#10227 优化subscribe时初始化性能，经过优化后，该场景在开发环境下从5~20秒性能提升至300~1000ms，提升5~20倍，基本上在30…

[tietang]

What is the purpose of the change

原来为使用redis scan命令来扫描 /dubbo/com.xxx.yyy.XxxService/*的key 按照https://dubbo.apache.org/zh/docsv2.7/user/references/registry/redis/对redis注册中心的介绍 只有/dubbo/com.xxx.yyy.XxxService/providers 和/dubbo/com.xxx.yyy.XxxService/consumers 2种可能性。 在在使用ClusterRedisClient时，scan命令（参考：org.apache.dubbo.remoting.redis.jedis.ClusterRedisClient.scan）是迭代循环所有cluster node 来扫描每一个node，并合并扫描结果完成的，scan命令本来就很慢，使用ClusterRedisClient时会随着节点越多越慢 我的场景中有6个节点，每次需要5 ~ 20秒的扫描时间，每次启动时很慢且卡在初始化reference阶段；或者泛化每接口第一次调用或者硬编码每接口第一次调用时，都会构建Reference，构建reference时花费了很多时间 如果项目中service 接口很多时，有可能在启动或者重启后会导致worker线程阻塞而请求无法正常调用，目前在测试环境已经遇到了该现象，高并发请求时有可能引起雪奔，特别是存在dubbo http网关时的场景。 经过优化后，该场景在开发环境下从5 ~ 20秒性能提升至300~1000ms，提升5 ~ 20倍，基本上在300 ~ 1000ms即可构建好reference。 测试环境多线程（50线程）预创建48个reference需要，同机房1985ms（优化前9839ms）提升5倍，跨机房（同地域）3276ms（优化前35303ms）提升10倍。 本地环境（远程连接测试环境redis）多线程（50线程）预创建48个reference需要18288ms（优化前436235ms，约7分钟多，提升23倍）。

[tietang]

#10227

[codecov-commenter]

Codecov Report

Merging #10234 (d3d1075) into master (c1a76a0) will decrease coverage by 0.06%. The diff coverage is 66.66%.

@@             Coverage Diff              @@
##             master   #10234      +/-   ##
============================================
- Coverage     60.95%   60.89%   -0.07%     
+ Complexity      448      446       -2     
============================================
  Files          1100     1100              
  Lines         44579    44531      -48     
  Branches       6493     6488       -5     
============================================
- Hits          27175    27119      -56     
- Misses        14437    14444       +7     
- Partials       2967     2968       +1     

Impacted Files	Coverage Δ
...dubbo/remoting/redis/jedis/ClusterRedisClient.java	0.00% <0.00%> (ø)
...ubbo/remoting/redis/jedis/SentinelRedisClient.java	0.00% <0.00%> (ø)
...org/apache/dubbo/registry/redis/RedisRegistry.java	59.20% <83.33%> (+0.77%)	:arrow_up:
...he/dubbo/remoting/redis/jedis/MonoRedisClient.java	74.41% <100.00%> (-7.64%)	:arrow_down:
...bo/remoting/redis/support/AbstractRedisClient.java	21.05% <0.00%> (-26.32%)	:arrow_down:
...in/java/org/apache/dubbo/common/utils/JVMUtil.java	81.13% <0.00%> (-11.33%)	:arrow_down:
...e/dubbo/remoting/transport/netty/NettyChannel.java	52.27% <0.00%> (-7.96%)	:arrow_down:
...ng/transport/dispatcher/all/AllChannelHandler.java	89.65% <0.00%> (-6.90%)	:arrow_down:
...he/dubbo/remoting/transport/netty/NettyServer.java	70.17% <0.00%> (-3.51%)	:arrow_down:
... and 7 more

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[chickenlj]

2.6.x has been announced as EOF. Please file another pr to 2.7.x or 3.1.x and fix the issues mentioned in the comments.