A proxy object with 'persistent=False'will bind and destroy a socket for each
call to the owserver. (If you call 'netstat -t’ after the timing test you will
see hundreds of lines like
tcp 0 0 localhost:45494 localhost:4304 TIME_WAIT
which is the debris that remains after you tear down a socket…)
On the contrary with ‘persistent=True'a single socket is bound at the
beginning of the transaction and reused for every subsequent owserver call. So
'persistent=False’ has a very small overhead (about 1ms) for each call.
Somehow your figures are consistent with this interpretation: non-persistent
overhead is a constant small delta with respect to persistent connection. Since
your owserver is apparently much slower than the one which I run my tests, you
have a smaller relative overhead.
Usually I would not care about the persistent/non persistent thing, unless you
are running out of available sockets.
This program
import itertools
from pyownet import protocol
p = protocol.proxy(‘myowserver', persistent=False)
freq = 1 << 12
for i in itertools.count():
try:
c = p.dir()
except protocol.Error as exc:
print('Iteration {0} raised exception: {1}'.format(i, exc))
break
None if i % freq else print('Iteration {}'.format(i))
prints
Iteration 0
Iteration 4096
Iteration 8192
Iteration 12288
Iteration 16384
Iteration 16977 raised exception: [Errno 49] Can't assign requested address
so it is possible to run out of sockets, although this is a rather edgy
situation, that I’ve never analysed in detail.
S.
> On 06 Nov 2015, at 02:26, Loren Amelang <[email protected]
> <mailto:[email protected]>> wrote:
>
> On Thu, 05 Nov 2015 13:02:13 +0100,
> Stefano Miccoli [email protected] <mailto:[email protected]> wrote:
> ...
>> Just a few numbers, collected with
>> https://github.com/miccoli/pyownet/blob/master/test/timing.py
>> <https://github.com/miccoli/pyownet/blob/master/test/timing.py>
>> <https://github.com/miccoli/pyownet/blob/master/test/timing.py> querying a
>> non localhost production owserver
>
>> pyownet: ver. 0.8.2
>> proxy_obj: ownet server at ('10.48.74.112', 4304)
>> server info: pid 2662, ver. unknown
>>
>> timeit:
>> statement: proxy_obj.dir("/")
>> number: 20
>> repetitions: 5
>>
>> ** non persistent : 1.29 ms, 1.30 ms, 1.30 ms, 1.33 ms, 1.36 ms,
>> ** persistent : 0.77 ms, 0.77 ms, 0.79 ms, 0.80 ms, 0.97 ms,
>
>> The figure reported here are time for a single call to the given method,
>> computed as the average of 20 consecutive calls. (Please note that I read
>> the cached temperature value? uncached is of course much slower, but this
>> is due to 1-wire)
>
>
> I was surprised by the timing numbers you posted. So I tried your test script
> with my BBB installation...
>
> Running on the BBB with the owserver:
> ---
> ubuntu@arm:~/Lpkg$ python3 StefanoTimingTest.py3
> pyownet: ver. 0.8.2
> (/usr/local/lib/python3.4/dist-packages/pyownet/__init__.py)
> proxy_obj: ownet server at ('127.0.0.1', 4304)
> server info: pid 1243, ver. unknown
>
> timeit:
> statement: proxy_obj.dir("/")
> number: 20
> repetitions: 5
>
> ** non persistent : 37.55 ms, 37.78 ms, 39.26 ms, 40.15 ms, 41.11 ms,
> ** persistent : 36.22 ms, 36.41 ms, 36.62 ms, 37.10 ms, 38.26 ms,
> ---
>
>
> Running Python on an external Windows machine, one Wi-Fi hop from the BBB:
> ---
> C:\Users\Loren\Documents\Projects\Computing\BeagleBone Black\BBB
> Projects\1-Wire\OWFS Python logging>python StefanoTimingTest.py3
> owserver://10.1.1.4:4304 <owserver://10.1.1.4:4304>
> pyownet: ver. 0.8.2 (C:\Apps\Python33\lib\site-packages\pyownet\__init__.py)
> proxy_obj: ownet server at ('10.1.1.4', 4304)
> server info: pid 22210, ver. unknown
>
> timeit:
> statement: proxy_obj.dir("/")
> number: 20
> repetitions: 5
>
> ** non persistent : 41.69 ms, 45.79 ms, 45.99 ms, 48.34 ms, 49.41 ms,
> ** persistent : 42.26 ms, 44.03 ms, 45.68 ms, 45.69 ms, 46.03 ms,
> ---
>
>
> Between those two tests was a long learning session. For those who don't
> know...
>
> In netstat, "0.0.0.0" addresses are accessible from outside machines,
> 127.0.0.1 addresses are not!
>
> The localhost setting is in (at least) two places in /etc/owfs.conf:
> ! server: server = 10.1.1.4:4304 # localhost:4304 LA151105 allow net access
> And:
> server: port = 4304 # localhost:4304 LA151105 allow net access
>
> After making those changes, I found "restart" does not notice them! You have
> to use "force-reload":
> ubuntu@arm:~/Lpkg$ sudo /etc/init.d/owserver force-reload
> * Restarting 1-Wire TCP Server owserver
>
> Suddenly it works from out on the network!
>
>
> So I wonder why persistence makes less than 10% difference here, while on
> your much faster machine it makes 25 to 40%...
>
> | Loren Amelang | [email protected] <mailto:[email protected]> |
>
>
>
>
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