func parseCompare(line string) (*clientv3.Cmp, error) {
var (
key string
op string
val string
)
lparenSplit := strings.SplitN(line, "(", 2)
if len(lparenSplit) != 2 {
return nil, fmt.Errorf("malformed comparison: %s", line)
}
target := lparenSplit[0]
n, serr := fmt.Sscanf(lparenSplit[1], "%q) %s %q", &key, &op, &val)
if n != 3 {
return nil, fmt.Errorf("malformed comparison: %s; got %s(%q) %s %q", line, target, key, op, val)
}
if serr != nil {
return nil, fmt.Errorf("malformed comparison: %s (%v)", line, serr)
}
var (
v int64
err error
cmp clientv3.Cmp
)
switch target {
case "ver", "version":
if v, err = strconv.ParseInt(val, 10, 64); err == nil {
cmp = clientv3.Compare(clientv3.Version(key), op, v)
}
case "c", "create":
if v, err = strconv.ParseInt(val, 10, 64); err == nil {
cmp = clientv3.Compare(clientv3.CreatedRevision(key), op, v)
}
case "m", "mod":
if v, err = strconv.ParseInt(val, 10, 64); err == nil {
cmp = clientv3.Compare(clientv3.ModifiedRevision(key), op, v)
}
case "val", "value":
cmp = clientv3.Compare(clientv3.Value(key), op, val)
default:
return nil, fmt.Errorf("malformed comparison: %s (unknown target %s)", line, target)
}
if err != nil {
return nil, fmt.Errorf("invalid txn compare request: %s", line)
}
return &cmp, nil
}
// Proclaim lets the leader announce a new value without another election.
func (e *Election) Proclaim(ctx context.Context, val string) error {
if e.leaderSession == nil {
return ErrElectionNotLeader
}
cmp := v3.Compare(v3.CreatedRevision(e.leaderKey), "=", e.leaderRev)
txn := e.client.Txn(ctx).If(cmp)
txn = txn.Then(v3.OpPut(e.leaderKey, val, v3.WithLease(e.leaderSession.Lease())))
tresp, terr := txn.Commit()
if terr != nil {
return terr
}
if !tresp.Succeeded {
e.leaderKey = ""
return ErrElectionNotLeader
}
return nil
}
func (m *Mutex) IsOwner() v3.Cmp {
return v3.Compare(v3.CreatedRevision(m.myKey), "=", m.myRev)
}