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Presents a simple, unchanging interface to get metadata about your EngineYard AppCloud instances running on Amazon EC2.

README.markdown

engineyard-metadata

Presents a simple interface to get metadata about your EngineYard AppCloud instances running on Amazon EC2.

Purpose

To define a simple interface to useful metadata (passwords, IP addresses, etc.) that is otherwise buried deep inside EngineYard's chef config files and various API calls.

Examples

Here's the current method list:

EY.metadata.app_master
EY.metadata.app_name
EY.metadata.app_servers
EY.metadata.app_slaves
EY.metadata.current_path
EY.metadata.database_host
EY.metadata.database_name
EY.metadata.database_password       (only works from cloud instances)
EY.metadata.database_username
EY.metadata.db_master
EY.metadata.db_servers
EY.metadata.db_slaves
EY.metadata.environment_name
EY.metadata.mysql_command           (only works from cloud instances)
EY.metadata.mysqldump_command       (only works from cloud instances)
EY.metadata.present_instance_id     (only works from cloud instances)
EY.metadata.present_instance_role   (only works from cloud instances)
EY.metadata.present_public_hostname (only works from cloud instances)
EY.metadata.present_security_group  (only works from cloud instances)
EY.metadata.repository_uri
EY.metadata.shared_path
EY.metadata.solo
EY.metadata.ssh_aliases
EY.metadata.ssh_password            (only works from cloud instances)
EY.metadata.ssh_username
EY.metadata.stack_name
EY.metadata.utilities

public_hostname, amazon_id, etc.

Thanks to Nick Marden, you can do things like:

?> EY.metadata.app_servers('amazon_id')
>> [ 'i-ff17d493', 'i-c217d423' ]

By default, you get the public hostname.

Use

See the documentation at (the engineyard-metadata documentation}[http://rubydoc.info/gems/engineyard-metadata].

When you're executing this gem from INSIDE the cloud

When you're executing the gem from your instances, you don't have to configure anything. Just require the gem.

If you see

Errno::EACCES: Permission denied - /etc/chef/dna.json

then I suggest adding something like this to deploy/before_bundle.rb

sudo 'chmod a+r /etc/chef/dna.json'

or find some other way to make the file readable.

The Engine Yard recipes will often reset the permissions on the file, so you can periodically fix that using a custom chef recipe like this:

# Only run on app server instances.
if ['app','app_master'].include?(node[:instance_role]) then
  cron "Make /etc/chef/dna.json readable" do 
    minute "*/5" 
    command "chmod a+r /etc/chef/dna.json" 
  end 
end

When you're executing this gem from OUTSIDE the cloud

You must...

  • have ~/.eyrc or set EY.metadata.ey_cloud_token= or set ENV['EY_CLOUD_TOKEN'].
  • execute the gem from the local copy of your application's repo or set EY.metadata.environment_name= or set ENV['EY_ENVIRONMENT_NAME'].

Where the methods are defined

Metadata getters are defined directly on EY.metadata (which in turn delegates out to various adapters). Even if EngineYard changes the structure of the config files or Amazon EC2's API changes, these methods will stay the same.

[...]
>> require 'rubygems'
[...]
>> require 'engineyard-metadata'
[...]
>> EY.metadata.database_host
=> "external_db_master.compute-1.amazonaws.com"
>> EY.metadata.app_servers
=> [ 'app_1.compute-1.amazonaws.com' , 'app_master.compute-1.amazonaws.com' ]
>> EY.metadata.db_servers
=> [ 'db_master.compute-1.amazonaws.com', 'db_slave_1.compute-1.amazonaws.com' ]
[...and many more...]

SSH alias helper

You can put the output of ey_ssh_aliases into ~/.ssh/config:

$ EY_ENVIRONMENT_NAME=my_env ey_ssh_aliases 
Host my_env-app_master
  Hostname ec2-11-11-111-11.compute-1.amazonaws.com
  User deploy
  StrictHostKeyChecking no

Host my_env-db_master
  Hostname ec2-111-11-11-11.compute-1.amazonaws.com
  User deploy
  StrictHostKeyChecking no

Known issues

  • Doesn't work with multiple apps per environment. [FIXED!]
  • It's not always clear what environment you're running in. For example, you say EY.metadata.something and you're just supposed to know what environment you're in. You can use .environment_name=, but you might not remember.
  • There are no factory methods. If we fully fleshed this out, it might be like my_env = EY::Environment.find('my_env') and my_app_master = my_env.app_master. Not sure that complexity would add a lot of value.

History

This is the second generation of http://rubygems.org/gems/ey_cloud_awareness.

Sample test output

engineyard-metadata (master) $ rake

EY.metadata
  being executed on an EngineYard AppCloud (i.e. Amazon EC2) instance
    it should behave like it does in all execution environments
      by getting the database username
      by getting the database name
      by getting the database host
      by getting the ssh username
      by getting the app server hostnames
      by getting the db server hostnames
      by getting the utilities hostnames
      by getting the app master hostname
      by getting the db master hostname
      by getting the db slave hostnames
      by getting the app slave hostnames
      by getting the solo hostname
      by getting the environment name
      by getting the stack name
      by getting the repository URI
      by getting the app name
      by getting the current path
      by getting the shared path
      by getting helpful ssh aliases
    it should behave like it's executing inside the cloud
      by refusing to get the list of all environment names
      by getting the present instance ID
      by getting the present instance role (as a string)
      by getting the present public hostname
      by getting the present security group
      by getting the database password
      by getting the ssh password
      by getting the mysql command
      by getting the mysqldump command
  being executed from a developer/administrator's local machine
    controlled with environment variables
      it should behave like it does in all execution environments
        by getting the database username
        by getting the database name
        by getting the database host
        by getting the ssh username
        by getting the app server hostnames
        by getting the db server hostnames
        by getting the utilities hostnames
        by getting the app master hostname
        by getting the db master hostname
        by getting the db slave hostnames
        by getting the app slave hostnames
        by getting the solo hostname
        by getting the environment name
        by getting the stack name
        by getting the repository URI
        by getting the app name
        by getting the current path
        by getting the shared path
        by getting helpful ssh aliases
      it should behave like it's executing outside the cloud
        by getting the list of all environment names
        by refusing to get the present instance ID
        by refusing to get the present instance role (as a string)
        by refusing to get the present public hostname
        by refusing to get the present security group
        by refusing to get the database password
        by refusing to get the ssh password
        by refusing to get the mysql command
        by refusing to get the mysqldump command
    controlled with attr writers
      it should behave like it does in all execution environments
        by getting the database username
        by getting the database name
        by getting the database host
        by getting the ssh username
        by getting the app server hostnames
        by getting the db server hostnames
        by getting the utilities hostnames
        by getting the app master hostname
        by getting the db master hostname
        by getting the db slave hostnames
        by getting the app slave hostnames
        by getting the solo hostname
        by getting the environment name
        by getting the stack name
        by getting the repository URI
        by getting the app name
        by getting the current path
        by getting the shared path
        by getting helpful ssh aliases
      it should behave like it's executing outside the cloud
        by getting the list of all environment names
        by refusing to get the present instance ID
        by refusing to get the present instance role (as a string)
        by refusing to get the present public hostname
        by refusing to get the present security group
        by refusing to get the database password
        by refusing to get the ssh password
        by refusing to get the mysql command
        by refusing to get the mysqldump command
    depending on .eyrc
      it should behave like it does in all execution environments
        by getting the database username
        by getting the database name
        by getting the database host
        by getting the ssh username
        by getting the app server hostnames
        by getting the db server hostnames
        by getting the utilities hostnames
        by getting the app master hostname
        by getting the db master hostname
        by getting the db slave hostnames
        by getting the app slave hostnames
        by getting the solo hostname
        by getting the environment name
        by getting the stack name
        by getting the repository URI
        by getting the app name
        by getting the current path
        by getting the shared path
        by getting helpful ssh aliases
      it should behave like it's executing outside the cloud
        by getting the list of all environment names
        by refusing to get the present instance ID
        by refusing to get the present instance role (as a string)
        by refusing to get the present public hostname
        by refusing to get the present security group
        by refusing to get the database password
        by refusing to get the ssh password
        by refusing to get the mysql command
        by refusing to get the mysqldump command

Finished in 0.95816 seconds
112 examples, 0 failures

Copyright

Copyright (c) 2012 Seamus Abshere. See LICENSE for details.

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