Add streaming upload example. (#206)

examples/streaming_upload/Gemfile

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+source 'https://rubygems.org'
+
+gem "falcon"

examples/streaming_upload/Gemfile.lock

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+GEM
+  remote: https://rubygems.org/
+  specs:
+    async (2.5.0)
+      console (~> 1.10)
+      io-event (~> 1.1)
+      timers (~> 4.1)
+    async-container (0.16.12)
+      async
+      async-io
+    async-http (0.60.1)
+      async (>= 1.25)
+      async-io (>= 1.28)
+      async-pool (>= 0.2)
+      protocol-http (~> 0.24.0)
+      protocol-http1 (~> 0.15.0)
+      protocol-http2 (~> 0.15.0)
+      traces (>= 0.8.0)
+    async-http-cache (0.4.3)
+      async-http (~> 0.56)
+    async-io (1.34.3)
+      async
+    async-pool (0.4.0)
+      async (>= 1.25)
+    build-environment (1.13.0)
+    console (1.16.2)
+      fiber-local
+    falcon (0.42.3)
+      async
+      async-container (~> 0.16.0)
+      async-http (~> 0.57)
+      async-http-cache (~> 0.4.0)
+      async-io (~> 1.22)
+      build-environment (~> 1.13)
+      bundler
+      localhost (~> 1.1)
+      openssl (~> 3.0)
+      process-metrics (~> 0.2.0)
+      protocol-rack (~> 0.1)
+      samovar (~> 2.1)
+    fiber-local (1.0.0)
+    io-event (1.1.7)
+    localhost (1.1.10)
+    mapping (1.1.1)
+    openssl (3.1.0)
+    process-metrics (0.2.1)
+      console (~> 1.8)
+      samovar (~> 2.1)
+    protocol-hpack (1.4.2)
+    protocol-http (0.24.1)
+    protocol-http1 (0.15.0)
+      protocol-http (~> 0.22)
+    protocol-http2 (0.15.1)
+      protocol-hpack (~> 1.4)
+      protocol-http (~> 0.18)
+    protocol-rack (0.2.4)
+      protocol-http (~> 0.23)
+      rack (>= 1.0)
+    rack (3.0.7)
+    samovar (2.1.4)
+      console (~> 1.0)
+      mapping (~> 1.0)
+    timers (4.3.5)
+    traces (0.9.1)
+
+PLATFORMS
+  x86_64-linux
+
+DEPENDENCIES
+  falcon
+
+BUNDLED WITH
+   2.4.6

examples/streaming_upload/README.txt

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+# Streaming Upload
+
+# ab Results
+
+The filesize was 82078050 bytes.
+
+
+
+
+## concurrent requests
+
+```
+bundle exec falcon host ./falcon.rb
+```
+
+
+```
+This is ApacheBench, Version 2.3 <$Revision: 1879490 $>
+Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
+Licensed to The Apache Software Foundation, http://www.apache.org/
+
+Benchmarking localhost (be patient).....done
+
+
+Server Software:        
+Server Hostname:        localhost
+Server Port:            9292
+
+Document Path:          /
+Document Length:        100 bytes
+
+Concurrency Level:      20
+Time taken for tests:   7.873 seconds
+Complete requests:      100
+Failed requests:        9
+   (Connect: 0, Receive: 0, Length: 9, Exceptions: 0)
+Total transferred:      16280 bytes
+Total body sent:        8628660682
+HTML transferred:       9989 bytes
+Requests per second:    12.70 [#/sec] (mean)
+Time per request:       1574.576 [ms] (mean)
+Time per request:       78.729 [ms] (mean, across all concurrent requests)
+Transfer rate:          2.02 [Kbytes/sec] received
+                        1070310.40 kb/s sent
+                        1070312.42 kb/s total
+
+Connection Times (ms)
+              min  mean[+/-sd] median   max
+Connect:        0   56  44.6     52     141
+Processing:   296 1384 725.4   1159    4456
+Waiting:       33  126  89.2    121     886
+Total:        297 1440 720.8   1236    4464
+
+Percentage of the requests served within a certain time (ms)
+  50%   1236
+  66%   1458
+  75%   1627
+  80%   1711
+  90%   2020
+  95%   3883
+  98%   4463
+  99%   4464
+ 100%   4464 (longest request)
+```
+
+EOFError errors cause the failed uploads....have to figure out why.

examples/streaming_upload/config.ru

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+# frozen_string_literal: true
+
+# run with: falcon serve -n 1 -b http://localhost:9292
+
+require 'digest'
+require 'securerandom'
+
+module Protocol
+  module HTTP1
+    class Connection
+      def write_continue
+        @stream.write("HTTP/1.1 100 Continue\r\n\r\n")
+        @stream.flush
+      end
+    end
+  end
+end
+
+class BodyHandler
+  attr_reader :time, :md5, :size, :uuid
+
+  def initialize(input, length)
+    @uuid = SecureRandom.uuid
+    @input = input
+    @length = length
+  end
+
+  def receive
+    start = Time.now
+    @md5 = Digest::MD5.new
+    @size = 0
+    @done = false
+
+    until @done
+      begin
+        chunk = @input.read(10_240) # read will raise EOF so we have to check
+      rescue EOFError
+        puts "Seems we're done"
+        chunk = nil
+      end
+      if chunk.nil?
+        @done = true
+      else
+        @md5.update(chunk)
+        @size += chunk.bytesize
+        @done = true if @length == @size
+      end
+    end
+
+    @time = Time.now - start
+  end
+end
+
+run lambda { |env|
+  request = env['protocol.http.request']
+  handler = BodyHandler.new(env['rack.input'], env['CONTENT_LENGTH'])
+  puts "#{env['REQUEST_METHOD']} #{handler.uuid}: #{request.path}  #{env['CONTENT_LENGTH']}"
+
+  if env['REQUEST_METHOD'] == 'POST'
+    request.connection.write_continue if request.headers['expect'] == ['100-continue']
+    handler.receive
+    msg = "Uploaded #{handler.uuid}: #{handler.md5} #{handler.time} #{handler.size}"
+    puts msg
+    [200, {}, [msg]]
+  else
+    sleep 1
+    [200, {}, ["#{env['REQUEST_METHOD']}: #{request.path}\n"]]
+  end
+}

examples/streaming_upload/falcon.rb

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+load :rack, :supervisor
+
+hostname = File.basename(__dir__)
+rack hostname do
+	endpoint Async::HTTP::Endpoint.parse('http://localhost:9292').with(protocol: Async::HTTP::Protocol::HTTP1)
+end
+
+supervisor