From 55dec28bbb4d99975b42a4f2a353fe5cb7266cce Mon Sep 17 00:00:00 2001
From: Leonard Lyubich <leonard@nspcc.ru>
Date: Thu, 4 Mar 2021 15:32:16 +0300
Subject: [PATCH] [#419] cmd/node: Cache network maps read from sidechain

Implement LRU cache of eACL tables read from sidechain. Use it as a netmap
storage in neofs-node app. Current cache size is set to 10 (constant).

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
---
 cmd/neofs-node/cache.go | 86 +++++++++++++++++++++++++++++++++++++++++
 cmd/neofs-node/morph.go |  2 +-
 2 files changed, 87 insertions(+), 1 deletion(-)

diff --git a/cmd/neofs-node/cache.go b/cmd/neofs-node/cache.go
index b50ba6277..be4c98d59 100644
--- a/cmd/neofs-node/cache.go
+++ b/cmd/neofs-node/cache.go
@@ -7,7 +7,9 @@ import (
 	lru "github.com/hashicorp/golang-lru"
 	eaclSDK "github.com/nspcc-dev/neofs-api-go/pkg/acl/eacl"
 	containerSDK "github.com/nspcc-dev/neofs-api-go/pkg/container"
+	netmapSDK "github.com/nspcc-dev/neofs-api-go/pkg/netmap"
 	"github.com/nspcc-dev/neofs-node/pkg/core/container"
+	"github.com/nspcc-dev/neofs-node/pkg/core/netmap"
 	"github.com/nspcc-dev/neofs-node/pkg/services/object/acl/eacl"
 )
 
@@ -78,6 +80,50 @@ func (c *ttlNetCache) get(key interface{}) (interface{}, error) {
 	return val, nil
 }
 
+// entity that provides LRU cache interface.
+type lruNetCache struct {
+	mtx sync.Mutex
+
+	cache *lru.Cache
+
+	netRdr netValueReader
+}
+
+// complicates netValueReader with LRU caching mechanism.
+func newNetworkLRUCache(sz int, netRdr netValueReader) *lruNetCache {
+	cache, err := lru.New(sz)
+	fatalOnErr(err)
+
+	return &lruNetCache{
+		cache:  cache,
+		netRdr: netRdr,
+	}
+}
+
+// reads value by the key.
+//
+// updates the value from the network on cache miss.
+//
+// returned value should not be modified.
+func (c *lruNetCache) get(key interface{}) (interface{}, error) {
+	c.mtx.Lock()
+	defer c.mtx.Unlock()
+
+	val, ok := c.cache.Get(key)
+	if ok {
+		return val, nil
+	}
+
+	val, err := c.netRdr(key)
+	if err != nil {
+		return nil, err
+	}
+
+	c.cache.Add(key, val)
+
+	return val, nil
+}
+
 // wrapper over TTL cache of values read from the network
 // that implements container storage.
 type ttlContainerStorage ttlNetCache
@@ -141,3 +187,43 @@ func (s *ttlEACLStorage) GetEACL(cid *containerSDK.ID) (*eaclSDK.Table, error) {
 
 	return val.(*eaclSDK.Table), nil
 }
+
+type lruNetmapSource struct {
+	netState netmap.State
+
+	cache *lruNetCache
+}
+
+func newCachedNetmapStorage(s netmap.State, v netmap.Source) netmap.Source {
+	const netmapCacheSize = 10
+
+	lruNetmapCache := newNetworkLRUCache(netmapCacheSize, func(key interface{}) (interface{}, error) {
+		return v.GetNetMapByEpoch(key.(uint64))
+	})
+
+	return &lruNetmapSource{
+		netState: s,
+		cache:    lruNetmapCache,
+	}
+}
+
+func (s *lruNetmapSource) GetNetMap(diff uint64) (*netmapSDK.Netmap, error) {
+	return s.getNetMapByEpoch(s.netState.CurrentEpoch() - diff)
+}
+
+func (s *lruNetmapSource) GetNetMapByEpoch(epoch uint64) (*netmapSDK.Netmap, error) {
+	return s.getNetMapByEpoch(epoch)
+}
+
+func (s *lruNetmapSource) getNetMapByEpoch(epoch uint64) (*netmapSDK.Netmap, error) {
+	val, err := s.cache.get(epoch)
+	if err != nil {
+		return nil, err
+	}
+
+	return val.(*netmapSDK.Netmap), nil
+}
+
+func (s *lruNetmapSource) Epoch() (uint64, error) {
+	return s.netState.CurrentEpoch(), nil
+}
diff --git a/cmd/neofs-node/morph.go b/cmd/neofs-node/morph.go
index 68b58e767..df78733ba 100644
--- a/cmd/neofs-node/morph.go
+++ b/cmd/neofs-node/morph.go
@@ -65,7 +65,7 @@ func initMorphComponents(c *cfg) {
 	wrap, err := wrapper.New(cli)
 	fatalOnErr(err)
 
-	c.cfgObject.netMapStorage = wrap
+	c.cfgObject.netMapStorage = newCachedNetmapStorage(c.cfgNetmap.state, wrap)
 	c.cfgNetmap.wrapper = wrap
 }