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Selena

Introduction

Selena is a tool for monitoring website performance by monitoring response times, response codes and site content (via keyword checks).

It's distributed by design via agents which can be geographically separate allowing for monitoring the user experience from multiple ISP-s.

Installation

Requirements

Selena requires Python 2.7 which is included in the latest Ubuntu Server 12.04 LTS systems:

$ sudo apt-get install python-dev python-virtualenv

Message queue

Selena communicates with a central queue with Redis as the broker. Install redis:

$ sudo apt-get install redis-server

Since lost tasks can always be resent, the durability guarantees that Redis provides by default are not necessary. You can significantly speed up the queue by commenting out the save lines from /etc/redis/redis.conf.

We can check the status of the Redis server:

$ redis-cli -h localhost -p 6379 -n 0 info

Virtual Environment

Let's create a virtual environment for Python in the user's home:

$ virtualenv . --distribute --no-site-packages

System User

Unprivileged and not owned by a person:

$ sudo adduser --home /home/selena selena
$ sudo su - selena

In any shell the user can activate the virtual environment. As a result of that, the default Python executable and helper scripts will point to those within the virtualenv directory structure:

$ which python
/usr/local/bin/python
$ . bin/activate
(selena)$ which python
/home/selena/bin/python

Database

Selena uses and supports MySQL. To install MySQL invoke:

$ sudo apt-get install mysql-server libmysqlclient-dev libmysqld-dev

You now have to create a database and a user for Selena system. You can find many tutorials for that on the Internet.

Cache

Selena requires some cache system like memcached. Install:

$ sudo apt-get install memcached

Installing from pip

Simply invoke:

(selena)$ pip install selena

Installing from sources

Alternatively, to live on the bleeding edge, you can clone the selena git repository to project and install it manually:

(selena)$ git clone git://github.com/allegro/selena.git project
(selena)$ cd project
(selena)$ pip install -e .

Selena Agent

To function properly, Selena needs Selena-agent package installed and configured.

Configuration

Create file /INSTALL_DIR/src/selena/selena/settings-local.py and fill in the appropriate data.

Fill MySQL connection data:

DATABASES = {
  'default': {
      'ENGINE': 'django.db.backends.mysql',
      'NAME': 'your database name',
      'USER': 'your database username',
      'PASSWORD': 'your database password',
      'HOST': 'localhost',
      'PORT': '3306',
      'OPTIONS': {
          'init_command': 'SET storage_engine=INNODB,character_set_connection=utf8,collation_connection=utf8_unicode_ci'
      }
  }
}

Generate new secret keys:

SECRET_KEY = 'very_unique_string'
AES_SECRET_KEY = b'sixteen byte key'

Set the number of minutes that will be displayed by the service errors, example 30:

ERROR_TIME_INTERVAL =  30

Define RQ queues. The default queue is required. You have to also define one queue for main selena agent, for example agent_1:

RQ_QUEUES = {
    'default': {
        'HOST': '127.0.0.1',  # Redis host
        'PORT': 6379,  # Redis port
        'DB': None,
        'PASSWORD': None,
    },
    'agent_1': {
        'HOST': '127.0.0.1',
        'PORT': 6379,
        'DB': None,
        'PASSWORD': None,
   },
}

You can define additional queues: planner, archiving, dispacher, monitors, stats. They are used as follows:

planner - enable or disable planned technical breaks

archiving - create partitions, archive data

dispacher - run monitoring tasks for services

monitors - collect results from agents

stats - calculate statistics

You also have to configure cache. Sample cache configuration (for default memcached configs):

CACHES = {
    'default': {
        'BACKEND': 'django.core.cache.backends.memcached.MemcachedCache',
        'LOCATION': '127.0.0.1:11211',
    }
}

Database preparation

After creating the settings-local.py file, synchronize the database with sources by running the standard syncdb management command:

$(selena): selena syncdb

then run migrations command:

$(selena): selena migrate

Create partitions in the database by using the command:

$(selena): selena createpartitions

Run web interface

To run selena web interface use the command:

(selena)$ selena runserver 8080

Configuration agents

When your selena web interface is running you must add a main agents to your selena instance. Open this link in your browser http://localhost:8080/admin/services/agent/add/ and log in into administration panel.

You will see a form where you have to fill the name of your main agent, add a queue (remember the name of the queue must be set in your Selena agent settings-local.py file), and check the main agent checkbox. After the agent is added you will see Salt column in your agent row. Copy this string and add to the Selena-agent settings-local.py file in SALT variable. It is very important, because without it there will be no communication with the Selena-agent.

Add monitored services

In administration panel add a service which will be monitored by Selena. Open this link in browser http://localhost:8080/admin/services/service/add/ and add a service URL to be monitored.

Commands

Run a single monitoring service:

(selena)$: selena monitorall

Search incidents:

(selena)$: selena searchincidents

Activate/Deactivate technical breaks:

(selena)$: selena technicalbreaks

For optimization, there are commands to archive service monitoring results. If you create partitions in MySQL database run command:

(selena)$: selena createpartitions

You will need to run the command that merges monitoring data older than 8 days and moves it to the archive:

(selena)$: selena makearchive

Calculate SLA for active services:

(selena)$: selena calculatesla

If you want to run the commands asynchronically, you can add an --async-mode=1 option to them.

Automation

You can configure Cron to monitor automatically in background. To edit crontab run command:

$(selena): crontab -e

and add this content:

*/1 * * * * /YOUR_VIRTUAL_ENV_PATH/bin/selena monitorall
*/1 * * * * /YOUR_VIRTUAL_ENV_PATH/bin/selena searchincidents --async-mode=1
*/5 * * * * /YOUR_VIRTUAL_ENV_PATH/bin/selena technicalbreaks --async-mode=1
0 1 * * * /YOUR_VIRTUAL_ENV_PATH/bin/selena createpartitions --async-mode=1
30 1 * * * /YOUR_VIRTUAL_ENV_PATH/bin/selena makearchive --async-mode=1
0 3 * * * /YOUR_VIRTUAL_ENV_PATH/bin/selena calculatesla

Of course you can set your own time to execute these commands in Cron.

To see the results of the monitoring in a browser, open the following address: http://localhost:8080

License

Selena is licensed under the Apache License, v2.0.

Copyright (c) 2013-2014 Allegro Group.