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Date: Tue, 16 Feb 2021 11:02:23 +0000
From: Bruce Richardson <bruce.richardson@intel.com>
To: "Burakov, Anatoly" <anatoly.burakov@intel.com>
Cc: dev@dpdk.org, Kevin Laatz <kevin.laatz@intel.com>
Message-ID: <20210216110223.GC136@bricha3-MOBL.ger.corp.intel.com>
References: <20210216094415.28000-1-bruce.richardson@intel.com>
<e5ff396d-befa-2119-da19-32e1cfa5fbaf@intel.com>
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Subject: Re: [dpdk-dev] [PATCH] usertools/dpdk-telemetry: print name of app
when connected
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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@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.
> > + 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.