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https://issues.apache.org/jira/browse/TINKERPOP-3282?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18124749#comment-18124749
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ASF GitHub Bot commented on TINKERPOP-3282:
-------------------------------------------
spmallette commented on code in PR #3639:
URL: https://github.com/apache/tinkerpop/pull/3639#discussion_r4212238653
##########
tinkergraph-gremlin/src/main/java/org/apache/tinkerpop/gremlin/tinkergraph/structure/storage/AbstractLogStorage.java:
##########
@@ -0,0 +1,485 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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 org.apache.tinkerpop.gremlin.tinkergraph.structure.storage;
+
+import org.apache.commons.configuration2.Configuration;
+import org.apache.tinkerpop.gremlin.structure.util.Attachable;
+import org.apache.tinkerpop.gremlin.structure.util.detached.DetachedEdge;
+import org.apache.tinkerpop.gremlin.structure.util.detached.DetachedVertex;
+import org.apache.tinkerpop.gremlin.tinkergraph.structure.AbstractTinkerGraph;
+import org.apache.tinkerpop.gremlin.tinkergraph.structure.TinkerEdge;
+import org.apache.tinkerpop.gremlin.tinkergraph.structure.TinkerGraph;
+import org.apache.tinkerpop.gremlin.tinkergraph.structure.TinkerVertex;
+
+import java.io.BufferedInputStream;
+import java.io.BufferedOutputStream;
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.EOFException;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.UncheckedIOException;
+import java.nio.channels.FileChannel;
+import java.nio.file.AtomicMoveNotSupportedException;
+import java.nio.file.Files;
+import java.nio.file.StandardCopyOption;
+import java.nio.file.StandardOpenOption;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.zip.CRC32;
+
+/**
+ * Log-structured durable storage machinery shared by {@link TinkerStorage}
engines, independent of how an element is
+ * encoded. It persists a {@code TinkerStorageGraph} as an append-only commit
log ({@code log.gbin}) plus an optional
+ * folded {@code snapshot.gbin}; on open the snapshot is read followed by the
log, last-write-wins per element id.
+ * <p/>
+ * This base owns everything that is not the element codec: the on-disk file
layout, the single-source-of-truth
+ * {@code VERSION} marker, length+CRC frame framing (which tells an
interrupted trailing append apart from genuine
+ * corruption), the replay fold loop, durability via {@link SyncMode}, and
crash-safe atomic compaction with a
+ * size threshold. Concrete engines supply only the codec through {@link
#encodeCommit}, {@link #decodeFrame},
+ * {@link #writeSnapshot}, and (optionally) {@link #beginReplay} for
per-replay decode state.
+ * <p/>
+ * The in-memory graph remains authoritative (write-through); this machinery
does not support graphs larger than memory.
+ */
+public abstract class AbstractLogStorage implements TinkerStorage {
+
+ /**
+ * Magic bytes ("TGSB" — TinkerGraph Storage Binary) at the start of every
storage file, so a file can be
+ * identified as one written by this engine (and a foreign or corrupt file
rejected) before any record is read.
+ */
+ static final byte[] MAGIC = { 'T', 'G', 'S', 'B' };
+
+ /**
+ * On-disk format version of the store. Recorded once per store in the
{@link #VERSION_FILE} marker rather than in
+ * every file, so a store has a single unambiguous version even when it
momentarily holds a snapshot and a log
+ * written at different times. A future format bump is detected against
this marker so an older store is rejected
+ * (never silently misread); the supported migration path is to export via
{@code g.io()} before upgrading.
+ */
+ static final byte FORMAT_VERSION = 1;
+
+ /**
+ * Store-level version marker file, holding {@link #MAGIC} followed by the
one-byte {@link #FORMAT_VERSION}.
+ */
+ static final String VERSION_FILE = "VERSION";
+
+ /**
+ * Bytes of the per-file header: just {@link #MAGIC}. The format version
lives in the store-level
+ * {@link #VERSION_FILE}, not in each file.
+ */
+ static final int HEADER_SIZE = MAGIC.length;
+
+ static final String SNAPSHOT_FILE = "snapshot.gbin";
+ static final String LOG_FILE = "log.gbin";
+
+ /**
+ * Default automatic-compaction threshold: 64 MB of appended log since the
last compaction.
+ */
+ static final long DEFAULT_COMPACT_THRESHOLD_BYTES = 64L * 1024 * 1024;
+
+ private File directory;
+ private File snapshotFile;
+ private File logFile;
+ private File versionFile;
+
+ private DataOutputStream logOut;
+ private FileOutputStream logFos;
+ private SyncMode syncMode = SyncMode.COMMIT;
+ private long compactThresholdBytes = DEFAULT_COMPACT_THRESHOLD_BYTES;
+ private long logBytesSinceCompaction = 0;
+ private boolean closed = false;
+
+ //
---------------------------------------------------------------------------------------
> TinkerGraph file persistence
> ----------------------------
>
> Key: TINKERPOP-3282
> URL: https://issues.apache.org/jira/browse/TINKERPOP-3282
> Project: TinkerPop
> Issue Type: Improvement
> Components: tinkergraph
> Affects Versions: 3.7.6
> Reporter: Stephen Mallette
> Assignee: Stephen Mallette
> Priority: Major
>
> Give TinkerGraph a basic file persistence option tied to its transactional
> usage so that it can support some more complex use cases.
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