From: phk <phk@d4fa192b-c00b-0410-8231-f00ffab90ce4>
Date: Mon, 10 Jul 2006 12:00:20 +0000 (+0000)
Subject: Rework the "connect to backend logic".
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7e8d83532c0df9247782d7b9a3db7546263b0c19;p=varnish

Rework the "connect to backend logic".

Avoid calling getaddrinfo() for every connect by catching the result
in the backend structure.

Minimize number of socket/connect calls by caching the last good
address in the backend structure.

If all addresses in the cached getaddrinfo() result fails, call
getaddrinfo() again (to catch DNS changes) and try the list again.



git-svn-id: svn+ssh://projects.linpro.no/svn/varnish/trunk@405 d4fa192b-c00b-0410-8231-f00ffab90ce4
---

diff --git a/varnish-cache/bin/varnishd/cache.h b/varnish-cache/bin/varnishd/cache.h
index ab0bc0e3..8013c0d3 100644
--- a/varnish-cache/bin/varnishd/cache.h
+++ b/varnish-cache/bin/varnishd/cache.h
@@ -157,8 +157,10 @@ struct backend {
 	const char	*hostname;
 	const char	*portname;
 	unsigned	ip;
-#if 0
+
 	struct addrinfo	*addr;
+	struct addrinfo	*last_addr;
+#if 0
 	double		responsetime;
 	double		timeout;
 	double		bandwidth;
diff --git a/varnish-cache/bin/varnishd/cache_backend.c b/varnish-cache/bin/varnishd/cache_backend.c
index 792afd69..394510ae 100644
--- a/varnish-cache/bin/varnishd/cache_backend.c
+++ b/varnish-cache/bin/varnishd/cache_backend.c
@@ -94,22 +94,17 @@ vbe_delete_conn(struct vbe_conn *vb)
 	free(vb->vbcm);
 }
 
-/*--------------------------------------------------------------------
- * XXX: we should not call getaddrinfo() every time, we should cache
- * and apply round-robin with blacklisting of entries that do not respond
- * etc.  Periodic re-lookups to capture changed DNS records would also 
- * be a good thing in that case.
- */
+/*--------------------------------------------------------------------*/
 
 static void
-connect_to_backend(struct vbe_conn *vc, struct backend *bp)
+vbe_lookup(struct backend *bp)
 {
-	struct addrinfo *res, *res0, hint;
-	int error, s;
-	char buf[TCP_ADDRBUFFSIZE * 2 + 1], *p;
+	struct addrinfo *res, hint;
+	int error;
+
+	if (bp->addr != NULL)
+		freeaddrinfo(bp->addr);
 
-	assert(bp != NULL);
-	assert(bp->hostname != NULL);
 	memset(&hint, 0, sizeof hint);
 	hint.ai_family = PF_UNSPEC;
 	hint.ai_socktype = SOCK_STREAM;
@@ -120,36 +115,95 @@ connect_to_backend(struct vbe_conn *vc, struct backend *bp)
 	if (error) {
 		if (res != NULL)
 			freeaddrinfo(res);
-		fprintf(stderr, "getaddrinfo: %s\n", 
-		    gai_strerror(error));
+		printf("getaddrinfo: %s\n", gai_strerror(error)); /* XXX */
+		bp->addr = NULL;
 		return;
 	}
-	res0 = res;
-	do {
-		s = socket(res0->ai_family, res0->ai_socktype,
-		    res0->ai_protocol);
-		if (s < 0) {
-			VSL(SLT_Debug, 0, "Socket errno=%d", errno);
-			continue;
-		}
-		error = connect(s, res0->ai_addr, res0->ai_addrlen);
-		if (!error) 
-			break;
-		VSL(SLT_Debug, 0, "Connect errno=%d", errno);
+	bp->addr = res;
+}
+
+/*--------------------------------------------------------------------*/
+
+static int
+vbe_sock_conn(struct addrinfo *ai)
+{
+	int s;
+
+	s = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
+	if (s < 0) 
+		return (s);
+	else if (connect(s, ai->ai_addr, ai->ai_addrlen)) {
 		close(s);
 		s = -1;
-	} while ((res0 = res0->ai_next) != NULL);
-	vc->fd = s;
-	if (s >= 0) {
-		TCP_myname(s, buf);
-		p = strchr(buf, '\0');
-		assert(p != NULL);
-		*p++ = ' ';
-		TCP_name(res0->ai_addr, res0->ai_addrlen, p);
-		VSL(SLT_BackendOpen, vc->fd, buf);
+	} 
+	return (s);
+}
+
+/*--------------------------------------------------------------------*/
+
+static int
+vbe_conn_try(struct backend *bp, struct addrinfo **pai)
+{
+	struct addrinfo *ai;
+	int s;
+
+	/* First try the cached good address, and any following it */
+	for (ai = bp->last_addr; ai != NULL; ai = ai->ai_next) {
+		s = vbe_sock_conn(ai);
+		if (s >= 0) {
+			bp->last_addr = ai;
+			*pai = ai;
+			return (s);
+		}
+	}
+
+	/* Then try the list until the cached last good address */
+	for (ai = bp->addr; ai != bp->last_addr; ai = ai->ai_next) {
+		s = vbe_sock_conn(ai);
+		if (s >= 0) {
+			bp->last_addr = ai;
+			*pai = ai;
+			return (s);
+		}
+	}
+
+	/* Then do another lookup to catch DNS changes */
+	vbe_lookup(bp);
+
+	/* And try the entire list */
+	for (ai = bp->addr; ai != NULL; ai = ai->ai_next) {
+		s = vbe_sock_conn(ai);
+		if (s >= 0) {
+			bp->last_addr = ai;
+			*pai = ai;
+			return (s);
+		}
 	}
-	freeaddrinfo(res);
-	return;
+
+	return (-1);
+}
+
+static int
+vbe_connect(struct backend *bp)
+{
+	int s;
+	char buf[TCP_ADDRBUFFSIZE * 2 + 1], *p;
+	struct addrinfo *ai;
+
+	assert(bp != NULL);
+	assert(bp->hostname != NULL);
+
+	s = vbe_conn_try(bp, &ai);
+	if (s < 0) 
+		return (s);
+
+	TCP_myname(s, buf);
+	p = strchr(buf, '\0');
+	assert(p != NULL);
+	*p++ = ' ';
+	TCP_name(ai->ai_addr, ai->ai_addrlen, p);
+	VSL(SLT_BackendOpen, s, buf);
+	return (s);
 }
 
 /*--------------------------------------------------------------------
@@ -278,7 +332,7 @@ VBE_GetFd(struct backend *bp, unsigned xid)
 		vc->inuse = 1;
 		TAILQ_INSERT_TAIL(&vp->bconn, vc, list);
 		AZ(pthread_mutex_unlock(&vbemtx));
-		connect_to_backend(vc, bp);
+		vc->fd = vbe_connect(bp);
 		if (vc->fd < 0) {
 			AZ(pthread_mutex_lock(&vbemtx));
 			TAILQ_REMOVE(&vc->vbe->bconn, vc, list);