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About Handlers

Use a handler to identify situations that arise during a chef-client run, and then tell the chef-client how to handle these situations when they occur.

There are three types of handlers:

Handler Description
exception An exception handler is used to identify situations that have caused a chef-client run to fail. An exception handler can be loaded at the start of a chef-client run by adding a recipe that contains the chef_handler resource to a node’s run-list. An exception handler runs when the failed? property for the run_status object returns true.
report A report handler is used when a chef-client run succeeds and reports back on certain details about that chef-client run. A report handler can be loaded at the start of a chef-client run by adding a recipe that contains the chef_handler resource to a node’s run-list. A report handler runs when the success? property for the run_status object returns true.
start A start handler is used to run events at the beginning of the chef-client run. A start handler can be loaded at the start of a chef-client run by adding the start handler to the start_handlers setting in the client.rb file or by installing the gem that contains the start handler by using the chef_gem resource in a recipe in the chef-client cookbook. (A start handler may not be loaded using the chef_handler resource.)

Exception/Report Handlers

Exception and report handlers are used to trigger certain behaviors in response to specific situations, typically identified during a chef-client run.

  • An exception handler is used to trigger behaviors when a defined aspect of a chef-client run fails.
  • A report handler is used to trigger behaviors when a defined aspect of a chef-client run is successful.

Both types of handlers can be used to gather data about a chef-client run and can provide rich levels of data about all types of usage, which can be used later for trending and analysis across the entire organization.

Exception and report handlers are made available to the chef-client run in one of the following ways:

  • By adding the chef_handler resource to a recipe, and then adding that recipe to the run-list for a node. (The chef_handler resource is available from the chef_handler cookbook.)
  • By adding the handler to one of the following settings in the node’s client.rb file: exception_handlers and/or report_handlers

Run from Recipes

The chef_handler resource allows exception and report handlers to be enabled from within recipes, which can then added to the run-list for any node on which the exception or report handler should run. The chef_handler resource is available from the chef_handler cookbook.

To use the chef_handler resource in a recipe, add code similar to the following:

chef_handler 'name_of_handler' do
  source '/path/to/handler/handler_name'
  action :enable
end

For example, a handler for Growl needs to be enabled at the beginning of the chef-client run:

chef_gem 'chef-handler-growl'

and then is activated in a recipe by using the chef_handler resource:

chef_handler 'Chef::Handler::Growl' do
  source 'chef/handler/growl'
  action :enable
end

Run from client.rb

A simple exception or report handler may be installed and configured at run-time. This requires editing of a node’s client.rb file to add the appropriate setting and information about that handler to the client.rb or solo.rb files. Depending on the handler type, one (or more) of the following settings must be added:

Setting Description
exception_handlers A list of exception handlers that are available to the chef-client during a chef-client run.
report_handlers A list of report handlers that are available to the chef-client during a chef-client run.

When this approach is used, the client.rb file must also tell the chef-client how to install and run the handler. There is no default install location for handlers. The simplest way to distribute and install them is via RubyGems, though other methods such as GitHub or HTTP will also work. Once the handler is installed on the system, enable it in the client.rb file by requiring it. After the handler is installed, it may require additional configuration. This will vary from handler to handler. If a handler is a very simple handler, it may only require the creation of a new instance. For example, if a handler named MyOrg::EmailMe is hardcoded for all of the values required to send email, a new instance is required. And then the custom handler must be associated with each of the handler types for which it will run.

For example:

require 'rubygems'
require '/var/chef/handlers/email_me'         # the installation path

email_handler = MyOrg::EmailMe.new            # a simple handler

start_handlers << email_handler               # run at the start of the run
report_handlers << email_handler              # run at the end of a successful run
exception_handlers << email_handler           # run at the end of a failed run

Start Handlers

A start handler is not loaded into the chef-client run from a recipe, but is instead listed in the client.rb file using the start_handlers attribute. The start handler must be installed on the node and be available to the chef-client prior to the start of the chef-client run. Use the chef-client cookbook to install the start handler.

Start handlers are made available to the chef-client run in one of the following ways:

  • By adding a start handler to the chef-client cookbook, which installs the handler on the node so that it is available to the chef-client at the start of the chef-client run
  • By adding the handler to one of the following settings in the node’s client.rb file: start_handlers

Run from Recipes

The chef-client cookbook can be configured to automatically install and configure gems that are required by a start handler. For example:

node.set['chef_client']['load_gems']['chef-reporting'] = {
  :require_name => 'chef_reporting',
  :action => :install
}

node.set['chef_client']['config']['start_handlers'] = [
  {
    :class => 'Chef::Reporting::StartHandler',
    :arguments => []
  }
]

include_recipe 'chef-client::config'

Run from client.rb

A start handler can be configured in the client.rb file by adding the following setting:

Setting Description
start_handlers A list of start handlers that are available to the chef-client at the start of a chef-client run.

For example, the Reporting start handler adds the following code to the top of the client.rb file:

begin
  require 'chef_reporting'
  start_handlers << Chef::Reporting::StartHandler.new()
rescue LoadError
  Chef::Log.warn 'Failed to load #{lib}. This should be resolved after a chef run.'
end

This ensures that when the chef-client run begins the chef_reporting event handler is enabled. The chef_reporting event handler is part of a gem named chef-reporting. The chef_gem resource is used to install this gem:

chef_gem 'chef-reporting' do
  action :install
end

Event Handlers

Use the Handler DSL to attach a callback to an event. If the event occurs during the chef-client run, the associated callback is executed. For example:

  • Sending email if a chef-client run fails
  • Sending a notification to chat application if an audit run fails
  • Aggregating statistics about resources updated during a chef-client runs to StatsD

on Method

Use the on method to associate an event type with a callback. The callback defines what steps are taken if the event occurs during the chef-client run and is defined using arbitrary Ruby code. The syntax is as follows:

Chef.event_handler do
  on :event_type do
    # some Ruby
  end
end

where

  • Chef.event_handler declares a block of code within a recipe that is processed when the named event occurs during a chef-client run
  • on defines the block of code that will tell the chef-client how to handle the event
  • :event_type is a valid exception event type, such as :run_start, :run_failed, :converge_failed, :resource_failed, or :recipe_not_found

For example:

Chef.event_handler do
  on :converge_start do
    puts "Ohai! I have started a converge."
  end
end

Event Types

The following table describes the events that may occur during a chef-client run. Each of these events may be referenced in an on method block by declaring it as the event type.

Event Description
:run_start The start of the chef-client run.
:run_started The chef-client run has started.
:ohai_completed The Ohai run has completed.
:skipping_registration The chef-client is not registering with the Chef server because it already has a private key or because it does not need one.
:registration_start The chef-client is attempting to create a private key with which to register to the Chef server.
:registration_completed The chef-client created its private key successfully.
:registration_failed The chef-client encountered an error and was unable to register with the Chef server.
:node_load_start The chef-client is attempting to load node data from the Chef server.
:node_load_failed The chef-client encountered an error and was unable to load node data from the Chef server.
:run_list_expand_failed The chef-client failed to expand the run-list.
:node_load_completed The chef-client successfully loaded node data from the Chef server. Default and override attributes for roles have been computed, but are not yet applied.
:policyfile_loaded The policy file was loaded.
:cookbook_resolution_start The chef-client is attempting to pull down the cookbook collection from the Chef server.
:cookbook_resolution_failed The chef-client failed to pull down the cookbook collection from the Chef server.
:cookbook_resolution_complete The chef-client successfully pulled down the cookbook collection from the Chef server.
:cookbook_clean_start The chef-client is attempting to remove unneeded cookbooks.
:removed_cookbook_file The chef-client removed a file from a cookbook.
:cookbook_clean_complete The chef-client is done removing cookbooks and/or cookbook files.
:cookbook_sync_start The chef-client is attempting to synchronize cookbooks.
:synchronized_cookbook The chef-client is attempting to synchronize the named cookbook.
:updated_cookbook_file The chef-client updated the named file in the named cookbook.
:cookbook_sync_failed The chef-client was unable to synchronize cookbooks.
:cookbook_sync_complete The chef-client is finished synchronizing cookbooks.
:library_load_start The chef-client is loading library files.
:library_file_loaded The chef-client successfully loaded the named library file.
:library_file_load_failed The chef-client was unable to load the named library file.
:library_load_complete The chef-client is finished loading library files.
:lwrp_load_start The chef-client is loading custom resources.
:lwrp_file_loaded The chef-client successfully loaded the named custom resource.
:lwrp_file_load_failed The chef-client was unable to load the named custom resource.
:lwrp_load_complete The chef-client is finished loading custom resources.
:attribute_load_start The chef-client is loading attribute files.
:attribute_file_loaded The chef-client successfully loaded the named attribute file.
:attribute_file_load_failed The chef-client was unable to load the named attribute file.
:attribute_load_complete The chef-client is finished loading attribute files.
:definition_load_start The chef-client is loading definitions.
:definition_file_loaded The chef-client successfully loaded the named definition.
:definition_file_load_failed The chef-client was unable to load the named definition.
:definition_load_complete The chef-client is finished loading definitions.
:recipe_load_start The chef-client is loading recipes.
:recipe_file_loaded The chef-client successfully loaded the named recipe.
:recipe_file_load_failed The chef-client was unable to load the named recipe.
:recipe_not_found The chef-client was unable to find the named recipe.
:recipe_load_complete The chef-client is finished loading recipes.
:converge_start The chef-client run converge phase has started.
:converge_complete The chef-client run converge phase is complete.
:converge_failed The chef-client run converge phase has failed.
:audit_phase_start The chef-client run audit phase has started.
:audit_phase_complete The chef-client run audit phase is finished.
:audit_phase_failed The chef-client run audit phase has failed.
:control_group_started The named control group is being processed.
:control_example_success The named control group has been processed.
:control_example_failure The named control group’s processing has failed.
:resource_action_start A resource action is starting.
:resource_skipped A resource action was skipped.
:resource_current_state_loaded A resource’s current state was loaded.
:resource_current_state_load_bypassed A resource’s current state was not loaded because the resource does not support why-run mode.
:resource_bypassed A resource action was skipped because the resource does not support why-run mode.
:resource_update_applied A change has been made to a resource. (This event occurs for each change made to a resource.)
:resource_failed_retriable A resource action has failed and will be retried.
:resource_failed A resource action has failed and will not be retried.
:resource_updated A resource requires modification.
:resource_up_to_date A resource is already correct.
:resource_completed All actions for the resource are complete.
:stream_opened A stream has opened.
:stream_closed A stream has closed.
:stream_output A chunk of data from a single named stream.
:handlers_start The handler processing phase of the chef-client run has started.
:handler_executed The named handler was processed.
:handlers_completed The handler processing phase of the chef-client run is complete.
:provider_requirement_failed An assertion declared by a provider has failed.
:whyrun_assumption An assertion declared by a provider has failed, but execution is allowed to continue because the chef-client is running in why-run mode.
:run_completed The chef-client run has completed.
:run_failed The chef-client run has failed.

Examples

The following examples show ways to use the Handler DSL.

Send Email

Use the on method to create an event handler that sends email when the chef-client run fails. This will require:

  • A way to tell the chef-client how to send email
  • An event handler that describes what to do when the :run_failed event is triggered
  • A way to trigger the exception and test the behavior of the event handler

Note

Read this scenario as an HTML presentation at https://docs.chef.io/decks/event_handlers.html.

Define How Email is Sent

Use a library to define the code that sends email when a chef-client run fails. Name the file helper.rb and add it to a cookbook’s /libraries directory:

require 'net/smtp'

module HandlerSendEmail
  class Helper

    def send_email_on_run_failure(node_name)

      message = "From: Chef <chef@chef.io>\n"
      message << "To: Grant <grantmc@chef.io>\n"
      message << "Subject: Chef run failed\n"
      message << "Date: #{Time.now.rfc2822}\n\n"
      message << "Chef run failed on #{node_name}\n"
      Net::SMTP.start('localhost', 25) do |smtp|
        smtp.send_message message, 'chef@chef.io', 'grantmc@chef.io'
      end
    end
  end
end

Add the Handler

Invoke the library helper in a recipe:

Chef.event_handler do
  on :run_failed do
    HandlerSendEmail::Helper.new.send_email_on_run_failure(
      Chef.run_context.node.name
    )
  end
end
  • Use Chef.event_handler to define the event handler
  • Use the on method to specify the event type

Within the on block, tell the chef-client how to handle the event when it’s triggered.

Test the Handler

Use the following code block to trigger the exception and have the chef-client send email to the specified email address:

ruby_block 'fail the run' do
  block do
    fail 'deliberately fail the run'
  end
end

etcd Locks

The following example shows how to prevent concurrent chef-client runs from both holding a lock on etcd:

lock_key = "#{node.chef_environment}/#{node.name}"

Chef.event_handler do
  on :converge_start do |run_context|
    Etcd.lock_acquire(lock_key)
  end
end

Chef.event_handler do
  on :converge_complete do
    Etcd.lock_release(lock_key)
  end
end

HipChat Notifications

Event messages can be sent to a team communication tool like HipChat. For example, if a chef-client run fails:

Chef.event_handler do
  on :run_failed do |exception|
    hipchat_notify exception.message
  end
end

or send an alert on a configuration change:

Chef.event_handler do
  on :resource_updated do |resource, action|
    if resource.to_s == 'template[/etc/nginx/nginx.conf]'
      Helper.hipchat_message("#{resource} was updated by chef")
    end
  end
end

Handlers and Cookbooks

The following cookbooks can be used to load handlers during the chef-client run.

chef_handler

Exception and report handlers can be distributed using the chef_handler cookbook. This cookbook is authored and maintained by Chef and exposes a custom resource that can be used to enable custom handlers from within recipes and to include product-specific handlers from cookbooks. The chef_handler cookbook can be accessed here: https://github.com/chef-cookbooks/chef_handler. See the README.md for additional information.

chef-client

Start handlers can be distributed using the chef-client cookbook, which will install the handler on the target node during the initial configuration of the node. This ensures that the start handler is always present on the node so that it is available to the chef-client at the start of every run.

Custom Handlers

A custom handler can be created to support any situation. The easiest way to build a custom handler:

  1. Download the chef_handler cookbook
  2. Create a custom handler
  3. Write a recipe using the chef_handler resource
  4. Add that recipe to a node’s run-list, often as the first recipe in that run-list

Syntax

The syntax for a handler can vary, depending on what the the situations the handler is being asked to track, the type of handler being used, and so on. All custom exception and report handlers are defined using Ruby and must be a subclass of the Chef::Handler class.

require 'chef/log'

module ModuleName
  class HandlerName < Chef::Handler
    def report
      # Ruby code goes here
    end
  end
end

where:

  • require ensures that the logging functionality of the chef-client is available to the handler
  • ModuleName is the name of the module as it exists within the Chef library
  • HandlerName is the name of the handler as it is used in a recipe
  • report is an interface that is used to define the custom handler

For example, the following shows a custom handler that sends an email that contains the exception data when a chef-client run fails:

require 'net/smtp'

module OrgName
  class SendEmail < Chef::Handler
    def report
      if run_status.failed? then
        message  = "From: sender_name <sender@example.com>\n"
        message << "To: recipient_address <recipient@example.com>\n"
        message << "Subject: chef-client Run Failed\n"
        message << "Date: #{Time.now.rfc2822}\n\n"
        message << "Chef run failed on #{node.name}\n"
        message << "#{run_status.formatted_exception}\n"
        message << Array(backtrace).join('\n')
        Net::SMTP.start('your.smtp.server', 25) do |smtp|
          smtp.send_message message, 'sender@example', 'recipient@example'
        end
      end
    end
  end
end

and then is used in a recipe like:

send_email 'blah' do
  # recipe code
end

report Interface

The report interface is used to define how a handler will behave and is a required part of any custom handler. The syntax for the report interface is as follows:

def report
  # Ruby code
end

The Ruby code used to define a custom handler will vary significantly from handler to handler. The chef-client includes two default handlers: error_report and json_file. Their use of the report interface is shown below.

The error_report handler:

require 'chef/handler'
require 'chef/resource/directory'

class Chef
  class Handler
    class ErrorReport < ::Chef::Handler
      def report
        Chef::FileCache.store('failed-run-data.json', Chef::JSONCompat.to_json_pretty(data), 0640)
        Chef::Log.fatal("Saving node information to #{Chef::FileCache.load('failed-run-data.json', false)}")
      end
    end
 end
end

The json_file handler:

require 'chef/handler'
require 'chef/resource/directory'

class Chef
  class Handler
    class JsonFile < ::Chef::Handler
      attr_reader :config
      def initialize(config={})
        @config = config
        @config[:path] ||= '/var/chef/reports'
        @config
      end
      def report
        if exception
          Chef::Log.error('Creating JSON exception report')
        else
          Chef::Log.info('Creating JSON run report')
        end
        build_report_dir
        savetime = Time.now.strftime('%Y%m%d%H%M%S')
        File.open(File.join(config[:path], 'chef-run-report-#{savetime}.json'), 'w') do |file|
          run_data = data
          run_data[:start_time] = run_data[:start_time].to_s
          run_data[:end_time] = run_data[:end_time].to_s
          file.puts Chef::JSONCompat.to_json_pretty(run_data)
        end
      end
      def build_report_dir
        unless File.exists?(config[:path])
          FileUtils.mkdir_p(config[:path])
          File.chmod(00700, config[:path])
        end
      end
    end
  end
end

Optional Interfaces

The following interfaces may be used in a handler in the same way as the report interface to override the default handler behavior in the chef-client. That said, the following interfaces are not typically used in a handler and, for the most part, are completely unnecessary for a handler to work properly and/or as desired.

data

The data method is used to return the Hash representation of the run_status object. For example:

def data
  @run_status.to_hash
end

run_report_safely

The run_report_safely method is used to run the report handler, rescuing and logging errors that may arise as the handler runs and ensuring that all handlers get a chance to run during the chef-client run (even if some handlers fail during that run). In general, this method should never be used as an interface in a custom handler unless this default behavior simply must be overridden.

def run_report_safely(run_status)
  run_report_unsafe(run_status)
rescue Exception => e
  Chef::Log.error('Report handler #{self.class.name} raised #{e.inspect}')
  Array(e.backtrace).each { |line| Chef::Log.error(line) }
ensure
  @run_status = nil
end

run_report_unsafe

The run_report_unsafe method is used to run the report handler without any error handling. This method should never be used directly in any handler, except during testing of that handler. For example:

def run_report_unsafe(run_status)
  @run_status = run_status
  report
end

run_status Object

The run_status object is initialized by the chef-client before the report interface is run for any handler. The run_status object keeps track of the status of the chef-client run and will contain some (or all) of the following properties:

Property Description
all_resources A list of all resources that are included in the resource_collection property for the current chef-client run.
backtrace A backtrace associated with the uncaught exception data that caused a chef-client run to fail, if present; nil for a successful chef-client run.
elapsed_time The amount of time between the start (start_time) and end (end_time) of a chef-client run.
end_time The time at which a chef-client run ended.
exception The uncaught exception data which caused a chef-client run to fail; nil for a successful chef-client run.
failed? Show that a chef-client run has failed when uncaught exceptions were raised during a chef-client run. An exception handler runs when the failed? indicator is true.
node The node on which the chef-client run occurred.
run_context An instance of the Chef::RunContext object; used by the chef-client to track the context of the run; provides access to the cookbook_collection, resource_collection, and definitions properties.
start_time The time at which a chef-client run started.
success? Show that a chef-client run succeeded when uncaught exceptions were not raised during a chef-client run. A report handler runs when the success? indicator is true.
updated_resources A list of resources that were marked as updated as a result of the chef-client run.

Note

These properties are not always available. For example, a start handler runs at the beginning of the chef-client run, which means that properties like end_time and elapsed_time are still unknown and will be unavailable to the run_status object.

Examples

The following sections show examples of handlers.

Cookbook Versions

Community member juliandunn created a custom report handler that logs all of the cookbooks and cookbook versions that were used during the chef-client run, and then reports after the run is complete. This handler requires the chef_handler resource (which is available from the chef_handler cookbook).

cookbook_versions.rb

The following custom handler defines how cookbooks and cookbook versions that are used during the chef-client run will be compiled into a report using the Chef::Log class in the chef-client:

require 'chef/log'

module Opscode
  class CookbookVersionsHandler < Chef::Handler

    def report
      cookbooks = run_context.cookbook_collection
      Chef::Log.info('Cookbooks and versions run: #{cookbooks.keys.map {|x| cookbooks[x].name.to_s + ' ' + cookbooks[x].version} }')
    end
  end
end

default.rb

The following recipe is added to the run-list for every node on which a list of cookbooks and versions will be generated as report output after every chef-client run.

include_recipe 'chef_handler'

cookbook_file "#{node['chef_handler']['handler_path']}/cookbook_versions.rb" do
  source 'cookbook_versions.rb'
  owner 'root'
  group 'root'
  mode '0755'
  action :create
end

chef_handler 'Opscode::CookbookVersionsHandler' do
  source "#{node['chef_handler']['handler_path']}/cookbook_versions.rb"
  supports :report => true
  action :enable
end

This recipe will generate report output similar to the following:

[2013-11-26T03:11:06+00:00] INFO: Chef Run complete in 0.300029878 seconds
[2013-11-26T03:11:06+00:00] INFO: Running report handlers
[2013-11-26T03:11:06+00:00] INFO: Cookbooks and versions run: ["chef_handler 1.1.4", "cookbook_versions_handler 1.0.0"]
[2013-11-26T03:11:06+00:00] INFO: Report handlers complete

Reporting

Start handler functionality was added when Chef started building add-ons for the Chef server. The Reporting add-on is designed to create reporting data based on a chef-client run. And since Reporting needs to be able to collect data for the entire chef-client run, Reporting needs to be enabled before anything else happens at the start of the chef-client run.

Note

The start handler used by the Reporting add-on for the Chef server is always installed using the chef-client cookbook.

start_handler.rb

The following code shows the start handler used by the Reporting add-in for the Chef server:

require 'chef/handler'
require 'chef/rest'
require 'chef/version_constraint'

class Chef
  class Reporting
    class StartHandler < ::Chef::Handler

      attr_reader :config

      def initialize(config={})
        @config = config
      end

      def report
        version_checker = Chef::VersionConstraint.new('< 11.6.0')
        if version_checker.include?(Chef::VERSION)
          Chef::Log.info('Enabling backported resource reporting Handler')
          rest = Chef::REST.new(Chef::Config[:chef_server_url], @run_status.node.name, Chef::Config[:client_key])
          resource_reporter = Chef::Reporting::ResourceReporter.new(rest)
          @run_status.events.register(resource_reporter)

          resource_reporter.run_started(@run_status)
        else
         Chef::Log.debug('Chef Version already has new Resource Reporter - skipping startup of backport version')
        end
      end
    end
  end
end

json_file Handler

The json_file handler is available from the chef_handler cookbook and can be used with exceptions and reports. It serializes run status data to a JSON file. This handler may be enabled in one of the following ways.

By adding the following lines of Ruby code to either the client.rb file or the solo.rb file, depending on how the chef-client is being run:

require 'chef/handler/json_file'
report_handlers << Chef::Handler::JsonFile.new(:path => '/var/chef/reports')
exception_handlers << Chef::Handler::JsonFile.new(:path => '/var/chef/reports')

By using the chef_handler resource in a recipe, similar to the following:

chef_handler 'Chef::Handler::JsonFile' do
  source 'chef/handler/json_file'
  arguments :path => '/var/chef/reports'
  action :enable
end

After it has run, the run status data can be loaded and inspected via Interactive Ruby (IRb):

irb(main):001:0> require 'rubygems' => true
irb(main):002:0> require 'json' => true
irb(main):003:0> require 'chef' => true
irb(main):004:0> r = JSON.parse(IO.read('/var/chef/reports/chef-run-report-20110322060731.json')) => ... output truncated
irb(main):005:0> r.keys => ['end_time', 'node', 'updated_resources', 'exception', 'all_resources', 'success', 'elapsed_time', 'start_time', 'backtrace']
irb(main):006:0> r['elapsed_time'] => 0.00246

error_report Handler

The error_report handler is built into the chef-client and can be used for both exceptions and reports. It serializes error report data to a JSON file. This handler may be enabled in one of the following ways.

By adding the following lines of Ruby code to either the client.rb file or the solo.rb file, depending on how the chef-client is being run:

require 'chef/handler/error_report'
report_handlers << Chef::Handler::ErrorReport.new()
exception_handlers << Chef::Handler::ErrorReport.new()

By using the chef_handler resource in a recipe, similar to the following:

chef_handler 'Chef::Handler::ErrorReport' do
  source 'chef/handler/error_report'
  action :enable
end

Community Handlers

The following open source handlers are available from the Chef community:

Handler Description
Airbrake A handler that sends exceptions (only) to Airbrake, an application that collects data and aggregates it for review.
Asynchronous Resources A handler that asynchronously pushes exception and report handler data to a STOMP queue, from which data can be processed into data storage.
Campfire A handler that collects exception and report handler data and reports it to Campfire, a web-based group chat tool.
Cloudkick A handler that collects exception and report handler data and sends it to Cloudkick, a set of cloud server monitoring and management tools.
Datadog A handler that collects chef-client stats and sends them into a DATADOG newsfeed.
Flowdock A handler that collects exception and report handler data and sends it to users via the Flowdock API..
Graphite A handler that collects exception and report handler data and reports it to Graphite, a graphic rendering application.
Graylog2 GELF A handler that provides exception and report handler status (including changes) to a Graylog2 server, so that the data can be viewed using Graylog Extended Log Format (GELF).
Growl A handler that collects exception and report handler data and then sends it as a Growl notification.
HipChat A handler that collects exception handler data and sends it to HipChat, a hosted private chat service for companies and teams.
IRC Snitch A handler that notifies administrators (via Internet Relay Chat (IRC)) when a chef-client run fails.
Journald A handler that logs an entry to the systemd journal with the chef-client run status, exception details, configurable priority, and custom details.
net/http A handler that reports the status of a Chef run to any API via net/HTTP.
Simple Email A handler that collects exception and report handler data and then uses pony to send email reports that are based on Erubis templates.
SendGrid Mail Handler A chef handler that collects exception and report handler data and then uses SendGrid Ruby gem to send email reports that are based on Erubis templates.
SNS A handler that notifies exception and report handler data and sends it to a SNS topic.
Slack A handler to send chef-client run notifications to a Slack channel.
Splunk Storm A handler that supports exceptions and reports for Splunk Storm.
Syslog A handler that logs basic essential information, such as about the success or failure of a chef-client run.
Updated Resources A handler that provides a simple way to display resources that were updated during a chef-client run.
ZooKeeper A Chef report handler to send Chef run notifications to ZooKeeper.

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https://docs.chef.io/release/12-13/handlers.html