Subject: Re: [PATCH] Introduce experimental remote object access mode

From: Junio C Hamano <[email-masked]>
Date: Tue, 11 Feb 2014 11:29:15 -0800

Shawn Pearce <[email-masked]> writes:

> Why would you do this? Perhaps you need more time in your day
> to consume tea or coffee. Set GIT_RTT and enjoy a beverage.

So the conclusion is that it is not practical to do a lazy fetch if
it is done extremely naively at "we want this object --- wait a bit
and we'll give you" level?

I am wondering if we can do a bit better, like "we want this object
--- wait a bit, ah that's a commit, so it is likely that you may
want the trees and blobs associated with it, too, if not right now
but in a near future, let me push a pack that holds them to you"?

>
> So-not-signed-off-by: this author or anyone else
> ---
>
>   :-)
>
>  sha1_file.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> diff --git a/sha1_file.c b/sha1_file.c
> index 6e8c05d..9bdcbc3 100644
> --- a/sha1_file.c
> +++ b/sha1_file.c
> @@ -38,6 +38,7 @@ const unsigned char null_sha1[20];
>
>  static const char *no_log_pack_access = "no_log_pack_access";
>  static const char *log_pack_access;
> +static useconds_t rtt;
>
>  /*
>   * This is meant to hold a *small* number of objects that you would
> @@ -436,9 +437,20 @@ void prepare_alt_odb(void)
>   read_info_alternates(get_object_directory(), 0);
>  }
>
> +static void apply_rtt()
> +{
> + if (!rtt) {
> + char *rtt_str = getenv("GIT_RTT");
> + rtt = rtt_str ? strtoul(rtt_str, NULL, 10) * 1000 : 1;
> + }
> + if (rtt > 1)
> + usleep(rtt);
> +}
> +
>  static int has_loose_object_local(const unsigned char *sha1)
>  {
>   char *name = sha1_file_name(sha1);
> + apply_rtt();
>   return !access(name, F_OK);
>  }
>
> @@ -1303,6 +1315,7 @@ void prepare_packed_git(void)
>
>   if (prepare_packed_git_run_once)
>   return;
> +
>   prepare_packed_git_one(get_object_directory(), 1);
>   prepare_alt_odb();
>   for (alt = alt_odb_list; alt; alt = alt->next) {
> @@ -1439,6 +1452,7 @@ static int open_sha1_file(const unsigned char *sha1)
>   struct alternate_object_database *alt;
>
>   fd = git_open_noatime(name);
> + apply_rtt();
>   if (fd >= 0)
>   return fd;