PATCH: stale-while-revalidate support

[Federico Schwindt]

Hi,

After Per's recent post (1) and discussing it with him here's a patch that
uses this to initialize beresp.grace.
I've reused cache_rfc2616.c but perhaps this should be moved into its own
file, i.e. cache_rfc5861.c.
Comments?

f.-

1.
https://www.varnish-software.com/blog/grace-varnish-4-stale-while-revalidate-semantics-varnish
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 bin/varnishd/cache/cache.h         |  3 ++-
 bin/varnishd/cache/cache_fetch.c   |  2 ++
 bin/varnishd/cache/cache_rfc2616.c | 32 +++++++++++++++++++++++++++++
 bin/varnishtest/tests/b00043.vtc   | 41 ++++++++++++++++++++++++++++++++++++++
 4 files changed, 77 insertions(+), 1 deletion(-)

diff --git a/bin/varnishd/cache/cache.h b/bin/varnishd/cache/cache.h
index 2b10f59..759633f 100644
--- a/bin/varnishd/cache/cache.h
+++ b/bin/varnishd/cache/cache.h
@@ -1244,12 +1244,13 @@ char *WS_Snapshot(struct ws *ws);
 int WS_Overflowed(const struct ws *ws);
 void *WS_Printf(struct ws *ws, const char *fmt, ...) __printflike(2, 3);
 
-/* rfc2616.c */
+/* cache_rfc2616.c */
 void RFC2616_Ttl(struct busyobj *, double now);
 enum body_status RFC2616_Body(struct busyobj *, struct dstat *);
 unsigned RFC2616_Req_Gzip(const struct http *);
 int RFC2616_Do_Cond(const struct req *sp);
 void RFC2616_Weaken_Etag(struct http *hp);
+void RFC5861_Stale(struct busyobj *);
 
 
 /* stevedore.c */
diff --git a/bin/varnishd/cache/cache_fetch.c b/bin/varnishd/cache/cache_fetch.c
index a768170..c4ad0f1 100644
--- a/bin/varnishd/cache/cache_fetch.c
+++ b/bin/varnishd/cache/cache_fetch.c
@@ -348,6 +348,8 @@ vbf_stp_startfetch(struct worker *wrk, struct busyobj *bo)
 	EXP_Clr(&bo->exp);
 	RFC2616_Ttl(bo, now);
 
+	RFC5861_Stale(bo);
+
 	/* private objects have negative TTL */
 	if (bo->fetch_objcore->flags & OC_F_PRIVATE)
 		bo->exp.ttl = -1.;
diff --git a/bin/varnishd/cache/cache_rfc2616.c b/bin/varnishd/cache/cache_rfc2616.c
index bb0a85e..3db28f6 100644
--- a/bin/varnishd/cache/cache_rfc2616.c
+++ b/bin/varnishd/cache/cache_rfc2616.c
@@ -365,3 +365,35 @@ RFC2616_Weaken_Etag(struct http *hp)
 	http_Unset(hp, H_ETag);
 	http_PrintfHeader(hp, "ETag: W/%s", p);
 }
+
+/*
+ * RFC5861 outlines a way to control the use of stale responses.
+ * We use this to initialize the grace period.
+ */
+
+void
+RFC5861_Stale(struct busyobj *bo)
+{
+	char *p;
+	const struct http *hp;
+	struct exp *expp;
+
+	expp = &bo->exp;
+
+	/*
+	 * If we are not meant to cache this ignore any potential
+	 * stale-while-revalidate values.
+	 */
+	if (expp->ttl <= 0.)
+		return;
+
+	hp = bo->beresp;
+
+	if (http_GetHdrField(hp, H_Cache_Control,
+	    "stale-while-revalidate", &p) && p != NULL) {
+		if (*p == '-')
+			expp->grace = 0;
+		else
+			expp->grace = strtoul(p, NULL, 0);
+	}
+}
diff --git a/bin/varnishtest/tests/b00043.vtc b/bin/varnishtest/tests/b00043.vtc
new file mode 100644
index 0000000..e5b5102
--- /dev/null
+++ b/bin/varnishtest/tests/b00043.vtc
@@ -0,0 +1,41 @@
+varnishtest "Test stale-while-revalidate"
+
+server s1 {
+	rxreq
+	txresp -hdr "Cache-Control: max-age=30, stale-while-revalidate=30"
+	rxreq
+	txresp -hdr "Cache-Control: max-age=0, stale-while-revalidate=30"
+	rxreq
+	txresp -hdr "Cache-Control: max-age=30, stale-while-revalidate=30" -hdr "Age: 40"
+	rxreq
+	txresp -status 500 -hdr "Cache-Control: max-age=30, stale-while-revalidate=30"
+} -start
+
+varnish v1 -vcl+backend {
+	sub vcl_backend_response {
+		set beresp.http.grace = beresp.grace;
+		set beresp.http.ttl = beresp.ttl;
+	}
+} -start
+
+client c1 {
+	txreq -url /1
+	rxresp
+	expect resp.http.grace == 30.000
+	expect resp.http.ttl == 30.000
+
+	txreq -url /2
+	rxresp
+	expect resp.http.grace == 10.000
+	expect resp.http.ttl == 0.000
+
+	txreq -url /3
+	rxresp
+	expect resp.http.grace == 10.000
+	expect resp.http.ttl == 0.000
+
+	txreq -url /4
+	rxresp
+	expect resp.http.grace == 10.000
+	expect resp.http.ttl == 0.000
+} -run