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New ServiceBrowsers now request QU in the first outgoing when unspecified#812

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bdraco:service_browser_first_question_qu_unspecified
Jun 22, 2021
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New ServiceBrowsers now request QU in the first outgoing when unspecified#812
bdraco merged 2 commits into
python-zeroconf:masterfrom
bdraco:service_browser_first_question_qu_unspecified

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@bdraco

@bdraco bdraco commented Jun 22, 2021 •
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https://datatracker.ietf.org/doc/html/rfc6762#section-5.4

When we start a ServiceBrowser and zeroconf has just started up, the known
answer list will be small. By asking a QU question first, it is likely
that we have a large known answer list by the time we ask the QM question
a second later (current default which is likely too low but would be
a breaking change to increase). This reduces the amount of traffic on
the network, and has the secondary advantage that most responders will
answer a QU question without the typical delay answering QM questions.

@bdraco
New ServiceBrowsers now request QU in the first outgoing when unspeci…
c4fe8f4 
…fied

https://datatracker.ietf.org/doc/html/rfc6762#section-5.4

When we start a ServiceBrowser and zeroconf has just started up, the known
answer list will be small. By asking a QU question first, it is likely
that we have a large known answer list by the time we ask the QM question
a second later (current default). This reduces the amount of traffic on
the network, and has the secondary advantage that most responders will
answer a QU question without the typical delay answering QM questions.
@bdraco bdraco force-pushed the service_browser_first_question_qu_unspecified branch from 2656889 to c4fe8f4 Compare June 22, 2021 21:19
@codecov-commenter

codecov-commenter commented Jun 22, 2021 •
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Codecov Report

Merging #812 (c4fe8f4) into master (13c558c) will increase coverage by 0.00%.
The diff coverage is 100.00%.

Impacted file tree graph

@@           Coverage Diff           @@
##           master     #812   +/-   ##
=======================================
  Coverage   98.69%   98.69%           
=======================================
  Files          22       22           
  Lines        2298     2303    +5     
  Branches      393      395    +2     
=======================================
+ Hits         2268     2273    +5     
  Misses         18       18           
  Partials       12       12
Impacted Files Coverage Δ
zeroconf/_services/browser.py 98.16% <100.00%> (+0.04%) ⬆️

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@bdraco

bdraco commented Jun 22, 2021

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Looks like PyPy is taking longer to get the first query started. We probably need some way to synchronize the threads a bit better in the test or move it to asyncio

also explains why #768 fails

DEBUG    zeroconf:net.py:175 Creating new socket with port 5353, ip_version IPVersion.V4Only, apple_p2p False and bind_addr ('',)
DEBUG    zeroconf:net.py:229 Created socket <socket.socket fd=14, family=AddressFamily.AF_INET, type=SocketKind.SOCK_DGRAM, proto=0, laddr=('0.0.0.0', 5353)>
DEBUG    zeroconf:net.py:243 Adding '127.0.0.1' (socket 14) to multicast group
DEBUG    zeroconf:net.py:175 Creating new socket with port 5353, ip_version IPVersion.V4Only, apple_p2p False and bind_addr ('127.0.0.1',)
DEBUG    zeroconf:net.py:229 Created socket <socket.socket fd=16, family=AddressFamily.AF_INET, type=SocketKind.SOCK_DGRAM, proto=0, laddr=('127.0.0.1', 5353)>
DEBUG    zeroconf:net.py:292 Configuring socket <socket.socket fd=16, family=AddressFamily.AF_INET, type=SocketKind.SOCK_DGRAM, proto=0, laddr=('127.0.0.1', 5353)> with multicast interface 127.0.0.1
DEBUG    zeroconf:_core.py:293 Listen socket <socket.socket fd=14, family=AddressFamily.AF_INET, type=SocketKind.SOCK_DGRAM, proto=0, laddr=('0.0.0.0', 5353)>, respond sockets [<socket.socket fd=16, family=AddressFamily.AF_INET, type=SocketKind.SOCK_DGRAM, proto=0, laddr=('127.0.0.1', 5353)>]
DEBUG    zeroconf:_protocol.py:595 offsets = questions=0, answers=0, authorities=0, additionals=0
DEBUG    zeroconf:_protocol.py:602 lengths = questions=1, answers=0, authorities=0, additionals=0
DEBUG    zeroconf:_protocol.py:624 now offsets = questions=1, answers=0, authorities=0, additionals=0
DEBUG    zeroconf:_core.py:667 Sending to (None, 5353) (39 bytes #1) <DNSOutgoing:{multicast=True, flags=0, questions=[ptr[question,QU,in,_quservice._tcp.local.]], answers=[], authorities=[], additionals=[]}> as b'\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\n_quservice\x04_tcp\x05local\x00\x00\x0c\x80\x01'...
DEBUG    zeroconf:_core.py:228 Received from '127.0.0.1':5353 (socket 14): <DNSIncoming:{id=0, flags=0, truncated=False, n_q=1, n_ans=0, n_auth=0, n_add=0, questions=[ptr[question,QU,in,_quservice._tcp.local.]], answers=[]}> (39 bytes) as [b'\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\n_quservice\x04_tcp\x05local\x00\x00\x0c\x80\x01']
DEBUG    zeroconf:_protocol.py:595 offsets = questions=0, answers=0, authorities=0, additionals=0
DEBUG    zeroconf:_protocol.py:602 lengths = questions=1, answers=0, authorities=0, additionals=0
DEBUG    zeroconf:_protocol.py:624 now offsets = questions=1, answers=0, authorities=0, additionals=0
DEBUG    zeroconf:_core.py:667 Sending to (None, 5353) (39 bytes #1) <DNSOutgoing:{multicast=True, flags=0, questions=[ptr[question,QM,in,_quservice._tcp.local.]], answers=[], authorities=[], additionals=[]}> as b'\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\n_quservice\x04_tcp\x05local\x00\x00\x0c\x00\x01'...

@bdraco

bdraco commented Jun 22, 2021

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We can decrease time between queries to work around the pypy startup delay. I'll look into making a helper that synchronizes the startup

@bdraco bdraco mentioned this pull request Jun 22, 2021
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@bdraco bdraco merged commit e32bb5d into python-zeroconf:master Jun 22, 2021
@bdraco bdraco deleted the service_browser_first_question_qu_unspecified branch June 22, 2021 23:24
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