From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: Taylor Blau <me@ttaylorr.com>
Cc: Josh Steadmon <steadmon@google.com>,
git@vger.kernel.org, gitster@pobox.com
Subject: Re: [PATCH v2 2/2] connect, protocol: log negotiated protocol version
Date: Thu, 05 Aug 2021 04:47:16 +0200 [thread overview]
Message-ID: <874kc4mwqc.fsf@evledraar.gmail.com> (raw)
In-Reply-To: <YQs+VQIYDO3pkCNS@nand.local>
On Wed, Aug 04 2021, Taylor Blau wrote:
> On Thu, Aug 05, 2021 at 01:40:51AM +0200, Ævar Arnfjörð Bjarmason wrote:
>>
>> On Wed, Aug 04 2021, Josh Steadmon wrote:
>>
>> > It is useful for performance monitoring and debugging purposes to know
>> > the wire protocol used for remote operations. This may differ from the
>> > version set in local configuration due to differences in version and/or
>> > configuration between the server and the client. Therefore, log the
>> > negotiated wire protocol version via trace2, for both clients and
>> > servers.
>> >
>> > Signed-off-by: Josh Steadmon <steadmon@google.com>
>> > ---
>>
>> I know Taylor asked you to change it to a string from in int upthread in
>> <YQmxSxTswHE/gTet@nand.local>, but I really don't see the point. But am
>> willing to be convinced otherwise.
>
> The conversion to log a string instead of an integer is necessary if
> Josh wants to write "<unknown>" instead of -1. To me, that seemed
> clearer, and I like that it makes the trace2 representation for a
> protocol version separate from the protocol_version enum.
Yes, having a magic -1 value would be bad, but since it seems we'll
never get it in practice...
>> It seems to me that both of these codepaths will never usefully use this
>> new "UNKNOWN_VERSION" string you added, i.e.:
>>
>> > connect.c | 3 +++
>> > protocol.c | 3 +++
>> > t/t5705-session-id-in-capabilities.sh | 12 ++++++++++++
>> > 3 files changed, 18 insertions(+)
>> >
>> > diff --git a/connect.c b/connect.c
>> > index 70b13389ba..5f0e113625 100644
>> > --- a/connect.c
>> > +++ b/connect.c
>> > @@ -150,6 +150,9 @@ enum protocol_version discover_version(struct packet_reader *reader)
>> > break;
>> > }
>> >
>> > + trace2_data_string("transfer", NULL, "negotiated-version",
>> > + format_protocol_version(version));
>>
>> Right after this.
>>
>> > switch (version) {
>> > case protocol_v2:
>> > process_capabilities_v2(reader);
>>
>> We'll die here with BUG("unknown protocol version") if it's unknown..
>
> Good eyes. In fact, the second switch statement shouldn't even need a
> case-arm for protocol_unknown_version (but has it to cover all
> enumerated values).
I didn't check if crafting an unknown version will be found earlier, or
if we'll actually reach that "unknown" case.
> I didn't realize before that the unknown case really is dead code, so
> we'll never log "<unknown>". And since the mapping from protocol_version
> to string is identical for known values, we could probably do without
> it.
>
> And I don't much care either way. I think the benefit is really pretty
> slim, and arguably my code is just adding unnecessary overhead. So I'm
> happy to go with or without it, but I'd be rather sad to spend much more
> of our collective time discussing it.
Yeah, I just think if we can be sure it's an integer *and* a valid
version when we log it, people writing future log summarizing code will
thank us, i.e. just 0, 1, 2, and in the future maybe 3, ..., but not -1
or "<unknown>" or other values we'll trust die() etc. to handle.
next prev parent reply other threads:[~2021-08-05 2:49 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-03 20:13 [PATCH] connect, protocol: log negotiated protocol version Josh Steadmon
2021-08-03 21:12 ` Taylor Blau
2021-08-04 21:37 ` Josh Steadmon
2021-08-04 21:56 ` Junio C Hamano
2021-08-04 22:17 ` [PATCH v2 0/2] " Josh Steadmon
2021-08-04 22:17 ` [PATCH v2 1/2] protocol: add protocol version formatting function Josh Steadmon
2021-08-04 23:32 ` Ævar Arnfjörð Bjarmason
2021-08-04 22:17 ` [PATCH v2 2/2] connect, protocol: log negotiated protocol version Josh Steadmon
2021-08-04 22:28 ` Eric Sunshine
2021-08-06 21:15 ` Josh Steadmon
2021-08-04 23:40 ` Ævar Arnfjörð Bjarmason
2021-08-05 1:26 ` Taylor Blau
2021-08-05 2:47 ` Ævar Arnfjörð Bjarmason [this message]
2021-08-06 21:22 ` Josh Steadmon
2021-08-10 17:20 ` [PATCH v3] " Josh Steadmon
2021-08-16 18:03 ` Taylor Blau
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