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1 #!/usr/bin/env python | |
2 # Copyright 2012 Google Inc. All Rights Reserved. | |
3 # | |
4 # Licensed under the Apache License, Version 2.0 (the "License"); | |
5 # you may not use this file except in compliance with the License. | |
6 # You may obtain a copy of the License at | |
7 # | |
8 # http://www.apache.org/licenses/LICENSE-2.0 | |
9 # | |
10 # Unless required by applicable law or agreed to in writing, software | |
11 # distributed under the License is distributed on an "AS IS" BASIS, | |
12 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
13 # See the License for the specific language governing permissions and | |
14 # limitations under the License. | |
15 | |
16 """Simulate network characteristics directly in Python. | |
17 | |
18 Allows running replay without dummynet. | |
19 """ | |
20 | |
21 import logging | |
22 import platformsettings | |
23 import re | |
24 import time | |
25 | |
26 | |
27 TIMER = platformsettings.timer | |
28 | |
29 | |
30 class ProxyShaperError(Exception): | |
31 """Module catch-all error.""" | |
32 pass | |
33 | |
34 class BandwidthValueError(ProxyShaperError): | |
35 """Raised for unexpected dummynet-style bandwidth value.""" | |
36 pass | |
37 | |
38 | |
39 class RateLimitedFile(object): | |
40 """Wrap a file like object with rate limiting. | |
41 | |
42 TODO(slamm): Simulate slow-start. | |
43 Each RateLimitedFile corresponds to one-direction of a | |
44 bidirectional socket. Slow-start can be added here (algorithm needed). | |
45 Will consider changing this class to take read and write files and | |
46 corresponding bit rates for each. | |
47 """ | |
48 BYTES_PER_WRITE = 1460 | |
49 | |
50 def __init__(self, request_counter, f, bps): | |
51 """Initialize a RateLimiter. | |
52 | |
53 Args: | |
54 request_counter: callable to see how many requests share the limit. | |
55 f: file-like object to wrap. | |
56 bps: an integer of bits per second. | |
57 """ | |
58 self.request_counter = request_counter | |
59 self.original_file = f | |
60 self.bps = bps | |
61 | |
62 def transfer_seconds(self, num_bytes): | |
63 """Seconds to read/write |num_bytes| with |self.bps|.""" | |
64 return 8.0 * num_bytes / self.bps | |
65 | |
66 def write(self, data): | |
67 num_bytes = len(data) | |
68 num_sent_bytes = 0 | |
69 while num_sent_bytes < num_bytes: | |
70 num_write_bytes = min(self.BYTES_PER_WRITE, num_bytes - num_sent_bytes) | |
71 num_requests = self.request_counter() | |
72 wait = self.transfer_seconds(num_write_bytes) * num_requests | |
73 logging.debug('write sleep: %0.4fs (%d requests)', wait, num_requests) | |
74 time.sleep(wait) | |
75 | |
76 self.original_file.write( | |
77 data[num_sent_bytes:num_sent_bytes + num_write_bytes]) | |
78 num_sent_bytes += num_write_bytes | |
79 | |
80 def _read(self, read_func, size): | |
81 start = TIMER() | |
82 data = read_func(size) | |
83 read_seconds = TIMER() - start | |
84 num_bytes = len(data) | |
85 num_requests = self.request_counter() | |
86 wait = self.transfer_seconds(num_bytes) * num_requests - read_seconds | |
87 if wait > 0: | |
88 logging.debug('read sleep: %0.4fs %d requests)', wait, num_requests) | |
89 time.sleep(wait) | |
90 return data | |
91 | |
92 def readline(self, size=-1): | |
93 return self._read(self.original_file.readline, size) | |
94 | |
95 def read(self, size=-1): | |
96 return self._read(self.original_file.read, size) | |
97 | |
98 def __getattr__(self, name): | |
99 """Forward any non-overriden calls.""" | |
100 return getattr(self.original_file, name) | |
101 | |
102 | |
103 def GetBitsPerSecond(bandwidth): | |
104 """Return bits per second represented by dummynet bandwidth option. | |
105 | |
106 See ipfw/dummynet.c:read_bandwidth for how it is really done. | |
107 | |
108 Args: | |
109 bandwidth: a dummynet-style bandwidth specification (e.g. "10Kbit/s") | |
110 """ | |
111 if bandwidth == '0': | |
112 return 0 | |
113 bw_re = r'^(\d+)(?:([KM])?(bit|Byte)/s)?$' | |
114 match = re.match(bw_re, str(bandwidth)) | |
115 if not match: | |
116 raise BandwidthValueError('Value, "%s", does not match regex: %s' % ( | |
117 bandwidth, bw_re)) | |
118 bw = int(match.group(1)) | |
119 if match.group(2) == 'K': | |
120 bw *= 1000 | |
121 if match.group(2) == 'M': | |
122 bw *= 1000000 | |
123 if match.group(3) == 'Byte': | |
124 bw *= 8 | |
125 return bw | |
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