[CELEBORN-313] Add rest endpoint to show master group info

### What changes were proposed in this pull request?

<img width="1347" alt="image" src="https://github.com/apache/incubator-celeborn/assets/3898450/43d10bff-6878-4591-9461-889494d797f9">

### Why are the changes needed?

### Does this PR introduce _any_ user-facing change?
No.

### How was this patch tested?

```bash
./bin/celeborn-ratis sh -Draft.rpc.type=NETTY  group info   -peers clb-1:9872,clb-2:9873,clb-3:9874
```

```
group id: c5196f6d-2c34-3ed3-8b8a-47bede733167
leader info: 1(clb-1:9872)

[server {
  id: "1"
  address: "clb-1:9872"
  clientAddress: "clb-1:9097"
  startupRole: FOLLOWER
}
commitIndex: 316
, server {
  id: "2"
  address: "clb-2:9873"
  clientAddress: "clb-2:9098"
  startupRole: FOLLOWER
}
commitIndex: 316
, server {
  id: "3"
  address: "clb-3:9874"
  clientAddress: "clb-3:9099"
  startupRole: FOLLOWER
}
commitIndex: 316
]
```

```bash
curl http://clb-3:9983/masterGroupInfo
```

```
====================== Master Group INFO ==============================
group id: c5196f6d-2c34-3ed3-8b8a-47bede733167
leader info: 1(clb-1:9872)

[server {
  id: "3"
  address: "clb-3:9874"
  clientAddress: "clb-3:9099"
  startupRole: FOLLOWER
}
commitIndex: 316
, server {
  id: "1"
  address: "clb-1:9872"
  clientAddress: "clb-1:9097"
  startupRole: FOLLOWER
}
commitIndex: 316
, server {
  id: "2"
  address: "clb-2:9873"
  clientAddress: "clb-2:9098"
  startupRole: FOLLOWER
}
commitIndex: 316
]
```

Closes #1946 from cxzl25/CELEBORN-313.

Authored-by: sychen <sychen@ctrip.com>
Signed-off-by: Cheng Pan <chengpan@apache.org>

docs/monitoring.md

@@ -291,6 +291,7 @@ API path listed as below:
 |-----------------------|-------------------------------------------------------------------------------------------------------------|
 | /metrics/prometheus   | List the metrics data in prometheus format of the master.                                                   |
 | /conf                 | List the conf setting of the master.                                                                        |
+| /masterGroupInfo      | List master group information of the service. It will list all master's LEADER, FOLLOWER information.       |
 | /workerInfo           | List worker information of the service. It will list all registered workers 's information.                 |
 | /lostWorkers          | List all lost workers of the master.                                                                        |
 | /excludedWorkers      | List all excluded workers of the master.                                                                    |

master/src/main/java/org/apache/celeborn/service/deploy/master/clustermeta/ha/HARaftServer.java

@@ -483,7 +483,7 @@ public class HARaftServer {
     }
   }
 
-  private GroupInfoReply getGroupInfo() throws IOException {
+  public GroupInfoReply getGroupInfo() throws IOException {
     GroupInfoRequest groupInfoRequest =
         new GroupInfoRequest(clientId, raftPeerId, RAFT_GROUP_ID, nextCallId());
     return server.getGroupInfo(groupInfoRequest);

master/src/main/scala/org/apache/celeborn/service/deploy/master/Master.scala

@@ -28,6 +28,8 @@ import scala.collection.mutable
 import scala.util.Random
 
 import org.apache.hadoop.fs.{FileSystem, Path}
+import org.apache.ratis.proto.RaftProtos
+import org.apache.ratis.proto.RaftProtos.RaftPeerRole
 
 import org.apache.celeborn.common.CelebornConf
 import org.apache.celeborn.common.client.MasterClient
@@ -840,6 +842,13 @@ private[celeborn] class Master(
     }.asJava
   }
 
+  override def getMasterGroupInfo: String = {
+    val sb = new StringBuilder
+    sb.append("====================== Master Group INFO ==============================\n")
+    sb.append(getMasterGroupInfoInternal())
+    sb.toString()
+  }
+
   override def getWorkerInfo: String = {
     val sb = new StringBuilder
     sb.append("====================== Workers Info in Master =========================\n")
@@ -940,6 +949,40 @@ private[celeborn] class Master(
     isActive
   }
 
+  private def getMasterGroupInfoInternal(): String = {
+    if (conf.haEnabled) {
+      val sb = new StringBuilder
+      val groupInfo = statusSystem.asInstanceOf[HAMasterMetaManager].getRatisServer.getGroupInfo
+      sb.append(s"group id: ${groupInfo.getGroup.getGroupId.getUuid}\n")
+
+      def getLeader(roleInfo: RaftProtos.RoleInfoProto): RaftProtos.RaftPeerProto = {
+        if (roleInfo == null) {
+          return null
+        }
+        if (roleInfo.getRole == RaftPeerRole.LEADER) {
+          return roleInfo.getSelf
+        }
+        val followerInfo = roleInfo.getFollowerInfo
+        if (followerInfo == null) {
+          return null
+        }
+        followerInfo.getLeaderInfo.getId
+      }
+
+      val leader = getLeader(groupInfo.getRoleInfoProto)
+      if (leader == null) {
+        sb.append("leader not found\n")
+      } else {
+        sb.append(s"leader info: ${leader.getId.toStringUtf8}(${leader.getAddress})\n\n")
+      }
+      sb.append(groupInfo.getCommitInfos)
+      sb.append("\n")
+      sb.toString()
+    } else {
+      "HA is not enabled"
+    }
+  }
+
   override def initialize(): Unit = {
     super.initialize()
     logInfo("Master started.")

service/src/main/scala/org/apache/celeborn/server/common/HttpService.scala

@@ -41,6 +41,8 @@ abstract class HttpService extends Service with Logging {
     sb.toString()
   }
 
+  def getMasterGroupInfo: String = throw new UnsupportedOperationException()
+
   def getWorkerInfo: String
 
   def getLostWorkers: String = throw new UnsupportedOperationException()

service/src/main/scala/org/apache/celeborn/server/common/http/HttpRequestHandler.scala

@@ -65,6 +65,8 @@ class HttpRequestHandler(
     path match {
       case "/conf" =>
         service.getConf
+      case "/masterGroupInfo" if service.serviceName == Service.MASTER =>
+        service.getMasterGroupInfo
       case "/workerInfo" =>
         service.getWorkerInfo
       case "/lostWorkers" if service.serviceName == Service.MASTER =>