core/state, tests: fix memory leak via fastcache (ethereum#28387)

This change fixes a memory leak, when running either state-tests or blockchain-tests, we allocate a `1MB` fastcache during snapshot generation. `fastcache` is a bit special, and requires a `Reset()` (it has it's own memory allocator). 

The `1MB` was hidden [here](https://github.com/ethereum/go-ethereum/blob/master/tests/state_test_util.go#L333) and [here](https://github.com/ethereum/go-ethereum/blob/master/tests/block_test_util.go#L146) respectively.

appveyor.yml

@@ -54,4 +54,4 @@ for:
       - go run build/ci.go archive -arch %GETH_ARCH% -type zip -signer WINDOWS_SIGNING_KEY -upload gethstore/builds
       - go run build/ci.go nsis -arch %GETH_ARCH% -signer WINDOWS_SIGNING_KEY -upload gethstore/builds
     test_script:
-      - go run build/ci.go test -dlgo -arch %GETH_ARCH% -cc %GETH_CC%
+      - go run build/ci.go test -dlgo -arch %GETH_ARCH% -cc %GETH_CC% -short

build/ci.go

@@ -285,6 +285,7 @@ func doTest(cmdline []string) {
 		coverage = flag.Bool("coverage", false, "Whether to record code coverage")
 		verbose  = flag.Bool("v", false, "Whether to log verbosely")
 		race     = flag.Bool("race", false, "Execute the race detector")
+		short     = flag.Bool("short", false, "Pass the 'short'-flag to go test")
 		cachedir = flag.String("cachedir", "./build/cache", "directory for caching downloads")
 	)
 	flag.CommandLine.Parse(cmdline)
@@ -318,6 +319,9 @@ func doTest(cmdline []string) {
 	if *race {
 		gotest.Args = append(gotest.Args, "-race")
 	}
+	if *short {
+		gotest.Args = append(gotest.Args, "-short")
+	}
 
 	packages := []string{"./..."}
 	if len(flag.CommandLine.Args()) > 0 {

core/blockchain.go

@@ -989,6 +989,7 @@ func (bc *BlockChain) Stop() {
 		if snapBase, err = bc.snaps.Journal(bc.CurrentBlock().Root); err != nil {
 			log.Error("Failed to journal state snapshot", "err", err)
 		}
+		bc.snaps.Release()
 	}
 	if bc.triedb.Scheme() == rawdb.PathScheme {
 		// Ensure that the in-memory trie nodes are journaled to disk properly.

core/state/snapshot/disklayer.go

@@ -45,6 +45,16 @@ type diskLayer struct {
 	lock sync.RWMutex
 }
 
+// Release releases underlying resources; specifically the fastcache requires
+// Reset() in order to not leak memory.
+// OBS: It does not invoke Close on the diskdb
+func (dl *diskLayer) Release() error {
+	if dl.cache != nil {
+		dl.cache.Reset()
+	}
+	return nil
+}
+
 // Root returns  root hash for which this snapshot was made.
 func (dl *diskLayer) Root() common.Hash {
 	return dl.root

core/state/snapshot/snapshot.go

@@ -656,6 +656,13 @@ func diffToDisk(bottom *diffLayer) *diskLayer {
 	return res
 }
 
+// Release releases resources
+func (t *Tree) Release() {
+	if dl := t.disklayer(); dl != nil {
+		dl.Release()
+	}
+}
+
 // Journal commits an entire diff hierarchy to disk into a single journal entry.
 // This is meant to be used during shutdown to persist the snapshot without
 // flattening everything down (bad for reorgs).

tests/state_test_util.go

@@ -200,6 +200,9 @@ func (t *StateTest) Run(subtest StateSubtest, vmconfig vm.Config, snapshotter bo
 		if triedb != nil {
 			triedb.Close()
 		}
+		if snaps != nil {
+			snaps.Release()
+		}
 	}()
 	checkedErr := t.checkError(subtest, err)
 	if checkedErr != nil {