threads / patch / 35080

patchsend-pack: don't send a thin pack when the server doesn't support it

Subject: [PATCH] send-pack: don't send a thin pack when the server doesn't support it

## tl;dr

6 messages between Oct 8, 2013 and Oct 19, 2013. Diffs are folded; open one to read it.

replies: 5people: 3as markdown or json

Carlos Martín Nieto· Oct 8, 2013, 08:44 UTC · lore

Not every server out there supports fixing thin packs, so let's send them a full pack.

Signed-off-by: Carlos Martín Nieto <cmn@elego.de>
---

It's not always possible to support thin packs (sometimes there isn't even an object database to grab bases out of). And in any case git shouldn't create thin packs if the server hasn't said it knows how to fix them, as per the point of the extension.

 send-pack.c | 2 ++
 1 file changed, 2 insertions(+)

Show changes to send-pack.c +2 −0

diff --git a/send-pack.c b/send-pack.c
index 7d172ef..7b88ac8 100644
--- a/send-pack.c
+++ b/send-pack.c
@@ -205,6 +205,8 @@ int send_pack(struct send_pack_args *args,
 		quiet_supported = 1;
 	if (server_supports("agent"))
 		agent_supported = 1;
+	if (!server_supports("thin-pack"))
+		args->use_thin_pack = 0;
 
 	if (!remote_refs) {
 		fprintf(stderr, "No refs in common and none specified; doing nothing.\n"

-- 
1.8.4.561.g1c3d45d

Duy Nguyen· Oct 8, 2013, 09:44 UTC · re: Carlos Martín Nieto · lore

Re: [PATCH] send-pack: don't send a thin pack when the server doesn't support it

On Tue, Oct 8, 2013 at 3:44 PM, Carlos Martín Nieto <cmn@elego.de> wrote:

Show 10 quoted lines

> diff --git a/send-pack.c b/send-pack.c
> index 7d172ef..7b88ac8 100644
> --- a/send-pack.c
> +++ b/send-pack.c
> @@ -205,6 +205,8 @@ int send_pack(struct send_pack_args *args,
>                 quiet_supported = 1;
>         if (server_supports("agent"))
>                 agent_supported = 1;
> +       if (!server_supports("thin-pack"))
> +               args->use_thin_pack = 0;

Hmm.. I think this introduces a regression in C Git because receive-pack never advertises "thin-pack" and so "git push" from now on will never send thin packs. It's too late now to add thin-pack to receive-pack, perhaps a new extension "no-thin-pack" for those servers? Alternatively, just run git push --no-thin (you'll need f7c815c (push: respect --no-thin - 2013-08-12) though).

>         if (!remote_refs) {
>                 fprintf(stderr, "No refs in common and none specified; doing nothing.\n"

-- 
Duy

Carlos Martin Nieto· Oct 8, 2013, 10:58 UTC · re: Duy Nguyen · lore

Re: [PATCH] send-pack: don't send a thin pack when the server doesn't support it

Duy Nguyen <pclouds@gmail.com> writes:

On Tue, 2013-10-08 at 16:44 +0700, Duy Nguyen wrote:

Show 16 quoted lines

>On Tue, Oct 8, 2013 at 3:44 PM, Carlos Martín Nieto <cmn@elego.de> wrote:
> > diff --git a/send-pack.c b/send-pack.c
> > index 7d172ef..7b88ac8 100644
> > --- a/send-pack.c
> > +++ b/send-pack.c
> > @@ -205,6 +205,8 @@ int send_pack(struct send_pack_args *args,
> >                 quiet_supported = 1;
> >         if (server_supports("agent"))
> >                 agent_supported = 1;
> > +       if (!server_supports("thin-pack"))
> > +               args->use_thin_pack = 0;
> 
> Hmm.. I think this introduces a regression in C Git because
> receive-pack never advertises "thin-pack" and so "git push" from now
> on will never send thin packs. It's too late now to add thin-pack to
>

Oh, I'd never noticed that when looking though the network traffic. This seems like something that breaks the compatibility that git otherwise tries so hard to maintain. How did it happen that it's fine for the client to assume that the server supports thin packs?

receive-pack, perhaps a new extension "no-thin-pack" for those

> servers? Alternatively, just run git push --no-thin (you'll need
> f7c815c (push: respect --no-thin - 2013-08-12) though).
>

Yeah, I had an older version in my PATH and was bitten by that when testing. Having --no-thin and the server's index-pack fail with missing bases is quite worrying when you're the one who wrote most of the server-side code.

Having to remember to run 'git push --no-thin' when pushing to one particular project is pretty bad experience as a user and I was hoping to avoid this with newer gits. We could advertise a "no-thin-pack" extension if a patch to support that would be accepted into mainline git.

Cheers,
   cmn

Duy Nguyen· Oct 8, 2013, 11:29 UTC · re: Duy Nguyen · lore

Re: [PATCH] send-pack: don't send a thin pack when the server doesn't support it

On Tue, Oct 8, 2013 at 4:44 PM, Duy Nguyen <pclouds@gmail.com> wrote:

Show 16 quoted lines

> On Tue, Oct 8, 2013 at 3:44 PM, Carlos Martín Nieto <cmn@elego.de> wrote:
>> diff --git a/send-pack.c b/send-pack.c
>> index 7d172ef..7b88ac8 100644
>> --- a/send-pack.c
>> +++ b/send-pack.c
>> @@ -205,6 +205,8 @@ int send_pack(struct send_pack_args *args,
>>                 quiet_supported = 1;
>>         if (server_supports("agent"))
>>                 agent_supported = 1;
>> +       if (!server_supports("thin-pack"))
>> +               args->use_thin_pack = 0;
>
> Hmm.. I think this introduces a regression in C Git because
> receive-pack never advertises "thin-pack" and so "git push" from now
> on will never send thin packs. It's too late now to add thin-pack to
> receive-pack

Or maybe it's not that late. How about you go with your patch and add thin-pack capability to receive-pack too?

When new "git push" is used against old server, thin pack is disabled. But that's not a big deal (I hope). The difference is traffic increases a bit more, but cpu consumption on the server side is also a bit less. Pushes are usually small, unless you do initial push, which is complete anyway. So a bit more or less does not really matter in practice.

We could mitigate the regression a bit by checking agent string and enable thin-pack for those versions even if thin-pack is not advertises. That goes back to v1.7.12. We may do the same for some other popular git servers. And this hack is maintained like 3-4 years, enough time for new versions to be deployed, then removed.

Hmm?

-- 
Duy

Jonathan Nieder· Oct 8, 2013, 22:22 UTC · re: Duy Nguyen · lore

Re: [PATCH] send-pack: don't send a thin pack when the server doesn't support it

Duy Nguyen wrote:

Show 5 quoted lines

> Or maybe it's not that late. How about you go with your patch and add
> thin-pack capability to receive-pack too?
>
> When new "git push" is used against old server, thin pack is disabled.
> But that's not a big deal (I hope).

Could we have separate patches to introduce the server-side capability and then to request it in the client? That way, people with old servers can apply the patch introducing the capability if they want.

The new meaning of the "thin-pack" capability should also be documented in Documentation/technical/protocol-capabilities.txt.

Done that way and with enough time between the server advertising the capability and the client looking for it, it seems like a good idea.

My two cents, Jonathan

Carlos Martín Nieto· Oct 19, 2013, 15:19 UTC · re: Jonathan Nieder · lore

Re: [PATCH] send-pack: don't send a thin pack when the server doesn't support it

On Tue, 2013-10-08 at 15:22 -0700, Jonathan Nieder wrote:

Show 11 quoted lines

> Duy Nguyen wrote:
> 
> > Or maybe it's not that late. How about you go with your patch and add
> > thin-pack capability to receive-pack too?
> >
> > When new "git push" is used against old server, thin pack is disabled.
> > But that's not a big deal (I hope).
> 
> Could we have separate patches to introduce the server-side capability
> and then to request it in the client?  That way, people with old
> servers can apply the patch introducing the capability if they want.

That could work.

> 
> The new meaning of the "thin-pack" capability should also be
> documented in Documentation/technical/protocol-capabilities.txt.

Oh, right; the capability as described is only about the server being able to generate a thin pack. Wouldn't his mean that git shouldn't assume that *any* remote can fix thin packs, though? (other than most servers you do talk to happen to).

Anyway, facts on the ground and all that. I'll prepare some

> 
> Done that way and with enough time between the server advertising the
> capability and the client looking for it, it seems like a good idea.

If such patches would be accepted, that would be great. By the time this all gets merged, we might have thin pack fixing merged into libgit2, but there will still be uses where fixing them isn't an issue due to other constraints.

Cheers,
   cmn