[PATCH] Handle If-None-Match HTTP header in plain view
John Keeping
john at keeping.me.uk
Tue Aug 12 21:15:23 CEST 2014
On Tue, Aug 12, 2014 at 12:38:35PM -0300, Damián Nohales wrote:
> Ah... I got it.
>
> We could implement cache disabling per command to disable it for the
> plain command. I don't know if there is another way since Etag is
> calculated at command execution.
Another way to do it would be to only handle "If-None-Match" if the
content is already cached and then parse the Etag header from the cached
content.
I think it comes back to what Lars wrote in the commit that added the
current level of Etag support (commit 488a214):
Todo: add support for HEAD requests...
If we have sufficient infrastructure to handle HEAD requests then it
should be trivial to add proper Etag handling on top, but I don't think
it's trivial to add that.
> 2014-08-12 6:00 GMT-03:00 John Keeping <john at keeping.me.uk>:
> > On Mon, Aug 11, 2014 at 07:45:53PM -0300, Damián 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, Damián 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: Damián 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
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