High Availability Opener p

HighAvailabilityOpenERP Documentation Release 0.2

OpenERP S.A.

June 26, 2012

CONTENTS

1

2

Load-Balancing 1.1 Synopsis . 1.2 Nginx . . . 1.3 Gunicorn . 1.4 OpenERP .

. . . .

3 3 3 4 4

High Availability 2.1 PostgreSQL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 PG-Pool II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5 5 7

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

i

ii

HighAvailabilityOpenERP Documentation, Release 0.2

Note: We use Ubuntu 12.04 LTS for this tutorial

CONTENTS

1

HighAvailabilityOpenERP Documentation, Release 0.2

2

CONTENTS

CHAPTER

ONE

LOAD-BALANCING 1.1 Synopsis In this part, we will explain how to create a load-balancer with nginx for a lot of OpenERP servers. The load-balancing and the multi-process mode of OpenERP only 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 proxy You can copy/paste the code in /etc/nginx/sites-enabled/ with a filename You 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;

3

HighAvailabilityOpenERP Documentation, Release 0.2

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 Gunicorn is 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/server gunicorn openerp:wsgi.proxied.application -c gunicorn.conf.py

4

Chapter 1. Load-Balancing

CHAPTER

TWO

HIGH AVAILABILITY 2.1 PostgreSQL 2.1.1 Synopsis PostgreSQL is a free and open source database server. In this documentation, we will use PostgreSQL 9.x because this is the first release with the Streaming 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 home home |-> openerp |-> postgresql |-> master |-> standby mkdir /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

5

HighAvailabilityOpenERP Documentation, Release 0.2

The wal_level parameter specifies the hot_standby mode and the max_wal_senders is the number of slave servers. In this case, the value is one. cat >> master/postgresql.conf include ’replication.conf’ > _EOF_ cat >> master/replication.conf 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 dedicated user for the replication. In our case, this is the openerp user. It’s a normal postgresql user, don’t forget to set all the rights for this user and a password. createuser openerp psql -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 process host 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 be /usr/lib/postgresql/9.1/bin/pg_ctl -D master restart

Slave To create a backup of the master for the slave, you can use the pg_basebackup command provided with PostgreSQL 9.1.

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 opene

We configure the standby server to listen to the port 5433 (because we are on the same physical server). If the standby server is another server, don’t forget to use 5432. cat > standby/replication.conf port = 5433 > hot_standby = on > _EOF_

The primary_conninfo is used by the Streaming Replication, the parameter have the hostname of the master with the port and the pair user/password.

6

Chapter 2. High Availability

HighAvailabilityOpenERP Documentation, Release 0.2

cat > standby/recovery.conf 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 will automatically 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. But don’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 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_

2.2. PG-Pool II

7