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[bytom/vapor.git] / vendor / github.com / golang / groupcache / peers.go

diff --git a/vendor/github.com/golang/groupcache/peers.go b/vendor/github.com/golang/groupcache/peers.go
new file mode 100644 (file)
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--- /dev/null
+++ b/vendor/github.com/golang/groupcache/peers.go
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+/*
+Copyright 2012 Google 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.
+*/
+
+// peers.go defines how processes find and communicate with their peers.
+
+package groupcache
+
+import (
+       pb "github.com/golang/groupcache/groupcachepb"
+)
+
+// Context is an opaque value passed through calls to the
+// ProtoGetter. It may be nil if your ProtoGetter implementation does
+// not require a context.
+type Context interface{}
+
+// ProtoGetter is the interface that must be implemented by a peer.
+type ProtoGetter interface {
+       Get(context Context, in *pb.GetRequest, out *pb.GetResponse) error
+}
+
+// PeerPicker is the interface that must be implemented to locate
+// the peer that owns a specific key.
+type PeerPicker interface {
+       // PickPeer returns the peer that owns the specific key
+       // and true to indicate that a remote peer was nominated.
+       // It returns nil, false if the key owner is the current peer.
+       PickPeer(key string) (peer ProtoGetter, ok bool)
+}
+
+// NoPeers is an implementation of PeerPicker that never finds a peer.
+type NoPeers struct{}
+
+func (NoPeers) PickPeer(key string) (peer ProtoGetter, ok bool) { return }
+
+var (
+       portPicker func(groupName string) PeerPicker
+)
+
+// RegisterPeerPicker registers the peer initialization function.
+// It is called once, when the first group is created.
+// Either RegisterPeerPicker or RegisterPerGroupPeerPicker should be
+// called exactly once, but not both.
+func RegisterPeerPicker(fn func() PeerPicker) {
+       if portPicker != nil {
+               panic("RegisterPeerPicker called more than once")
+       }
+       portPicker = func(_ string) PeerPicker { return fn() }
+}
+
+// RegisterPerGroupPeerPicker registers the peer initialization function,
+// which takes the groupName, to be used in choosing a PeerPicker.
+// It is called once, when the first group is created.
+// Either RegisterPeerPicker or RegisterPerGroupPeerPicker should be
+// called exactly once, but not both.
+func RegisterPerGroupPeerPicker(fn func(groupName string) PeerPicker) {
+       if portPicker != nil {
+               panic("RegisterPeerPicker called more than once")
+       }
+       portPicker = fn
+}
+
+func getPeers(groupName string) PeerPicker {
+       if portPicker == nil {
+               return NoPeers{}
+       }
+       pk := portPicker(groupName)
+       if pk == nil {
+               pk = NoPeers{}
+       }
+       return pk
+}