Warn about too many (>100) VCLs.

Two new paramters allow the limit and than handling (ignore, warn, fail)
to be configured.

Fixes #2713

bin/varnishd/mgt/mgt_vcl.c

@@ -53,6 +53,7 @@
 #include "tbl/vcl_states.h"
 
 static const char * const VCL_STATE_LABEL = "label";
+static int vcl_count;
 
 struct vclprog;
 struct vmodfile;
@@ -252,6 +253,8 @@ mgt_vcl_add(const char *name, const char *state)
 		vp->warm = 1;
 
 	VTAILQ_INSERT_TAIL(&vclhead, vp, list);
+	if (vp->state != VCL_STATE_LABEL)
+		vcl_count++;
 	return (vp);
 }
 
@@ -269,6 +272,8 @@ mgt_vcl_del(struct vclprog *vp)
 		mgt_vcl_dep_del(VTAILQ_FIRST(&vp->dfrom));
 
 	VTAILQ_REMOVE(&vclhead, vp, list);
+	if (vp->state != VCL_STATE_LABEL)
+		vcl_count--;
 	if (vp->fname != NULL) {
 		if (!MGT_DO_DEBUG(DBG_VCL_KEEP))
 			AZ(unlink(vp->fname));
@@ -566,6 +571,12 @@ mgt_new_vcl(struct cli *cli, const char *vclname, const char *vclsrc,
 	if (C_flag) {
 		bprintf(buf, ".CflagTest.%d", (int)getpid());
 		vclname = buf;
+	} else if (vcl_count >= mgt_param.max_vcl &&
+	    mgt_param.max_vcl_handling == 2) {
+		VCLI_Out(cli, "Too many (%d) VCLs already loaded\n", vcl_count);
+		VCLI_Out(cli, "(See max_vcl and max_vcl_handling parameters)");
+		VCLI_SetResult(cli, CLIS_CANT);
+		return;
 	}
 
 	if (state == NULL)
@@ -592,6 +603,14 @@ mgt_new_vcl(struct cli *cli, const char *vclname, const char *vclsrc,
 	if (active_vcl == NULL)
 		active_vcl = vp;
 
+	if (cli->result == CLIS_OK &&
+	    vcl_count > mgt_param.max_vcl &&
+	    mgt_param.max_vcl_handling == 1) {
+		VCLI_Out(cli, "%d VCLs loaded\n", vcl_count);
+		VCLI_Out(cli, "Remember to vcl.discard the old/unused VCLs.\n");
+		VCLI_Out(cli, "(See max_vcl and max_vcl_handling parameters)");
+	}
+
 	if (!MCH_Running())
 		return;
 

bin/varnishtest/tests/v00025.vtc

@@ -7,7 +7,23 @@ server s1 {
 	txresp
 } -start
 
-varnish v1 -syntax 4.0 -arg "-i J.F.Nobody" -vcl+backend {
+# Test max_vcl param
+varnish v1 -arg "-i J.F.Nobody" -vcl+backend { } -start
+
+varnish v1 -cliok "param.set max_vcl 2"
+varnish v1 -cliok "param.set max_vcl_handling 2"
+
+varnish v1 -vcl+backend { }
+varnish v1 -errvcl {Too many (2) VCLs already loaded} {}
+
+varnish v1 -cliok "param.set max_vcl_handling 1"
+
+varnish v1 -cliexpect "Remember to vcl.discard the old/unused VCLs." \
+	{vcl.inline foobar "vcl 4.1; backend b1 {.host=\"${s1_addr}\";}"}
+
+varnish v1 -cliok "param.set max_vcl 100"
+
+varnish v1 -syntax 4.0 -vcl+backend {
 
 	import std;
 	import directors;
@@ -78,7 +94,7 @@ varnish v1 -syntax 4.0 -arg "-i J.F.Nobody" -vcl+backend {
 		set bereq.connect_timeout = 10s;
 	}
 
-} -start
+}
 
 client c1 {
 	txreq

include/tbl/params.h

@@ -1537,6 +1537,38 @@ PARAM(
 	/* func */	NULL
 )
 
+PARAM(
+	/* name */	max_vcl_handling,
+	/* typ */	uint,
+	/* min */	"0",
+	/* max */	"2",
+	/* default */	"1",
+	/* units */	NULL,
+	/* flags */	0,
+	/* s-text */
+	"Behaviour when attempting to exceed max_vcl loaded VCL.\n"
+	"\n*  0 - Ignore max_vcl parameter.\n"
+	"\n*  1 - Issue warning.\n"
+	"\n*  2 - Refuse loading VCLs.",
+	/* l-text */	"",
+	/* func */	NULL
+)
+
+PARAM(
+	/* name */	max_vcl,
+	/* typ */	uint,
+	/* min */	"0",
+	/* max */	NULL,
+	/* default */	"100",
+	/* units */	NULL,
+	/* flags */	0,
+	/* s-text */
+	"Threshold of loaded VCL programs.  (VCL labels are not counted.)"
+	"  Parameter max_vcl_handling determines behaviour.",
+	/* l-text */	"",
+	/* func */	NULL
+)
+
 PARAM(
 	/* name */	vsm_free_cooldown,
 	/* typ */	timeout,