Subject: Re: [PATCH] fetch-pack: write effective filter to trace2

From: Junio C Hamano <[email-masked]>
Date: Fri, 15 Jul 2022 11:28:22 -0700

Jeff Hostetler <[email-masked]> writes:

> On 7/15/22 1:29 PM, Jonathan Tan wrote:
>> Administrators of a managed Git environment (like the one at $DAYJOB)
>> might want to quantify the performance change of fetches with and
>> without partial clone from the client's point of view. Therefore, log
>> the effective filter being sent to the server whenever a fetch (or
>> clone) occurs. Note that this is not necessarily the same as what's
>> specified on the CLI, because during a fetch, the configured filter is
>> used whenever a filter is not specified on the CLI.
>> This is implemented for protocol v0, v1, and v2.

Is that different to say "for all protocols"?  I am wondering if it
is worth saying (unlike in a hypothetical case where we do not
support v0 and v1 we may want to state why we only support v2).

>> Signed-off-by: Jonathan Tan <[email-masked]>
>> ---
>>   fetch-pack.c | 10 ++++++++--
>>   1 file changed, 8 insertions(+), 2 deletions(-)
>> diff --git a/fetch-pack.c b/fetch-pack.c
>> index cb6647d657..dec8743bec 100644
>> --- a/fetch-pack.c
>> +++ b/fetch-pack.c
>> @@ -392,7 +392,10 @@ static int find_common(struct fetch_negotiator *negotiator,
>>   	if (server_supports_filtering && args->filter_options.choice) {
>>   		const char *spec =
>>   			expand_list_objects_filter_spec(&args->filter_options);
>> +		trace2_data_string("fetch", the_repository, "fetch/effective-filter", spec);
>>   		packet_buf_write(&req_buf, "filter %s", spec);
>> +	} else {
>> +		trace2_data_string("fetch", the_repository, "fetch/effective-filter", "none");

Do we show "none" anywhere else where an expanded list objects
filter spec is expected?

I am wondering two things: 

 - The lack of this line would be a cleaner implementation of a
   signal to say "this client did not ask any filtering".

 - It would be good if we keep what report here more-or-less the
   same as what we can pass "--filter=" on the command line of
   "git pack-objects".

If "--filter=none" meant "this --filter passes everything", then
saying "none" here makes perfect sense wrt the latter, but I doubt
it is the case.

>>   	}
>>   	packet_buf_flush(&req_buf);
>>   	state_len = req_buf.len;
>> @@ -1328,9 +1331,12 @@ static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
>>   		const char *spec =
>>   			expand_list_objects_filter_spec(&args->filter_options);
>>   		print_verbose(args, _("Server supports filter"));
>> +		trace2_data_string("fetch", the_repository, "fetch/effective-filter", spec);
>>   		packet_buf_write(&req_buf, "filter %s", spec);
>> -	} else if (args->filter_options.choice) {
>> -		warning("filtering not recognized by server, ignoring");
>> +	} else {
>> +		if (args->filter_options.choice)
>> +			warning("filtering not recognized by server, ignoring");
>> +		trace2_data_string("fetch", the_repository, "fetch/effective-filter", "none");

At the first glance, this seems to lose data, because you should be
able to use expand_list_objects_filter_spec() to report the filter
spec.  But this is reporting the filter that was actually in effect,
so it is OK.

But the same question about "none" remains.

>>   	}
>>     	if (server_supports_feature("fetch", "packfile-uris", 0)) {
>> 
>
> This looks nice.  Thanks!
> Jeff

Will queue with your Acked-by, then?

Thanks, both.