// deleteRevKey deletes a key by revision, returning false if key is missing
func deleteRevKey(kv v3.KV, key string, rev int64) (bool, error) {
cmp := v3.Compare(v3.ModRevision(key), "=", rev)
req := v3.OpDelete(key)
txnresp, err := kv.Txn(context.TODO()).If(cmp).Then(req).Commit()
if err != nil {
return false, err
} else if !txnresp.Succeeded {
return false, nil
}
return true, nil
}
// putNewKV attempts to create the given key, only succeeding if the key did
// not yet exist.
func putNewKV(kv v3.KV, key, val string, leaseID v3.LeaseID) (int64, error) {
cmp := v3.Compare(v3.Version(key), "=", 0)
req := v3.OpPut(key, val, v3.WithLease(leaseID))
txnresp, err := kv.Txn(context.TODO()).If(cmp).Then(req).Commit()
if err != nil {
return 0, err
}
if !txnresp.Succeeded {
return 0, ErrKeyExists
}
return txnresp.Header.Revision, nil
}
func NewUniqueKV(ctx context.Context, kv v3.KV, pfx, val string, opts ...v3.OpOption) (string, int64, error) {
for {
newKey := fmt.Sprintf("%s/%v", pfx, time.Now().UnixNano())
put := v3.OpPut(newKey, val, opts...)
cmp := v3.Compare(v3.ModifiedRevision(newKey), "=", 0)
resp, err := kv.Txn(ctx).If(cmp).Then(put).Commit()
if err != nil {
return "", 0, err
}
if !resp.Succeeded {
continue
}
return newKey, resp.Header.Revision, nil
}
}
func cas(key, value, newValue string, kvc clientv3.KV) error {
ctx, cancel := context.WithTimeout(context.Background(), requestTimeout)
tnxRes, err := kvc.Txn(ctx).
If(clientv3.Compare(clientv3.Value(key), "=", value)).
Then(clientv3.OpPut(key, newValue)).
Else(clientv3.OpGet(key)).
Commit()
cancel()
if err != nil {
return err
}
if tnxRes.Succeeded {
return nil
}
log.Println(string(tnxRes.Responses[0].GetResponseRange().Kvs[0].Value))
return errors.New("release error")
}
// newSequentialKV allocates a new sequential key <prefix>/nnnnn with a given
// value and lease. Note: a bookkeeping node __<prefix> is also allocated.
func newSequentialKV(kv v3.KV, prefix, val string, leaseID v3.LeaseID) (*RemoteKV, error) {
resp, err := kv.Get(context.TODO(), prefix, v3.WithLastKey()...)
if err != nil {
return nil, err
}
// add 1 to last key, if any
newSeqNum := 0
if len(resp.Kvs) != 0 {
fields := strings.Split(string(resp.Kvs[0].Key), "/")
_, serr := fmt.Sscanf(fields[len(fields)-1], "%d", &newSeqNum)
if serr != nil {
return nil, serr
}
newSeqNum++
}
newKey := fmt.Sprintf("%s/%016d", prefix, newSeqNum)
// base prefix key must be current (i.e., <=) with the server update;
// the base key is important to avoid the following:
// N1: LastKey() == 1, start txn.
// N2: New Key 2, New Key 3, Delete Key 2
// N1: txn succeeds allocating key 2 when it shouldn't
baseKey := "__" + prefix
// current revision might contain modification so +1
cmp := v3.Compare(v3.ModRevision(baseKey), "<", resp.Header.Revision+1)
reqPrefix := v3.OpPut(baseKey, "", v3.WithLease(leaseID))
reqNewKey := v3.OpPut(newKey, val, v3.WithLease(leaseID))
txn := kv.Txn(context.TODO())
txnresp, err := txn.If(cmp).Then(reqPrefix, reqNewKey).Commit()
if err != nil {
return nil, err
}
if !txnresp.Succeeded {
return newSequentialKV(kv, prefix, val, leaseID)
}
return &RemoteKV{kv, newKey, txnresp.Header.Revision, val}, nil
}