An explanatory comment.

git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@4184 d4fa192b-c00b-0410-8231-f00ffab90ce4

bin/varnishd/cache_acceptor.c

@@ -69,6 +69,13 @@ static struct waiter const *vca_act;
 pthread_t		VCA_thread;
 static struct timeval	tv_sndtimeo;
 static struct timeval	tv_rcvtimeo;
+
+/*
+ * We want to get out of any kind of touble-hit TCP connections as fast
+ * as absolutely possible, so we set them LINGER enabled with zero timeout,
+ * so that even if there are outstanding write data on the socket, a close(2)
+ * will return immediately.
+ */
 static const struct linger linger = {
 	.l_onoff	=	1,
 };

bin/varnishd/cache_backend_poll.c

@@ -242,18 +242,85 @@ vbp_poke(struct vbp_target *vt)
 }
 
 /*--------------------------------------------------------------------
- * One thread per backend to be poked.
+ * Record pokings...
  */
 
-static void *
-vbp_wrk_poll_backend(void *priv)
+static void
+vbp_start_poke(struct vbp_target *vt)
+{
+	CHECK_OBJ_NOTNULL(vt, VBP_TARGET_MAGIC);
+
+#define BITMAP(n, c, t, b)	vt->n <<= 1;
+#include "cache_backend_poll.h"
+#undef BITMAP
+
+	vt->last = 0;
+	vt->resp_buf[0] = '\0';
+}
+
+static void
+vbp_has_poked(struct vbp_target *vt)
 {
-	struct vbp_target *vt;
 	unsigned i, j;
 	uint64_t u;
 	const char *logmsg;
 	char bits[10];
 
+	CHECK_OBJ_NOTNULL(vt, VBP_TARGET_MAGIC);
+
+	/* Calculate exponential average */
+	if (vt->happy & 1) {
+		if (vt->rate < AVG_RATE)
+			vt->rate += 1.0;
+		vt->avg += (vt->last - vt->avg) / vt->rate;
+	}
+
+	i = 0;
+#define BITMAP(n, c, t, b)	bits[i++] = (vt->n & 1) ? c : '-';
+#include "cache_backend_poll.h"
+#undef BITMAP
+	bits[i] = '\0';
+
+	u = vt->happy;
+	for (i = j = 0; i < vt->probe.window; i++) {
+		if (u & 1)
+			j++;
+		u >>= 1;
+	}
+	vt->good = j;
+
+	if (vt->good >= vt->probe.threshold) {
+		if (vt->backend->healthy)
+			logmsg = "Still healthy";
+		else
+			logmsg = "Back healthy";
+		vt->backend->healthy = 1;
+	} else {
+		if (vt->backend->healthy)
+			logmsg = "Went sick";
+		else
+			logmsg = "Still sick";
+		vt->backend->healthy = 0;
+	}
+	VSL(SLT_Backend_health, 0, "%s %s %s %u %u %u %.6f %.6f %s",
+	    vt->backend->vcl_name, logmsg, bits,
+	    vt->good, vt->probe.threshold, vt->probe.window,
+	    vt->last, vt->avg, vt->resp_buf);
+
+	if (!vt->stop)
+		TIM_sleep(vt->probe.interval);
+}
+
+/*--------------------------------------------------------------------
+ * One thread per backend to be poked.
+ */
+
+static void *
+vbp_wrk_poll_backend(void *priv)
+{
+	struct vbp_target *vt;
+	unsigned u;
+
 	THR_SetName("backend poll");
 
 	CAST_OBJ_NOTNULL(vt, priv, VBP_TARGET_MAGIC);
@@ -273,59 +340,29 @@ vbp_wrk_poll_backend(void *priv)
 	if (vt->probe.threshold == 0)
 		vt->probe.threshold = 3;
 
-	printf("Probe(\"%s\", %g, %g)\n",
-	    vt->req,
-	    vt->probe.timeout,
-	    vt->probe.interval);
+	if (vt->probe.threshold == ~0)
+		vt->probe.initial = vt->probe.threshold - 1;
 
-	/*lint -e{525} indent */
-	while (!vt->stop) {
-#define BITMAP(n, c, t, b)	vt->n <<= 1;
-#include "cache_backend_poll.h"
-#undef BITMAP
-		vt->last = 0;
-		vt->resp_buf[0] = '\0';
-		vbp_poke(vt);
+	if (vt->probe.initial > vt->probe.threshold)
+		vt->probe.initial = vt->probe.threshold;
 
-		/* Calculate exponential average */
-		if (vt->happy & 1) {
-			if (vt->rate < AVG_RATE)
-				vt->rate += 1.0;
-			vt->avg += (vt->last - vt->avg) / vt->rate;
-		}
+printf("Initial %u\n", vt->probe.initial);
 
-		i = 0;
-#define BITMAP(n, c, t, b)	bits[i++] = (vt->n & 1) ? c : '-';
-#include "cache_backend_poll.h"
-#undef BITMAP
-		bits[i] = '\0';
+	printf("Probe(\"%s\", %g, %g)\n",
+	    vt->req, vt->probe.timeout, vt->probe.interval);
 
-		u = vt->happy;
-		for (i = j = 0; i < vt->probe.window; i++) {
-			if (u & 1)
-				j++;
-			u >>= 1;
-		}
-		vt->good = j;
-
-		if (vt->good >= vt->probe.threshold) {
-			if (vt->backend->healthy)
-				logmsg = "Still healthy";
-			else
-				logmsg = "Back healthy";
-			vt->backend->healthy = 1;
-		} else {
-			if (vt->backend->healthy)
-				logmsg = "Went sick";
-			else
-				logmsg = "Still sick";
-			vt->backend->healthy = 0;
-		}
-		VSL(SLT_Backend_health, 0, "%s %s %s %u %u %u %.6f %.6f %s",
-		    vt->backend->vcl_name, logmsg, bits,
-		    vt->good, vt->probe.threshold, vt->probe.window,
-		    vt->last, vt->avg, vt->resp_buf);
+if (0) {
+	for (u = 0; u < vt->probe.initial; u++) {
+		vbp_start_poke(vt);
+		vt->happy |= 1;
+		vbp_has_poked(vt);
+	}
+}
 
+	while (!vt->stop) {
+		vbp_start_poke(vt);
+		vbp_poke(vt);
+		vbp_has_poked(vt);
 		if (!vt->stop)
 			TIM_sleep(vt->probe.interval);
 	}