git resource

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Use the git resource to manage source control resources that exist in a git repository. git version 1.6.5 (or higher) is required to use all of the functionality in the git resource.

Syntax

A git resource block manages source control resources that exist in a git repository:

git "#{Chef::Config[:file_cache_path]}/app_name" do
  repository node[:app_name][:git_repository]
  revision node[:app_name][:git_revision]
  action :sync
end

The full syntax for all of the properties that are available to the git resource is:

git 'name' do
  additional_remotes      Hash
  checkout_branch         String # default value: "deploy"
  depth                   Integer
  destination             String # default value: 'name' unless specified
  enable_checkout         true, false # default value: true
  enable_submodules       true, false # default value: false
  environment             Hash
  group                   String, Integer
  remote                  String # default value: "origin"
  repository              String
  revision                String # default value: "HEAD"
  ssh_wrapper             String
  timeout                 Integer
  user                    String, Integer
  action                  Symbol # defaults to :sync if not specified
end

where:

  • git is the resource.
  • name is the name given to the resource block.
  • action identifies which steps the chef-client will take to bring the node into the desired state.
  • additional_remotes, checkout_branch, depth, destination, enable_checkout, enable_submodules, environment, group, remote, repository, revision, ssh_wrapper, timeout, and user are the properties available to this resource.

Actions

The git resource has the following actions:

:checkout
Clone or check out the source. When a checkout is available, this provider does nothing.
:export
Export the source, excluding or removing any version control artifacts.
:nothing
This resource block does not act unless notified by another resource to take action. Once notified, this resource block either runs immediately or is queued up to run at the end of the Chef Client run.
:sync
Default. Update the source to the specified version, or get a new clone or checkout. This action causes a hard reset of the index and working tree, discarding any uncommitted changes.

Properties

The git resource has the following properties:

additional_remotes

Ruby Type: Hash

A Hash of additional remotes that are added to the git repository configuration.

checkout_branch

Ruby Type: String | Default Value: deploy

Do a one-time checkout from git or use when a branch in the upstream repository is named deploy. To prevent the git resource from attempting to check out master from master, set enable_checkout to false when using the checkout_branch property. See revision.

depth

Ruby Type: Integer

The number of past revisions to be included in the git shallow clone. The default behavior will do a full clone.

destination

Ruby Type: String | Default Value: The resource block's name

The location path to which the source is to be cloned, checked out, or exported. Default value: the name of the resource block. See “Syntax” section above for more information.

enable_checkout

Ruby Type: true, false | Default Value: true

Check out a repo from master. Set to false when using the checkout_branch attribute to prevent the git resource from attempting to check out master from master.

enable_submodules

Ruby Type: true, false | Default Value: false

Perform a sub-module initialization and update.

environment

Ruby Type: Hash

A Hash of environment variables in the form of ({"ENV_VARIABLE" => "VALUE"}). (These variables must exist for a command to be run successfully.)

Note

The git provider automatically sets the ENV['HOME'] and ENV['GIT_SSH'] environment variables. To override this behavior and provide different values, add ENV['HOME'] and/or ENV['GIT_SSH'] to the environment Hash.

group

Ruby Type: String, Integer

The system group that is responsible for the checked-out code.

remote

Ruby Type: String | Default Value: "origin"

The remote repository to use when synchronizing an existing clone.

repository

Ruby Type: String

The URI for the git repository.

revision

Ruby Type: String | Default Value: HEAD

A branch, tag, or commit to be synchronized with git. This can be symbolic, like HEAD or it can be a source control management-specific revision identifier. See checkout_branch.

The value of the revision attribute may change over time. From one branch to another, to a tag, to a specific SHA for a commit, and then back to a branch. The revision attribute may even be changed in a way where history gets rewritten.

Instead of tracking a specific branch or doing a headless checkout, the chef-client maintains its own branch (via the git resource) that does not exist in the upstream repository. The chef-client is then free to forcibly check out this branch to any commit without destroying the local history of an existing branch.

For example, to explicitly track an upstream repository’s master branch:

revision 'master'

Use the git rev-parse and git ls-remote commands to verify that the chef-client is synchronizing commits correctly. (The chef-client always runs git ls-remote on the upstream repository to verify the commit is made to the correct repository.)

ssh_wrapper

Ruby Type: String

The path to the wrapper script used when running SSH with git. The GIT_SSH environment variable is set to this.

timeout

Ruby Type: Integer

The amount of time (in seconds) to wait for a command to execute before timing out. When this property is specified using the deploy resource, the value of the timeout property is passed from the deploy resource to the git resource.

user

Ruby Type: String, Integer

The system user that is responsible for the checked-out code. Default value: the home directory of this user, as indicated by the HOME environment variable.

Common Resource Functionality

Chef resources include common properties, notifications, and resource guards.

Common Properties

The following properties are common to every resource:

ignore_failure

Ruby Type: true, false | Default Value: false

Continue running a recipe if a resource fails for any reason.

retries

Ruby Type: Integer | Default Value: 0

The number of attempts to catch exceptions and retry the resource.

retry_delay

Ruby Type: Integer | Default Value: 2

The retry delay (in seconds).

sensitive

Ruby Type: true, false | Default Value: false

Ensure that sensitive resource data is not logged by the chef-client.

Notifications

notifies

Ruby Type: Symbol, ‘Chef::Resource[String]’

A resource may notify another resource to take action when its state changes. Specify a 'resource[name]', the :action that resource should take, and then the :timer for that action. A resource may notify more than one resource; use a notifies statement for each resource to be notified.

A timer specifies the point during the Chef Client run at which a notification is run. The following timers are available:

:before
Specifies that the action on a notified resource should be run before processing the resource block in which the notification is located.
:delayed
Default. Specifies that a notification should be queued up, and then executed at the end of the Chef Client run.
:immediate, :immediately
Specifies that a notification should be run immediately, per resource notified.

The syntax for notifies is:

notifies :action, 'resource[name]', :timer
subscribes
Ruby Type: Symbol, ‘Chef::Resource[String]’

A resource may listen to another resource, and then take action if the state of the resource being listened to changes. Specify a 'resource[name]', the :action to be taken, and then the :timer for that action.

Note that subscribes does not apply the specified action to the resource that it listens to - for example:

file '/etc/nginx/ssl/example.crt' do
  mode '0600'
  owner 'root'
end

service 'nginx' do
  subscribes :reload, 'file[/etc/nginx/ssl/example.crt]', :immediately
end

In this case the subscribes property reloads the nginx service whenever its certificate file, located under /etc/nginx/ssl/example.crt, is updated. subscribes does not make any changes to the certificate file itself, it merely listens for a change to the file, and executes the :reload action for its resource (in this example nginx) when a change is detected.

A timer specifies the point during the Chef Client run at which a notification is run. The following timers are available:

:before
Specifies that the action on a notified resource should be run before processing the resource block in which the notification is located.
:delayed
Default. Specifies that a notification should be queued up, and then executed at the end of the Chef Client run.
:immediate, :immediately
Specifies that a notification should be run immediately, per resource notified.

The syntax for subscribes is:

subscribes :action, 'resource[name]', :timer

Guards

A guard property can be used to evaluate the state of a node during the execution phase of the chef-client run. Based on the results of this evaluation, a guard property is then used to tell the chef-client if it should continue executing a resource. A guard property accepts either a string value or a Ruby block value:

  • A string is executed as a shell command. If the command returns 0, the guard is applied. If the command returns any other value, then the guard property is not applied. String guards in a powershell_script run Windows PowerShell commands and may return true in addition to 0.
  • A block is executed as Ruby code that must return either true or false. If the block returns true, the guard property is applied. If the block returns false, the guard property is not applied.

A guard property is useful for ensuring that a resource is idempotent by allowing that resource to test for the desired state as it is being executed, and then if the desired state is present, for the chef-client to do nothing.

The following properties can be used to define a guard that is evaluated during the execution phase of the chef-client run:

not_if
Prevent a resource from executing when the condition returns true.
only_if
Allow a resource to execute only if the condition returns true.

Examples

The following examples demonstrate various approaches for using resources in recipes:

Use the git mirror

git '/opt/mysources/couch' do
  repository 'git://git.apache.org/couchdb.git'
  revision 'master'
  action :sync
end

Use different branches

To use different branches, depending on the environment of the node:

if node.chef_environment == 'QA'
   branch_name = 'staging'
else
   branch_name = 'master'
end

git '/home/user/deployment' do
   repository 'git@github.com:gitsite/deployment.git'
   revision branch_name
   action :sync
   user 'user'
   group 'test'
end

where the branch_name variable is set to staging or master, depending on the environment of the node. Once this is determined, the branch_name variable is used to set the revision for the repository. If the git status command is used after running the example above, it will return the branch name as deploy, as this is the default value. Run the chef-client in debug mode to verify that the correct branches are being checked out:

$ sudo chef-client -l debug

Install an application from git using bash

The following example shows how Bash can be used to install a plug-in for rbenv named ruby-build, which is located in git version source control. First, the application is synchronized, and then Bash changes its working directory to the location in which ruby-build is located, and then runs a command.

 git "#{Chef::Config[:file_cache_path]}/ruby-build" do
   repository 'git://github.com/sstephenson/ruby-build.git'
   reference 'master'
   action :sync
 end

 bash 'install_ruby_build' do
   cwd '#{Chef::Config[:file_cache_path]}/ruby-build'
   user 'rbenv'
   group 'rbenv'
   code <<-EOH
     ./install.sh
     EOH
   environment 'PREFIX' => '/usr/local'
end

To read more about ruby-build, see here: https://github.com/sstephenson/ruby-build.

Upgrade packages from git

The following example uses the git resource to upgrade packages:

# the following code sample comes from the ``source`` recipe
# in the ``libvpx-cookbook`` cookbook:
# https://github.com/enmasse-entertainment/libvpx-cookbook

git "#{Chef::Config[:file_cache_path]}/libvpx" do
  repository node[:libvpx][:git_repository]
  revision node[:libvpx][:git_revision]
  action :sync
  notifies :run, 'bash[compile_libvpx]', :immediately
end

Pass in environment variables

git '/opt/mysources/couch' do
  repository 'git://git.apache.org/couchdb.git'
  revision 'master'
  environment 'VAR' => 'whatever'
  action :sync
end