auth/rpc: Take remote disk offline after maximum allowed attempts. (#3288)

Disks when are offline for a long period of time, we should
ignore the disk after trying Login upto 5 times.

This is to reduce the network chattiness, this also reduces
the overall time spent on `net.Dial`.

Fixes #3286

cmd/auth-rpc-client_test.go

@@ -0,0 +1,51 @@
+/*
+ * Minio Cloud Storage, (C) 2016 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package cmd
+
+import "testing"
+
+// Tests authorized RPC client.
+func TestAuthRPCClient(t *testing.T) {
+	authCfg := &authConfig{
+		accessKey:   "123",
+		secretKey:   "123",
+		secureConn:  false,
+		address:     "localhost:9000",
+		path:        "/rpc/disk",
+		loginMethod: "MyPackage.LoginHandler",
+	}
+	authRPC := newAuthClient(authCfg)
+	if authRPC.Node() != authCfg.address {
+		t.Fatalf("Unexpected node value %s, but expected %s", authRPC.Node(), authCfg.address)
+	}
+	if authRPC.RPCPath() != authCfg.path {
+		t.Fatalf("Unexpected node value %s, but expected %s", authRPC.RPCPath(), authCfg.path)
+	}
+	authCfg = &authConfig{
+		accessKey:   "123",
+		secretKey:   "123",
+		secureConn:  false,
+		loginMethod: "MyPackage.LoginHandler",
+	}
+	authRPC = newAuthClient(authCfg)
+	if authRPC.Node() != authCfg.address {
+		t.Fatalf("Unexpected node value %s, but expected %s", authRPC.Node(), authCfg.address)
+	}
+	if authRPC.RPCPath() != authCfg.path {
+		t.Fatalf("Unexpected node value %s, but expected %s", authRPC.RPCPath(), authCfg.path)
+	}
+}