// kvsUnlockTxn is the inner method that does an unlock inside an existing
// transaction.
func (s *StateStore) kvsUnlockTxn(tx *memdb.Txn, idx uint64, entry *structs.DirEntry) (bool, error) {
// Verify that a session is present.
if entry.Session == "" {
return false, fmt.Errorf("missing session")
}
// Retrieve the existing entry.
existing, err := tx.First("kvs", "id", entry.Key)
if err != nil {
return false, fmt.Errorf("failed kvs lookup: %s", err)
}
// Bail if there's no existing key.
if existing == nil {
return false, nil
}
// Make sure the given session is the lock holder.
e := existing.(*structs.DirEntry)
if e.Session != entry.Session {
return false, nil
}
// Clear the lock and update the entry.
entry.Session = ""
entry.LockIndex = e.LockIndex
entry.CreateIndex = e.CreateIndex
entry.ModifyIndex = idx
// If we made it this far, we should perform the set.
if err := s.kvsSetTxn(tx, idx, entry, true); err != nil {
return false, err
}
return true, nil
}
// kvsSetTxn is used to insert or update a key/value pair in the state
// store. It is the inner method used and handles only the actual storage.
// If updateSession is true, then the incoming entry will set the new
// session (should be validated before calling this). Otherwise, we will keep
// whatever the existing session is.
func (s *StateStore) kvsSetTxn(tx *memdb.Txn, idx uint64, entry *structs.DirEntry, updateSession bool) error {
// Retrieve an existing KV pair
existing, err := tx.First("kvs", "id", entry.Key)
if err != nil {
return fmt.Errorf("failed kvs lookup: %s", err)
}
// Set the indexes.
if existing != nil {
entry.CreateIndex = existing.(*structs.DirEntry).CreateIndex
} else {
entry.CreateIndex = idx
}
entry.ModifyIndex = idx
// Preserve the existing session unless told otherwise. The "existing"
// session for a new entry is "no session".
if !updateSession {
if existing != nil {
entry.Session = existing.(*structs.DirEntry).Session
} else {
entry.Session = ""
}
}
// Store the kv pair in the state store and update the index.
if err := tx.Insert("kvs", entry); err != nil {
return fmt.Errorf("failed inserting kvs entry: %s", err)
}
if err := tx.Insert("index", &IndexEntry{"kvs", idx}); err != nil {
return fmt.Errorf("failed updating index: %s", err)
}
tx.Defer(func() { s.kvsWatch.Notify(entry.Key, false) })
return nil
}
// kvsSet is the internal setter
func (s *StateStore) kvsSet(
index uint64,
d *structs.DirEntry,
mode kvMode) (bool, error) {
// Start a new txn
tx, err := s.tables.StartTxn(false)
if err != nil {
return false, err
}
defer tx.Abort()
// Get the existing node
res, err := s.kvsTable.GetTxn(tx, "id", d.Key)
if err != nil {
return false, err
}
// Get the existing node if any
var exist *structs.DirEntry
if len(res) > 0 {
exist = res[0].(*structs.DirEntry)
}
// Use the ModifyIndex as the constraint. A modify of time of 0
// means we are doing a set-if-not-exists, while any other value
// means we expect that modify time.
if mode == kvCAS {
if d.ModifyIndex == 0 && exist != nil {
return false, nil
} else if d.ModifyIndex > 0 && (exist == nil || exist.ModifyIndex != d.ModifyIndex) {
return false, nil
}
}
// If attempting to lock, check this is possible
if mode == kvLock {
// Verify we have a session
if d.Session == "" {
return false, fmt.Errorf("Missing session")
}
// Bail if it is already locked
if exist != nil && exist.Session != "" {
return false, nil
}
// Verify the session exists
res, err := s.sessionTable.GetTxn(tx, "id", d.Session)
if err != nil {
return false, err
}
if len(res) == 0 {
return false, fmt.Errorf("Invalid session")
}
// Update the lock index
if exist != nil {
exist.LockIndex++
exist.Session = d.Session
} else {
d.LockIndex = 1
}
}
// If attempting to unlock, verify the key exists and is held
if mode == kvUnlock {
if exist == nil || exist.Session != d.Session {
return false, nil
}
// Clear the session to unlock
exist.Session = ""
}
// Set the create and modify times
if exist == nil {
d.CreateIndex = index
} else {
d.CreateIndex = exist.CreateIndex
d.LockIndex = exist.LockIndex
d.Session = exist.Session
}
d.ModifyIndex = index
if err := s.kvsTable.InsertTxn(tx, d); err != nil {
return false, err
}
if err := s.kvsTable.SetLastIndexTxn(tx, index); err != nil {
return false, err
}
tx.Defer(func() { s.watch[s.kvsTable].Notify() })
return true, tx.Commit()
}