From mboxrd@z Thu Jan  1 00:00:00 1970
From: john at keeping.me.uk (John Keeping)
Date: Tue, 12 Aug 2014 10:00:37 +0100
Subject: [PATCH] Handle If-None-Match HTTP header in plain view
In-Reply-To: <CALUQbeqEdt5a6ekC61bv=275joRfbTrrO+d-fJs7C08gNZ+NfQ@mail.gmail.com>
References: <1407790403-12468-1-git-send-email-damiannohales@gmail.com>
 <20140811213205.GD1261@serenity.lan>
 <CALUQbeqEdt5a6ekC61bv=275joRfbTrrO+d-fJs7C08gNZ+NfQ@mail.gmail.com>
Message-ID: <20140812090037.GE1261@serenity.lan>

On Mon, Aug 11, 2014 at 07:45:53PM -0300, Dami?n Nohales wrote:
> (Sorry, I forgot to include the list address in my response.)
> 
> This does not interact with CGit's cache at all, this interacts with
> client side cache.
> 
> If the client sends an Etag it means "Hey, I have the content cached
> for this URL in the client and its Etag is abc123", so, for a given
> URL, if server calculates the Etag and results to the same as the Etag
> sent by client, it means "Ok, client has the same Etag than me, so
> client's cached content is up-to-date".
> 
> The Etag is calculated from the requested object hash. I'm not a Git
> expert, but I know that the hash will be modified when the file is
> modified by a commit.
> 
> So, if we request a file, then, one year later, we request the same
> file and we still have it cached with its Etag, CGit will respond 304
> Not Modified if the file was not modified by newer commits (CGit
> doesn't check its internal cache, it checks the client's cache).
> 
> Actually, we should avoid send "Expires" and "Last-Modified" when
> "Etag" is available, so the caching information is consistent (and
> also, using Etag we have a more precise and smart caching).

Yes, but I think the code you've changed comes after CGit has duplicated
stdout into the cache file.  So if a request comes in with an
If-None-Match header, then CGit will cache the 304 response and send it
in response to all future request for the same page (until the cached
copy times out).

> 2014-08-11 18:32 GMT-03:00 John Keeping <john at keeping.me.uk>:
> > On Mon, Aug 11, 2014 at 05:53:23PM -0300, Dami?n Nohales wrote:
> >> We are sending Etag to clients but this header is basically unusefulness
> >> if the server doesn't tell the client if the content has been changed or
> >> not for a given Path/Etag pair.
> >>
> >> Signed-off-by: Dami?n Nohales <damiannohales at gmail.com>
> >> ---
> >
> > How does this interact with CGit's cache?  What happens if the original
> > page expires from the cache and then a request comes in with a matching
> > Etag?
> >
> >>  cgit.c      |  1 +
> >>  cgit.h      |  1 +
> >>  ui-plain.c  | 41 +++++++++++++++++++++--------------------
> >>  ui-shared.c | 20 ++++++++++++++++++++
> >>  ui-shared.h |  1 +
> >>  5 files changed, 44 insertions(+), 20 deletions(-)
> >>
> >> diff --git a/cgit.c b/cgit.c
> >> index 8c4517d..7af7712 100644
> >> --- a/cgit.c
> >> +++ b/cgit.c
> >> @@ -385,6 +385,7 @@ static void prepare_context(void)
> >>       ctx.env.server_port = getenv("SERVER_PORT");
> >>       ctx.env.http_cookie = getenv("HTTP_COOKIE");
> >>       ctx.env.http_referer = getenv("HTTP_REFERER");
> >> +     ctx.env.if_none_match = getenv("HTTP_IF_NONE_MATCH");
> >>       ctx.env.content_length = getenv("CONTENT_LENGTH") ? strtoul(getenv("CONTENT_LENGTH"), NULL, 10) : 0;
> >>       ctx.env.authenticated = 0;
> >>       ctx.page.mimetype = "text/html";
> >> diff --git a/cgit.h b/cgit.h
> >> index 0badc64..eddd4c7 100644
> >> --- a/cgit.h
> >> +++ b/cgit.h
> >> @@ -282,6 +282,7 @@ struct cgit_environment {
> >>       const char *server_port;
> >>       const char *http_cookie;
> >>       const char *http_referer;
> >> +     const char *if_none_match;
> >>       unsigned int content_length;
> >>       int authenticated;
> >>  };
> >> diff --git a/ui-plain.c b/ui-plain.c
> >> index 30fff89..a08dc5b 100644
> >> --- a/ui-plain.c
> >> +++ b/ui-plain.c
> >> @@ -103,8 +103,8 @@ static int print_object(const unsigned char *sha1, const char *path)
> >>       ctx.page.filename = path;
> >>       ctx.page.size = size;
> >>       ctx.page.etag = sha1_to_hex(sha1);
> >> -     cgit_print_http_headers();
> >> -     html_raw(buf, size);
> >> +     if (!cgit_print_http_headers_matching_etag())
> >> +             html_raw(buf, size);
> >>       /* If we allocated this, then casting away const is safe. */
> >>       if (freemime)
> >>               free((char*) ctx.page.mimetype);
> >> @@ -128,24 +128,25 @@ static void print_dir(const unsigned char *sha1, const char *base,
> >>       fullpath = buildpath(base, baselen, path);
> >>       slash = (fullpath[0] == '/' ? "" : "/");
> >>       ctx.page.etag = sha1_to_hex(sha1);
> >> -     cgit_print_http_headers();
> >> -     htmlf("<html><head><title>%s", slash);
> >> -     html_txt(fullpath);
> >> -     htmlf("</title></head>\n<body>\n<h2>%s", slash);
> >> -     html_txt(fullpath);
> >> -     html("</h2>\n<ul>\n");
> >> -     len = strlen(fullpath);
> >> -     if (len > 1) {
> >> -             fullpath[len - 1] = 0;
> >> -             slash = strrchr(fullpath, '/');
> >> -             if (slash)
> >> -                     *(slash + 1) = 0;
> >> -             else
> >> -                     fullpath = NULL;
> >> -             html("<li>");
> >> -             cgit_plain_link("../", NULL, NULL, ctx.qry.head, ctx.qry.sha1,
> >> -                             fullpath);
> >> -             html("</li>\n");
> >> +     if (!cgit_print_http_headers_matching_etag()) {
> >> +             htmlf("<html><head><title>%s", slash);
> >> +             html_txt(fullpath);
> >> +             htmlf("</title></head>\n<body>\n<h2>%s", slash);
> >> +             html_txt(fullpath);
> >> +             html("</h2>\n<ul>\n");
> >> +             len = strlen(fullpath);
> >> +             if (len > 1) {
> >> +                     fullpath[len - 1] = 0;
> >> +                     slash = strrchr(fullpath, '/');
> >> +                     if (slash)
> >> +                             *(slash + 1) = 0;
> >> +                     else
> >> +                             fullpath = NULL;
> >> +                     html("<li>");
> >> +                     cgit_plain_link("../", NULL, NULL, ctx.qry.head, ctx.qry.sha1,
> >> +                                     fullpath);
> >> +                     html("</li>\n");
> >> +             }
> >>       }
> >>       free(fullpath);
> >>  }
> >> diff --git a/ui-shared.c b/ui-shared.c
> >> index 9dde0a3..84c7efd 100644
> >> --- a/ui-shared.c
> >> +++ b/ui-shared.c
> >> @@ -661,6 +661,26 @@ void cgit_print_http_headers(void)
> >>               exit(0);
> >>  }
> >>
> >> +int cgit_print_http_headers_matching_etag(void)
> >> +{
> >> +     int match = 0;
> >> +     char *etag;
> >> +     if (ctx.page.etag && ctx.env.if_none_match) {
> >> +             etag = fmtalloc("\"%s\"", ctx.page.etag);
> >> +             if (!strcmp(etag, ctx.env.if_none_match)) {
> >> +                     ctx.page.status = 304;
> >> +                     ctx.page.statusmsg = "Not Modified";
> >> +                     ctx.page.mimetype = NULL;
> >> +                     ctx.page.size = 0;
> >> +                     ctx.page.filename = NULL;
> >> +                     match = 1;
> >> +             }
> >> +             free(etag);
> >> +     }
> >> +     cgit_print_http_headers();
> >> +     return match;
> >> +}
> >> +
> >>  void cgit_print_docstart(void)
> >>  {
> >>       if (ctx.cfg.embedded) {
> >> diff --git a/ui-shared.h b/ui-shared.h
> >> index 3e7a91b..e279f42 100644
> >> --- a/ui-shared.h
> >> +++ b/ui-shared.h
> >> @@ -60,6 +60,7 @@ extern void cgit_vprint_error(const char *fmt, va_list ap);
> >>  extern void cgit_print_date(time_t secs, const char *format, int local_time);
> >>  extern void cgit_print_age(time_t t, time_t max_relative, const char *format);
> >>  extern void cgit_print_http_headers(void);
> >> +extern int cgit_print_http_headers_matching_etag(void);
> >>  extern void cgit_print_docstart(void);
> >>  extern void cgit_print_docend();
> >>  extern void cgit_print_pageheader(void);
> >> --
> >> 2.0.4