! This repository is in beta and does not contain content which can be used without adaptions so far
Ansible is an IT automation tool. It can configure systems, deploy software, and orchestrate more advanced IT tasks and its free. There is a ui which costs money. Ansible executes command on remote hosts by using ssh. Thats the idea and the rest of it is syntactic sugar and additional workarounds if native openSSH is not available in a fitting version.
http://www.ansible.com/home http://docs.ansible.com/index.html
- Install it:
http://docs.ansible.com/intro_installation.html
If the hosts can change, disbale host key checkeing e.g.g by
$ export ANSIBLE_HOST_KEY_CHECKING=False
2.Create an inventory file:
Thats a file which contains known hosts, groups them together and add varaibles related to the hosts. Its stored in /etc/ansible/hosts or you have to add the file as parameter if you want to execute commands A file could look like this:
mail.example.com
other2.example.com ansible_connection=ssh ansible_ssh_user=mdehaan
[webservers]
www[01:50].example.com
[webservers:vars]
ntp_server=ntp.atlanta.example.com
proxy=proxy.atlanta.example.com
[dbservers]
one.example.com
two.example.com
[databases]
db-[a:f].example.com
Details can be found at: http://docs.ansible.com/intro_inventory.html
3.Execute commands
e.g. hello on all hosts in /etc/ansible/hosts
ansible all -a "/bin/echo hello"
e.g. hello on the host1 (limit) from the local host file (-i)
ansible -i ./hosts --limit localhost all -a "/bin/echo hello"
4.Playbooks
Instead of executing ad-hoc commands, you probably want to write scripts. They are called playbooks and they are written in yaml syntax. You can use commands in this playbooks or you can use an so called ansible modules (http://docs.ansible.com/modules.html, http://docs.ansible.com/modules_by_category.html) which aggregate environment commands userfriendly.
Again a simple example (playbook.yml):
---
- hosts: webservers
vars:
http_port: 80
max_clients: 200
remote_user: root
tasks:
- name: ensure apache is at the latest version
yum: pkg=httpd state=latest
- name: write the apache config file
template: src=/srv/httpd.j2 dest=/etc/httpd.conf
notify:
- restart apache
- name: ensure apache is running
service: name=httpd state=started
handlers:
- name: restart apache
service: name=httpd state=restarted
Each play contains a list of tasks. Tasks are executed in order, one at a time, against all machines matched by the host pattern, before moving on to the next task. Modules are ‘idempotent’, meaning if you run them again, they will make only the changes they must in order to bring the system to the desired state.
You can execute it (e.g. with parallelism level of 10)
ansible-playbook playbook.yml -f 10
5.Handle more complex playbooks
The best way to handle more complex stuff is the usage of includes or so called roles. See for example http://docs.ansible.com/playbooks_roles.html
Includes can look like this:
- name: this is a play at the top level of a file
hosts: all
remote_user: root
tasks:
- name: say hi
tags: foo
shell: echo "hi..."
- include: load_balancers.yml
- include: webservers.yml
- include: dbservers.yml
Roles are just automation around ‘include’ directives by conventions. If you would organize your structure like this:
site.yml
webservers.yml
fooservers.yml
roles/
common/
files/
templates/
tasks/
handlers/
vars/
meta/
webservers/
files/
templates/
tasks/
handlers/
vars/
meta/
You could simple write something like this:
---
- hosts: webservers
roles:
- common
- webservers
6.Where can you find more:
logstash is a tool for managing events and logs. You can use it to collect logs, parse them, and store them for later use
Or in my words:
- It can use several inputs (e.g. logs, streams, ...)
- It can manipulate the data (e.g. filtering, extracting fields, ...)
- It can push data out
So its for example perfect to collect log files from distributed nodes, filter data and send the data to a cetral datastore where the data can be analyzed.
In this example I will use logstash to parse local logfiles and push that data to a central redis database. This part is called shipper
On a central node (where the database is stored), I will use the data from the redis database to add this data to an elastic search database which then can be used by kibana to show the log data. I will call it indexer.
This setup can be used to handle several nodes, because it collect the data from the nodes and mergen the data together and because of the usage of redis as middleware it will perform well and is able to handle peaks.
I will assume we will use ubuntu and install everything in a folder called /monitoring
sudo apt-get update
sudo apt-get upgrade
sudo mkdir /monitoring
We need java
sudo apt-get install openjdk-6-jre-headless -y
We need redis
sudo apt-get install redis-server -y
cd /etc/redis
sudo sed -i 's/bind 127.0.0.1/bind 0.0.0.0/g' redis.conf
sudo service redis-server restart
We need elastic search with some nice plugins
cd /monitoring
sudo wget https://download.elasticsearch.org/elasticsearch/elasticsearch/elasticsearch-1.0.1.tar.gz
sudo tar zxvf elasticsearch-1.0.1.tar.gz
sudo mv elasticsearch-1.0.1 elasticsearch
cd /monitoring/elasticsearch/config/
sudo mv elasticsearch.yml elasticsearch-Default.yml
sudo sed 's/# cluster.name: elasticsearch/cluster.name: elasticsearch-monitoring/g' elasticsearch-Default.yml > elasticsearch.yml
cd /monitoring/elasticsearch/bin
sudo ./plugin -install royrusso/elasticsearch-HQ
sudo ./elasticsearch -d
And we need logstash itself
cd /monitoring
sudo wget https://download.elasticsearch.org/logstash/logstash/logstash-1.4.0.tar.gz
sudo tar zxvf logstash-1.4.0.tar.gz
sudo mv logstash-1.4.0 logstash
cd /monitoring/logstash/bin
A config could look like logstash-indexer.conf
sudo ./logstash -f logstash-indexer.conf
What we need is only logstash e.g. by
sudo wget https://download.elasticsearch.org/logstash/logstash/logstash-1.4.0.tar.gz
sudo tar zxvf logstash-1.4.0.tar.gz
Then we should add the log files as input e.g. by a config see logstashShipper.conf
Then we can start the shipper by
sudo ./logstash -f logstashShipper.conf
TODO
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