RongtongJin opened a new pull request, #4484: URL: https://github.com/apache/rocketmq/pull/4484
## What is the purpose of the change After the release of RocketMQ 4.5.0, the DLedger mode (raft) was introduced. The raft commitlog under this architecture is used to replace the original commitlog so that it has the ability to failover. However, there are some disadvantages going with this architecture due to the raft capability on replication, including: 1. To have failover ability, the number of replicas in the broker group must be 3 or more 2. Acks from replicas need to strictly follow the majority rule of the Raft protocol, that is, 3-replica architecture requires acks from 2 replicas to return, and 5-replica architecture requires acks from 3 to return 3. Since the store repository relies on OpenMessaging DLedger in DLedger mode, Native storage and replication capabilities of RocketMQ (such as transientStorePool and zero-copy capabilities) cannot be reused, and maintenance becomes difficult as well. To handle those mentioned problems, I would like to start an RIP-44 Support DLedger Controller. With this improvement, DLedger (Raft) capability will be abstracted onto the upper layer, becoming an optional and loosely coupled coordination component named DLedger Controller. After the deployment of DLedger Controller, the master-slave architecture will also equip with failover capability. The DLedger Controller can optionally be embedded into the NameServer (the NameServer itself remains stateless and cannot provide electoral capabilities when the majority is down), or it can be deployed independently. DLedger controller is an optional component that does not change the previous operation and maintenance mode. Compared with other components, its downtime will not affect online services. In addition, RIP-44 unifies the storage and replication of RocketMQ, resulting in lower maintenance costs and faster development iterations. In terms of compatibility, the master-slave architecture can upgrade without compatibility problems. I've already done part of the work with @hzh0425 . Our proposals are provided at the links below： https://docs.google.com/document/d/1tSJkor_3Js4NBaVA0UENGyM8Mh0SrRMXszRyI91hjJ8/edit?usp=sharing Chinese version： https://shimo.im/docs/N2A1Mz9QZltQZoAD/ ## Brief changelog Refer https://shimo.im/docs/N2A1Mz9QZltQZoAD#anchor-qJhl ## Verifying this change Refer UTs, ITs and [testing report](https://shimo.im/docs/0l3NVLR2PdhwJy3R) Follow this checklist to help us incorporate your contribution quickly and easily. Notice, `it would be helpful if you could finish the following 5 checklist(the last one is not necessary)before request the community to review your PR`. - [x] Make sure there is a [Github issue](https://github.com/apache/rocketmq/issues) filed for the change (usually before you start working on it). Trivial changes like typos do not require a Github issue. Your pull request should address just this issue, without pulling in other changes - one PR resolves one issue. - [x] Format the pull request title like `[ISSUE #123] Fix UnknownException when host config not exist`. Each commit in the pull request should have a meaningful subject line and body. - [x] Write a pull request description that is detailed enough to understand what the pull request does, how, and why. - [x] Write necessary unit-test(over 80% coverage) to verify your logic correction, more mock a little better when cross module dependency exist. If the new feature or significant change is committed, please remember to add integration-test in [test module](https://github.com/apache/rocketmq/tree/master/test). - [x] Run `mvn -B clean apache-rat:check findbugs:findbugs checkstyle:checkstyle` to make sure basic checks pass. Run `mvn clean install -DskipITs` to make sure unit-test pass. Run `mvn clean test-compile failsafe:integration-test` to make sure integration-test pass. - [ ] If this contribution is large, please file an [Apache Individual Contributor License Agreement](http://www.apache.org/licenses/#clas). -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
