真正构造IndexWriter
IndexWriter indexWriter = new IndexWriter(directory, config);
构造过程
1 public IndexWriter(Directory d, IndexWriterConfig conf) throws IOException {
2 conf.setIndexWriter(this); // prevent reuse by other instances 防止被其他实例使用，这个引用被设置在IndexWriterConfig中
3 config = new LiveIndexWriterConfig(conf);//将IndexWriterConfig中的配置重新赋给LiveIndexWriterConfig，完全是this.x=config.getX()，既然new IndexWriterConfig是直接调用父类构造器，也就是LiveIndexWriterConfig，为什么还要重新来一遍呢？
4 directory = d;//索引目录
5 analyzer = config.getAnalyzer();//解析器
6 infoStream = config.getInfoStream();//NoOutput
7 mergePolicy = config.getMergePolicy();//合并策略
8 mergePolicy.setIndexWriter(this);//同样在合并策略中设置一份该IndexWriter引用，同第2行一样，MergePolicy中同样维护了SetOnce<IndexWriter>
9 mergeScheduler = config.getMergeScheduler();//merge调度器
10 codec = config.getCodec();//header校验
11
12 bufferedUpdatesStream = new BufferedUpdatesStream(infoStream);//在写线程flush的时候，所有的delete和update数据会放在该缓冲区
13 poolReaders = config.getReaderPooling();//默认false
14
15 writeLock = directory.makeLock(WRITE_LOCK_NAME);//创建写锁，write.lock
16
17 if (!writeLock.obtain(config.getWriteLockTimeout())) // obtain write lock 获取写锁
18 throw new LockObtainFailedException("Index locked for write: " + writeLock);
19
20 boolean success = false;
21 try {
22 OpenMode mode = config.getOpenMode();//默认create and appen
23 boolean create;
24 if (mode == OpenMode.CREATE) {
25 create = true;
26 } else if (mode == OpenMode.APPEND) {
27 create = false;
28 } else {//默认条件
29 // CREATE_OR_APPEND - create only if an index does not exist 如果索引文件不存在，则create=true
30 create = !DirectoryReader.indexExists(directory);//判断索引文件是否存在根据index dir下是否含有segment文件
31 }
32
33 // If index is too old, reading the segments will throw
34 // IndexFormatTooOldException.
35 segmentInfos = new SegmentInfos();
36
37 boolean initialIndexExists = true;
38
39 if (create) {//如果索引文件不存在，策略为先读取该目录下segment文件，根据异常
40 // Try to read first. This is to allow create
41 // against an index that‘s currently open for
42 // searching. In this case we write the next
43 // segments_N file with no segments:
44 try {
45 segmentInfos.read(directory);//read方法见lucene之段元数据文件，lucene在针对segment读取有三种策略，不做详解，出现任何问题都会抛出IOException异常
46 segmentInfos.clear();//确认完毕清空segment信息
47 } catch (IOException e) {
48 // Likely this means it‘s a fresh directory
49 initialIndexExists = false;
50 }
51
52 // Record that we have a change (zero out all
53 // segments) pending:
54 changed();//indexwriter中changecount加1，segmentInfos中version加1
55 } else {//如果已经存在索引文件
56 segmentInfos.read(directory);//依然读取段信息
57
58 IndexCommit commit = config.getIndexCommit();
59 if (commit != null) {//初始化commit为null
60 // Swap out all segments, but, keep metadata in
61 // SegmentInfos, like version & generation, to
62 // preserve write-once. This is important if
63 // readers are open against the future commit
64 // points.
65 if (commit.getDirectory() != directory)
66 throw new IllegalArgumentException("IndexCommit‘s directory doesn‘t match my directory");
67 SegmentInfos oldInfos = new SegmentInfos();
68 oldInfos.read(directory, commit.getSegmentsFileName());
69 segmentInfos.replace(oldInfos);
70 changed();
71 if (infoStream.isEnabled("IW")) {
72 infoStream.message("IW", "init: loaded commit \"" + commit.getSegmentsFileName() + "\"");
73 }
74 }
75 }
76
77 rollbackSegments = segmentInfos.createBackupSegmentInfos();//for roll back
78
79 // start with previous field numbers, but new FieldInfos
80 globalFieldNumberMap = getFieldNumberMap();//加载field信息，fieldname，fieldnumber，docValue，解析如下
81 config.getFlushPolicy().init(config);//初始化flush策略,设置config引用，获取NoOutput，init方法为同步方法
82 docWriter = new DocumentsWriter(this, config, directory);//创建DocumentWriter对象，详细如下，主要初始化一个config中的配置
83 eventQueue = docWriter.eventQueue();//获取事件队列，在上步中进行初始化，concurrentLinkedQueue
84
85 // Default deleter (for backwards compatibility) is
86 // KeepOnlyLastCommitDeleter:
########################################## 下一篇解析 ###########################################################
87 synchronized(this) {//构建索引管理对象
88 deleter = new IndexFileDeleter(directory,
89 config.getIndexDeletionPolicy(),//默认策略为KeepOnlyLastCommitDeleter
90 segmentInfos, infoStream, this,
91 initialIndexExists);
92 }
93
94 if (deleter.startingCommitDeleted) {
95 // Deletion policy deleted the "head" commit point.
96 // We have to mark ourself as changed so that if we
97 // are closed w/o any further changes we write a new
98 // segments_N file.
99 changed();
100 }
101
102 if (infoStream.isEnabled("IW")) {
103 infoStream.message("IW", "init: create=" + create);
104 messageState();
105 }
106
107 success = true;
108
109 } finally {
110 if (!success) {
111 if (infoStream.isEnabled("IW")) {
112 infoStream.message("IW", "init: hit exception on init; releasing write lock");
113 }
114 IOUtils.closeWhileHandlingException(writeLock);
115 writeLock = null;
116 }
117 }
118 }
第2行：在IndexWriteConfig中维护一个SetOnce，并非Set集合，dexWriter时会把该引用存入SetOnce中，lucene给出的注释是防止其他实例调用
// indicates whether this config instance is already attached to a writer.
// not final so that it can be cloned properly.
private SetOnce<IndexWriter> writer = new SetOnce<IndexWriter>();
/**
* Sets the {@link IndexWriter} this config is attached to.
*
* @throws AlreadySetException
* if this config is already attached to a writer.
*/
IndexWriterConfig setIndexWriter(IndexWriter writer) {
this.writer.set(writer);//SetOnce保证了多线程的情况，IndexWriter对象引用会被set一次
return this;
}
以下是SetOnce的结构
/**
* A convenient class which offers a semi-immutable object wrapper
* implementation which allows one to set the value of an object exactly once,
* and retrieve it many times. If {@link #set(Object)} is called more than once,
* {@link AlreadySetException} is thrown and the operation
* will fail.
*
* @lucene.experimental
*/
public final class SetOnce<T> implements Cloneable {
/** Thrown when {@link SetOnce#set(Object)} is called more than once. */
public static final class AlreadySetException extends IllegalStateException {
public AlreadySetException() {
super("The object cannot be set twice!");
}
}
private volatile T obj = null;//volatile类型
private final AtomicBoolean set;//原子boolean类型
/**
* A default constructor which does not set the internal object, and allows
* setting it by calling {@link #set(Object)}.
*/
public SetOnce() {
set = new AtomicBoolean(false);//初始化false
}
/**
* Creates a new instance with the internal object set to the given object.
* Note that any calls to {@link #set(Object)} afterwards will result in
* {@link AlreadySetException}
*
* @throws AlreadySetException if called more than once
* @see #set(Object)
*/
public SetOnce(T obj) {
this.obj = obj;
set = new AtomicBoolean(true);
}
/** Sets the given object. If the object has already been set, an exception is thrown. */
public final void set(T obj) {//调用set
if (set.compareAndSet(false, true)) {//更新原子boolean值，保证只有一个线程能够set成功
this.obj = obj;//volatile类型保证对所有线程立即可见
} else {//当其他线程检测到obj已经被设置，则抛出异常
throw new AlreadySetException();
}
}
/** Returns the object set by {@link #set(Object)}. */
public final T get() {
return obj;
}
@Override
public SetOnce<T> clone() {
return obj == null ? new SetOnce<T>() : new SetOnce<T>(obj);
}
第17行，获取写锁,Lock
/** Attempts to obtain an exclusive lock within amount of
* time given. Polls once per {@link #LOCK_POLL_INTERVAL}
* (currently 1000) milliseconds until lockWaitTimeout is
* passed.
* @param lockWaitTimeout length of time to wait in
* milliseconds or {@link
* #LOCK_OBTAIN_WAIT_FOREVER} to retry forever
* @return true if lock was obtained
* @throws LockObtainFailedException if lock wait times out
* @throws IllegalArgumentException if lockWaitTimeout is
* out of bounds
* @throws IOException if obtain() throws IOException
*/
public boolean obtain(long lockWaitTimeout) throws IOException {
failureReason = null;
boolean locked = obtain();//尝试获取锁，见下方代码
if (lockWaitTimeout < 0 && lockWaitTimeout != LOCK_OBTAIN_WAIT_FOREVER)//
throw new IllegalArgumentException("lockWaitTimeout should be LOCK_OBTAIN_WAIT_FOREVER or a non-negative number (got " + lockWaitTimeout + ")");
long maxSleepCount = lockWaitTimeout / LOCK_POLL_INTERVAL;
long sleepCount = 0;
while (!locked) {//循环获取锁
if (lockWaitTimeout != LOCK_OBTAIN_WAIT_FOREVER && sleepCount++ >= maxSleepCount) {//默认情况下是无限循环下去，
String reason = "Lock obtain timed out: " + this.toString();
if (failureReason != null) {
reason += ": " + failureReason;
}
LockObtainFailedException e = new LockObtainFailedException(reason);
if (failureReason != null) {
e.initCause(failureReason);
}
throw e;
}
try {
Thread.sleep(LOCK_POLL_INTERVAL);//睡眠间隔
} catch (InterruptedException ie) {
throw new ThreadInterruptedException(ie);
}
locked = obtain();
}
return locked;
}
SimpleFSDirectory获取锁实现
@Override
public boolean obtain() throws IOException {
// Ensure that lockDir exists and is a directory:
if (!lockDir.exists()) {//lockDir在Directory directory = FSDirectory.open的时候就已经设置好了，确定索引目录
if (!lockDir.mkdirs())//如果没有就创建，创建失败就抛异常
throw new IOException("Cannot create directory: " +
lockDir.getAbsolutePath());
} else if (!lockDir.isDirectory()) {//非目录抛异常
// TODO: NoSuchDirectoryException instead?
throw new IOException("Found regular file where directory expected: " +
lockDir.getAbsolutePath());
}
return lockFile.createNewFile();//创建write.lock，返回创建结果，利用文件系统限制并发操作
}
第80行，
/**
* Loads or returns the already loaded the global field number map for this {@link SegmentInfos}.
* If this {@link SegmentInfos} has no global field number map the returned instance is empty
*/
private FieldNumbers getFieldNumberMap() throws IOException {
final FieldNumbers map = new FieldNumbers();//
for(SegmentCommitInfo info : segmentInfos) {
for(FieldInfo fi : SegmentReader.readFieldInfos(info)) {
map.addOrGet(fi.name, fi.number, fi.getDocValuesType());
}
}
return map;
}
FieldNumbers作为FieldInfos的一个静态内部类，维护以下3个hashmap，主要涉及到了field的三个属性
1.fieldname，顾名思义，2.fileNumber，fileNumber使用一个byte的8位记录了该filed的属性，是否索引，是否存储，是否含有docValue等等，详情已在域元文件解析文章中说明，3.docValueType
private final Map<Integer,String> numberToName;
private final Map<String,Integer> nameToNumber;
// We use this to enforce that a given field never
// changes DV type, even across segments / IndexWriter
// sessions:
private final Map<String,DocValuesType> docValuesType;//key：fieldname，value：docValueType
提供同步addOrGet接口，支持多线程
/**
* Returns the global field number for the given field name. If the name
* does not exist yet it tries to add it with the given preferred field
* number assigned if possible otherwise the first unassigned field number
* is used as the field number.
*/
synchronized int addOrGet(String fieldName, int preferredFieldNumber, DocValuesType dvType) {
if (dvType != null) {
DocValuesType currentDVType = docValuesType.get(fieldName);//docValueType 使用byte记录类型，前4位为标准类型，后4位为docValues类型，lucene支持4种docValueType，分别为BINARY，NUMBERIC，STORED，STORED_SET
if (currentDVType == null) {
docValuesType.put(fieldName, dvType);
} else if (currentDVType != null && currentDVType != dvType) {
throw new IllegalArgumentException("cannot change DocValues type from " + currentDVType + " to " + dvType + " for field \"" + fieldName + "\"");
}
}
Integer fieldNumber = nameToNumber.get(fieldName);//判断是否已经含有该field
if (fieldNumber == null) {
final Integer preferredBoxed = Integer.valueOf(preferredFieldNumber);
if (preferredFieldNumber != -1 && !numberToName.containsKey(preferredBoxed)) {//如果fieldnum不为-1，并且还没有存储该域值，则赋值给fieldnum
// cool - we can use this number globally
fieldNumber = preferredBoxed;
} else {//否则，寻找一个新的fieldnumber，这个寻找的规则就是从-1开始逐步加1，直到numberToName中没有存储该域值，记录此时数值做为域值，因为numberToName的key是域值，而域值的范围根据8为bit的类型是有限的，相同类型的field数值是冲突的，所以有冲突的域值就做加1操作，作为累加之后的fieldnumber怎么在使用的时候去解析呢？
// find a new FieldNumber
while (numberToName.containsKey(++lowestUnassignedFieldNumber)) {//默认lowestUnassignedFieldNumber=-1，
// might not be up to date - lets do the work once needed
}
fieldNumber = lowestUnassignedFieldNumber;
}
numberToName.put(fieldNumber, fieldName);
nameToNumber.put(fieldName, fieldNumber);
}
return fieldNumber.intValue();//返回该值
}
第82行，DocumentWriter初始化
DocumentsWriter(IndexWriter writer, LiveIndexWriterConfig config, Directory directory) {
this.directory = directory;
this.config = config;
this.infoStream = config.getInfoStream();
this.perThreadPool = config.getIndexerThreadPool();
flushPolicy = config.getFlushPolicy();
this.writer = writer;
this.events = new ConcurrentLinkedQueue<Event>();//初始化了一个事件队列，并且是线程安全的
flushControl = new DocumentsWriterFlushControl(this, config, writer.bufferedUpdatesStream);
}
接上，初始化一个文档flush控制器DocumentWriterFlushControl
DocumentsWriterFlushControl(DocumentsWriter documentsWriter, LiveIndexWriterConfig config, BufferedUpdatesStream bufferedUpdatesStream) {
this.infoStream = config.getInfoStream();
this.stallControl = new DocumentsWriterStallControl();
this.perThreadPool = documentsWriter.perThreadPool;
this.flushPolicy = documentsWriter.flushPolicy;
this.config = config;
this.hardMaxBytesPerDWPT = config.getRAMPerThreadHardLimitMB() * 1024 * 1024;
this.documentsWriter = documentsWriter;
this.bufferedUpdatesStream = bufferedUpdatesStream;//出现了，在IndexWriter构造的时候初始化了该属性，用于线程delete和update时候存放缓冲数据
}
时间： 2024-08-24 12:39:04