will use the
Hot Standby
mode for the Streaming Replication.In this tutorial, we suppose that you use an unix account, named
openerp
.Firstly, we have to configure two PostgreSQL servers, the master and the slave.
2.1.2 Streaming Replication
Here is the directory structure for the tutorial
root@vm:/# tree homehome|-> openerp|-> postgresql|-> master|-> standbymkdir /home/openerp/postgresql
Master
Via this command we initialize a new PostgreSQL cluster.
cd/home/openerp/postgresql/usr/lib/postgresql/9.1/bin/initdb -D master
The
wal_level
parameter specifies the
hot_standby
mode and the
max_wal_senders
is the number of slaveservers. In this case, the value is one.
cat >> master/postgresql.conf<< _EOF_ > include ’replication.conf’> _EOF_ cat >> master/replication.conf<< _EOF_ > wal_level = ’hot_standby’> max_wal_senders = 1> archive_mode = on> #archive_command = ’cp %p /home/stephane/postgresql/test/archives_xlog/%f’> _EOF_
We start the new PostgreSQL cluster
/usr/lib/postgresql/9.1/bin/pg_ctl -D master start
Authentication
We will use the replication via the network, in this case, we have to configure the PostgreSQL server to use a dedicateduser for the replication. In our case, this is the openerp user. It’s a normal postgresql user, don’t forget to set all therights for this user and a password.
createuser openerppsql -d postgres -c"ALTER USER openerp PASSWORD ’secret’;"
Note:
Here is a part of the content of the
master/pg_hba.conf
file
# The replication database is a virtual database used by the replication processhost replication openerp 127.0.0.1/32 md5
# Don’t forget to restart the master server before the slave because without that, the slave can’t b
/usr/lib/postgresql/9.1/bin/pg_ctl -D master restart
Slave
Tocreateabackupofthemasterfortheslave, youcanusethe
pg_basebackup
commandprovidedwithPostgreSQL9.1.
cd/home/openerp/postgresql/usr/lib/postgresql/9.1/bin/pg_ctl/pg_basebackup -D standby -v -P -Fp -l backup -h 127.0.0.1 -U open
We configure the standby server to listen to the port 5433 (because we are on the same physical server). If the standbyserver is another server, don’t forget to use 5432.
cat > standby/replication.conf<< _EOF_ > port = 5433> hot_standby = on> _EOF_
The
primary_conninfo
is used by the Streaming Replication, the parameter have the hostname of the master withthe port and the pair user/password.
cat > standby/recovery.conf<< _EOF_ > standby_mode = ’on’> primary_conninfo = ’host=127.0.0.1 port=5432 user=openerp password=secret’> trigger_file = ’/tmp/standby’> _EOF_
In this config file, the trigger_file key will be used by the server, if there is a touch on this file, the standby server willautomatically pass in the master mode with the read/write accesses.
2.2 PG-Pool II
For the load-balancing and the failover features, we will use PgPool2.
2.2.1 Installation
# apt-get install pgpool2# apt-get install postgresql-9.1-pgpool2
2.2.2 Configuration
Here is the basic configuration for the load-balancing and the failover.The
failover_command
is important because if pgpool can’t make a connection to the master, it will
touch/tmp/standby
file and this file will be triggered by the standby server.If you want to use this feature with a remote standby server, you can use
ssh
to touch a file on a remote server. Butdon’t forget to change the config file of the standby server and set the right value for the
trigger_file
parameter.
cat >> /etc/pgpool2/pgpool.conf << _EOF_ > port = 5434> load_balance_mode = on> backend_hostname0 = ’localhost’> backend_port0=5432> backend_weight0=1> backend_flag0 = ’ALLOW_TO_FAILOVER’> backend_hostname1 = ’localhost’> backend_port1=5433> backend_weight0=1> backend_flag1 = ’ALLOW_TO_FAILOVER’> failover_command = ’touch /tmp/standby’> _EOF_
