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 ab0bc0e306fceb03f02c22c0180a96696dcd34c5..8013c0d3cafbc8d851687aaf0ff69dc7dfb5595b 100644 (file)
--- 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 792afd6948aaca3c196736420a65693ed14a68dc..394510aecd8b329c9665b8551de79a323dc18c01 100644 (file)
--- 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);