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RATIS-2559. Add linearizable check for streaming read request #1490

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RATIS-2559. Add linearizable check for streaming read request #1490

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87 changes: 70 additions & 17 deletions ratis-netty/src/main/java/org/apache/ratis/netty/server/ReadStreamManagement.java
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@
*/
package org.apache.ratis.netty.server;

import org.apache.ratis.client.impl.OrderedAsync;
import org.apache.ratis.conf.RaftProperties;
import org.apache.ratis.datastream.impl.DataStreamReplyByteBuffer;
import org.apache.ratis.datastream.impl.DataStreamRequestByteBuf;
Expand Down Expand Up @@ -47,6 +48,7 @@

import static org.apache.ratis.client.impl.ClientProtoUtils.toRaftClientRequest;
import static org.apache.ratis.client.impl.ClientProtoUtils.toRaftClientReplyProto;
import static org.apache.ratis.netty.server.DataStreamManagement.newDataStreamReplyByteBuffer;
import static org.apache.ratis.netty.server.DataStreamManagement.replyDataStreamException;

public class ReadStreamManagement {
Expand All @@ -60,24 +62,12 @@ static class ReadStream implements WritableByteChannel {
private final DataStreamReplyByteBuffer terminalReply;
private long streamOffset;

ReadStream(RaftClientRequest request, long streamId, ChannelHandlerContext ctx) {
ReadStream(RaftClientRequest request, long streamId, ChannelHandlerContext ctx, RaftClientReply terminalReply) {
this.clientId = request.getClientId();
this.streamId = streamId;
this.ctx = ctx;

final RaftClientReply reply = RaftClientReply.newBuilder()
.setRequest(request)
.setSuccess()
.build();
this.terminalReply = DataStreamReplyByteBuffer.newBuilder()
.setClientId(clientId)
.setType(Type.STREAM_HEADER)
.setStreamId(streamId)
.setStreamOffset(0)
.setBuffer(toRaftClientReplyProto(reply).toByteString().asReadOnlyByteBuffer())
.setSuccess(true)
.setBytesWritten(0)
.build();
this.terminalReply = newReadStreamTerminalReply(clientId, streamId, terminalReply);
}

@Override
Expand Down Expand Up @@ -186,17 +176,80 @@ private boolean processImpl(DataStreamRequestByteBuf requestBuf, ChannelHandlerC
return true;
}

final ReadStream stream = new ReadStream(request, requestBuf.getStreamId(), ctx);
requestExecutor.execute(() -> {
final CompletableFuture<RaftClientReply> readOnlyCheck;
try {
readOnlyCheck = server.submitClientRequestAsync(newDummyReadRequest(request));
} catch (IOException e) {
replyDataStreamException(server, e, request, requestBuf, ctx);
return true;
}

readOnlyCheck.whenCompleteAsync((reply, exception) -> {
if (exception != null) {
replyDataStreamException(server, exception, request, requestBuf, ctx);
return;
}

final RaftClientReply terminalReply = toReadStreamReply(request, reply);
if (!reply.isSuccess()) {
ctx.writeAndFlush(newDataStreamReplyByteBuffer(requestBuf, terminalReply));
return;
}
Comment on lines +193 to +197

@szetszwo szetszwo Jun 26, 2026

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Since server returns a DUMMY_SUCCESS_REPLY, we could build the failed reply directly:

      if (!readCheckReply.isSuccess()) {
        final RaftClientReply reply = RaftClientReply.newBuilder()
            .setRequest(request)
            .setSuccess(false)
            .build();
        ctx.writeAndFlush(newDataStreamReplyByteBuffer(requestBuf, reply));
        return;
      }

      final ReadStream stream = new ReadStream(request, requestBuf.getStreamId(), ctx);


final ReadStream stream = new ReadStream(request, requestBuf.getStreamId(), ctx, terminalReply);
try {
division.getStateMachine().data().query(request.getMessage(), stream);
} catch (Throwable t) {
LOG.error("{}: Failed read-only data stream query for {}", this, request, t);
}
});
}, requestExecutor);
return true;
}

private static RaftClientRequest newDummyReadRequest(RaftClientRequest request) {
final RaftClientRequest.Builder builder = RaftClientRequest.newBuilder()
.setClientId(request.getClientId())
.setGroupId(request.getRaftGroupId())
.setCallId(request.getCallId())
.setMessage(OrderedAsync.DUMMY)
.setType(request.getType())
.setRepliedCallIds(request.getRepliedCallIds())
.setSlidingWindowEntry(request.getSlidingWindowEntry())
.setRoutingTable(request.getRoutingTable())
.setTimeoutMs(request.getTimeoutMs())
.setSpanContext(request.getSpanContext());
if (request.isToLeader()) {
builder.setLeaderId(request.getServerId());
} else {
builder.setServerId(request.getServerId());
}
return builder.build();
Comment on lines +210 to +226

@szetszwo szetszwo Jun 26, 2026

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Let's add a set(RaftClientRequest request) to Builder to copy everything.

}

private static RaftClientReply toReadStreamReply(RaftClientRequest request, RaftClientReply reply) {
return RaftClientReply.newBuilder()
.setRequest(request)
.setSuccess(reply.isSuccess())
.setException(reply.getException())
.setLogIndex(reply.getLogIndex())
.setCommitInfos(reply.getCommitInfos())
.build();
}

private static DataStreamReplyByteBuffer newReadStreamTerminalReply(
ClientId clientId, long streamId, RaftClientReply reply) {
return DataStreamReplyByteBuffer.newBuilder()
.setClientId(clientId)
.setType(Type.STREAM_HEADER)
.setStreamId(streamId)
.setStreamOffset(0)
.setBuffer(toRaftClientReplyProto(reply).toByteString().asReadOnlyByteBuffer())
.setSuccess(reply.isSuccess())
.setBytesWritten(0)
.setCommitInfos(reply.getCommitInfos())
.build();
}

@Override
public String toString() {
return name;
Expand Down
18 changes: 12 additions & 6 deletions ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerImpl.java
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Original file line number Diff line number Diff line change
Expand Up @@ -1113,11 +1113,12 @@ private CompletableFuture<RaftClientReply> readAsync(RaftClientRequest request)
if (request.getType().getRead().getPreferNonLinearizable()
|| readOption == RaftServerConfigKeys.Read.Option.DEFAULT) {
final CompletableFuture<RaftClientReply> reply = checkLeaderState(request);
if (reply != null) {
return reply;
}
return queryStateMachine(request);
} else if (readOption == RaftServerConfigKeys.Read.Option.LINEARIZABLE){
if (reply != null) {
return reply;
}
return isDummyRead(request) ? CompletableFuture.completedFuture(newSuccessReply(request))

@amaliujia amaliujia Jun 26, 2026

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Just to learn the context, why do we need this dummy read in Ratis streaming read while we do not have it for Ratis streaming write?

@szetszwo szetszwo Jun 26, 2026

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It is to run the linearizable check; see #1469 (comment)

: queryStateMachine(request);
Comment on lines +1119 to +1120

@szetszwo szetszwo Jun 26, 2026

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Let's add a DUMMY_SUCCESS_REPLY and move it to queryStateMachine:

  static final CompletableFuture<RaftClientReply> DUMMY_SUCCESS_REPLY
      = CompletableFuture.completedFuture(RaftClientReply.newBuilder().setSuccess().build());
  CompletableFuture<RaftClientReply> queryStateMachine(RaftClientRequest request) {
    if (request.getType().getRead().getDummy()) {
      return DUMMY_SUCCESS_REPLY;
    }
    return processQueryFuture(stateMachine.query(request.getMessage()), request);
  }

} else if (readOption == RaftServerConfigKeys.Read.Option.LINEARIZABLE) {
final LeaderStateImpl leader = role.getLeaderState().orElse(null);
final CompletableFuture<Long> replyFuture;
if (leader != null) {
Expand All @@ -1136,12 +1137,17 @@ private CompletableFuture<RaftClientReply> readAsync(RaftClientRequest request)
return replyFuture
.thenCompose(readIndex -> getState().getReadRequests().waitToAdvance(readIndex,
() -> getReadException("add", snapshotInstallationHandler.getInProgressInstallSnapshotIndex(), false)))
.thenCompose(readIndex -> queryStateMachine(request))
.thenCompose(readIndex -> isDummyRead(request)
? CompletableFuture.completedFuture(newSuccessReply(request)) : queryStateMachine(request))
.exceptionally(e -> readException2Reply(request, e));
} else {
throw new IllegalStateException("Unexpected read option: " + readOption);
}
}
private static boolean isDummyRead(RaftClientRequest request) {
return request.getMessage() != null && OrderedAsync.DUMMY.getContent().equals(request.getMessage().getContent());
}
Comment on lines +1147 to +1149

@szetszwo szetszwo Jun 26, 2026

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We cannot use DUMMY since user applications can set any message. They may already have used it in their messages. We probably need to add a flag to the proto:

+++ b/ratis-proto/src/main/proto/Raft.proto
@@ -302,6 +302,7 @@ message ForwardRequestTypeProto {
 message ReadRequestTypeProto {
   bool preferNonLinearizable = 1;
   bool readAfterWriteConsistent = 2;
+  bool dummy = 3;
 }


private RaftClientReply readException2Reply(RaftClientRequest request, Throwable e) {
e = JavaUtils.unwrapCompletionException(e);
if (e instanceof StateMachineException ) {
Expand Down
122 changes: 120 additions & 2 deletions ratis-test/src/test/java/org/apache/ratis/netty/server/TestDataStreamManagement.java
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@

import org.apache.ratis.client.impl.ClientProtoUtils;
import org.apache.ratis.client.impl.DataStreamClientImpl.DataStreamOutputImpl;
import org.apache.ratis.client.impl.OrderedAsync;
import org.apache.ratis.conf.RaftProperties;
import org.apache.ratis.datastream.impl.DataStreamReplyByteBuffer;
import org.apache.ratis.datastream.impl.DataStreamRequestByteBuf;
Expand All @@ -28,10 +29,12 @@
import org.apache.ratis.protocol.ClientId;
import org.apache.ratis.protocol.DataStreamReply;
import org.apache.ratis.protocol.Message;
import org.apache.ratis.protocol.RaftClientReply;
import org.apache.ratis.protocol.RaftClientRequest;
import org.apache.ratis.protocol.RaftGroupId;
import org.apache.ratis.protocol.RaftPeer;
import org.apache.ratis.protocol.RaftPeerId;
import org.apache.ratis.protocol.exceptions.ReadIndexException;
import org.apache.ratis.server.RaftServer;
import org.apache.ratis.statemachine.StateMachine;
import org.apache.ratis.statemachine.StateMachine.DataApi;
Expand Down Expand Up @@ -59,14 +62,17 @@
import java.util.Collections;
import java.util.List;
import java.util.Set;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Function;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertFalse;
import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertNull;
import static org.junit.jupiter.api.Assertions.assertTrue;

class TestDataStreamManagement {
Expand Down Expand Up @@ -96,8 +102,9 @@ public void query(Message request, WritableByteChannel stream) {
assertTrue(management.process(readOnlyRequest.request, embeddedChannel.pipeline().firstContext()));
assertEquals(0, readOnlyRequest.headerBuf.refCnt());

JavaUtils.attempt(() -> assertNotNull(streamRef.get()), 10,
TimeDuration.valueOf(100, TimeUnit.MILLISECONDS), "read-only stream", null);
final WritableByteChannel stream = streamRef.get();
assertNotNull(stream);
stream.write(response.asReadOnlyByteBuffer());
stream.close();

Expand All @@ -116,6 +123,99 @@ public void query(Message request, WritableByteChannel stream) {
assertTrue(ClientProtoUtils.getRaftClientReply(replies.get(1)).isSuccess());
} finally {
embeddedChannel.finishAndReleaseAll();
management.shutdown();
}
}

@Test
void readOnlyRequestWaitsForLinearizableCheck() throws Exception {
final RaftPeerId serverId = RaftPeerId.valueOf("s1");
final ClientId clientId = ClientId.randomId();
final RaftGroupId groupId = RaftGroupId.randomId();
final ByteString query = ByteString.copyFromUtf8("query");
final CompletableFuture<RaftClientReply> readOnlyCheck = new CompletableFuture<>();
final AtomicReference<RaftClientRequest> submittedReadOnlyCheck = new AtomicReference<>();
final AtomicReference<Message> messageRef = new AtomicReference<>();
final AtomicReference<WritableByteChannel> streamRef = new AtomicReference<>();

final DataApi dataApi = new DataApi() {
@Override
public void query(Message request, WritableByteChannel stream) {
messageRef.set(request);
streamRef.set(stream);
}
};
final ReadStreamManagement management = newReadStreamManagement(serverId, groupId, dataApi, request -> {
submittedReadOnlyCheck.set(request);
return readOnlyCheck;
});
final EmbeddedChannel embeddedChannel = new EmbeddedChannel(new ChannelInboundHandlerAdapter());
final ReadOnlyRequest readOnlyRequest = newReadOnlyRequest(clientId, serverId, groupId, 1L, query);

try {
assertTrue(management.process(readOnlyRequest.request, embeddedChannel.pipeline().firstContext()));
assertEquals(0, readOnlyRequest.headerBuf.refCnt());

final RaftClientRequest checkRequest = submittedReadOnlyCheck.get();
assertNotNull(checkRequest);
assertEquals(OrderedAsync.DUMMY.getContent(), checkRequest.getMessage().getContent());
assertNull(streamRef.get(), "state machine query should wait for the read-only check");

readOnlyCheck.complete(RaftClientReply.newBuilder().setRequest(checkRequest).setSuccess().build());
JavaUtils.attempt(() -> assertNotNull(streamRef.get()), 10,
TimeDuration.valueOf(100, TimeUnit.MILLISECONDS), "linearizable read-only stream", null);
assertEquals(query, messageRef.get().getContent());
} finally {
embeddedChannel.finishAndReleaseAll();
management.shutdown();
}
}

@Test
void readOnlyCheckFailureSkipsStateMachineQuery() throws Exception {
final RaftPeerId serverId = RaftPeerId.valueOf("s1");
final ClientId clientId = ClientId.randomId();
final RaftGroupId groupId = RaftGroupId.randomId();
final ByteString query = ByteString.copyFromUtf8("query");
final AtomicBoolean queryCalled = new AtomicBoolean();

final DataApi dataApi = new DataApi() {
@Override
public void query(Message request, WritableByteChannel stream) {
queryCalled.set(true);
}
};
final ReadStreamManagement management = newReadStreamManagement(serverId, groupId, dataApi, request ->
CompletableFuture.completedFuture(RaftClientReply.newBuilder()
.setRequest(request)
.setException(new ReadIndexException("read index failed"))
.build()));
final EmbeddedChannel embeddedChannel = new EmbeddedChannel(new ChannelInboundHandlerAdapter());
final ReadOnlyRequest readOnlyRequest = newReadOnlyRequest(clientId, serverId, groupId, 1L, query);

try {
assertTrue(management.process(readOnlyRequest.request, embeddedChannel.pipeline().firstContext()));
assertEquals(0, readOnlyRequest.headerBuf.refCnt());

final List<DataStreamReply> replies = new ArrayList<>();
JavaUtils.attempt(() -> {
for (Object outbound; (outbound = embeddedChannel.readOutbound()) != null;) {
replies.add((DataStreamReply) outbound);
}
assertEquals(1, replies.size());
}, 10, TimeDuration.valueOf(100, TimeUnit.MILLISECONDS), "read-only check failure reply", null);

assertFalse(queryCalled.get(), "state machine query should not run when the read-only check fails");
final DataStreamReply reply = replies.get(0);
assertEquals(Type.STREAM_HEADER, reply.getType());
assertFalse(reply.isSuccess());
final RaftClientReply clientReply = ClientProtoUtils.getRaftClientReply(reply);
assertFalse(clientReply.isSuccess());
assertNotNull(clientReply.getReadIndexException());
assertEquals(serverId, clientReply.getServerId());
} finally {
embeddedChannel.finishAndReleaseAll();
management.shutdown();
}
}

Expand Down Expand Up @@ -231,13 +331,19 @@ private static class ReadOnlyRequest {

private static ReadStreamManagement newReadStreamManagement(
RaftPeerId serverId, RaftGroupId groupId, DataApi dataApi) {
return newReadStreamManagement(serverId, groupId, dataApi, TestDataStreamManagement::successReply);
}

private static ReadStreamManagement newReadStreamManagement(RaftPeerId serverId, RaftGroupId groupId,
DataApi dataApi, Function<RaftClientRequest, CompletableFuture<RaftClientReply>> submitClientRequestAsync) {
final StateMachine stateMachine = new BaseStateMachine() {
@Override
public DataApi data() {
return dataApi;
}
};
final RaftServer server = newRaftServer(serverId, new RaftProperties(), groupId, newDivision(stateMachine));
final RaftServer server = newRaftServer(serverId, new RaftProperties(), groupId, newDivision(stateMachine),
submitClientRequestAsync);
return new ReadStreamManagement(server);
}

Expand Down Expand Up @@ -275,6 +381,16 @@ private static RaftServer newRaftServer(RaftPeerId serverId, RaftProperties prop

private static RaftServer newRaftServer(RaftPeerId serverId, RaftProperties properties,
RaftGroupId groupId, RaftServer.Division division) {
return newRaftServer(serverId, properties, groupId, division, TestDataStreamManagement::successReply);
}

private static CompletableFuture<RaftClientReply> successReply(RaftClientRequest request) {
return CompletableFuture.completedFuture(RaftClientReply.newBuilder().setRequest(request).setSuccess().build());
}

private static RaftServer newRaftServer(RaftPeerId serverId, RaftProperties properties,
RaftGroupId groupId, RaftServer.Division division,
Function<RaftClientRequest, CompletableFuture<RaftClientReply>> submitClientRequestAsync) {
return (RaftServer) Proxy.newProxyInstance(RaftServer.class.getClassLoader(), new Class<?>[]{RaftServer.class},
(proxy, method, args) -> {
switch (method.getName()) {
Expand All @@ -287,6 +403,8 @@ private static RaftServer newRaftServer(RaftPeerId serverId, RaftProperties prop
return division;
}
throw new IOException("Division not found: " + args[0]);
case "submitClientRequestAsync":
return submitClientRequestAsync.apply((RaftClientRequest) args[0]);
case "close":
return null;
case "toString":
Expand Down
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