[GitHub] [iceberg] steveloughran commented on a diff in pull request #4518: core: Provide mechanism to cache manifest file content

[GitBox <gi...@apache.org>]

steveloughran commented on code in PR #4518:
URL: https://github.com/apache/iceberg/pull/4518#discussion_r864026701


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core/src/main/java/org/apache/iceberg/io/CachingFileIO.java:
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@@ -0,0 +1,355 @@
+/*
+ * 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.iceberg.io;
+
+import com.github.benmanes.caffeine.cache.Cache;
+import com.github.benmanes.caffeine.cache.Caffeine;
+import com.github.benmanes.caffeine.cache.Weigher;
+import com.github.benmanes.caffeine.cache.stats.CacheStats;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.time.Duration;
+import java.util.List;
+import java.util.Map;
+import org.apache.iceberg.CatalogProperties;
+import org.apache.iceberg.exceptions.NotFoundException;
+import org.apache.iceberg.exceptions.RuntimeIOException;
+import org.apache.iceberg.relocated.com.google.common.base.Preconditions;
+import org.apache.iceberg.relocated.com.google.common.collect.Lists;
+import org.apache.iceberg.util.PropertyUtil;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Implementation of FileIO that adds metadata content caching features.
+ * <p>
+ * CachingFileIO intend to speedup scan planning by caching most of the table metadata files in memory and reduce
+ * remote reads. It is not meant to be dynamically loaded. Instead, set
+ * {@link CatalogProperties#IO_CACHE_ENABLED} to true and use
+ * {@link org.apache.iceberg.CatalogUtil#loadFileIO(String, Map, Object)} to wrap another FileIO with this
+ * CachingFileIO.
+ */
+public class CachingFileIO implements FileIO {
+  private static final Logger LOG = LoggerFactory.getLogger(CachingFileIO.class);
+  private static final int BUFFER_CHUNK_SIZE = 4 * 1024 * 1024; // 4MB
+  private static ContentCache sharedCache;
+
+  private static ContentCache createCache(Map<String, String> properties) {
+    long durationMs = PropertyUtil.propertyAsLong(properties,
+        CatalogProperties.IO_CACHE_EXPIRATION_INTERVAL_MS,
+        CatalogProperties.IO_CACHE_EXPIRATION_INTERVAL_MS_DEFAULT);
+    long totalBytes = PropertyUtil.propertyAsLong(properties,
+        CatalogProperties.IO_CACHE_MAX_TOTAL_BYTES,
+        CatalogProperties.IO_CACHE_MAX_TOTAL_BYTES_DEFAULT);
+    long contentLength = PropertyUtil.propertyAsLong(properties,
+        CatalogProperties.IO_CACHE_MAX_CONTENT_LENGTH,
+        CatalogProperties.IO_CACHE_MAX_CONTENT_LENGTH_DEFAULT);
+
+    if (durationMs >= 0 && totalBytes > 0) {
+      return new ContentCache(durationMs, totalBytes, contentLength);
+    } else {
+      return null;
+    }
+  }
+
+  public static synchronized ContentCache getOrCreate(Map<String, String> properties) {
+    if (sharedCache == null) {
+      sharedCache = createCache(properties);
+    }
+    return sharedCache;
+  }
+
+  public static boolean ioCacheEnabled(Map<String, String> properties) {
+    boolean enabled = PropertyUtil.propertyAsBoolean(properties,
+        CatalogProperties.IO_CACHE_ENABLED,
+        CatalogProperties.IO_CACHE_ENABLED_DEFAULT);
+    long durationMs = PropertyUtil.propertyAsLong(properties,
+        CatalogProperties.IO_CACHE_EXPIRATION_INTERVAL_MS,
+        CatalogProperties.IO_CACHE_EXPIRATION_INTERVAL_MS_DEFAULT);
+    long totalBytes = PropertyUtil.propertyAsLong(properties,
+        CatalogProperties.IO_CACHE_MAX_TOTAL_BYTES,
+        CatalogProperties.IO_CACHE_MAX_TOTAL_BYTES_DEFAULT);
+
+    return enabled && durationMs >= 0 && totalBytes > 0;
+  }
+
+  private ContentCache fileContentCache;
+  private Map<String, String> properties;
+  private FileIO wrappedIO;
+
+  /**
+   * CachingFileIO is not meant to be dynamically loaded.
+   */
+  private CachingFileIO() {
+  }
+
+  public CachingFileIO(FileIO io) {
+    assignIO(io);
+  }
+
+  public void assignIO(FileIO io) {
+    this.wrappedIO = io;
+  }
+
+  /**
+   * Initialize File IO from catalog properties.
+   * <p>
+   * It assumes that the inner FileIO is already initialized and therefore does not reinitialize it.
+   * If this is a reinitialization, it is the caller responsibility to call {@link #close()} and
+   * {@link #assignIO(FileIO)} prior to reinitialization to close the previously assigned FileIO and reassign a new one.
+   * Otherwise, previously assigned FileIO will be kept in use.
+   * <p>
+   * Reinitialization will discard previous content cache unless shared cache is being used
+   * ({@link CatalogProperties#IO_CACHE_SHARED} stays true).
+   * @param newProperties catalog properties
+   */
+  @Override
+  public void initialize(Map<String, String> newProperties) {
+    this.properties = newProperties;
+    initCache();
+  }
+
+  private void initCache() {
+    boolean isSharedCache = PropertyUtil.propertyAsBoolean(properties,
+        CatalogProperties.IO_CACHE_SHARED,
+        CatalogProperties.IO_CACHE_SHARED_DEFAULT);
+    if (isSharedCache) {
+      this.fileContentCache = getOrCreate(properties);
+      LOG.info("CachingFileIO created with shared cache. {} ", this.fileContentCache);
+    } else {
+      this.fileContentCache = createCache(properties);
+      LOG.info("CachingFileIO created. {} ", this.fileContentCache);
+    }
+  }
+
+  @Override
+  public void close() {
+    if (wrappedIO != null) {
+      wrappedIO.close();
+      wrappedIO = null;
+    }
+  }
+
+  @Override
+  public InputFile newInputFile(String path) {
+    InputFile inFile = wrappedIO.newInputFile(path);
+    if (fileContentCache != null && path.contains("/metadata/")) {
+      // TODO: Currently we just believe that this is a metadata file if it has "metadata" dir on its path. But metadata
+      //  location can be set differently for different tables. A table might have different metadata path by
+      //  setting custom "write.metadata.path" TableProperties.
+      //  We might need to extend FileIO interface. Add method 'newMetadataInputFile' and let caller use it to
+      //  differentiate metadata files vs other files.
+      return new CachingInputFile(fileContentCache, inFile);
+    }
+    return inFile;
+  }
+
+  @Override
+  public OutputFile newOutputFile(String path) {
+    return wrappedIO.newOutputFile(path);
+  }
+
+  @Override
+  public void deleteFile(String path) {
+    wrappedIO.deleteFile(path);
+    if (fileContentCache != null) {
+      fileContentCache.cache.invalidate(path);
+    }
+  }
+
+  public ContentCache getCache() {
+    return fileContentCache;
+  }
+
+  public long cacheEstimatedSize() {
+    return fileContentCache == null ? 0 : fileContentCache.cache.estimatedSize();
+  }
+
+  private static class CacheEntry {
+    private final int length;
+    private final List<ByteBuffer> buffers;
+
+    private CacheEntry(int length, List<ByteBuffer> buffers) {
+      this.length = length;
+      this.buffers = buffers;
+    }
+  }
+
+  public static class ContentCache {
+    private final long expireAfterAccessMs;
+    private final long maxTotalBytes;
+    private final long maxContentLength;
+    private final Cache<String, CacheEntry> cache;
+
+    private ContentCache(long expireAfterAccessMs, long maxTotalBytes, long maxContentLength) {
+      this.expireAfterAccessMs = expireAfterAccessMs;
+      this.maxTotalBytes = maxTotalBytes;
+      this.maxContentLength = maxContentLength;
+
+      Caffeine<Object, Object> builder = Caffeine.newBuilder();
+      if (expireAfterAccessMs > 0) {
+        builder = builder.expireAfterAccess(Duration.ofMillis(expireAfterAccessMs));
+      }
+
+      this.cache = builder.maximumWeight(maxTotalBytes)
+          .weigher((Weigher<String, CacheEntry>) (key, value) -> value.length)
+          .recordStats()
+          .build();
+    }
+
+    public long expireAfterAccess() {
+      return expireAfterAccessMs;
+    }
+
+    public long maxContentLength() {
+      return maxContentLength;
+    }
+
+    public long maxTotalBytes() {
+      return maxTotalBytes;
+    }
+
+    public Cache<String, CacheEntry> cache() {
+      return cache;
+    }
+
+    public CacheStats stats() {
+      return cache.stats();
+    }
+
+    @Override
+    public String toString() {
+      return getClass().getSimpleName() + '{' +
+          "expireAfterAccessMs=" + expireAfterAccessMs + ", " +
+          "maxContentLength=" + maxContentLength + ", " +
+          "maxTotalBytes=" + maxTotalBytes + ", " +
+          "cacheStats=" + cache.stats() + '}';
+    }
+  }
+
+  private static class CachingInputFile implements InputFile {
+    private final ContentCache contentCache;
+    private final InputFile wrappedInputFile;
+
+    private CachingInputFile(ContentCache cache, InputFile inFile) {
+      this.contentCache = cache;
+      this.wrappedInputFile = inFile;
+    }
+
+    @Override
+    public long getLength() {
+      CacheEntry buf = contentCache.cache.getIfPresent(location());
+      return (buf != null) ? buf.length : wrappedInputFile.getLength();
+    }
+
+    /**
+     * Opens a new {@link SeekableInputStream} for the underlying data file, either through cache or through the
+     * inner FileIO.
+     * <p>
+     * If data file is not cached yet, and it can fit in the cache, the file content will be cached first before
+     * returning a {@link ByteBufferInputStream}. Otherwise, return a new SeekableInputStream from the inner FIleIO.
+     *
+     * @return a {@link ByteBufferInputStream} if file exist in the cache or can fit in the cache. Otherwise, return a
+     * new SeekableInputStream from the inner FIleIO.
+     */
+    @Override
+    public SeekableInputStream newStream() {
+      try {
+        // read-through cache if file length is less than or equal to maximum length allowed to cache.
+        if (getLengthChecked() <= contentCache.maxContentLength()) {
+          return cachedStream();
+        }
+
+        // fallback to non-caching input stream.
+        return wrappedInputFile.newStream();
+      } catch (FileNotFoundException e) {
+        throw new NotFoundException(e, "Failed to open input stream for file: %s", wrappedInputFile.location());
+      } catch (IOException e) {
+        throw new RuntimeIOException(e, "Failed to open input stream for file: %s", wrappedInputFile.location());
+      }
+    }
+
+    @Override
+    public String location() {
+      return wrappedInputFile.location();
+    }
+
+    @Override
+    public boolean exists() {
+      CacheEntry buf = contentCache.cache.getIfPresent(location());
+      return buf != null || wrappedInputFile.exists();
+    }
+
+    public long getLengthChecked() throws IOException {
+      try {
+        return getLength();
+      } catch (RuntimeIOException ex) {
+        throw ex.getCause();
+      }
+    }
+
+    private CacheEntry getFileContent() {
+      try {
+        int fileLength = (int) getLength();

Review Comment:
   something bigger than an int long should automatically be excluded from caching, presumably. though if someone did want to declare a cache of > 2GB then it may be needed



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