Add InfluxDB support for traefik metrics

vendor/github.com/influxdata/influxdb/node.go

@@ -0,0 +1,121 @@
+package influxdb
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strconv"
+)
+
+const (
+	nodeFile      = "node.json"
+	oldNodeFile   = "id"
+	peersFilename = "peers.json"
+)
+
+type Node struct {
+	path string
+	ID   uint64
+}
+
+// LoadNode will load the node information from disk if present
+func LoadNode(path string) (*Node, error) {
+	// Always check to see if we are upgrading first
+	if err := upgradeNodeFile(path); err != nil {
+		return nil, err
+	}
+
+	n := &Node{
+		path: path,
+	}
+
+	f, err := os.Open(filepath.Join(path, nodeFile))
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	if err := json.NewDecoder(f).Decode(n); err != nil {
+		return nil, err
+	}
+
+	return n, nil
+}
+
+// NewNode will return a new node
+func NewNode(path string) *Node {
+	return &Node{
+		path: path,
+	}
+}
+
+// Save will save the node file to disk and replace the existing one if present
+func (n *Node) Save() error {
+	file := filepath.Join(n.path, nodeFile)
+	tmpFile := file + "tmp"
+
+	f, err := os.Create(tmpFile)
+	if err != nil {
+		return err
+	}
+
+	if err = json.NewEncoder(f).Encode(n); err != nil {
+		f.Close()
+		return err
+	}
+
+	if err = f.Close(); nil != err {
+		return err
+	}
+
+	return os.Rename(tmpFile, file)
+}
+
+func upgradeNodeFile(path string) error {
+	oldFile := filepath.Join(path, oldNodeFile)
+	b, err := ioutil.ReadFile(oldFile)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil
+		}
+		return err
+	}
+	// We shouldn't have an empty ID file, but if we do, ignore it
+	if len(b) == 0 {
+		return nil
+	}
+
+	peers := []string{}
+	pb, err := ioutil.ReadFile(filepath.Join(path, peersFilename))
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil
+		}
+		return err
+	}
+
+	err = json.Unmarshal(pb, &peers)
+	if err != nil {
+		return err
+	}
+
+	if len(peers) > 1 {
+		return fmt.Errorf("to upgrade a cluster, please contact support at influxdata")
+	}
+
+	n := &Node{
+		path: path,
+	}
+	if n.ID, err = strconv.ParseUint(string(b), 10, 64); err != nil {
+		return err
+	}
+	if err := n.Save(); err != nil {
+		return err
+	}
+	if err := os.Remove(oldFile); err != nil {
+		return err
+	}
+	return nil
+}