feature: define the interface SupernodeLocator

Signed-off-by: lowzj <[email protected]>

dfget/core/locator/locator.go

@@ -0,0 +1,65 @@
+/*
+ * Copyright The Dragonfly Authors.
+ *
+ * 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 locator
+
+// SupernodeLocator defines the way how to get available supernodes.
+// Developers can implement their own locator more flexibly , not just get the
+// supernode list from configuration or CLI.
+type SupernodeLocator interface {
+	// Get returns the current selected supernode, it should be idempotent.
+	Get() *Supernode
+
+	// Next chooses the next available supernode for retrying or other
+	// purpose. The current supernode should be set as this result.
+	Next() *Supernode
+
+	// GetGroup returns the group.
+	GetGroup(name string) *SupernodeGroup
+
+	// All returns all the supernodes.
+	All() []*SupernodeGroup
+
+	// Report records the metrics of the current supernode in order to choose a
+	// more appropriate supernode for the next time if necessary.
+	Report(ip string, metrics *SupernodeMetrics)
+
+	// Refresh refreshes all the supernodes.
+	Refresh() bool
+}
+
+// SupernodeGroup groups supernodes which has same attributes.
+type SupernodeGroup struct {
+	Name  string
+	Nodes []*Supernode
+
+	// Infos stores other information that user can customized.
+	Infos map[string]string
+}
+
+// Supernode basic information of supernodes.
+type Supernode struct {
+	Schema  string
+	IP      string
+	Port    int
+	Weight  int
+	Metrics *SupernodeMetrics
+}
+
+// SupernodeMetrics the metrics used for locator to choose supernode.
+type SupernodeMetrics struct {
+	Metrics map[string]interface{}
+}

dfget/core/locator/static_locator.go

@@ -0,0 +1,76 @@
+/*
+ * Copyright The Dragonfly Authors.
+ *
+ * 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 locator
+
+import (
+	"go.uber.org/atomic"
+)
+
+type StaticLocator struct {
+	idx   atomic.Int32
+	Group *SupernodeGroup
+}
+
+// NewStaticLocator constructs StaticLocator which uses the nodes passed from
+// configuration or CLI.
+func NewStaticLocator(nodes []string) *StaticLocator {
+	// TODO: initialize Group
+	return &StaticLocator{}
+}
+
+func (s *StaticLocator) Get() *Supernode {
+	if s.Group == nil {
+		return nil
+	}
+	idx := int(s.idx.Load())
+	if idx >= len(s.Group.Nodes) {
+		return nil
+	}
+	return s.Group.Nodes[idx]
+}
+
+func (s *StaticLocator) Next() *Supernode {
+	if s.Group == nil || int(s.idx.Load()) >= len(s.Group.Nodes) {
+		return nil
+	}
+	idx := int(s.idx.Inc())
+	if idx >= len(s.Group.Nodes) {
+		return nil
+	}
+	return s.Group.Nodes[idx]
+}
+
+func (s *StaticLocator) GetGroup(name string) *SupernodeGroup {
+	return s.Group
+}
+
+func (s *StaticLocator) All() []*SupernodeGroup {
+	if s.Group == nil {
+		return []*SupernodeGroup{}
+	}
+	return []*SupernodeGroup{s.Group}
+}
+
+func (s *StaticLocator) Report(ip string, metrics *SupernodeMetrics) {
+	// unnecessary to implement this method
+	return
+}
+
+func (s *StaticLocator) Refresh() bool {
+	s.idx.Store(0)
+	return true
+}