[dpdk-dev] [PATCH] usertools/dpdk-telemetry: print name of app when connected
Burakov, Anatoly
anatoly.burakov at intel.com
Tue Feb 16 12:13:38 CET 2021
On 16-Feb-21 11:02 AM, Bruce Richardson wrote:
> On Tue, Feb 16, 2021 at 10:40:36AM +0000, Burakov, Anatoly wrote:
>> On 16-Feb-21 9:44 AM, Bruce Richardson wrote:
>>> When the dpdk-telemetry client connects to a DPDK instance, we can use the
>>> PID provided in the initial connection message to query from /proc the name
>>> of the process we are connected to, and display that to the user. We use
>>> the "cmdline" procfs entry for the query since that is available on both
>>> Linux and FreeBSD (assuming procfs is mounted on the BSD instance).
>>>
>>> Signed-off-by: Bruce Richardson <bruce.richardson at intel.com>
>>> ---
>>> usertools/dpdk-telemetry.py | 5 +++++
>>> 1 file changed, 5 insertions(+)
>>>
>>> diff --git a/usertools/dpdk-telemetry.py b/usertools/dpdk-telemetry.py
>>> index 181859658f..82b91f346f 100755
>>> --- a/usertools/dpdk-telemetry.py
>>> +++ b/usertools/dpdk-telemetry.py
>>> @@ -45,6 +45,11 @@ def handle_socket(path):
>>> return
>>> json_reply = read_socket(sock, 1024)
>>> output_buf_len = json_reply["max_output_len"]
>>> + pid = json_reply["pid"]
>>> + if os.path.exists('/proc/' + str(pid) + '/cmdline'):
>>> + with open('/proc/' + str(pid) + '/cmdline') as f:
>>
>> First of all, this is better done using os.path.join:
>>
>> path = os.path.join('/proc', str(pid), 'cmdline')
>> if os.path.exists(path):
>> with open(path) as f:
>> ...
>
> Ok, I forgot that os.path.join can take > 2 parameters.
>
>>
>> More importantly this isn't terribly Pythonic as it's not over-using
>> exceptions :) IMO a better way would be:
>>
>> try:
>> with open(path) as f:
>> ...
>> except IOError as e:
>> # ignore if doesn't exist
>> if e.errno != errno.ENOENT:
>> raise
>>
>
> Yes, I was thinking that I just wanted any exceptions to be raised, but you
> right that I should just ignore the not-found one and skip the printout.
'raise' will raise the exception up the stack, so you'll still get your
exceptions that way - you'll just skip the one that says the file
doesn't exist. plus, it also has a benefit of avoiding TOCTOU race :)
>
>>> + argv0 = f.read(1024).split('\0')[0]
>>> + print("Connected to application: '" + os.path.basename(argv0) + "'")
>>
>> Also, formatting is better than concatenation, e.g. at least:
>>
>> bname = os.path.basename(argv0)
>> print("Connected to application: '{}'".format(bname))
>>
> And f-strings are best of all, but we need python 3.6 for those. :-) I
> consider use of format vs concat a matter of taste, but I'll update as you
> suggest.
>
> Thanks for the review.
>
> /Bruce
>
> PS: Python 3.5 has had its final release late last year:
> https://www.python.org/downloads/release/python-3510/
> We should soon consider updating our minimum required version to Python
> 3.6, allowing us to use f-strings in our python code rather than
> concatenation or explicit format calls.
>
I seem to have a lot of difficulty remembering syntax for f-strings :P
--
Thanks,
Anatoly
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