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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
#
# Provider Resolution
# ===================
#
# Provider resolution is the process of taking a Resource object and an
# action, and determining the Provider class that should be instantiated to
# handle the action.
#
# If the resource has its `provider` set, that is used.
#
# Otherwise, we take the lists of Providers that have registered as
# providing the DSL through `provides :dsl_name, <filters>` or
# `Chef.set_resource_priority_array :dsl_name, <filters>`. We filter each
# list of Providers through:
#
# 1. The filters it was registered with (such as `os: 'linux'` or
# `platform_family: 'debian'`)
# 2. `provides?(node, resource)`
# 3. `supports?(resource, action)`
#
# Anything that passes the filter and returns `true` to provides and supports,
# is considered a match. The first matching Provider in the *most recently
# registered list* is selected and returned.
#
class ProviderResolver
attr_reader :node
attr_reader :resource
attr_reader :action
def initialize(node, resource, action)
@node = node
@resource = resource
@action = action
end
def resolve
maybe_explicit_provider(resource) ||
maybe_dynamic_provider_resolution(resource, action) ||
maybe_chef_platform_lookup(resource)
end
def provided_by?(provider_class)
prioritized_handlers.include?(provider_class)
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)
Chef::Log.debug "Providers for generic #{resource.resource_name} resource enabled on node include: #{enabled_handlers}"
# Get all the handlers in the priority bucket
handlers = prioritized_handlers
# Narrow it down to handlers that return `true` to `provides?`
# TODO deprecate this and don't bother calling--the fact that they said
# `provides` should be enough. But we need to do it right now because
# some classes implement additional handling.
enabled_handlers = prioritized_handlers.select { |handler| handler.provides?(node, resource) }
# Narrow it down to handlers that return `true` to `supports?`
# TODO deprecate this and allow actions to be passed as a filter to
# `provides` so we don't have to have two separate things.
supported_handlers = enabled_handlers.select { |handler| handler.supports?(resource, action) }
if supported_handlers.empty?
# 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. FIXME we should only do this in why-run mode then.
Chef::Log.debug "No providers responded true to `supports?` for action #{action} on resource #{resource}, falling back to enabled handlers so we can return something anyway."
handler = enabled_handlers.first
else
handler = supported_handlers.first
end
if handler
Chef::Log.debug "Provider for action #{action} on resource #{resource} is #{handler}"
else
Chef::Log.debug "Dynamic provider resolver FAILED to resolve a provider for action #{action} on resource #{resource}"
end
handler
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
def provider_priority_map
Chef::Platform::ProviderPriorityMap.instance
end
def prioritized_handlers
@prioritized_handlers ||=
provider_priority_map.list_handlers(node, resource.resource_name).flatten(1).uniq
end
module Deprecated
# return a deterministically sorted list of Chef::Provider subclasses
def providers
@providers ||= Chef::Provider.descendants
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|
# NB: this is different from resource_resolver which must pass a resource_name
# FIXME: deprecate this and normalize on passing resource_name here
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
# If there are no providers for a DSL, we search through the
def prioritized_handlers
@prioritized_handlers ||= super || begin
result = providers.select { |handler| handler.provides?(node, resource) }.sort_by(:name)
if !result.empty?
Chef::Log.deprecation("#{resource.resource_name.to_sym} is marked as providing DSL #{method_symbol}, but provides #{resource.resource_name.to_sym.inspect} was never called!")
Chef::Log.deprecation("In Chef 13, this will break: you must call provides to mark the names you provide, even if you also override provides? yourself.")
end
result
end
end
end
prepend Deprecated
end
end
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