org.eclipse.jgit.storage.dht/src/org/eclipse/jgit/storage/dht/DhtReaderOptions.java

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 * Copyright (C) 2011, Google Inc.
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 * This program and the accompanying materials are made available
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package org.eclipse.jgit.storage.dht;

import org.eclipse.jgit.lib.Config;

/** Options controlling how objects are read from a DHT stored repository. */
public class DhtReaderOptions {
	/** 1024 (number of bytes in one kibibyte/kilobyte) */
	public static final int KiB = 1024;

	/** 1024 {@link #KiB} (number of bytes in one mebibyte/megabyte) */
	public static final int MiB = 1024 * KiB;

	private Timeout timeout;

	private boolean prefetchFollowEdgeHints;

	private int prefetchLimit;

	private int objectIndexConcurrentBatches;

	private int objectIndexBatchSize;

	private int deltaBaseCacheSize;

	private int deltaBaseCacheLimit;

	private int recentInfoCacheSize;

	private int recentChunkCacheSize;

	private boolean trackFirstChunkLoad;

	/** Create a default reader configuration. */
	public DhtReaderOptions() {
		setTimeout(Timeout.seconds(5));
		setPrefetchFollowEdgeHints(true);
		setPrefetchLimit(5 * MiB);

		setObjectIndexConcurrentBatches(2);
		setObjectIndexBatchSize(512);

		setDeltaBaseCacheSize(1024);
		setDeltaBaseCacheLimit(10 * MiB);

		setRecentInfoCacheSize(4096);
		setRecentChunkCacheSize(4);
	}

	/** @return default timeout to wait on long operations before aborting. */
	public Timeout getTimeout() {
		return timeout;
	}

	/**
	 * Set the default timeout to wait on long operations.
	 *
	 * @param maxWaitTime
	 *            new wait time.
	 * @return {@code this}
	 */
	public DhtReaderOptions setTimeout(Timeout maxWaitTime) {
		if (maxWaitTime == null || maxWaitTime.getTime() < 0)
			throw new IllegalArgumentException();
		timeout = maxWaitTime;
		return this;
	}

	/** @return if the prefetcher should follow edge hints (experimental) */
	public boolean isPrefetchFollowEdgeHints() {
		return prefetchFollowEdgeHints;
	}

	/**
	 * Enable (or disable) the experimental edge following feature.
	 *
	 * @param follow
	 *            true to follow the edge hints.
	 * @return {@code this}
	 */
	public DhtReaderOptions setPrefetchFollowEdgeHints(boolean follow) {
		prefetchFollowEdgeHints = follow;
		return this;
	}

	/** @return number of bytes to load during prefetching. */
	public int getPrefetchLimit() {
		return prefetchLimit;
	}

	/**
	 * Set the number of bytes the prefetcher should hold onto.
	 *
	 * @param maxBytes
	 * @return {@code this}
	 */
	public DhtReaderOptions setPrefetchLimit(int maxBytes) {
		prefetchLimit = Math.max(1024, maxBytes);
		return this;
	}

	/** @return number of concurrent reads against ObjectIndexTable. */
	public int getObjectIndexConcurrentBatches() {
		return objectIndexConcurrentBatches;
	}

	/**
	 * Set the number of concurrent readers on ObjectIndexTable.
	 *
	 * @param batches
	 *            number of batches.
	 * @return {@code this}
	 */
	public DhtReaderOptions setObjectIndexConcurrentBatches(int batches) {
		objectIndexConcurrentBatches = Math.max(1, batches);
		return this;
	}

	/** @return number of objects to lookup in one batch. */
	public int getObjectIndexBatchSize() {
		return objectIndexBatchSize;
	}

	/**
	 * Set the number of objects to lookup at once.
	 *
	 * @param objectCnt
	 *            the number of objects in a lookup batch.
	 * @return {@code this}
	 */
	public DhtReaderOptions setObjectIndexBatchSize(int objectCnt) {
		objectIndexBatchSize = Math.max(1, objectCnt);
		return this;
	}

	/** @return size of the delta base cache hash table, in object entries. */
	public int getDeltaBaseCacheSize() {
		return deltaBaseCacheSize;
	}

	/**
	 * Set the size of the delta base cache hash table.
	 *
	 * @param slotCnt
	 *            number of slots in the hash table.
	 * @return {@code this}
	 */
	public DhtReaderOptions setDeltaBaseCacheSize(int slotCnt) {
		deltaBaseCacheSize = Math.max(1, slotCnt);
		return this;
	}

	/** @return maximum number of bytes to hold in per-reader DeltaBaseCache. */
	public int getDeltaBaseCacheLimit() {
		return deltaBaseCacheLimit;
	}

	/**
	 * Set the maximum number of bytes in the DeltaBaseCache.
	 *
	 * @param maxBytes
	 *            the new limit.
	 * @return {@code this}
	 */
	public DhtReaderOptions setDeltaBaseCacheLimit(int maxBytes) {
		deltaBaseCacheLimit = Math.max(0, maxBytes);
		return this;
	}

	/** @return number of objects to cache information on. */
	public int getRecentInfoCacheSize() {
		return recentInfoCacheSize;
	}

	/**
	 * Set the number of objects to cache information on.
	 *
	 * @param objectCnt
	 *            the number of objects to cache.
	 * @return {@code this}
	 */
	public DhtReaderOptions setRecentInfoCacheSize(int objectCnt) {
		recentInfoCacheSize = Math.max(0, objectCnt);
		return this;
	}

	/** @return number of recent chunks to hold onto per-reader. */
	public int getRecentChunkCacheSize() {
		return recentChunkCacheSize;
	}

	/**
	 * Set the number of chunks each reader holds onto for recently used access.
	 *
	 * @param chunkCnt
	 *            the number of chunks each reader retains of recently used
	 *            chunks to smooth out access.
	 * @return {@code this}
	 */
	public DhtReaderOptions setRecentChunkCacheSize(int chunkCnt) {
		recentChunkCacheSize = Math.max(0, chunkCnt);
		return this;
	}

	/**
	 * @return true if {@link DhtReader.Statistics} includes the stack trace for
	 *         the first time a chunk is loaded. Supports debugging DHT code.
	 */
	public boolean isTrackFirstChunkLoad() {
		return trackFirstChunkLoad;
	}

	/**
	 * Set whether or not the initial load of each chunk should be tracked.
	 *
	 * @param track
	 *            true to track the stack trace of the first load.
	 * @return {@code this}.
	 */
	public DhtReaderOptions setTrackFirstChunkLoad(boolean track) {
		trackFirstChunkLoad = track;
		return this;
	}

	/**
	 * Update properties by setting fields from the configuration.
	 * <p>
	 * If a property is not defined in the configuration, then it is left
	 * unmodified.
	 *
	 * @param rc
	 *            configuration to read properties from.
	 * @return {@code this}
	 */
	public DhtReaderOptions fromConfig(Config rc) {
		setTimeout(Timeout.getTimeout(rc, "core", "dht", "timeout", getTimeout()));
		setPrefetchFollowEdgeHints(rc.getBoolean("core", "dht", "prefetchFollowEdgeHints", isPrefetchFollowEdgeHints()));
		setPrefetchLimit(rc.getInt("core", "dht", "prefetchLimit", getPrefetchLimit()));

		setObjectIndexConcurrentBatches(rc.getInt("core", "dht", "objectIndexConcurrentBatches", getObjectIndexConcurrentBatches()));
		setObjectIndexBatchSize(rc.getInt("core", "dht", "objectIndexBatchSize", getObjectIndexBatchSize()));

		setDeltaBaseCacheSize(rc.getInt("core", "dht", "deltaBaseCacheSize", getDeltaBaseCacheSize()));
		setDeltaBaseCacheLimit(rc.getInt("core", "dht", "deltaBaseCacheLimit", getDeltaBaseCacheLimit()));

		setRecentInfoCacheSize(rc.getInt("core", "dht", "recentInfoCacheSize", getRecentInfoCacheSize()));
		setRecentChunkCacheSize(rc.getInt("core", "dht", "recentChunkCacheSize", getRecentChunkCacheSize()));

		setTrackFirstChunkLoad(rc.getBoolean("core", "dht", "debugTrackFirstChunkLoad", isTrackFirstChunkLoad()));
		return this;
	}
}