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Chef orchestration layer -- your system diagram come to life. Provision EC2, OpenStack or Vagrant without changes to cookbooks or configuration
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Ironfan Core: knife tools and core models

The ironfan project is an expressive toolset for constructing scalable, resilient architectures. It works in the cloud, in the data center, and on your laptop, and makes your system diagram visible and inevitable.

This repo implements

  • core models to describe your system diagram with a clean, expressive domain-specific language
  • knife plugins to orchestrate clusters of machines using simple commands like knife cluster launch
  • logic to coordinate truth among chef server and cloud providers.

It works together with the full ironfan toolset:

  • ironfan-homebase: centralizes the cookbooks, roles and clusters. A solid foundation for any chef user.
  • ironfan gem: core ironfan models, and knife plugins to orchestrate machines and coordinate truth among you homebase, cloud and chef server.
  • ironfan-pantry: Our collection of industrial-strength, cloud-ready recipes for Hadoop, HBase, Cassandra, Elasticsearch, Zabbix and more.
  • silverware cookbook: coordinate discovery of services ("list all the machines for awesome_webapp, that I might load balance them") and aspects ("list all components that write logs, that I might logrotate them, or that I might monitor the free space on their volumes".
  • ironfan-ci: Continuous integration testing of not just your cookbooks but your architecture.

  • ironfan wiki: high-level documentation and install instructions

  • ironfan issues: bugs, questions and feature requests for any part of the ironfan toolset.
  • ironfan gem docs: rdoc docs for ironfan

Please file all issues on ironfan issues.


Infrastructure as code: describe and orchestrate whole clusters of cloud or virtual machines.


Here's a very simple cluster:

Ironfan.cluster 'webapp_demo' do
  cloud(:ec2) do
    flavor              't1.micro'

  role                  :base_role
  role                  :chef_client
  role                  :ssh

  # The database server
  facet :dbnode do
    instances           1
    role                :mysql_server

    cloud do
      flavor           'm1.large'
      backing          'ebs'

  # A throwaway facet for development.
  facet :webnode do
    instances           2
    role                :nginx_server
    role                :awesome_webapp

This code defines a cluster named demosimple. A cluster is a group of servers united around a common purpose, in this case to serve a scalable web application.

The webapp_demo cluster has two 'facets' -- dbnode and webnode. A facet is a subgroup of interchangeable servers that provide a logical set of systems: in this case, the systems that store the website's data and those that render it.

The dbnode facet has one server, which will be named webapp_demo-dbnode-0; the webnode facet has two servers, webapp_demo-webnode-0 and webapp_demo-webnode-1.

Each server inherits the appropriate behaviors from its facet and cluster. All the servers in this cluster have the base_role, chef_client and ssh roles. The dbnode machines additionally house a MySQL server, while the webnodes have an nginx reverse proxy for the custom webapp_demo_webapp.

As you can see, the dbnode facet asks for a different flavor of machine (m1.large) than the cluster default (t1.micro). Settings in the facet override those in the server, and settings in the server override those of its facet. You economically describe only what's significant about each machine.

Cluster-level tools

$ knife cluster show webapp_demo

  | Name               | Chef? | InstanceID | State       | Public IP    | Private IP    | Created At      | Flavor   | Image        | AZ         | SSH Key    |
  | webapp_demo-dbnode-0   | yes   | i-43c60e20 | running     | | | 20111029-204156 | t1.micro | ami-cef405a7 | us-east-1a | webapp_demo    |
  | webapp_demo-webnode-0  | yes   | i-1233aef1 | running     | | | 20111029-204156 | t1.micro | ami-cef405a7 | us-east-1a | webapp_demo    |
  | webapp_demo-webnode-1  | yes   | i-0986423b | not running |              |               |                 |          |              |            |            |

The commands available are

  • list -- lists known clusters
  • show -- show the named servers
  • launch -- launch server
  • bootstrap
  • sync
  • ssh
  • start/stop
  • kill
  • kick -- trigger a chef-client run on each named machine, tailing the logs until the run completes

Advanced clusters remain simple

Let's say that app is truly awesome, and the features and demand increases. This cluster adds an ElasticSearch server for searching, a haproxy loadbalancer, and spreads the webnodes across two availability zones.

Ironfan.cluster 'webserver_demo_2' do
  cloud(:ec2) do
    image_name          "maverick"
    flavor              "t1.micro"
    availability_zones  ['us-east-1a']

  # The database server
  facet :dbnode do
    instances           1
    role                :mysql_server
    cloud do
      flavor           'm1.large'
      backing          'ebs'

    volume(:data) do
      size              20
      keep              true                        
      device            '/dev/sdi'                  
      mount_point       '/data'              
      snapshot_id       'snap-a10234f'             
      attachable        :ebs

  facet :webnode do
    instances           6
    cloud.availability_zones  ['us-east-1a', 'us-east-1b']

    role                :nginx_server
    role                :awesome_webapp
    role                :elasticsearch_client

    volume(:server_logs) do
      size              5                           
      keep              true                        
      device            '/dev/sdi'                  
      mount_point       '/server_logs'              
      snapshot_id       'snap-d9c1edb1'             

  facet :esnode do
    instances           1
    role                "elasticsearch_data_esnode"
    role                "elasticsearch_http_esnode"
    cloud.flavor        "m1.large"

  facet :loadbalancer do
    instances           1
    role                "haproxy"
    cloud.flavor        "m1.xlarge"
    elastic_ip          ""

    :elasticsearch => {
      :version => '0.17.8',

The facets are described and scale independently. If you'd like to add more webnodes, just increase the instance count. If a machine misbehaves, just terminate it. Running knife cluster launch webapp_demo webnode will note which machines are missing, and launch and configure them appropriately.

Ironfan speaks naturally to both Chef and your cloud provider. The esnode's cluster_role.override_attributes statement will be synchronized to the chef server, pinning the elasticsearch version across the clients and server.. Your chef roles should focus system-specific information; the cluster file lets you see the architecture as a whole.

With these simple settings, if you have already set up chef's knife to launch cloud servers, typing knife cluster launch demosimple --bootstrap will (using Amazon EC2 as an example):

  • Synchronize to the chef server:
    • create chef roles on the server for the cluster and each facet.
    • apply role directives (eg the homebase's default_attributes declaration).
    • create a node for each machine
    • apply the runlist to each node
  • Set up security isolation:
    • uses a keypair (login ssh key) isolated to that cluster
    • Recognizes the ssh role, and add a security group ssh that by default opens port 22.
    • Recognize the nfs_server role, and adds security groups nfs_server and nfs_client
    • Authorizes the nfs_server to accept connections from all nfs_clients. Machines in other clusters that you mark as nfs_clients can connect to the NFS server, but are not automatically granted any other access to the machines in this cluster. Ironfan's opinionated behavior is about more than saving you effort -- tying this behavior to the chef role means you can't screw it up.
  • Launches the machines in parallel:
    • using the image name and the availability zone, it determines the appropriate region, image ID, and other implied behavior.
    • passes a JSON-encoded user_data hash specifying the machine's chef node_name and client key. An appropriately-configured machine image will need no further bootstrapping -- it will connect to the chef server with the appropriate identity and proceed completely unattended.
  • Syncronizes to the cloud provider:
    • Applies EC2 tags to the machine, making your console intelligible: AWS Console screenshot
    • Connects external (EBS) volumes, if any, to the correct mount point -- it uses (and applies) tags to the volumes, so they know which machine to adhere to. If you've manually added volumes, just make sure they're defined correctly in your cluster file and run knife cluster sync {cluster_name}; it will paint them with the correct tags.
    • Associates an elastic IP, if any, to the machine
  • Bootstraps the machine using knife bootstrap

Getting Started

@sya add the contents of here


Some general principles of how we use chef.

  • Chef server is never the repository of truth -- it only mirrors the truth.
    • a file is tangible and immediate to access
  • Specifically, we want truth to live in the git repo, and be enforced by the chef server. There is no truth but git, and chef is its messenger.
    • this means that everything is versioned, documented and exchangeable.
  • Systems, services and significant modifications cluster should be obvious from the clusters file. I don't want to have to bounce around nine different files to find out which thing installed a redis:server.
    • basically, the existence of anything that opens a port should be obvious when I look at the cluster file.
  • Roles define systems, clusters assemble systems into a machine.
    • For example, a resque worker queue has a redis, a webserver and some config files -- your cluster should invoke a @whatever_queue@ role, and the @whatever_queue@ role should include recipes for the component services.
    • the existence of anything that opens a port or runs as a service should be obvious when I look at the roles file.
  • include_recipe considered harmful Do NOT use include_recipe for anything that a) provides a service, b) launches a daemon or c) is interesting in any way. (so: @include_recipe java@ yes; @include_recipe iptables@ no.) You should note the dependency in the metadata.rb. This seems weird, but the breaking behavior is purposeful: it makes you explicitly state all dependencies.
  • It's nice when machines are in full control of their destiny.
    • initial setup (elastic IP, attaching a drive) is often best enforced externally
    • but machines should be ablt independently assert things like load balancer registration that that might change at any point in the lifetime.
  • It's even nicer, though, to have full idempotency from the command line: I can at any time push truth from the git repo to the chef server and know that it will take hold.

Advanced Superpowers

Set up Knife on your local machine, and a Chef Server in the cloud

If you already have a working chef installation you can skip this section.

To get started with knife and chef, follow the "Chef Quickstart,": We use the hosted chef service and are very happy, but there are instructions on the wiki to set up a chef server too. Stop when you get to "Bootstrap the Ubuntu system" -- cluster chef is going to make that much easier.

Auto-vivifying machines (no bootstrap required!)

On EC2, you can make a machine that auto-vivifies -- no bootstrap necessary. Burn an AMI that has the config/client.rb file in /etc/chef/client.rb. It will use the ec2 userdata (passed in by knife) to realize its purpose in life, its identity, and the chef server to connect to; everything happens automagically from there. No parallel ssh required!

EBS Volumes

Define a snapshot_id for your volumes, and set create_at_launch true.

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