dubbo启动报错多个资源争缓存问题

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]

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"/>

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

另一个方法：

我们使用的Dubbo最近老是遇到WARN [DubboSaveRegistryCache-thread-1] (AbstractRegistry.java:221) method:doSaveProperties - [DUBBO] Failed to save registry store file, cause: Can not lock the registry cache file /home/newad/.dubbo/dubbo-registry-*.*.*.*.cache, ignore and retry later, maybe multi java process use the file, please config: dubbo.registry.file=xxx.properties, dubbo version: 2.5.3, current host: *.*.*.*
java.io.IOException: Can not lock the registry cache file /home/newad/.dubbo/dubbo-registry-*.*.*.*.cache, ignore and retry later, maybe multi java process use the file, please config: dubbo.registry.file=xxx.properties

从异常中很清楚的看到，Dubbo在保存服务列表时失败，失败的原因也很简单，异常里面都说得很清楚了，Can not lock the registry cache file /home/newad/.dubbo/dubbo-registry-*.*.*.*.cache，拿不到文件锁，无法保存服务列表。

Dubbo通过注册中心发现服务，发现的服务Dubbo同时也会保存到本地缓存一份，缓存的好处有很多，比如不需要每次使用的时候都通过注册中心获取，注册中心不可用了，不影响消费端的调用，因为本地缓存了一份服务提供者列表。Dubbo本地缓存默认采用的文件，会根据注册中心自动在当前用户目录下生成一个缓存文件，类似/home/newad/.dubbo/dubbo-registry-*.*.*.*.cache，星号表示注册中心的IP地址，当同一台机器上同时启动多个进程，就会出现多个进程争夺此文件的写入权限，觖此问题的方法也很简单，日志里面都说了重新配置一下这个缓存文件就。

主要在启动脚本里面添加配置： -Ddubbo.registry.file=/home/newad/.dubbo/dubbo-registry-Order-0.cache

Shell代码

#!/bin/sh
CU=/home/www/WEB-INF/release/
#LANG="zh_CN"
#export LANG
CP=$CU":./"
LIB=$CU"lib/*.jar"
for i in $LIB
do
CP="$i:$CP"
done
export CP
JAVA=/home/www/jvm/jdk1.7.0_02/bin/java
export JAVA
cd "$CUorder"
lock=./lock
if [ ! -f "$lock" ]
then
touch "$lock"
echo "classpath:" $CP
$JAVA -server -Xms1024m -Xmx1024m -XX:PermSize=256m -DOrder=Order-0 -Dlog4j.configuration=file:/home/www/WEB-INF/release/order/log4j.properties -Ddubbo.registry.file=/home/newad/.dubbo/dubbo-registry-Order-0.cache -cp $CP com.product.PServer
rm "$lock"
else
echo " already startup!"
fi