1+ # Copyright 2020 Google LLC
2+ #
3+ # Licensed under the Apache License, Version 2.0 (the "License");
4+ # you may not use this file except in compliance with the License.
5+ # You may obtain a copy of the License at
6+ #
7+ # http://www.apache.org/licenses/LICENSE-2.0
8+ #
9+ # Unless required by applicable law or agreed to in writing, software
10+ # distributed under the License is distributed on an "AS IS" BASIS,
11+ # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12+ # See the License for the specific language governing permissions and
13+ # limitations under the License.
14+
15+ # [START app]
16+ import logging
17+
18+ from flask import Flask , make_response
19+
20+ # [START imports]
21+ import requests
22+ from requests_futures .sessions import FuturesSession
23+ from time import sleep
24+ # [END imports]
25+
26+
27+ TIMEOUT = 10 # Wait this many seconds for background calls to finish
28+ app = Flask (__name__ )
29+
30+
31+ @app .route ('/' ) # Fetch and return remote page asynchronously
32+ def get_async ():
33+ # [START requests_get]
34+ session = FuturesSession ()
35+ url = 'http://www.google.com/humans.txt'
36+
37+ rpc = session .get (url )
38+
39+ # ... do other things ...
40+
41+ resp = make_response (rpc .result ().text )
42+ resp .headers ['Content-type' ] = 'text/plain'
43+ return resp
44+ # [END requests_get]
45+
46+
47+ @app .route ('/callback' ) # Fetch and return remote pages using callback
48+ def get_callback ():
49+ global response_text
50+ global counter
51+
52+ response_text = ''
53+ counter = 0
54+
55+ def cb (resp , * args , ** kwargs ):
56+ global response_text
57+ global counter
58+
59+ if 300 <= resp .status_code < 400 :
60+ return # ignore intermediate redirection responses
61+
62+ counter += 1
63+ response_text += 'Response number {} is {} bytes from {}\n ' .format (
64+ counter , len (resp .text ), resp .url )
65+
66+
67+ session = FuturesSession ()
68+ urls = [
69+ 'https://google.com/' ,
70+ 'https://www.google.com/humans.txt' ,
71+ 'https://www.github.com' ,
72+ 'https://www.travis-ci.org'
73+ ]
74+
75+ futures = [session .get (url , hooks = {'response' : cb }) for url in urls ]
76+
77+ # No wait functionality in requests_futures, so check every second to
78+ # see if all callbacks are done, up to TIMEOUT seconds
79+ for elapsed_time in range (TIMEOUT + 1 ):
80+ all_done = True
81+ for future in futures :
82+ if not future .done ():
83+ all_done = False
84+ break
85+ if all_done :
86+ break
87+ sleep (1 )
88+
89+ resp = make_response (response_text )
90+ resp .headers ['Content-type' ] = 'text/plain'
91+ return resp
92+
93+
94+ @app .errorhandler (500 )
95+ def server_error (e ):
96+ logging .exception ('An error occurred during a request.' )
97+ return """
98+ An internal error occurred: <pre>{}</pre>
99+ See logs for full stacktrace.
100+ """ .format (e ), 500
101+ # [END app]
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