ec distribution: register each node id once

Adding the same node twice appended it to RackToNodes twice, so every
count that walks rack nodes double-counted its shards.

weed/storage/erasure_coding/distribution/analysis.go

@@ -16,8 +16,11 @@ func NewTopologyAnalysis() *TopologyAnalysis {
 }
 
 // AddNode registers a node in the topology, including any shards it already
-// holds for the volume being analyzed.
+// holds for the volume being analyzed. A node id may only register once.
 func (a *TopologyAnalysis) AddNode(node *TopologyNode) {
+	if _, ok := a.AllNodes[node.NodeID]; ok {
+		return
+	}
 	a.AllNodes[node.NodeID] = node
 	a.RackToNodes[rackKey(node.DataCenter, node.Rack)] = append(a.RackToNodes[rackKey(node.DataCenter, node.Rack)], node)
 	if !contains(a.DCToRacks[node.DataCenter], node.Rack) {

weed/storage/erasure_coding/distribution/distribution_test.go

@@ -125,6 +125,18 @@ func TestTopologyAnalysis(t *testing.T) {
 	assert.Equal(t, []int{0, 1, 2}, a.RackToShards[rackKey("dc1", "r1")])
 }
 
+// A node registered twice must still count once in rack and shard totals.
+func TestTopologyAnalysisDuplicateNode(t *testing.T) {
+	a := NewTopologyAnalysis()
+	a.AddNode(makeNode("n1", "dc1", "r1", 5, 0, 1))
+	a.AddNode(makeNode("n1", "dc1", "r1", 5, 0, 1))
+	a.Finalize()
+
+	assert.Equal(t, 1, a.TotalNodes)
+	assert.Len(t, a.RackToNodes[rackKey("dc1", "r1")], 1)
+	assert.Equal(t, 2, a.ShardsByNode["n1"])
+}
+
 // Shards may be registered either through TopologyNode.ShardIDs or through
 // AddShardLocation — both must leave the node holding the shards.
 func TestTopologyAnalysisAddShardLocation(t *testing.T) {