Quorum support

[Artur Bergman]

Attached is a patch that implements quorum support. You specify the %  
of servers that need to be up, and if less than that is up it marks  
the entire director as down. This avoids the whack-a-mole problem when  
bringing up servers.
Comments please.
Artur
----------

diff -u -r varnish-2.1.3/bin/varnishd/cache_dir_random.c varnish- 
quorum/bin/varnishd/cache_dir_random.c
--- varnish-2.1.3/bin/varnishd/cache_dir_random.c	2010-03-24  
09:44:13.000000000 +0000
+++ varnish-quorum/bin/varnishd/cache_dir_random.c	2010-10-07  
18:07:37.126411696 +0000
@@ -75,6 +75,7 @@

  	enum crit_e		criteria;
  	unsigned		retries;
+	unsigned                quorum_weight;
  	double			tot_weight;
  	struct vdi_random_host	*hosts;
  	unsigned		nhosts;
@@ -155,7 +156,9 @@
  			if (VBE_Healthy_sp(sp, d2))
  				s1 += vs->hosts[i].weight;
  		}
-
+		if (s1 < vs->quorum_weight)
+			return (NULL);
+		
  		if (s1 == 0.0)
  			return (NULL);

@@ -258,6 +261,7 @@
  		vh->backend = bp[te->host];
  		AN(vh->backend);
  	}
+	vs->quorum_weight = (vs->tot_weight * t->quorum / 100);
  	vs->nhosts = t->nmember;
  	bp[idx] = &vs->dir;
  }
diff -u -r varnish-2.1.3/include/vrt.h varnish-quorum/include/vrt.h
--- varnish-2.1.3/include/vrt.h	2010-07-13 11:07:03.000000000 +0000
+++ varnish-quorum/include/vrt.h	2010-10-07 17:42:13.476408083 +0000
@@ -91,6 +91,7 @@
  	const char				*name;
  	unsigned				retries;
  	unsigned				nmember;
+	unsigned                                quorum;
  	const struct vrt_dir_random_entry	*members;
  };

diff -u -r varnish-2.1.3/lib/libvcl/vcc_dir_random.c varnish-quorum/ 
lib/libvcl/vcc_dir_random.c
--- varnish-2.1.3/lib/libvcl/vcc_dir_random.c	2010-07-28  
11:11:58.000000000 +0000
+++ varnish-quorum/lib/libvcl/vcc_dir_random.c	2010-10-07  
18:01:23.526408498 +0000
@@ -55,13 +55,14 @@
  	struct token *t_field, *t_be;
  	int nelem;
  	struct fld_spec *fs, *mfs;
-	unsigned u, retries;
+	unsigned u, retries, quorum;
  	const char *first;
  	char *p;

-	fs = vcc_FldSpec(tl, "?retries", NULL);
+	fs = vcc_FldSpec(tl, "?retries","?quorum", NULL);

  	retries = 0;
+	quorum = 0;
  	while (tl->t->tok != '{') {
  		vcc_IsField(tl, &t_field, fs);
  		ERRCHK(tl);
@@ -70,6 +71,11 @@
  			retries = vcc_UintVal(tl);
  			ERRCHK(tl);
  			SkipToken(tl, ';');
+		} else if (vcc_IdIs(t_field, "quorum")) {
+			ExpectErr(tl, CNUM);
+			quorum = vcc_UintVal(tl);
+			ERRCHK(tl);
+			SkipToken(tl, ';');
  		} else {
  			ErrInternal(tl);
  		}
@@ -134,6 +140,7 @@
  	    PF(tl->t_dir));
  	Fc(tl, 0, "\t.name = \"%.*s\",\n", PF(tl->t_dir));
  	Fc(tl, 0, "\t.retries = %u,\n", retries);
+	Fc(tl, 0, "\t.quorum = %u,\n", quorum);
  	Fc(tl, 0, "\t.nmember = %d,\n", nelem);
  	Fc(tl, 0, "\t.members = vdre_%.*s,\n", PF(tl->t_dir));
  	Fc(tl, 0, "};\n");
diff -u -r varnish-2.1.3/lib/libvcl/vcc_fixed_token.c varnish-quorum/ 
lib/libvcl/vcc_fixed_token.c
--- varnish-2.1.3/lib/libvcl/vcc_fixed_token.c	2010-07-28  
09:48:29.000000000 +0000
+++ varnish-quorum/lib/libvcl/vcc_fixed_token.c	2010-10-07  
17:42:14.888909071 +0000
@@ -258,8 +258,9 @@
  	vsb_cat(sb, "\tint\t\t\t\t\thost;\n\tdouble\t\t\t\t\tweight;\n");
  	vsb_cat(sb, "};\n\nstruct vrt_dir_random {\n");
  	vsb_cat(sb, "\tconst char\t\t\t\t*name;\n\tunsigned\t\t\t 
\tretries;");
-	vsb_cat(sb, "\n\tunsigned\t\t\t\tnmember;\n\tconst struct vrt_dir_r");
-	vsb_cat(sb, "andom_entry\t*members;\n};\n\n/*\n");
+	vsb_cat(sb, "\n\tunsigned\t\t\t\tnmember;\n\tunsigned              ");
+	vsb_cat(sb, "                  quorum;\n\tconst struct vrt_dir_rand");
+	vsb_cat(sb, "om_entry\t*members;\n};\n\n/*\n");
  	vsb_cat(sb, " * A director with round robin selection\n");
  	vsb_cat(sb, " */\n\nstruct vrt_dir_round_robin_entry {\n");
  	vsb_cat(sb, "\tint\t\t\t\t\thost;\n};\n\nstruct  
vrt_dir_round_robin");
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