Client

Spanner

Environment

All, on latest master

Code and Dependencies

In spanner/mutation.go, mutationsProto unnecessary allocates slices and rand objects:

func mutationsProto(ms []*Mutation) ([]*sppb.Mutation, *sppb.Mutation, error) {
	var selectedMutation *Mutation
	var nonInsertMutations []*Mutation
...
	if len(nonInsertMutations) > 0 {
		selectedMutation = nonInsertMutations[rand.New(rand.NewSource(time.Now().UnixNano())).Intn(len(nonInsertMutations))]
	}
...
}

All production callers of this function ignore the second return value. The only functionality of tracking selectedMutation, nonInsertMutations seem to be for test.

Expected behavior

There are fewer unnecessary allocations.

Actual behavior

Allocations due to rand and slices only used for test cause massive amounts of allocations, increasing CPU and memory usage. See screenshot for a heap profile taken on a pod that performs a large number of BatchWrite calls.

Screenshots

Heap profile viewing "alloc - space" showing large amounts of allocated space: