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io.permazen.kv.raft.SnapshotTransmit Maven / Gradle / Ivy


/*
 * Copyright (C) 2015 Archie L. Cobbs. All rights reserved.
 */

package io.permazen.kv.raft;

import com.google.common.base.Preconditions;

import io.permazen.kv.CloseableKVStore;
import io.permazen.kv.KVPair;
import io.permazen.kv.KVStore;
import io.permazen.kv.util.KeyListEncoder;
import io.permazen.util.CloseableIterator;

import java.io.Closeable;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.Map;

import org.dellroad.stuff.io.ByteBufferOutputStream;

/**
 * Represents an in-progress snapshot installation from the leader's point of view.
 *
 * 

* Instances are not thread safe. */ class SnapshotTransmit implements Closeable { private static final int MAX_CHUNK_SIZE = 10250; // about 7 TCP packets private final Timestamp createTime = new Timestamp(); private final long snapshotTerm; private final long snapshotIndex; private final Map snapshotConfig; private CloseableKVStore snapshot; // snapshot view of key/value store private CloseableIterator iterator; private long pairIndex; // count of how many key/value pairs sent so far private KVPair nextPair; private byte[] previousKey; private boolean anyChunksSent; // Constructors SnapshotTransmit(long snapshotTerm, long snapshotIndex, Map snapshotConfig, CloseableKVStore snapshot, KVStore view) { Preconditions.checkArgument(snapshot != null); Preconditions.checkArgument(snapshotTerm > 0); Preconditions.checkArgument(snapshotIndex > 0); Preconditions.checkArgument(snapshotConfig != null); this.snapshotTerm = snapshotTerm; this.snapshotIndex = snapshotIndex; this.snapshotConfig = snapshotConfig; this.snapshot = snapshot; this.iterator = view.getRange(null, null); this.advance(); } // Public methods /** * Get the age of this instance since instantiation. * * @return age in milliseconds */ public int getAge() { return -this.createTime.offsetFromNow(); } public long getSnapshotTerm() { return this.snapshotTerm; } public long getSnapshotIndex() { return this.snapshotIndex; } public Map getSnapshotConfig() { return this.snapshotConfig; } public long getPairIndex() { return this.pairIndex; } public boolean hasMoreChunks() { return this.nextPair != null; } public ByteBuffer getNextChunk() { // Any more key/value pairs? if (this.nextPair == null) { // In the case of a completely empty snapshot, ensure we send at least one (empty) chunk if (!this.anyChunksSent) { this.anyChunksSent = true; return ByteBuffer.allocate(0); } // Done return null; } // Allocate buffer final ByteBuffer buf = Util.allocateByteBuffer(Math.max(this.nextPairLength(), MAX_CHUNK_SIZE)); // Fill buffer with the next chunk of key/value pairs final ByteBufferOutputStream output = new ByteBufferOutputStream(buf); do { final byte[] key = this.nextPair.getKey(); final byte[] value = this.nextPair.getValue(); try { KeyListEncoder.write(output, key, this.previousKey); KeyListEncoder.write(output, value, null); } catch (IOException e) { throw new RuntimeException("unexpected exception"); } this.previousKey = key; this.pairIndex++; } while (this.advance() && buf.remaining() >= this.nextPairLength()); // Done this.anyChunksSent = true; return (ByteBuffer)buf.flip(); } // Private methods private boolean advance() { if (!this.iterator.hasNext()) { this.nextPair = null; return false; } this.nextPair = this.iterator.next(); return true; } private int nextPairLength() { return KeyListEncoder.writeLength(this.nextPair.getKey(), this.previousKey) + KeyListEncoder.writeLength(this.nextPair.getValue(), null); } // Closeable @Override public void close() { this.snapshot.close(); this.iterator.close(); this.snapshot = null; this.iterator = null; this.nextPair = null; } // Object @Override public String toString() { return this.getClass().getSimpleName() + "[snapshotTerm=" + this.snapshotTerm + ",snapshotIndex=" + this.snapshotIndex + ",snapshotConfig=" + this.snapshotConfig + ",pairIndex=" + this.pairIndex + (this.snapshot == null ? ",closed" : "") + "]"; } }





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