[RIP-44] Support DLedger Controller

[hzh0425]

Background

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 the work with @RongtongJin . 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/

The following prs are the main jobs:

• Add statemachine mode for dledger: Feature: add statemachine for dledger openmessaging/dledger#128

• Embed a strongly consistent controller based on dledger in name-srv: [Summer of Code] Dledger controller #4195

• Add a new HaService -- AutoSwitchHAService, which use new log replicating protocol to support switch role in haService level.: [Summer of Code] Support switch role for ha service #4236

• Connecting the interface of Dledger-controller at the Broker level, so that the Broker has the ability of master-slave switching:
  [Summer of Code] Support switch role for broker #4272

• Add learner role, which does not join inSyncStateSet and only asynchronously replicates logs from Master:
  [Summer of code] Support async learner in controller mode #4367

The following prs are for optimization and adjustment

• Make the controller independent from name-srv and can be deployed independently:[Summer of code] Stand alone a new controller module #4333

  • Add a option {isControllerDeployedStandAlone} on the broker side, let broker send heartbeat to contrller:[Summer of code] Let broker send heartbeat to controller #4341

• Modify the definition of syncStateSet in AutoSwitchHASerivce, and introduce the confirmOffset mechanism:[Summer of code] Shrink and expand InSyncStateSet #4355

• Add admin tools for controler mode (GetSyncStateSet and GetBrokerEpochCahce): [Summer of code] Add admin tools for controller mode #4388

• Reuse the remotingServer in dledger: [Summer of code] Reuse dledger remotingServer in controller mode. #4409

Document

• document: [Summer of code] Add design and quick_start document for controller mode #4413

Test design

• OpenChaos test: https://shimo.im/docs/0l3NVLR2PdhwJy3R

RIP42

https://shimo.im/docs/N2A1Mz9QZltQZoAD