Jonathan Tan <jonathantanmy@xxxxxxxxxx> writes:
>> Jonathan Tan <jonathantanmy@xxxxxxxxxx> writes:
>>
>> > @@ -126,6 +129,12 @@ static int read_pack_objects_stdout(int outfd, struct output_state *os)
>> > }
>> > os->used += readsz;
>> >
>> > + if (!os->packfile_started) {
>> > + os->packfile_started = 1;
>> > + if (use_protocol_v2)
>> > + packet_write_fmt(1, "packfile\n");
>>
>> If we fix this function so that the only byte in the buffer is held
>> back without emitted when os->used == 1 as I alluded to, this may
>> have to be done a bit later, as with such a change, it is no longer
>> guaranteed that send_client_data() will be called after this point.
>
> I'm not sure what you mean about there being no guarantee that
> send_client_data() is not called - in create_pack_file(), there is an
> "if (output_state.used > 0)" line (previously "if (0 <= buffered)") that
> outputs anything remaining.
I was referring to this part of the review on the previous step,
which you may not yet have read.
OK, this corresponds to the "*cp++ = buffered" in the original just
before xread().
> + os->used = 1;
> + } else {
> + send_client_data(1, os->buffer, os->used);
> + os->used = 0;
I am not sure if the code is correct when os->used happens to be 1
(shouldn't we hold the byte, skip the call to send_client_data(),
and go back to poll() to expect more data?), but this is a faithful
code movement and rewrite of the original.
The point of this logic is to make sure we always hold back some
bytes and do not feed *all* the bytes to the other side by calling
"send-client-data" until we made sure the upstream of what we are
relaying (pack-objects?) successfully exited, but it looks to me
that the "else" clause above ends up flushing everything when
os->used is 1, which goes against the whole purpose of the code.
And the "fix" I was alluding to was to update that "else" clause to
make it a no-op that keeps os->used non-zero, which would not call
send-client-data.
When that fix happens, the part that early in the function this
patch added "now we know we will call send-client-data, so let's say
'here comes packdata' unless we have already said that" is making
the decision too early. Depending on the value of os->used when we
enter the code and the number of bytes xread() reads from the
upstream, we might not call send-client-data yet (namely, when we
have no buffered data and we happened to get only one byte).
> ... it might be
> better if the server can send sideband throughout the whole response -
> perhaps that should be investigated first.
Yup. It just looked quite crazy, and it is even more crazy to
buffer keepalives ;-)
