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/*
 * 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.jackrabbit.oak.segment;

import static com.google.common.base.Preconditions.checkNotNull;

import java.io.IOException;
import java.io.InputStream;

import org.apache.jackrabbit.oak.api.Blob;
import org.apache.jackrabbit.oak.plugins.memory.MemoryNodeBuilder;
import org.apache.jackrabbit.oak.spi.blob.BlobStore;
import org.apache.jackrabbit.oak.spi.state.NodeState;
import org.apache.jackrabbit.oak.stats.MeterStats;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * A node builder that keeps track of the number of updates
 * (set property calls and so on). If there are too many updates,
 * getNodeState() is called, which will write the records to the segment,
 * and that might persist the changes (if the segment is flushed).
 */
public class SegmentNodeBuilder extends MemoryNodeBuilder {
    private static final Logger LOG = LoggerFactory.getLogger(SegmentNodeBuilder.class);

    /**
     * Number of content updates that need to happen before the updates
     * are automatically purged to the underlying segments.
     */
    private static final int UPDATE_LIMIT =
            Integer.getInteger("update.limit", 10000);

    @Nullable
    private final BlobStore blobStore;

    @NotNull
    private final SegmentReader reader;

    @NotNull
    private final SegmentWriter writer;

    private final MeterStats readStats;

    /**
     * Local update counter for the root builder.
     * 
     * The value encodes both the counter and the type of the node builder:
     * 
    *
  • value >= {@code 0} represents a root builder (builder keeps * counter updates)
  • *
  • value = {@code -1} represents a child builder (value doesn't * change, builder doesn't keep an updated counter)
  • *
* */ private long updateCount; SegmentNodeBuilder( @NotNull SegmentNodeState base, @Nullable BlobStore blobStore, @NotNull SegmentReader reader, @NotNull SegmentWriter writer, MeterStats readStats ) { super(base); this.blobStore = blobStore; this.reader = reader; this.writer = checkNotNull(writer); this.updateCount = 0; this.readStats = readStats; } private SegmentNodeBuilder( @NotNull SegmentNodeBuilder parent, @NotNull String name, @Nullable BlobStore blobStore, @NotNull SegmentReader reader, @NotNull SegmentWriter writer, MeterStats readStats ) { super(parent, name); this.blobStore = blobStore; this.reader = reader; this.writer = checkNotNull(writer); this.updateCount = -1; this.readStats = readStats; } /** * @return {@code true} iff this builder has been acquired from a root node state. */ boolean isRootBuilder() { return isRoot(); } //-------------------------------------------------< MemoryNodeBuilder >-- @Override protected void updated() { if (isChildBuilder()) { super.updated(); } else { updateCount++; if (updateCount > UPDATE_LIMIT) { getNodeState(); } } } private boolean isChildBuilder() { return updateCount < 0; } //-------------------------------------------------------< NodeBuilder >-- @NotNull @Override public SegmentNodeState getNodeState() { try { NodeState state = super.getNodeState(); SegmentNodeState sState = new SegmentNodeState(reader, writer, blobStore, writer.writeNode(state), readStats); if (state != sState) { set(sState); if(!isChildBuilder()) { updateCount = 0; } } return sState; } catch (IOException e) { LOG.error("Error flushing changes", e); throw new IllegalStateException("Unexpected IOException", e); } } @Override protected MemoryNodeBuilder createChildBuilder(String name) { return new SegmentNodeBuilder(this, name, blobStore, reader, writer, readStats); } @Override public Blob createBlob(InputStream stream) throws IOException { return new SegmentBlob(blobStore, writer.writeStream(stream)); } }




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