Add cache_capacity option to dnssec middleware for the capacity of LRU cache (#339)

This fix adds a `cache_capacity` option to dnssec middleware, so that
it is possible to specify the capacity of the LRU cache used by dnssec
middleware.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

middleware/dnssec/README.md

@@ -26,6 +26,7 @@ TODO(miek): think about key rollovers, and how to do them automatically.
 ~~~
 dnssec [ZONES... ] {
     key file KEY...
+    cache_capacity CAPACITY
 }
 ~~~
 
@@ -33,4 +34,9 @@ dnssec [ZONES... ] {
   will be signed with all keys. Generating a key can be done with `dnssec-keygen`: `dnssec-keygen -a
   ECDSAP256SHA256 <zonename>`. A key created for zone *A* can be safely used for zone *B*.
 
+
+* `cache_capacity` indicates the capacity of the LRU cache. The dnssec middleware uses LRU cache to manage
+  objects and the default capacity is 10000.
+
+
 ## Examples

middleware/dnssec/setup.go

@@ -1,6 +1,7 @@
 package dnssec
 
 import (
+	"strconv"
 	"strings"
 
 	"github.com/miekg/coredns/core/dnsserver"
@@ -18,12 +19,12 @@ func init() {
 }
 
 func setup(c *caddy.Controller) error {
-	zones, keys, err := dnssecParse(c)
+	zones, keys, capacity, err := dnssecParse(c)
 	if err != nil {
 		return middleware.Error("dnssec", err)
 	}
 
-	cache, err := lru.New(defaultCap)
+	cache, err := lru.New(capacity)
 	if err != nil {
 		return err
 	}
@@ -34,10 +35,12 @@ func setup(c *caddy.Controller) error {
 	return nil
 }
 
-func dnssecParse(c *caddy.Controller) ([]string, []*DNSKEY, error) {
+func dnssecParse(c *caddy.Controller) ([]string, []*DNSKEY, int, error) {
 	zones := []string{}
 
 	keys := []*DNSKEY{}
+
+	capacity := defaultCap
 	for c.Next() {
 		if c.Val() == "dnssec" {
 			// dnssec [zones...]
@@ -49,30 +52,41 @@ func dnssecParse(c *caddy.Controller) ([]string, []*DNSKEY, error) {
 			}
 
 			for c.NextBlock() {
+				switch c.Val() {
+				case "key":
 					k, e := keyParse(c)
 					if e != nil {
-					return nil, nil, e
+						return nil, nil, 0, e
 					}
 					keys = append(keys, k...)
+				case "cache_capacity":
+					if !c.NextArg() {
+						return nil, nil, 0, c.ArgErr()
+					}
+					value := c.Val()
+					cacheCap, err := strconv.Atoi(value)
+					if err != nil {
+						return nil, nil, 0, err
+					}
+					capacity = cacheCap
+				}
+
 			}
 		}
 	}
 	for i := range zones {
 		zones[i] = middleware.Host(zones[i]).Normalize()
 	}
-	return zones, keys, nil
+	return zones, keys, capacity, nil
 }
 
 func keyParse(c *caddy.Controller) ([]*DNSKEY, error) {
 	keys := []*DNSKEY{}
 
-	what := c.Val()
 	if !c.NextArg() {
 		return nil, c.ArgErr()
 	}
 	value := c.Val()
-	switch what {
-	case "key":
 	if value == "file" {
 		ks := c.RemainingArgs()
 		for _, k := range ks {
@@ -91,6 +105,5 @@ func keyParse(c *caddy.Controller) ([]*DNSKEY, error) {
 			keys = append(keys, k)
 		}
 	}
-	}
 	return keys, nil
 }

middleware/dnssec/setup_test.go

@@ -13,19 +13,25 @@ func TestSetupDnssec(t *testing.T) {
 		shouldErr          bool
 		expectedZones      []string
 		expectedKeys       []string
+		expectedCapacity   int
 		expectedErrContent string
 	}{
 		{
-			`dnssec`, false, nil, nil, "",
+			`dnssec`, false, nil, nil, defaultCap, "",
 		},
 		{
-			`dnssec miek.nl`, false, []string{"miek.nl."}, nil, "",
+			`dnssec miek.nl`, false, []string{"miek.nl."}, nil, defaultCap, "",
+		},
+		{
+			`dnssec miek.nl {
+				cache_capacity 100
+			}`, false, []string{"miek.nl."}, nil, 100, "",
 		},
 	}
 
 	for i, test := range tests {
 		c := caddy.NewTestController("dns", test.input)
-		zones, keys, err := dnssecParse(c)
+		zones, keys, capacity, err := dnssecParse(c)
 
 		if test.shouldErr && err == nil {
 			t.Errorf("Test %d: Expected error but found %s for input %s", i, err, test.input)
@@ -51,6 +57,9 @@ func TestSetupDnssec(t *testing.T) {
 					t.Errorf("Dnssec not correctly set for input %s. Expected: '%s', actual: '%s'", test.input, k, keys[i].K.Header().Name)
 				}
 			}
+			if capacity != test.expectedCapacity {
+				t.Errorf("Dnssec not correctly set capacity for input '%s' Expected: '%d', actual: '%d'", test.input, capacity, test.expectedCapacity)
+			}
 		}
 	}
 }