[ISSUE #4852] Support Jraft algorithm as meta storage

[karsonto]

Fixes #4852

Motivation

Support Jraft algorithm as meta storage

Modifications
Removed unused variable responseEventMeshCommand in SendSyncMessageProcessor#processRequest

Documentation
New Configuration Information Explanation

• eventMesh.metaStorage.raft.dataPath=/tmp/server1 // Path to local snapshot storage for raft data
• eventMesh.metaStorage.raft.self=127.0.0.1:9091 // Raft protocol local ip and port
• eventMesh.metaStorage.raft.members=127.0.0.1:9092,127.0.0.1:9093 // Raft members node ip and port
• eventMesh.metaStorage.raft.electionTimeout=5 // Raft Election Leader Timeout second
• eventMesh.metaStorage.raft.snapshotInterval=30 // Raft snapshot Interval Timeout second
• eventMesh.metaStorage.raft.refreshLeaderInterval=3 // Raft refresh Leader node Interval Timeout second

[Pil0tXia]

Please be noted that you're linking an irrelavant issue.

[Pil0tXia]

May you please introduce briefly that how JRaft stores metadata and how to retrieve them (such as subscription info) from clients (such as EventMesh Dashboard or user)?

[Pil0tXia]

Overall good job.

[Pil0tXia]

May you please leave a usage document/comment/URL that explains the meaning of these properties?

[Pil0tXia]

eventMesh.metaStorage.raft.dataPath=/tmp/server1 // Path to local snapshot storage for raft data

Is server1 the recommended path of JRaft? Maybe /tmp/eventmesh-meta-raft would be better to understand.

eventMesh.metaStorage.raft.members=127.0.0.1:9092,127.0.0.1:9093 // Raft members node ip and port

My guess is that the IP addresses are different for different nodes, but the port should be the same to allow scaling. The example here requires changing the IP address and maintaining the default port number.

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May you please add these comments into eventmesh.properties?

[karsonto]

Yes, this example was configured locally for ease of testing, and it should be more appropriate to keep the same port numbers

[karsonto]

May you please introduce briefly that how JRaft stores metadata and how to retrieve them (such as subscription info) from clients (such as EventMesh Dashboard or user)?

My understanding, Jraft is to synchronise the data to the cluster internal machine, each machine above the data is consistent, this PR is to save the data in memory, every once in a while will snapshot the data to the local disk, start the server will snapshot the data loaded into memory, EventMesh Runtime needs to provide restful api in order to allow EventMesh Dashboard to get the data saved by the jraft!

[Pil0tXia]

EventMesh Runtime needs to provide restful api in order to allow EventMesh Dashboard to get the data saved by the jraft!

May you please indicate which class to interact with in order to get JRaft data?

[karsonto]

EventMesh Runtime needs to provide restful api in order to allow EventMesh Dashboard to get the data saved by the jraft!

May you please indicate which class to interact with in order to get JRaft data?

You can get MetaStorage in the Runtime, and then get MetaService, which is the implementation class of RaftMetaService.

[Pil0tXia]

Please add known dependencies~

[Pil0tXia]

Implemented JRaft Feature in this PR

In the current implementation of this PR, if a new node is added to the cluster, users need to add the new node to the eventmesh.properties of the existing nodes before it can be added to the cluster.

Hopefully you can implement CliService in a next PR to support service registration when automatic scaling up and down of the cluster. Because the complete list of online nodes of the cluster cannot be maintained in real time.

After it's implemented, the newly added node can connect to any online node in the cluster. If connected to a follower, the current leader will be returned to new node by the follower.

[Pil0tXia]

LGTM

[karsonto]

If you get bugs during use, I will continue to improve it later, thanks!

[mxsm]

@karsonto Please fix conflicts

[karsonto]

@mxsm Done,please review.

[mxsm]

LGTM