> GroupMismatchException: n4: group-ABB3109A44C2 not found. I guess you might not have started n4 with group-ABB3109A44C2. We should start n4 with group-ABB3109A44C2 and an empty list of peers.
Tsz-Wo On Wed, Mar 11, 2026 at 4:43 AM Snehasish Roy <[email protected]> wrote: > Hi everyone, > > I was following the documentation ( > > https://jojochuang.github.io/ratis-site/docs/developer-guide/membership-change/#adding-a-new-server > ) > for adding a new server to an existing group but faced an error. > These are the steps I followed > > 1. Started three servers n1, n2 and n3 with a hardcoded groupID > ABB3109A44C2 > 2. Started fourth server n4 with empty group and no peer information. > 3. Issued a setConfiguration on n2 (the leader instance) with n1,n2,n3,n4 > in the peer list, but faced an error citing GroupMismatchException. > > Did I miss some step? Kindly advise. > > n2 logs > ``` > INFO [2026-03-11 16:47:35,651] [n2-server-thread1] [RaftServer$Division]: > n2@group-ABB3109A44C2: receive setConfiguration > SetConfigurationRequest:client-26207F9175D5->n2@group-ABB3109A44C2, cid=1, > seq=null, RW, null, SET_UNCONDITIONALLY, servers:[n1|0.0.0.0:9000, n2| > 0.0.0.0:9001, n3|0.0.0.0:9002, n4|0.0.0.0:9003], listeners:[] > INFO [2026-03-11 16:47:35,652] [n2-server-thread1] [RaftServer$Division]: > n2@group-ABB3109A44C2-LeaderStateImpl: startSetConfiguration > SetConfigurationRequest:client-26207F9175D5->n2@group-ABB3109A44C2, cid=1, > seq=null, RW, null, SET_UNCONDITIONALLY, servers:[n1|0.0.0.0:9000, n2| > 0.0.0.0:9001, n3|0.0.0.0:9002, n4|0.0.0.0:9003], listeners:[] > INFO [2026-03-11 16:47:35,655] > [n2@group-ABB3109A44C2->n4-GrpcLogAppender-LogAppenderDaemon] > [FollowerInfo]: Follower n2@group-ABB3109A44C2->n4 acknowledged installing > snapshot > INFO [2026-03-11 16:47:35,655] > [n2@group-ABB3109A44C2->n4-GrpcLogAppender-LogAppenderDaemon] > [GrpcServerProtocolClient]: Build channel for n4|0.0.0.0:9003 > WARN [2026-03-11 16:47:35,887] [grpc-default-executor-5] > [GrpcLogAppender]: n2@group-ABB3109A44C2->n4-AppendLogResponseHandler: > Failed appendEntries > org.apache.ratis.protocol.exceptions.GroupMismatchException: n4: > group-ABB3109A44C2 not found. > at > > org.apache.ratis.server.impl.RaftServerProxy$ImplMap.get(RaftServerProxy.java:161) > at > > org.apache.ratis.server.impl.RaftServerProxy.getImplFuture(RaftServerProxy.java:373) > at > > org.apache.ratis.server.impl.RaftServerProxy.appendEntriesAsync(RaftServerProxy.java:653) > at > > org.apache.ratis.grpc.server.GrpcServerProtocolService$1.process(GrpcServerProtocolService.java:248) > at > > org.apache.ratis.grpc.server.GrpcServerProtocolService$1.process(GrpcServerProtocolService.java:245) > at > > org.apache.ratis.grpc.server.GrpcServerProtocolService$ServerRequestStreamObserver.onNext(GrpcServerProtocolService.java:152) > at > > org.apache.ratis.thirdparty.io.grpc.stub.ServerCalls$StreamingServerCallHandler$StreamingServerCallListener.onMessage(ServerCalls.java:262) > at > > org.apache.ratis.thirdparty.io.grpc.internal.ServerCallImpl$ServerStreamListenerImpl.messagesAvailableInternal(ServerCallImpl.java:334) > at > > org.apache.ratis.thirdparty.io.grpc.internal.ServerCallImpl$ServerStreamListenerImpl.messagesAvailable(ServerCallImpl.java:319) > at > > org.apache.ratis.thirdparty.io.grpc.internal.ServerImpl$JumpToApplicationThreadServerStreamListener$1MessagesAvailable.runInContext(ServerImpl.java:834) > at > > org.apache.ratis.thirdparty.io.grpc.internal.ContextRunnable.run(ContextRunnable.java:37) > at > > org.apache.ratis.thirdparty.io.grpc.internal.SerializingExecutor.run(SerializingExecutor.java:133) > at > > java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136) > at > > java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635) > at java.base/java.lang.Thread.run(Thread.java:840) > INFO [2026-03-11 16:47:35,888] [grpc-default-executor-5] [LogAppender]: > Decrease nextIndex to 0 > INFO [2026-03-11 16:47:35,888] [grpc-default-executor-5] [LogAppender]: > Decrease nextIndex to 0 > INFO [2026-03-11 16:47:35,888] [grpc-default-executor-5] [FollowerInfo]: > n2@group-ABB3109A44C2->n4: computeNextIndex nextIndex: > updateUnconditionally 1 -> 0 > .... > ``` > > n4 logs > ``` > WARN [2026-03-11 16:47:35,866] [grpc-default-executor-0] > [GrpcServerProtocolService]: n4: Failed APPEND_ENTRIES request > n2->n4#1-t1,previous=<PROTO_DEFAULT>,leaderCommit=0,initializing? > true,entries: size=1, first=(t:1, i:0), > CONFIGURATIONENTRY(current:id:"n1"address:"0.0.0.0:9000 > "startupRole:FOLLOWER, > id:"n2"address:"0.0.0.0:9001"startupRole:FOLLOWER, id:"n3"address:" > 0.0.0.0:9002"startupRole:FOLLOWER, old:) > java.util.concurrent.CompletionException: > org.apache.ratis.protocol.exceptions.GroupMismatchException: n4: > group-ABB3109A44C2 not found. > at > > java.base/java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:332) > at > > java.base/java.util.concurrent.CompletableFuture.uniComposeStage(CompletableFuture.java:1177) > at > > java.base/java.util.concurrent.CompletableFuture.thenCompose(CompletableFuture.java:2309) > at > > org.apache.ratis.server.impl.RaftServerProxy.appendEntriesAsync(RaftServerProxy.java:654) > at > > org.apache.ratis.grpc.server.GrpcServerProtocolService$1.process(GrpcServerProtocolService.java:248) > at > > org.apache.ratis.grpc.server.GrpcServerProtocolService$1.process(GrpcServerProtocolService.java:245) > at > > org.apache.ratis.grpc.server.GrpcServerProtocolService$ServerRequestStreamObserver.onNext(GrpcServerProtocolService.java:152) > at > > org.apache.ratis.thirdparty.io.grpc.stub.ServerCalls$StreamingServerCallHandler$StreamingServerCallListener.onMessage(ServerCalls.java:262) > at > > org.apache.ratis.thirdparty.io.grpc.internal.ServerCallImpl$ServerStreamListenerImpl.messagesAvailableInternal(ServerCallImpl.java:334) > at > > org.apache.ratis.thirdparty.io.grpc.internal.ServerCallImpl$ServerStreamListenerImpl.messagesAvailable(ServerCallImpl.java:319) > at > > org.apache.ratis.thirdparty.io.grpc.internal.ServerImpl$JumpToApplicationThreadServerStreamListener$1MessagesAvailable.runInContext(ServerImpl.java:834) > at > > org.apache.ratis.thirdparty.io.grpc.internal.ContextRunnable.run(ContextRunnable.java:37) > at > > org.apache.ratis.thirdparty.io.grpc.internal.SerializingExecutor.run(SerializingExecutor.java:133) > at > > java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136) > at > > java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635) > at java.base/java.lang.Thread.run(Thread.java:840) > Caused by: org.apache.ratis.protocol.exceptions.GroupMismatchException: n4: > group-ABB3109A44C2 not found. > at > > org.apache.ratis.server.impl.RaftServerProxy$ImplMap.get(RaftServerProxy.java:161) > at > > org.apache.ratis.server.impl.RaftServerProxy.getImplFuture(RaftServerProxy.java:373) > at > > org.apache.ratis.server.impl.RaftServerProxy.appendEntriesAsync(RaftServerProxy.java:653) > ... 12 common frames omitted > ``` > > Regards, > Snehasish >
