[#1248] placement: Decouple ContainerNodes() cache from the placement builder.

Also, write tests.

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

pkg/services/object_manager/placement/cache_test.go

@@ -0,0 +1,95 @@
+package placement_test
+
+import (
+	"strconv"
+	"testing"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/services/object_manager/placement"
+	cid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container/id"
+	cidtest "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container/id/test"
+	netmapSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/netmap"
+	"github.com/stretchr/testify/require"
+)
+
+func TestContainerNodesCache(t *testing.T) {
+	const size = 3
+
+	nodes := [6]netmapSDK.NodeInfo{}
+	for i := range nodes {
+		nodes[i].SetAttribute("ATTR", strconv.Itoa(i))
+	}
+
+	nm := func(epoch uint64, nodes []netmapSDK.NodeInfo) *netmapSDK.NetMap {
+		var nm netmapSDK.NetMap
+		nm.SetEpoch(epoch)
+		nm.SetNodes(nodes)
+		return &nm
+	}
+
+	var pp netmapSDK.PlacementPolicy
+	require.NoError(t, pp.DecodeString("REP 1"))
+
+	t.Run("update netmap on the new epoch", func(t *testing.T) {
+		c := placement.NewContainerNodesCache(size)
+
+		cnr := cidtest.ID()
+		res, err := c.ContainerNodes(nm(1, nodes[0:1]), cnr, pp)
+		require.NoError(t, err)
+
+		// Use other nodes in the argument to ensure the result is taken from cache.
+		resCached, err := c.ContainerNodes(nm(1, nodes[1:2]), cnr, pp)
+		require.NoError(t, err)
+		require.Equal(t, res, resCached)
+
+		// Update epoch, netmap should be purged.
+		resCached, err = c.ContainerNodes(nm(2, nodes[2:3]), cnr, pp)
+		require.NoError(t, err)
+		require.NotEqual(t, res, resCached)
+	})
+	t.Run("cache uses container as a key", func(t *testing.T) {
+		c := placement.NewContainerNodesCache(size)
+
+		res1, err := c.ContainerNodes(nm(1, nodes[0:1]), cidtest.ID(), pp)
+		require.NoError(t, err)
+
+		res2, err := c.ContainerNodes(nm(1, nodes[1:2]), cidtest.ID(), pp)
+		require.NoError(t, err)
+
+		require.NotEqual(t, res1, res2)
+	})
+	t.Run("cache respects size parameter", func(t *testing.T) {
+		c := placement.NewContainerNodesCache(size)
+
+		nm1 := nm(1, nodes[0:1])
+		nm2 := nm(1, nodes[1:2])
+		cnr := [size * 2]cid.ID{}
+		res := [size * 2][][]netmapSDK.NodeInfo{}
+		for i := 0; i < size*2; i++ {
+			cnr[i] = cidtest.ID()
+
+			var err error
+			res[i], err = c.ContainerNodes(nm1, cnr[i], pp)
+			require.NoError(t, err)
+		}
+
+		for i := size; i < size*2; i++ {
+			r, err := c.ContainerNodes(nm2, cnr[i], pp)
+			require.NoError(t, err)
+			require.Equal(t, res[i], r)
+		}
+		for i := 0; i < size; i++ {
+			r, err := c.ContainerNodes(nm2, cnr[i], pp)
+			require.NoError(t, err)
+			require.NotEqual(t, res[i], r)
+		}
+	})
+	t.Run("the error is propagated", func(t *testing.T) {
+		var pp netmapSDK.PlacementPolicy
+		require.NoError(t, pp.DecodeString("REP 1 SELECT 1 FROM X FILTER ATTR EQ 42 AS X"))
+
+		c := placement.NewContainerNodesCache(size)
+		_, err := c.ContainerNodes(nm(1, nodes[0:1]), cidtest.ID(), pp)
+		require.Error(t, err)
+	})
+
+}