consul/state: add CAS method for kv set

This commit is contained in:
Ryan Uber 2015-09-02 13:27:49 -07:00 committed by James Phillips
parent 8a70ba2cc5
commit a0dc2ded8d
2 changed files with 106 additions and 0 deletions

View File

@ -848,3 +848,34 @@ func (s *StateStore) KVSDeleteCAS(idx, cidx uint64, key string) (bool, error) {
tx.Commit()
return true, nil
}
// KVSSetCAS is used to do a check-and-set operation on a KV entry. The
// ModifyIndex in the provided entry is used to determine if we should
// write the entry to the state store or bail. Returns a bool indicating
// if a write happened and any error.
func (s *StateStore) KVSSetCAS(idx uint64, entry *structs.DirEntry) (bool, error) {
tx := s.db.Txn(true)
defer tx.Abort()
// Retrieve the existing entry
existing, err := tx.First("kvs", "id", entry.Key)
if err != nil {
return false, fmt.Errorf("failed kvs lookup: %s", err)
}
// Check if the we should do the set. A ModifyIndex of 0 means that
// we are doing a set-if-not-exists.
if entry.ModifyIndex == 0 && existing != nil {
return false, nil
}
if entry.ModifyIndex != 0 && existing == nil {
return false, nil
}
e, ok := existing.(*structs.DirEntry)
if ok && entry.ModifyIndex != 0 && entry.ModifyIndex != e.ModifyIndex {
return false, nil
}
// If we made it this far, we should perform the set.
return true, s.kvsSetTxn(idx, entry, tx)
}

View File

@ -986,3 +986,78 @@ func TestStateStore_KVSDeleteCAS(t *testing.T) {
t.Fatalf("entry should be deleted")
}
}
func TestStateStore_KVSSetCAS(t *testing.T) {
s := testStateStore(t)
// Doing a CAS with ModifyIndex != 0 and no existing entry
// is a no-op.
entry := &structs.DirEntry{
Key: "foo",
Value: []byte("foo"),
RaftIndex: structs.RaftIndex{
CreateIndex: 1,
ModifyIndex: 1,
},
}
ok, err := s.KVSSetCAS(2, entry)
if ok || err != nil {
t.Fatalf("expected (false, nil), got: (%#v, %#v)", ok, err)
}
// Check that nothing was actually stored
tx := s.db.Txn(false)
if e, err := tx.First("kvs", "id", "foo"); e != nil || err != nil {
t.Fatalf("expected (nil, nil), got: (%#v, %#v)", e, err)
}
tx.Abort()
// Doing a CAS with a ModifyIndex of zero when no entry exists
// performs the set and saves into the state store.
entry = &structs.DirEntry{
Key: "foo",
Value: []byte("foo"),
RaftIndex: structs.RaftIndex{
CreateIndex: 0,
ModifyIndex: 0,
},
}
ok, err = s.KVSSetCAS(2, entry)
if !ok || err != nil {
t.Fatalf("expected (true, nil), got: (%#v, %#v)", ok, err)
}
// Entry was inserted
tx = s.db.Txn(false)
if e, err := tx.First("kvs", "id", "foo"); e == nil || err != nil {
t.Fatalf("expected kvs to exist, got: (%#v, %#v)", e, err)
}
tx.Abort()
// Doing a CAS with a ModifyIndex which does not match the current
// index does not do anything.
entry = &structs.DirEntry{
Key: "foo",
Value: []byte("bar"),
RaftIndex: structs.RaftIndex{
CreateIndex: 3,
ModifyIndex: 3,
},
}
ok, err = s.KVSSetCAS(3, entry)
if ok || err != nil {
t.Fatalf("expected (false, nil), got: (%#v, %#v)", ok, err)
}
// Entry was not updated in the store
tx = s.db.Txn(false)
e, err := tx.First("kvs", "id", "foo")
if err != nil {
t.Fatalf("err: %s", err)
}
result, ok := e.(*structs.DirEntry)
if !ok || result.CreateIndex != 2 ||
result.ModifyIndex != 2 || string(result.Value) != "foo" {
t.Fatalf("bad: %#v", result)
}
}