Add bucket metadata state client/handler (Fixes #3022) (#3152)

- Adds an interface to update in-memory bucket metadata state called
  BucketMetaState - this interface has functions to:
     - update bucket notification configuration,
     - bucket listener configuration,
     - bucket policy configuration, and
     - send bucket event

- This interface is implemented by `localBMS` a type for manipulating
  local node in-memory bucket metadata, and by `remoteBMS` a type for
  manipulating remote node in-memory bucket metadata.

- The remote node interface, makes an RPC call, but the local node
  interface does not - it updates in-memory bucket state directly.

- Rename mkPeersFromEndpoints to makeS3Peers and refactored it.

- Use arrayslice instead of map in s3Peers struct

- `s3Peers.SendUpdate` now receives an arrayslice of peer indexes to
  send the request to, with a special nil value slice indicating that
  all peers should be sent the update.

- `s3Peers.SendUpdate` now returns an arrayslice of errors, representing
  errors from peers when sending an update. The array positions
  correspond to peer array s3Peers.peers

Improve globalS3Peers:

- Make isDistXL a global `globalIsDistXL` and remove from s3Peers

- Make globalS3Peers an array of (address, bucket-meta-state) pairs.

- Fix code and tests.

cmd/bucket-metadata.go

@@ -0,0 +1,152 @@
+/*
+ * Minio Cloud Storage, (C) 2014-2016 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 (
+	"encoding/json"
+	"net/rpc"
+)
+
+// BucketMetaState - Interface to update bucket metadata in-memory
+// state.
+type BucketMetaState interface {
+	// Updates bucket notification
+	UpdateBucketNotification(args *SetBNPArgs) error
+
+	// Updates bucket listener
+	UpdateBucketListener(args *SetBLPArgs) error
+
+	// Updates bucket policy
+	UpdateBucketPolicy(args *SetBPPArgs) error
+
+	// Sends event
+	SendEvent(args *EventArgs) error
+}
+
+// Type that implements BucketMetaState for local node.
+type localBMS struct {
+	ObjectAPI func() ObjectLayer
+}
+
+// localBMS.UpdateBucketNotification - updates in-memory global bucket
+// notification info.
+func (lc *localBMS) UpdateBucketNotification(args *SetBNPArgs) error {
+	// check if object layer is available.
+	objAPI := lc.ObjectAPI()
+	if objAPI == nil {
+		return errServerNotInitialized
+	}
+
+	globalEventNotifier.SetBucketNotificationConfig(args.Bucket, args.NCfg)
+
+	return nil
+}
+
+// localBMS.UpdateBucketListener - updates in-memory global bucket
+// listeners info.
+func (lc *localBMS) UpdateBucketListener(args *SetBLPArgs) error {
+	// check if object layer is available.
+	objAPI := lc.ObjectAPI()
+	if objAPI == nil {
+		return errServerNotInitialized
+	}
+
+	// Update in-memory notification config.
+	return globalEventNotifier.SetBucketListenerConfig(args.Bucket, args.LCfg)
+}
+
+// localBMS.UpdateBucketPolicy - updates in-memory global bucket
+// policy info.
+func (lc *localBMS) UpdateBucketPolicy(args *SetBPPArgs) error {
+	// check if object layer is available.
+	objAPI := lc.ObjectAPI()
+	if objAPI == nil {
+		return errServerNotInitialized
+	}
+
+	var pCh policyChange
+	if err := json.Unmarshal(args.PChBytes, &pCh); err != nil {
+		return err
+	}
+
+	return globalBucketPolicies.SetBucketPolicy(args.Bucket, pCh)
+}
+
+// localBMS.SendEvent - sends event to local event notifier via
+// `globalEventNotifier`
+func (lc *localBMS) SendEvent(args *EventArgs) error {
+	// check if object layer is available.
+	objAPI := lc.ObjectAPI()
+	if objAPI == nil {
+		return errServerNotInitialized
+	}
+
+	return globalEventNotifier.SendListenerEvent(args.Arn, args.Event)
+}
+
+// Type that implements BucketMetaState for remote node.
+type remoteBMS struct {
+	*AuthRPCClient
+}
+
+// remoteBMS.UpdateBucketNotification - sends bucket notification
+// change to remote peer via RPC call.
+func (rc *remoteBMS) UpdateBucketNotification(args *SetBNPArgs) error {
+	reply := GenericReply{}
+	err := rc.Call("S3.SetBucketNotificationPeer", args, &reply)
+	// Check for network error and retry once.
+	if err != nil && err.Error() == rpc.ErrShutdown.Error() {
+		err = rc.Call("S3.SetBucketNotificationPeer", args, &reply)
+	}
+	return err
+}
+
+// remoteBMS.UpdateBucketListener - sends bucket listener change to
+// remote peer via RPC call.
+func (rc *remoteBMS) UpdateBucketListener(args *SetBLPArgs) error {
+	reply := GenericReply{}
+	err := rc.Call("S3.SetBucketListenerPeer", args, &reply)
+	// Check for network error and retry once.
+	if err != nil && err.Error() == rpc.ErrShutdown.Error() {
+		err = rc.Call("S3.SetBucketListenerPeer", args, &reply)
+	}
+	return err
+}
+
+// remoteBMS.UpdateBucketPolicy - sends bucket policy change to remote
+// peer via RPC call.
+func (rc *remoteBMS) UpdateBucketPolicy(args *SetBPPArgs) error {
+	reply := GenericReply{}
+	err := rc.Call("S3.SetBucketPolicyPeer", args, &reply)
+	// Check for network error and retry once.
+	if err != nil && err.Error() == rpc.ErrShutdown.Error() {
+		err = rc.Call("S3.SetBucketPolicyPeer", args, &reply)
+	}
+	return err
+}
+
+// remoteBMS.SendEvent - sends event for bucket listener to remote
+// peer via RPC call.
+func (rc *remoteBMS) SendEvent(args *EventArgs) error {
+	reply := GenericReply{}
+	err := rc.Call("S3.Event", args, &reply)
+	// Check for network error and retry once.
+	if err != nil && err.Error() == rpc.ErrShutdown.Error() {
+		err = rc.Call("S3.Event", args, &reply)
+	}
+	return err
+}