看遍了各种基于数据库（主键；版本号；排他等），基于缓存（Redis；Redlock等），基于分布式（ZooKeeper；Consul等）的分布式锁，来个简单的基于文件的分布式锁
场景
- 假设这块共享存储挂载在各应用服务器中（比如
/nfsroot/nfs1）
实现
package org.shaneking.demo.nfs.file.lock;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
import java.text.MessageFormat;
public class NFSFileLock {
public static final int MAX_TRY_TIMES = 10;
public static final String FMT_FAILED = "Lock file {0} failed, th{1}.";
public static final String FMT_SUCCESSFULLY = "Lock file {0} successfully, th{1}.";
public static void main(String[] args) {
RandomAccessFile randomAccessFile = null;
FileChannel fileChannel = null;
FileLock fileLock = null;
try {
File lockFile = new File(args[0]);
if (!lockFile.exists()) {
lockFile.getParentFile().mkdirs();
lockFile.createNewFile();
}
randomAccessFile = new RandomAccessFile(lockFile, "rw");
fileChannel = randomAccessFile.getChannel();
int tryTimes = 0;
while (fileLock == null && tryTimes < MAX_TRY_TIMES) {
try {
fileLock = fileChannel.tryLock();
} catch (IOException e) {
e.printStackTrace();
}
if (fileLock == null) {
System.out.println(MessageFormat.format(FMT_FAILED, lockFile.getAbsolutePath(), tryTimes));
if (!lockFile.exists()) {
lockFile.getParentFile().mkdirs();
lockFile.createNewFile();
}
tryTimes++;
Thread.sleep(10000);//10
} else {
System.out.println(MessageFormat.format(FMT_SUCCESSFULLY, lockFile.getAbsolutePath(), tryTimes));
}
}
if (fileLock != null) {
//TODO some logic here
Thread.sleep(100000);//100, Just to make the test more obvious
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (fileLock != null) {
try {
fileLock.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (fileChannel != null) {
try {
fileChannel.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (randomAccessFile != null) {
try {
randomAccessFile.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
测试
准备
[user@dev-cluster-s1 ~]% df -h | grep cluster
abcdefghig-12345.cn-shanghai.nas.aliyuncs.com:/ 10P 106M 10P 1% /dev-nas-cluster
ossfs 256T 0 256T 0% /dev-oss-cluster
[user@dev-cluster-s2 ~]% df -h | grep cluster
abcdefghig-12345.cn-shanghai.nas.aliyuncs.com:/ 10P 106M 10P 1% /dev-nas-cluster
ossfs 256T 0 256T 0% /dev-oss-cluster
[user@dev-cluster-s2 ~]% mkdir -p /dev-nas-cluster/workspace/github/shaneking/org.shaneking.demo.nfs.file.lock
[user@dev-cluster-s2 ~]% mkdir -p /dev-oss-cluster/workspace/github/shaneking/org.shaneking.demo.nfs.file.lock
[user@dev-cluster-s2 org.shaneking.demo.nfs.file.lock]% yum -y list java*
[user@dev-cluster-s2 org.shaneking.demo.nfs.file.lock]% yum -y install java-11-openjdk*
[user@dev-cluster-s2 org.shaneking.demo.nfs.file.lock]% yum -y install java-1.8.0-openjdk*
nas
[user@dev-cluster-s1 org.shaneking.demo.nfs.file.lock]% java -cp org.shaneking.demo.nfs.file.lock-0.10.0.jar org.shaneking.demo.nfs.file.lock.NFSFileLock /dev-nas-cluster/workspace/github/shaneking/org.shaneking.demo.nfs.file.lock/test.lock
Lock file /dev-nas-cluster/workspace/github/shaneking/org.shaneking.demo.nfs.file.lock/test.lock successfully, th0.
[user@dev-cluster-s2 org.shaneking.demo.nfs.file.lock]% java -cp org.shaneking.demo.nfs.file.lock-0.10.0.jar org.shaneking.demo.nfs.file.lock.NFSFileLock /dev-nas-cluster/workspace/github/shaneking/org.shaneking.demo.nfs.file.lock/test.lock
Lock file /dev-nas-cluster/workspace/github/shaneking/org.shaneking.demo.nfs.file.lock/test.lock failed, th0.
Lock file /dev-nas-cluster/workspace/github/shaneking/org.shaneking.demo.nfs.file.lock/test.lock failed, th1.
oss
[user@dev-cluster-s1 org.shaneking.demo.nfs.file.lock]% java -cp org.shaneking.demo.nfs.file.lock-0.10.0.jar org.shaneking.demo.nfs.file.lock.NFSFileLock /dev-oss-cluster/workspace/github/shaneking/org.shaneking.demo.nfs.file.lock/test.lock
Lock file /dev-oss-cluster/workspace/github/shaneking/org.shaneking.demo.nfs.file.lock/test.lock successfully, th0.
[user@dev-cluster-s2 org.shaneking.demo.nfs.file.lock]% java -cp org.shaneking.demo.nfs.file.lock-0.10.0.jar org.shaneking.demo.nfs.file.lock.NFSFileLock /dev-oss-cluster/workspace/github/shaneking/org.shaneking.demo.nfs.file.lock/test.lock
Lock file /dev-oss-cluster/workspace/github/shaneking/org.shaneking.demo.nfs.file.lock/test.lock successfully, th0.
结论
NAS（NFS）支持分布式文件锁，OSS（S3FS）不支持。
源码
https://github.com/ShaneKingBlog/org.shaneking.demo.nfs.file.lock
