Flume的source选哪个？
taildir source首选！
1.断点还原 positionFile可以记录偏移量
2.可配置文件组，里面使用正则表达式配置多个要监控的文件
就凭第一点其他的source都被比下去了！
这么好的taildir source有一点不完美，不能支持递归监控文件夹。
所以就只能修改源代码了……好玩，我喜欢~
改源码，先读源码
Flume的taildir source启动会调用start()方法作初始化，里面创建一个ReliableTaildirEventReader,这里用到了建造者模式
@Override
public synchronized void start() {
logger.info("{} TaildirSource source starting with directory: {}", getName(), filePaths);
try {
reader = new ReliableTaildirEventReader.Builder()
.filePaths(filePaths)
.headerTable(headerTable)
.positionFilePath(positionFilePath)
.skipToEnd(skipToEnd)
.addByteOffset(byteOffsetHeader)
.cachePatternMatching(cachePatternMatching)
.recursive(isRecursive)
.annotateFileName(fileHeader)
.fileNameHeader(fileHeaderKey)
.build();
} catch (IOException e) {
throw new FlumeException("Error instantiating ReliableTaildirEventReader", e);
}
idleFileChecker = Executors.newSingleThreadScheduledExecutor(
new ThreadFactoryBuilder().setNameFormat("idleFileChecker").build());
idleFileChecker.scheduleWithFixedDelay(new idleFileCheckerRunnable(),
idleTimeout, checkIdleInterval, TimeUnit.MILLISECONDS);
positionWriter = Executors.newSingleThreadScheduledExecutor(
new ThreadFactoryBuilder().setNameFormat("positionWriter").build());
positionWriter.scheduleWithFixedDelay(new PositionWriterRunnable(),
writePosInitDelay, writePosInterval, TimeUnit.MILLISECONDS);
super.start();
logger.debug("TaildirSource started");
sourceCounter.start();
}taildir source属于PollableSource，
/**
* A {@link Source} that requires an external driver to poll to determine
* whether there are {@linkplain Event events} that are available to ingest
* from the source.
*
* @see org.apache.flume.source.EventDrivenSourceRunner
*/
public interface PollableSource extends Source {
...这段注释的意思是PollableSource是需要一个外部驱动去查看有没有需要消费的事件，从而拉取事件，讲白了就是定时拉取。所以flume也不一定是真正实时的，只是隔一会儿不停地来查看事件而已。(与之相应的是另一种EventDrivenSourceRunner)
那么taildir source在定时拉取事件的时候是调用的process方法
@Override
public Status process() {
Status status = Status.READY;
try {
existingInodes.clear();
existingInodes.addAll(reader.updateTailFiles());
for (long inode : existingInodes) {
TailFile tf = reader.getTailFiles().get(inode);
if (tf.needTail()) {
tailFileProcess(tf, true);
}
}
closeTailFiles();
try {
TimeUnit.MILLISECONDS.sleep(retryInterval);
} catch (InterruptedException e) {
logger.info("Interrupted while sleeping");
}
} catch (Throwable t) {
logger.error("Unable to tail files", t);
status = Status.BACKOFF;
}
return status;
}重点就是下面这几行
existingInodes.addAll(reader.updateTailFiles());
for (long inode : existingInodes) {
TailFile tf = reader.getTailFiles().get(inode);
if (tf.needTail()) {
tailFileProcess(tf, true);
} }
从reader.updateTailFiles()获取需要监控的文件，然后对每一个进行处理，查看最后修改时间，判定是否需要tail，需要tail就tail
那么进入reader.updateTailFiles()
for (TaildirMatcher taildir : taildirCache) {
Map headers = headerTable.row(taildir.getFileGroup());
for (File f : taildir.getMatchingFiles()) {
long inode = getInode(f);
TailFile tf = tailFiles.get(inode);
if (tf == null || !tf.getPath().equals(f.getAbsolutePath())) {
long startPos = skipToEnd ? f.length() : 0;
tf = openFile(f, headers, inode, startPos); 遍历每一个正则表达式匹配对应的匹配器，每个匹配器去获取匹配的文件！taildir.getMatchingFiles()
List getMatchingFiles() {
long now = TimeUnit.SECONDS.toMillis(
TimeUnit.MILLISECONDS.toSeconds(System.currentTimeMillis()));
long currentParentDirMTime = parentDir.lastModified();
List result;
// calculate matched files if
// - we don't want to use cache (recalculate every time) OR
// - directory was clearly updated after the last check OR
// - last mtime change wasn't already checked for sure
// (system clock hasn't passed that second yet)
if (!cachePatternMatching ||
lastSeenParentDirMTime < currentParentDirMTime ||
!(currentParentDirMTime < lastCheckedTime)) {
lastMatchedFiles = sortByLastModifiedTime(getMatchingFilesNoCache(isRecursive));
lastSeenParentDirMTime = currentParentDirMTime;
lastCheckedTime = now;
}
return lastMatchedFiles;
} 可以看到getMatchingFilesNoCache(isRecursive)就是获取匹配的文件的方法，也就是需要修改的方法了！
ps：这里的isRecursive是我加的~
点进去：
private List getMatchingFilesNoCache() {
List result = Lists.newArrayList();
try (DirectoryStream stream = Files.newDirectoryStream(parentDir.toPath(), fileFilter)) {
for (Path entry : stream) {
result.add(entry.toFile());
}
} catch (IOException e) {
logger.error("I/O exception occurred while listing parent directory. " +
"Files already matched will be returned. " + parentDir.toPath(), e);
}
return result;
} 源码是用了Files.newDirectoryStream(parentDir.toPath(), fileFilter))，将父目录下符合正则表达式的文件都添加到一个迭代器里。（这里还用了try (...)的语法糖）
找到地方了，开始改！
我在这个getMatchingFilesNoCache()方法下面下了一个重载的方法, 可增加扩展性：
private List getMatchingFilesNoCache(boolean recursion) {
if (!recursion) {
return getMatchingFilesNoCache();
}
List result = Lists.newArrayList();
// 使用非递归的方式遍历文件夹
Queue dirs = new ArrayBlockingQueue<>(10);
dirs.offer(parentDir);
while (dirs.size() > 0) {
File dir = dirs.poll();
try {
DirectoryStream stream = Files.newDirectoryStream(dir.toPath(), fileFilter);
stream.forEach(path -> result.add(path.toFile()));
} catch (IOException e) {
logger.error("I/O exception occurred while listing parent directory. " +
"Files already matched will be returned. (recursion)" + parentDir.toPath(), e);
}
File[] dirList = dir.listFiles();
assert dirList != null;
for (File f : dirList) {
if (f.isDirectory()) {
dirs.add(f);
}
}
}
return result;
} 我使用了非递归的方式遍历文件夹，就是树到队列的转换。
到这里，核心部分就改完了。接下来要处理这个recursion的参数
华丽的分割线后，顺腾摸瓜！
一路改构造方法，添加这个参数，最终参数从哪来呢？
flume的source启动时会调用configure方法，将Context中的内容配置进reader等对象中。isRecursive = context.getBoolean(RECURSIVE, DEFAULT_RECURSIVE);context从TaildirSourceConfigurationConstants中获取配置名和默认值
/**
* Whether to support recursion. */
public static final String RECURSIVE = "recursive";
public static final boolean DEFAULT_RECURSIVE = false;这里的recursive也就是flume配置文件里配置项了
# Whether to support recusion
a1.sources.r1.recursive = true大功告成，打包试试！
用maven只对这一个module打包。我把这个module的pom改了下artifactId，加上了自己名字作个纪念，哈哈
可惜pom里面不能写中文……
org.apache.flume.flume-ng-sources
flume-taildir-source-recursive-by-Wish000
Flume Taildir Source 执行package将其放在flume的lib下，替换原来的flume-taildir-source***.jar
启动，测试，成功！
具体代码见GitHub地址：https://github.com/Wish000/me...