Make the number of restarts a parameter.

git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@2068 d4fa192b-c00b-0410-8231-f00ffab90ce4

bin/varnishd/cache_center.c

@@ -69,6 +69,7 @@ DOT start -> recv [style=bold,color=green,weight=4]
 
 #include "shmlog.h"
 #include "vcl.h"
+#include "heritage.h"
 #include "cache.h"
 
 static unsigned xids;
@@ -707,6 +708,10 @@ cnt_recv(struct sess *sp)
 
 	AZ(sp->obj);
 
+	if (sp->restarts > params->max_restarts) {
+		sp->step = STP_ERROR;
+		return (0);
+	}
 	if (sp->restarts == 0) {
 		AZ(sp->vcl);
 		/* Update stats of various sorts */

bin/varnishd/heritage.h

@@ -125,6 +125,9 @@ struct params {
 	/* LRU list ordering interval */
 	unsigned		lru_timeout;
 
+	/* Maximum restarts allowed */
+	unsigned		max_restarts;
+
 };
 
 extern volatile struct params *params;

bin/varnishd/mgt_param.c

@@ -555,6 +555,14 @@ tweak_cc_command(struct cli *cli, struct parspec *par, const char *arg)
 	}
 }
 
+static void
+tweak_max_restarts(struct cli *cli, struct parspec *par, const char *arg)
+{
+
+	(void)par;
+	tweak_generic_uint(cli, &master.max_restarts, arg, 0, UINT_MAX);
+}
+
 /*--------------------------------------------------------------------*/
 
 /*
@@ -760,6 +768,14 @@ static struct parspec parspec[] = {
 		"exec cc -nostdinc -fpic -shared -Wl,-x -o %s -x c - < %s"
 #endif
 		, NULL },
+	{ "max_restarts", tweak_max_restarts,
+		"Upper limit on how many times a request can restart."
+#ifdef NOT_YET
+		"  ESI:include counts as a restart in this context."
+#endif
+		"\nBe aware that restarts are likely to cause a hit against "
+		"the backend, so don't increase thoughtlessly.\n",
+		"4", "restarts" },
 	{ NULL, NULL, NULL }
 };