feature: define the interface SupernodeLocator

dfget/config/constants.go

@@ -120,7 +120,8 @@ const (
 	ServerAliveTime        = 5 * time.Minute
 	DefaultDownloadTimeout = 5 * time.Minute
 
-	DefaultSupernodePort = 8002
+	DefaultSupernodeSchema = "http"
+	DefaultSupernodePort   = 8002
 )
 
 /* errors code */

dfget/locator/locator.go

@@ -0,0 +1,77 @@
+/*
+ * 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 with the giving name.
+	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(node string, metrics *SupernodeMetrics)
+
+	// Refresh refreshes all the supernodes.
+	Refresh() bool
+}
+
+// SupernodeGroup groups supernodes which have same attributes.
+// For example, we can group supernodes by region, business, version and so on.
+// The implementation of SupernodeLocator can select a supernode based on the
+// group.
+type SupernodeGroup struct {
+	Name  string
+	Nodes []*Supernode
+
+	// Infos stores other information that user can customized.
+	Infos map[string]string
+}
+
+// GetNode return the node with the giving index.
+func (sg *SupernodeGroup) GetNode(idx int) *Supernode {
+	if idx < 0 || idx >= len(sg.Nodes) {
+		return nil
+	}
+	return sg.Nodes[idx]
+}
+
+// Supernode holds the basic information of supernodes.
+type Supernode struct {
+	Schema    string
+	IP        string
+	Port      int
+	Weight    int
+	GroupName string
+	Metrics   *SupernodeMetrics
+}
+
+// SupernodeMetrics holds metrics used for the locator to choose supernode.
+type SupernodeMetrics struct {
+	Metrics map[string]interface{}
+}

dfget/locator/static_locator.go

@@ -0,0 +1,147 @@
+/*
+ * 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 (
+	"math/rand"
+	"sync/atomic"
+	"time"
+
+	"github.com/dragonflyoss/Dragonfly/dfget/config"
+	"github.com/dragonflyoss/Dragonfly/pkg/algorithm"
+	"github.com/dragonflyoss/Dragonfly/pkg/netutils"
+)
+
+func init() {
+	rand.Seed(time.Now().UnixNano())
+}
+
+const staticLocatorGroupName = "config"
+
+// StaticLocator uses the nodes passed from configuration or CLI.
+type StaticLocator struct {
+	idx   int32
+	Group *SupernodeGroup
+}
+
+// ----------------------------------------------------------------------------
+// constructors
+
+// NewStaticLocator constructs StaticLocator which uses the nodes passed from
+// configuration or CLI.
+func NewStaticLocator(nodes []*config.NodeWeight) *StaticLocator {
+	locator := &StaticLocator{}
+	if len(nodes) == 0 {
+		return locator
+	}
+	group := &SupernodeGroup{
+		Name: staticLocatorGroupName,
+	}
+	for _, node := range nodes {
+		ip, port := netutils.GetIPAndPortFromNode(node.Node, config.DefaultSupernodePort)
+		if ip == "" {
+			continue
+		}
+		supernode := &Supernode{
+			Schema:    config.DefaultSupernodeSchema,
+			IP:        ip,
+			Port:      port,
+			Weight:    node.Weight,
+			GroupName: staticLocatorGroupName,
+		}
+		for i := 0; i < supernode.Weight; i++ {
+			group.Nodes = append(group.Nodes, supernode)
+		}
+	}
+	shuffleNodes(group.Nodes)
+	locator.Group = group
+	return locator
+}
+
+// NewStaticLocatorFromStr constructs StaticLocator from string list.
+// The format of nodes is: ip:port=weight
+func NewStaticLocatorFromStr(nodes []string) (*StaticLocator, error) {
+	nodeWeight, err := config.ParseNodesSlice(nodes)
+	if err != nil {
+		return nil, err
+	}
+	return NewStaticLocator(nodeWeight), nil
+}
+
+// ----------------------------------------------------------------------------
+// implement api methods
+
+func (s *StaticLocator) Get() *Supernode {
+	if s.Group == nil {
+		return nil
+	}
+	return s.Group.GetNode(s.load())
+}
+
+func (s *StaticLocator) Next() *Supernode {
+	if s.Group == nil || s.load() >= len(s.Group.Nodes) {
+		return nil
+	}
+	return s.Group.GetNode(s.inc())
+}
+
+func (s *StaticLocator) GetGroup(name string) *SupernodeGroup {
+	if s.Group == nil || s.Group.Name != name {
+		return nil
+	}
+	return s.Group
+}
+
+func (s *StaticLocator) All() []*SupernodeGroup {
+	if s.Group == nil {
+		return nil
+	}
+	return []*SupernodeGroup{s.Group}
+}
+
+func (s *StaticLocator) Report(node string, metrics *SupernodeMetrics) {
+	// unnecessary to implement this method
+	return
+}
+
+func (s *StaticLocator) Refresh() bool {
+	atomic.StoreInt32(&s.idx, 0)
+	return true
+}
+
+// ----------------------------------------------------------------------------
+// private methods of StaticLocator
+
+func (s *StaticLocator) load() int {
+	return int(atomic.LoadInt32(&s.idx))
+}
+
+func (s *StaticLocator) inc() int {
+	return int(atomic.AddInt32(&s.idx, 1))
+}
+
+// ----------------------------------------------------------------------------
+// helper functions
+
+func shuffleNodes(nodes []*Supernode) []*Supernode {
+	if length := len(nodes); length > 1 {
+		algorithm.Shuffle(length, func(i, j int) {
+			nodes[i], nodes[j] = nodes[j], nodes[i]
+		})
+	}
+	return nodes
+}