Re: [dpdk-dev] [PATCH] app/testpmd: send failure logs to stderr

[Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>]

On 6/15/21 11:52 AM, Ferruh Yigit wrote:
> On 6/15/2021 9:14 AM, Andrew Rybchenko wrote:
>> On 6/15/21 10:59 AM, Ferruh Yigit wrote:
>>> On 6/14/2021 5:56 PM, Andrew Rybchenko wrote:
>>>> On 6/11/21 1:35 PM, Ferruh Yigit wrote:
>>>>> On 6/11/2021 10:19 AM, Andrew Rybchenko wrote:
>>>>>> On 6/11/21 5:06 AM, Li, Xiaoyun wrote:
>>>>>>> Hi
>>>>>>> -----Original Message-----
>>>>>>> From: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
>>>>>>> Sent: Friday, May 28, 2021 00:25
>>>>>>> To: Li, Xiaoyun <xiaoyun.li@intel.com>
>>>>>>> Cc: dev@dpdk.org
>>>>>>> Subject: [PATCH] app/testpmd: send failure logs to stderr
>>>>>>>
>>>>>>> Running with stdout suppressed or redirected for further processing is very
>>>>>>> confusing in the case of errors.
>>>>>>>
>>>>>>> Signed-off-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
>>>>>>> ---
>>>>>>>
>>>>>>> This patch looks good to me.
>>>>>>> But what do you think about make it as a fix and backport to stable branches?
>>>>>>> Anyway works for me.
>>>>>> I have no strong opinion on the topic.
>>>>>>
>>>>>> @Ferruh, what do you think?
>>>>>>
>>>>> Same here, no strong opinion.
>>>>> Sending errors to 'stderr' looks correct thing to do, but changing behavior in
>>>>> the LTS may cause some unexpected side affect, if it is scripted and testpmd
>>>>> output is parsed etc... For this possibility I would wait for the next LTS.
>>>> So, I guess all agree that backporting to LTS is a bad idea because of
>>>> behaviour change.
>>>>
>>>> As I said in a sub-thread I tend to apply in v21.08 since it is a right
>>>> thing to do like a fix, but the fix is not that required to be
>>>> backported to change behaviour of LTS releases.
>>>>
>>>>> And because of same reason perhaps a release note can be added.
>>>> I'll make v2 with release notes added. Good point.
>>>>
>>>>> Also there is 'TESTPMD_LOG' macro for logs in testpmd, (as well as 'RTE_LOG'
>>>>> macro), I don't know if we should switch all logs, including 'printf', to
>>>>> 'TESTPMD_LOG' macro?
>>>>> Later stdout/sderr can be managed in rte_log level, instead of any specific
>>>>> logic for the testpmd.
>>>> I think fprintf() is a better option for debug tool, since its
>>>> messages should not go to syslog etc. It should go to stdout/stderr
>>>> regardless of logging configuration and log level settings.
>>>>
>>> Why application should not take log configuration and log level settings into
>>> account? I think this is a feature we can benefit.
>> For me it sounds like an extra way to shoot its own leg.
>>
> Please explain what is the cons of it?

Possibility to silent error logs for test tools.

May be it is just mine paranoia.

>>> And for not logging to syslog, I think it is DPDK wide concern, not specific to
>>> testpmd, we should have way to say don't log to syslog or only log error to
>>> syslog etc.. When it is done, using 'TESTPMD_LOG' enables benefiting from that.
>> Logging configuration should be flexible to support various
>> logging backends. IMHO, we don't need the flexibility here.
>> testpmd is a command-line test application and errors should
>> simply go to stderr. That's it. Since the result is the
>> same in both ways, my opinion is not strong, I'm just trying
>> to explain why I slightly prefer suggested way.
>>
> Ability to make it less or more verbose seems good opinion to me, just
> printf/fprintf doesn't enable it.

Yes, for helper tracing and extra information logging. IMHO, no for
error logs.

So, the strong argument here is to use uniform logging in the
code everywhere and hope that if somebody disables/redirects
errors it is really intended.

But in this case all printf's should be converted as well.

> And testpmd sometimes used in non-interactive mode for functional testing,
> flexible logging can help there too, I think at least.

in this case stdout/stderr are simply intercepted and processed.
Yes, it could be a bit easier if we redirect it to an interface which
natively provides messages boundaries - a bit easier to parse/match.

>> I can switch to TESTPMD_LOG() (or define TESTPMD_ERR() and use
>> it) easily. I just need maintainers decision on it.
>>
>>>>> Even there was a defect for this in the rte_log level, that logs should go to
>>>>> stderr: https://bugs.dpdk.org/show_bug.cgi?id=8
>>>>>
>>>>>
>>>>>>> Acked-by: Xiaoyun Li <xiaoyun.li@intel.com>