[#1689] node/config: Allow zero max_ops in RPC limits config

The limiter allows zeros for limits, meaning "this operation is
disabled".  However, the config didn't allow zero due to the lack of
distinction between "no value" and "zero" - cast functions read both
`nil` and zero as zero.

Now, the config allows a zero limit. Added tests.

Managing such cases should be easier after #1610.

Change-Id: Ifc840732390b2feb975f230573b34bf479406e05
Signed-off-by: Aleksey Savchuk <a.savchuk@yadro.com>

cmd/frostfs-node/config/rpc/config.go

@@ -31,12 +31,11 @@ func Limits(c *config.Config) []LimitConfig {
 			break
 		}
 
-		maxOps := config.IntSafe(sc, "max_ops")
-		if maxOps == 0 {
+		if sc.Value("max_ops") == nil {
 			panic("no max operations for method group")
 		}
 
-		limits = append(limits, LimitConfig{methods, maxOps})
+		limits = append(limits, LimitConfig{methods, config.IntSafe(sc, "max_ops")})
 	}
 
 	return limits

cmd/frostfs-node/config/rpc/config_test.go

@@ -38,7 +38,7 @@ func TestRPCSection(t *testing.T) {
 	})
 
 	t.Run("no max operations", func(t *testing.T) {
-		const path = "testdata/node"
+		const path = "testdata/no_max_ops"
 
 		fileConfigTest := func(c *config.Config) {
 			require.Panics(t, func() { _ = Limits(c) })
@@ -50,4 +50,28 @@ func TestRPCSection(t *testing.T) {
 			configtest.ForEnvFileType(t, path, fileConfigTest)
 		})
 	})
+
+	t.Run("zero max operations", func(t *testing.T) {
+		const path = "testdata/zero_max_ops"
+
+		fileConfigTest := func(c *config.Config) {
+			limits := Limits(c)
+			require.Len(t, limits, 2)
+
+			limit0 := limits[0]
+			limit1 := limits[1]
+
+			require.ElementsMatch(t, limit0.Methods, []string{"/neo.fs.v2.object.ObjectService/PutSingle", "/neo.fs.v2.object.ObjectService/Put"})
+			require.Equal(t, limit0.MaxOps, int64(0))
+
+			require.ElementsMatch(t, limit1.Methods, []string{"/neo.fs.v2.object.ObjectService/Get"})
+			require.Equal(t, limit1.MaxOps, int64(10000))
+		}
+
+		configtest.ForEachFileType(path, fileConfigTest)
+
+		t.Run("ENV", func(t *testing.T) {
+			configtest.ForEnvFileType(t, path, fileConfigTest)
+		})
+	})
 }

cmd/frostfs-node/config/rpc/testdata/zero_max_ops.env

@@ -0,0 +1,4 @@
+FROSTFS_RPC_LIMITS_0_METHODS="/neo.fs.v2.object.ObjectService/PutSingle /neo.fs.v2.object.ObjectService/Put"
+FROSTFS_RPC_LIMITS_0_MAX_OPS=0
+FROSTFS_RPC_LIMITS_1_METHODS="/neo.fs.v2.object.ObjectService/Get"
+FROSTFS_RPC_LIMITS_1_MAX_OPS=10000

cmd/frostfs-node/config/rpc/testdata/zero_max_ops.json

@@ -0,0 +1,19 @@
+{
+  "rpc": {
+    "limits": [
+      {
+        "methods": [
+          "/neo.fs.v2.object.ObjectService/PutSingle",
+          "/neo.fs.v2.object.ObjectService/Put"
+        ],
+        "max_ops": 0
+      },
+      {
+        "methods": [
+          "/neo.fs.v2.object.ObjectService/Get"
+        ],
+        "max_ops": 10000
+      }
+    ]
+  }
+}

cmd/frostfs-node/config/rpc/testdata/zero_max_ops.yaml

@@ -0,0 +1,9 @@
+rpc:
+  limits:
+    - methods:
+      - /neo.fs.v2.object.ObjectService/PutSingle
+      - /neo.fs.v2.object.ObjectService/Put
+      max_ops: 0
+    - methods:
+      - /neo.fs.v2.object.ObjectService/Get
+      max_ops: 10000