Adding dep files and dependencies.

vendor/github.com/samuel/go-zookeeper/zk/lock.go

@@ -0,0 +1,150 @@
+package zk
+
+import (
+	"errors"
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+var (
+	// ErrDeadlock is returned by Lock when trying to lock twice without unlocking first
+	ErrDeadlock = errors.New("zk: trying to acquire a lock twice")
+	// ErrNotLocked is returned by Unlock when trying to release a lock that has not first be acquired.
+	ErrNotLocked = errors.New("zk: not locked")
+)
+
+// Lock is a mutual exclusion lock.
+type Lock struct {
+	c        *Conn
+	path     string
+	acl      []ACL
+	lockPath string
+	seq      int
+}
+
+// NewLock creates a new lock instance using the provided connection, path, and acl.
+// The path must be a node that is only used by this lock. A lock instances starts
+// unlocked until Lock() is called.
+func NewLock(c *Conn, path string, acl []ACL) *Lock {
+	return &Lock{
+		c:    c,
+		path: path,
+		acl:  acl,
+	}
+}
+
+func parseSeq(path string) (int, error) {
+	parts := strings.Split(path, "-")
+	return strconv.Atoi(parts[len(parts)-1])
+}
+
+// Lock attempts to acquire the lock. It will wait to return until the lock
+// is acquired or an error occurs. If this instance already has the lock
+// then ErrDeadlock is returned.
+func (l *Lock) Lock() error {
+	if l.lockPath != "" {
+		return ErrDeadlock
+	}
+
+	prefix := fmt.Sprintf("%s/lock-", l.path)
+
+	path := ""
+	var err error
+	for i := 0; i < 3; i++ {
+		path, err = l.c.CreateProtectedEphemeralSequential(prefix, []byte{}, l.acl)
+		if err == ErrNoNode {
+			// Create parent node.
+			parts := strings.Split(l.path, "/")
+			pth := ""
+			for _, p := range parts[1:] {
+				var exists bool
+				pth += "/" + p
+				exists, _, err = l.c.Exists(pth)
+				if err != nil {
+					return err
+				}
+				if exists == true {
+					continue
+				}
+				_, err = l.c.Create(pth, []byte{}, 0, l.acl)
+				if err != nil && err != ErrNodeExists {
+					return err
+				}
+			}
+		} else if err == nil {
+			break
+		} else {
+			return err
+		}
+	}
+	if err != nil {
+		return err
+	}
+
+	seq, err := parseSeq(path)
+	if err != nil {
+		return err
+	}
+
+	for {
+		children, _, err := l.c.Children(l.path)
+		if err != nil {
+			return err
+		}
+
+		lowestSeq := seq
+		prevSeq := -1
+		prevSeqPath := ""
+		for _, p := range children {
+			s, err := parseSeq(p)
+			if err != nil {
+				return err
+			}
+			if s < lowestSeq {
+				lowestSeq = s
+			}
+			if s < seq && s > prevSeq {
+				prevSeq = s
+				prevSeqPath = p
+			}
+		}
+
+		if seq == lowestSeq {
+			// Acquired the lock
+			break
+		}
+
+		// Wait on the node next in line for the lock
+		_, _, ch, err := l.c.GetW(l.path + "/" + prevSeqPath)
+		if err != nil && err != ErrNoNode {
+			return err
+		} else if err != nil && err == ErrNoNode {
+			// try again
+			continue
+		}
+
+		ev := <-ch
+		if ev.Err != nil {
+			return ev.Err
+		}
+	}
+
+	l.seq = seq
+	l.lockPath = path
+	return nil
+}
+
+// Unlock releases an acquired lock. If the lock is not currently acquired by
+// this Lock instance than ErrNotLocked is returned.
+func (l *Lock) Unlock() error {
+	if l.lockPath == "" {
+		return ErrNotLocked
+	}
+	if err := l.c.Delete(l.lockPath, -1); err != nil {
+		return err
+	}
+	l.lockPath = ""
+	l.seq = 0
+	return nil
+}