[PAN-2819] [PAN-2820] Mark Sweep Pruner

* Mark Sweep Pruner 
* add `unload` method on Node interface, which is a noop everywhere but on `StoredNode`
Signed-off-by: Adrian Sutton <adrian.sutton@consensys.net>

ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/storage/StorageProvider.java

@@ -18,6 +18,7 @@
 import tech.pegasys.pantheon.ethereum.privacy.PrivateTransactionStorage;
 import tech.pegasys.pantheon.ethereum.worldstate.WorldStatePreimageStorage;
 import tech.pegasys.pantheon.ethereum.worldstate.WorldStateStorage;
+import tech.pegasys.pantheon.services.kvstore.KeyValueStorage;
 
 import java.io.Closeable;
 
@@ -32,4 +33,6 @@ public interface StorageProvider extends Closeable {
   PrivateTransactionStorage createPrivateTransactionStorage();
 
   PrivateStateStorage createPrivateStateStorage();
+
+  KeyValueStorage createPruningStorage();
 }

ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/storage/keyvalue/KeyValueStorageProvider.java

@@ -76,6 +76,7 @@ public PrivateStateStorage createPrivateStateStorage() {
     return new PrivateStateKeyValueStorage(privateStateStorage);
   }
 
+  @Override
   public KeyValueStorage createPruningStorage() {
     return pruningStorage;
   }

ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/worldstate/MarkSweepPruner.java

@@ -0,0 +1,181 @@
+/*
+ * Copyright 2019 ConsenSys AG.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package tech.pegasys.pantheon.ethereum.worldstate;
+
+import tech.pegasys.pantheon.ethereum.core.Hash;
+import tech.pegasys.pantheon.ethereum.rlp.RLP;
+import tech.pegasys.pantheon.ethereum.trie.MerklePatriciaTrie;
+import tech.pegasys.pantheon.ethereum.trie.StoredMerklePatriciaTrie;
+import tech.pegasys.pantheon.metrics.Counter;
+import tech.pegasys.pantheon.metrics.MetricsSystem;
+import tech.pegasys.pantheon.metrics.PantheonMetricCategory;
+import tech.pegasys.pantheon.services.kvstore.KeyValueStorage;
+import tech.pegasys.pantheon.services.kvstore.KeyValueStorage.Transaction;
+import tech.pegasys.pantheon.util.bytes.Bytes32;
+import tech.pegasys.pantheon.util.bytes.BytesValue;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+public class MarkSweepPruner {
+  private static final Logger LOG = LogManager.getLogger();
+  private static final BytesValue IN_USE = BytesValue.of(1);
+  private static final int MARKS_PER_TRANSACTION = 1000;
+  private final WorldStateStorage worldStateStorage;
+  private final KeyValueStorage markStorage;
+  private final Counter markedNodesCounter;
+  private final Counter markOperationCounter;
+  private final Counter sweepOperationCounter;
+  private final Counter sweptNodesCounter;
+  private volatile long nodeAddedListenerId;
+  private final ReentrantLock markLock = new ReentrantLock(true);
+  private final Set<BytesValue> pendingMarks = Collections.newSetFromMap(new ConcurrentHashMap<>());
+
+  public MarkSweepPruner(
+      final WorldStateStorage worldStateStorage,
+      final KeyValueStorage markStorage,
+      final MetricsSystem metricsSystem) {
+    this.worldStateStorage = worldStateStorage;
+    this.markStorage = markStorage;
+
+    markedNodesCounter =
+        metricsSystem.createCounter(
+            PantheonMetricCategory.PRUNER,
+            "marked_nodes_total",
+            "Total number of nodes marked as in use");
+    markOperationCounter =
+        metricsSystem.createCounter(
+            PantheonMetricCategory.PRUNER,
+            "mark_operations_total",
+            "Total number of mark operations performed");
+
+    sweptNodesCounter =
+        metricsSystem.createCounter(
+            PantheonMetricCategory.PRUNER,
+            "swept_nodes_total",
+            "Total number of unused nodes removed");
+    sweepOperationCounter =
+        metricsSystem.createCounter(
+            PantheonMetricCategory.PRUNER,
+            "sweep_operations_total",
+            "Total number of sweep operations performed");
+  }
+
+  public void prepare() {
+    worldStateStorage.removeNodeAddedListener(nodeAddedListenerId); // Just in case.
+    nodeAddedListenerId = worldStateStorage.addNodeAddedListener(this::markNewNodes);
+  }
+
+  public void cleanup() {
+    worldStateStorage.removeNodeAddedListener(nodeAddedListenerId);
+  }
+
+  public void mark(final Hash rootHash) {
+    markOperationCounter.inc();
+    markStorage.clear();
+    createStateTrie(rootHash)
+        .visitAll(
+            node -> {
+              if (Thread.interrupted()) {
+                // Since we don't expect to abort marking ourselves,
+                // our abort process consists only of handling interrupts
+                throw new RuntimeException("Interrupted while marking");
+              }
+              markNode(node.getHash());
+              node.getValue().ifPresent(this::processAccountState);
+            });
+    LOG.info("Completed marking used nodes for pruning");
+  }
+
+  public void sweep() {
+    flushPendingMarks();
+    sweepOperationCounter.inc();
+    LOG.info("Sweeping unused nodes");
+    final long prunedNodeCount = worldStateStorage.prune(markStorage::containsKey);
+    sweptNodesCounter.inc(prunedNodeCount);
+    worldStateStorage.removeNodeAddedListener(nodeAddedListenerId);
+    markStorage.clear();
+    LOG.info("Completed sweeping unused nodes");
+  }
+
+  private MerklePatriciaTrie<Bytes32, BytesValue> createStateTrie(final Bytes32 rootHash) {
+    return new StoredMerklePatriciaTrie<>(
+        worldStateStorage::getAccountStateTrieNode,
+        rootHash,
+        Function.identity(),
+        Function.identity());
+  }
+
+  private MerklePatriciaTrie<Bytes32, BytesValue> createStorageTrie(final Bytes32 rootHash) {
+    return new StoredMerklePatriciaTrie<>(
+        worldStateStorage::getAccountStorageTrieNode,
+        rootHash,
+        Function.identity(),
+        Function.identity());
+  }
+
+  private void processAccountState(final BytesValue value) {
+    final StateTrieAccountValue accountValue = StateTrieAccountValue.readFrom(RLP.input(value));
+    markNode(accountValue.getCodeHash());
+
+    createStorageTrie(accountValue.getStorageRoot())
+        .visitAll(storageNode -> markNode(storageNode.getHash()));
+  }
+
+  private void markNode(final Bytes32 hash) {
+    markedNodesCounter.inc();
+    markLock.lock();
+    try {
+      pendingMarks.add(hash);
+      maybeFlushPendingMarks();
+    } finally {
+      markLock.unlock();
+    }
+  }
+
+  private void maybeFlushPendingMarks() {
+    if (pendingMarks.size() > MARKS_PER_TRANSACTION) {
+      flushPendingMarks();
+    }
+  }
+
+  void flushPendingMarks() {
+    markLock.lock();
+    try {
+      final Transaction transaction = markStorage.startTransaction();
+      pendingMarks.forEach(node -> transaction.put(node, IN_USE));
+      transaction.commit();
+      pendingMarks.clear();
+    } finally {
+      markLock.unlock();
+    }
+  }
+
+  private void markNewNodes(final Collection<Bytes32> nodeHashes) {
+    markedNodesCounter.inc(nodeHashes.size());
+    markLock.lock();
+    try {
+      pendingMarks.addAll(nodeHashes);
+      maybeFlushPendingMarks();
+    } finally {
+      markLock.unlock();
+    }
+  }
+}

ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/worldstate/Pruner.java

@@ -0,0 +1,127 @@
+/*
+ * Copyright 2019 ConsenSys AG.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package tech.pegasys.pantheon.ethereum.worldstate;
+
+import tech.pegasys.pantheon.ethereum.chain.BlockAddedEvent;
+import tech.pegasys.pantheon.ethereum.chain.Blockchain;
+import tech.pegasys.pantheon.ethereum.core.BlockHeader;
+import tech.pegasys.pantheon.ethereum.core.Hash;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicReference;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+public class Pruner {
+  private static final Logger LOG = LogManager.getLogger();
+
+  private final MarkSweepPruner pruningStrategy;
+  private final Blockchain blockchain;
+  private final ExecutorService executorService;
+  private final long retentionPeriodInBlocks;
+  private final AtomicReference<State> state = new AtomicReference<>(State.IDLE);
+  private volatile long markBlockNumber = 0;
+  private volatile BlockHeader markedBlockHeader;
+  private long transientForkThreshold;
+
+  public Pruner(
+      final MarkSweepPruner pruningStrategy,
+      final Blockchain blockchain,
+      final ExecutorService executorService,
+      final long transientForkThreshold,
+      final long retentionPeriodInBlocks) {
+    this.pruningStrategy = pruningStrategy;
+    this.executorService = executorService;
+    this.blockchain = blockchain;
+    if (transientForkThreshold < 0 || retentionPeriodInBlocks < 0) {
+      throw new IllegalArgumentException(
+          String.format(
+              "TransientForkThreshold and RetentionPeriodInBlocks must be non-negative. transientForkThreshold=%d, retentionPeriodInBlocks=%d",
+              transientForkThreshold, retentionPeriodInBlocks));
+    }
+    this.retentionPeriodInBlocks = retentionPeriodInBlocks;
+    this.transientForkThreshold = transientForkThreshold;
+  }
+
+  public void start() {
+    blockchain.observeBlockAdded((event, blockchain) -> handleNewBlock(event));
+  }
+
+  public void stop() throws InterruptedException {
+    pruningStrategy.cleanup();
+    executorService.awaitTermination(10, TimeUnit.SECONDS);
+  }
+
+  private void handleNewBlock(final BlockAddedEvent event) {
+    if (!event.isNewCanonicalHead()) {
+      return;
+    }
+
+    final long blockNumber = event.getBlock().getHeader().getNumber();
+    if (state.compareAndSet(State.IDLE, State.TRANSIENT_FORK_OUTLIVING)) {
+      pruningStrategy.prepare();
+      markBlockNumber = blockNumber;
+    } else if (blockNumber >= markBlockNumber + transientForkThreshold
+        && state.compareAndSet(State.TRANSIENT_FORK_OUTLIVING, State.MARKING)) {
+      markedBlockHeader = blockchain.getBlockHeader(markBlockNumber).get();
+      mark(markedBlockHeader);
+    } else if (blockNumber >= markBlockNumber + retentionPeriodInBlocks
+        && blockchain.blockIsOnCanonicalChain(markedBlockHeader.getHash())
+        && state.compareAndSet(State.MARKING_COMPLETE, State.SWEEPING)) {
+      sweep();
+    }
+  }
+
+  private void mark(final BlockHeader header) {
+    markBlockNumber = header.getNumber();
+    final Hash stateRoot = header.getStateRoot();
+    LOG.info(
+        "Begin marking used nodes for pruning. Block number: {} State root: {}",
+        markBlockNumber,
+        stateRoot);
+    execute(
+        () -> {
+          pruningStrategy.mark(stateRoot);
+          state.compareAndSet(State.MARKING, State.MARKING_COMPLETE);
+        });
+  }
+
+  private void sweep() {
+    LOG.info(
+        "Begin sweeping unused nodes for pruning. Retention period: {}", retentionPeriodInBlocks);
+    execute(
+        () -> {
+          pruningStrategy.sweep();
+          state.compareAndSet(State.SWEEPING, State.IDLE);
+        });
+  }
+
+  private void execute(final Runnable action) {
+    try {
+      executorService.execute(action);
+    } catch (final Throwable t) {
+      LOG.error("Pruning failed", t);
+      state.set(State.IDLE);
+    }
+  }
+
+  private enum State {
+    IDLE,
+    TRANSIENT_FORK_OUTLIVING,
+    MARKING,
+    MARKING_COMPLETE,
+    SWEEPING;
+  }
+}

ethereum/core/src/test-support/java/tech/pegasys/pantheon/ethereum/core/InMemoryStorageProvider.java

@@ -32,6 +32,7 @@
 import tech.pegasys.pantheon.ethereum.worldstate.WorldStateStorage;
 import tech.pegasys.pantheon.metrics.noop.NoOpMetricsSystem;
 import tech.pegasys.pantheon.services.kvstore.InMemoryKeyValueStorage;
+import tech.pegasys.pantheon.services.kvstore.KeyValueStorage;
 
 public class InMemoryStorageProvider implements StorageProvider {
 
@@ -86,6 +87,11 @@ public PrivateStateStorage createPrivateStateStorage() {
     return new PrivateStateKeyValueStorage(new InMemoryKeyValueStorage());
   }
 
+  @Override
+  public KeyValueStorage createPruningStorage() {
+    return new InMemoryKeyValueStorage();
+  }
+
   @Override
   public void close() {}
 }