summaryrefslogtreecommitdiff
path: root/lib/chef/provider_resolver.rb
blob: 439a7e9f5f3a1aefaec08556fcd366310a9cd0e3 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
#
# Author:: Richard Manyanza (<liseki@nyikacraftsmen.com>)
# Copyright:: Copyright 2014-2016, 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/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) ||
        raise(Chef::Exceptions::ProviderNotFound, "Cannot find a provider for #{resource} on #{node["platform"]} version #{node["platform_version"]}")
    end

    # Does NOT call provides? on the resource (it is assumed this is being
    # called *from* provides?).
    def provided_by?(provider_class)
      potential_handlers.include?(provider_class)
    end

    def enabled_handlers
      @enabled_handlers ||= potential_handlers.select { |handler| !overrode_provides?(handler) || handler.provides?(node, resource) }
    end

    # TODO deprecate this and allow actions to be passed as a filter to
    # `provides` so we don't have to have two separate things.
    # @api private
    def supported_handlers
      enabled_handlers.select { |handler| handler.supports?(resource, action) }
    end

    private

    def potential_handlers
      handler_map.list(node, resource.resource_name).uniq
    end

    # The list of handlers, with any in the priority_map moved to the front
    def prioritized_handlers
      @prioritized_handlers ||= begin
        supported_handlers = self.supported_handlers
        if supported_handlers.empty?
          # We always require a provider to be able to call define_resource_requirements on.  In the why-run case we need
          # a provider to say "assuming /etc/init.d/whatever would have been installed" and in the non-why-run case we
          # need to make a best guess at "cannot find /etc/init.d/whatever".  We are essentially defining a "default" provider
          # for the platform, which is the best we can do, but which might give misleading errors, but we cannot read minds.
          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."
          supported_handlers = enabled_handlers
        end

        prioritized = priority_map.list(node, resource.resource_name).flatten(1)
        prioritized &= supported_handlers # Filter the priority map by the actual enabled handlers
        prioritized |= supported_handlers # Bring back any handlers that aren't in the priority map, at the *end* (ordered set)
        prioritized
      end
    end

    # 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}"

      handler = prioritized_handlers.first

      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

    def priority_map
      Chef.provider_priority_map
    end

    def handler_map
      Chef.provider_handler_map
    end

    def overrode_provides?(handler)
      handler.method(:provides?).owner != Chef::Provider.method(:provides?).owner
    end

    module Deprecated
      # return a deterministically sorted list of Chef::Provider subclasses
      def providers
        @providers ||= Chef::Provider.descendants
      end

      def enabled_handlers
        @enabled_handlers ||= begin
          handlers = super
          if handlers.empty?
            # Look through all providers, and find ones that return true to provides.
            # Don't bother with ones that don't override provides?, since they
            # would have been in enabled_handlers already if that were so. (It's a
            # perf concern otherwise.)
            handlers = providers.select { |handler| overrode_provides?(handler) && handler.provides?(node, resource) }
            handlers.each do |handler|
              message = "#{handler}.provides? returned true when asked if it provides DSL #{resource.resource_name}, but provides #{resource.resource_name.inspect} was never called!  In Chef 13, this will break: you must call provides to mark the names you provide, even if you also override provides? yourself."
              Chef.deprecated(:custom_resource, message)
            end
          end
          handlers
        end
      end
    end
    prepend Deprecated
  end
end