Dubbo Failed to save registry store file, cause: Can not lock the registry cache file

启动的Dubbo 服务的时候报错，异常信息如下：

2016-08-22 16:44:40.588 | DubboSaveRegistryCache-thread-1 | WARN  | com.alibaba.dubbo.common.logger.log4j.Log4jLogger:Log4jLogger.java(78) |  [DUBBO] Failed to save registry store file, cause: Can not lock the registry cache file /root/.dubbo/dubbo-registry-10.141.4.168.cache, ignore and retry later, maybe multi java process use the file, please config: dubbo.registry.file=xxx.properties, dubbo version: 2.8.3, current host: 127.0.0.1
java.io.IOException: Can not lock the registry cache file /root/.dubbo/dubbo-registry-10.141.4.168.cache, ignore and retry later, maybe multi java process use the file, please config: dubbo.registry.file=xxx.properties
        at com.alibaba.dubbo.registry.support.AbstractRegistry.doSaveProperties(AbstractRegistry.java:193) ~[dubbo-2.8.3.jar:2.8.3]
        at com.alibaba.dubbo.registry.support.AbstractRegistry$SaveProperties.run(AbstractRegistry.java:150) [dubbo-2.8.3.jar:2.8.3]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) [na:1.7.0_60]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) [na:1.7.0_60]
        at java.lang.Thread.run(Thread.java:745) [na:1.7.0_60]
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报错的大概意思是 Dubbo在保存服务列表时失败，Can not lock the registry cache file /root/.dubbo/dubbo-registry-10.141.4.168.cache，拿不到文件锁，无法保存服务列表。

错误原因

出现这个的原因是服务向ZK注册的同时，会缓存Consumer的列表，写入user.home/.dubbo/dubbo-registry-” + url.getHost() + “.cache 这个文件，当在同一个机器上启动多个Provider的时候，就会出现文件锁争用的问题，报上面这个错误。

解决办法

既然是由于竞争文件锁导致的，那么让服务模块各自缓存自己的cache文件就可以避免这样的问题了。

具体做法是：在provider的xml配置文件中加入 file=”${catalina.home}/dubbo-registry/dubbo-registry.properties” ，如下：

<dubbo:registry id="zkcenter" protocol="zookeeper" address="${dubbo.zk_address}" file="${catalina.home}/dubbo-registry/dubbo-registry.properties"/>
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这样就会在catalina.home目录下生成dubbo-registry这个目录，cache文件就缓存在这个里边了。

参考资料

AbstractRegistry lock problem：https://github.com/alibaba/dubbo/issues/81