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#
# Author:: Richard Manyanza (<liseki@nyikacraftsmen.com>)
# Copyright:: Copyright (c) 2014 Richard Manyanza.
# License:: Apache License, Version 2.0
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
require 'chef/exceptions'
require 'chef/platform/provider_priority_map'
class Chef
class ProviderResolver
attr_reader :node
attr_reader :resource
attr_reader :action
def initialize(node, resource, action)
@node = node
@resource = resource
@action = action
end
# return a deterministically sorted list of Chef::Provider subclasses
def providers
@providers ||= Chef::Provider.descendants
end
def resolve
maybe_explicit_provider(resource) ||
maybe_dynamic_provider_resolution(resource, action) ||
maybe_chef_platform_lookup(resource)
end
# this cut looks at if the provider can handle the resource type on the node
def enabled_handlers
@enabled_handlers ||=
providers.select do |klass|
klass.provides?(node, resource)
end.sort {|a,b| a.to_s <=> b.to_s }
end
# this cut looks at if the provider can handle the specific resource and action
def supported_handlers
@supported_handlers ||=
enabled_handlers.select do |klass|
klass.supports?(resource, action)
end
end
private
# if resource.provider is set, just return one of those objects
def maybe_explicit_provider(resource)
return nil unless resource.provider
resource.provider
end
# try dynamically finding a provider based on querying the providers to see what they support
def maybe_dynamic_provider_resolution(resource, action)
# log this so we know what providers will work for the generic resource on the node (early cut)
Chef::Log.debug "providers for generic #{resource.resource_name} resource enabled on node include: #{enabled_handlers}"
# what providers were excluded by machine state (late cut)
Chef::Log.debug "providers that refused resource #{resource} were: #{enabled_handlers - supported_handlers}"
Chef::Log.debug "providers that support resource #{resource} include: #{supported_handlers}"
# if none of the providers specifically support the resource, we still need to pick one of the providers that are
# enabled on the node to handle the why-run use case.
handlers = supported_handlers.empty? ? enabled_handlers : supported_handlers
Chef::Log.debug "no providers supported the resource, falling back to enabled handlers" if supported_handlers.empty?
if handlers.count >= 2
# this magic stack ranks the providers by where they appear in the provider_priority_map, it is mostly used
# to pick amongst N different ways to start init scripts on different debian/ubuntu systems.
priority_list = [ get_provider_priority_map(resource.resource_name, node) ].flatten.compact
handlers = handlers.sort_by { |x| i = priority_list.index x; i.nil? ? Float::INFINITY : i }
handlers = [ handlers.first ]
end
Chef::Log.debug "providers that survived replacement include: #{handlers}"
raise Chef::Exceptions::AmbiguousProviderResolution.new(resource, handlers) if handlers.count >= 2
Chef::Log.debug "dynamic provider resolver FAILED to resolve a provider" if handlers.empty?
return nil if handlers.empty?
handlers[0]
end
# try the old static lookup of providers by platform
def maybe_chef_platform_lookup(resource)
Chef::Platform.find_provider_for_node(node, resource)
end
# dep injection hooks
def get_provider_priority_map(resource_name, node)
provider_priority_map.get(node, resource_name)
end
def provider_priority_map
Chef::Platform::ProviderPriorityMap.instance.priority_map
end
end
end
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