aboutsummaryrefslogtreecommitdiffstats
path: root/actionpack/lib/action_controller/metal/live.rb
blob: 667c7f87ca90e9111e6bb15dedbbf73aaadf2f99 (plain) (blame)
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
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
require 'action_dispatch/http/response'
require 'delegate'
require 'active_support/json'

module ActionController
  # Mix this module in to your controller, and all actions in that controller
  # will be able to stream data to the client as it's written.
  #
  #   class MyController < ActionController::Base
  #     include ActionController::Live
  #
  #     def stream
  #       response.headers['Content-Type'] = 'text/event-stream'
  #       100.times {
  #         response.stream.write "hello world\n"
  #         sleep 1
  #       }
  #     ensure
  #       response.stream.close
  #     end
  #   end
  #
  # There are a few caveats with this use. You *cannot* write headers after the
  # response has been committed (Response#committed? will return truthy).
  # Calling +write+ or +close+ on the response stream will cause the response
  # object to be committed. Make sure all headers are set before calling write
  # or close on your stream.
  #
  # You *must* call close on your stream when you're finished, otherwise the
  # socket may be left open forever.
  #
  # The final caveat is that your actions are executed in a separate thread than
  # the main thread. Make sure your actions are thread safe, and this shouldn't
  # be a problem (don't share state across threads, etc).
  module Live
    extend ActiveSupport::Concern

    module ClassMethods
      def make_response!(request)
        if request.env["HTTP_VERSION"] == "HTTP/1.0"
          super
        else
          Live::Response.new.tap do |res|
            res.request = request
          end
        end
      end
    end

    # This class provides the ability to write an SSE (Server Sent Event)
    # to an IO stream. The class is initialized with a stream and can be used
    # to either write a JSON string or an object which can be converted to JSON.
    #
    # Writing an object will convert it into standard SSE format with whatever
    # options you have configured. You may choose to set the following options:
    #
    #   1) Event. If specified, an event with this name will be dispatched on
    #   the browser.
    #   2) Retry. The reconnection time in milliseconds used when attempting
    #   to send the event.
    #   3) Id. If the connection dies while sending an SSE to the browser, then
    #   the server will receive a +Last-Event-ID+ header with value equal to +id+.
    #
    # After setting an option in the constructor of the SSE object, all future
    # SSEs sent across the stream will use those options unless overridden.
    #
    # Example Usage:
    #
    #   class MyController < ActionController::Base
    #     include ActionController::Live
    #
    #     def index
    #       response.headers['Content-Type'] = 'text/event-stream'
    #       sse = SSE.new(response.stream, retry: 300, event: "event-name")
    #       sse.write({ name: 'John'})
    #       sse.write({ name: 'John'}, id: 10)
    #       sse.write({ name: 'John'}, id: 10, event: "other-event")
    #       sse.write({ name: 'John'}, id: 10, event: "other-event", retry: 500)
    #     ensure
    #       sse.close
    #     end
    #   end
    #
    # Note: SSEs are not currently supported by IE. However, they are supported
    # by Chrome, Firefox, Opera, and Safari.
    class SSE

      WHITELISTED_OPTIONS = %w( retry event id )

      def initialize(stream, options = {})
        @stream = stream
        @options = options
      end

      def close
        @stream.close
      end

      def write(object, options = {})
        case object
        when String
          perform_write(object, options)
        else
          perform_write(ActiveSupport::JSON.encode(object), options)
        end
      end

      private

        def perform_write(json, options)
          current_options = @options.merge(options).stringify_keys

          WHITELISTED_OPTIONS.each do |option_name|
            if (option_value = current_options[option_name])
              @stream.write "#{option_name}: #{option_value}\n"
            end
          end

          message = json.gsub("\n".freeze, "\ndata: ".freeze)
          @stream.write "data: #{message}\n\n"
        end
    end

    class ClientDisconnected < RuntimeError
    end

    class Buffer < ActionDispatch::Response::Buffer #:nodoc:
      include MonitorMixin

      # Ignore that the client has disconnected.
      #
      # If this value is `true`, calling `write` after the client
      # disconnects will result in the written content being silently
      # discarded. If this value is `false` (the default), a
      # ClientDisconnected exception will be raised.
      attr_accessor :ignore_disconnect

      def initialize(response)
        @error_callback = lambda { true }
        @cv = new_cond
        @aborted = false
        @ignore_disconnect = false
        super(response, SizedQueue.new(10))
      end

      def write(string)
        unless @response.committed?
          @response.set_header "Cache-Control", "no-cache"
          @response.delete_header "Content-Length"
        end

        super

        unless connected?
          @buf.clear

          unless @ignore_disconnect
            # Raise ClientDisconnected, which is a RuntimeError (not an
            # IOError), because that's more appropriate for something beyond
            # the developer's control.
            raise ClientDisconnected, "client disconnected"
          end
        end
      end

      def each
        @response.sending!
        while str = @buf.pop
          yield str
        end
        @response.sent!
      end

      # Write a 'close' event to the buffer; the producer/writing thread
      # uses this to notify us that it's finished supplying content.
      #
      # See also #abort.
      def close
        synchronize do
          super
          @buf.push nil
          @cv.broadcast
        end
      end

      # Inform the producer/writing thread that the client has
      # disconnected; the reading thread is no longer interested in
      # anything that's being written.
      #
      # See also #close.
      def abort
        synchronize do
          @aborted = true
          @buf.clear
        end
      end

      # Is the client still connected and waiting for content?
      #
      # The result of calling `write` when this is `false` is determined
      # by `ignore_disconnect`.
      def connected?
        !@aborted
      end

      def on_error(&block)
        @error_callback = block
      end

      def call_on_error
        @error_callback.call
      end
    end

    class Response < ActionDispatch::Response #:nodoc: all
      class Header < DelegateClass(Hash) # :nodoc:
        def initialize(response, header)
          @response = response
          super(header)
        end

        def []=(k,v)
          if @response.committed?
            raise ActionDispatch::IllegalStateError, 'header already sent'
          end

          super
        end

        def merge(other)
          self.class.new @response, __getobj__.merge(other)
        end

        def to_hash
          __getobj__.dup
        end
      end

      private

      def before_committed
        super
        jar = request.cookie_jar
        # The response can be committed multiple times
        jar.write self unless committed?
      end

      def before_sending
        super
        request.cookie_jar.commit!
        headers.freeze
      end

      def build_buffer(response, body)
        buf = Live::Buffer.new response
        body.each { |part| buf.write part }
        buf
      end

      def merge_default_headers(original, default)
        Header.new self, super
      end

      def handle_conditional_get!
        super unless committed?
      end
    end

    def process(name)
      t1 = Thread.current
      locals = t1.keys.map { |key| [key, t1[key]] }

      error = nil
      # This processes the action in a child thread. It lets us return the
      # response code and headers back up the rack stack, and still process
      # the body in parallel with sending data to the client
      Thread.new {
        t2 = Thread.current
        t2.abort_on_exception = true

        # Since we're processing the view in a different thread, copy the
        # thread locals from the main thread to the child thread. :'(
        locals.each { |k,v| t2[k] = v }

        begin
          super(name)
        rescue => e
          if @_response.committed?
            begin
              @_response.stream.write(ActionView::Base.streaming_completion_on_exception) if request.format == :html
              @_response.stream.call_on_error
            rescue => exception
              log_error(exception)
            ensure
              log_error(e)
              @_response.stream.close
            end
          else
            error = e
          end
        ensure
          @_response.commit!
        end
      }

      @_response.await_commit
      raise error if error
    end

    def log_error(exception)
      logger = ActionController::Base.logger
      return unless logger

      logger.fatal do
        message = "\n#{exception.class} (#{exception.message}):\n"
        message << exception.annoted_source_code.to_s if exception.respond_to?(:annoted_source_code)
        message << "  " << exception.backtrace.join("\n  ")
        "#{message}\n\n"
      end
    end

    def response_body=(body)
      super
      response.close if response
    end

    def set_response!(request)
      @_response = self.class.make_response! request
    end
  end
end