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fix(mqtt): drop max-retried entries after the resend iteration completes — fixes #289 #296

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fix(mqtt): drop max-retried entries after the resend iteration completes — fixes #289 #296

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12 changes: 9 additions & 3 deletions ...bifromq-mqtt-server/src/main/java/org/apache/bifromq/mqtt/handler/MQTTSessionHandler.java
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Original file line number Diff line number Diff line change
Expand Up @@ -77,6 +77,7 @@
import io.netty.handler.codec.mqtt.MqttTopicSubscription;
import io.netty.handler.codec.mqtt.MqttUnsubscribeMessage;
import java.time.Duration;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashMap;
Expand Down Expand Up @@ -1286,6 +1287,7 @@ private void scheduleResend() {
private void resend() {
long now = sessionCtx.nanoTime();
boolean flush = false;
List<ConfirmingMessage> toDrop = new ArrayList<>();
for (ConfirmingMessage confirmingMsg : unconfirmedPacketIds.values()) {
if (confirmingMsg.sentCount <= settings.maxResendTimes) {
if (ctx.channel().isWritable()) {
Expand All @@ -1306,14 +1308,18 @@ private void resend() {
break;
}
} else {
reportDropConfirmableMsgEvent(confirmingMsg.message, DropReason.MaxRetried);
confirm(confirmingMsg, false);
receiveQuota.onErrorSignal(now);
toDrop.add(confirmingMsg);
}
}
if (flush) {
flush(true);
}
// drop after the iteration completes: confirm() structurally modifies unconfirmedPacketIds
for (ConfirmingMessage dropped : toDrop) {
reportDropConfirmableMsgEvent(dropped.message, DropReason.MaxRetried);
confirm(dropped, false);
receiveQuota.onErrorSignal(now);
}
if (!unconfirmedPacketIds.isEmpty()) {
scheduleResend();
}
Expand Down
48 changes: 48 additions & 0 deletions ...er/src/test/java/org/apache/bifromq/mqtt/handler/v3/MQTT3TransientSessionHandlerTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -1730,4 +1730,52 @@ public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
verify(eventCollector, atLeast(1)).report(argThat(e ->
e instanceof QoS1Confirmed c && !c.delivered()));
}

@Test
public void resendDroppingHeadAbortsDropOfRemaining() {
when(settingProvider.provide(eq(ResendTimeoutSeconds), anyString())).thenReturn(1);
when(settingProvider.provide(eq(MaxResendTimes), anyString())).thenReturn(1);
when(settingProvider.provide(eq(ReceivingMaximum), anyString())).thenReturn(2);

channel.pipeline().removeLast();
channel.pipeline().addLast(new ChannelDuplexHandler() {
@Override
public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
super.handlerAdded(ctx);
ctx.pipeline().addLast(
MQTT3TransientSessionHandler.builder().settings(new TenantSettings(tenantId, settingProvider))
.tenantMeter(tenantMeter).oomCondition(oomCondition).userSessionId(userSessionId(clientInfo))
.keepAliveTimeSeconds(120).clientInfo(clientInfo).willMessage(null).ctx(ctx).build());
ctx.pipeline().remove(this);
}
});
transientSessionHandler = (MQTT3TransientSessionHandler) channel.pipeline().last();

mockCheckPermission(true);
mockDistMatch(true);
transientSessionHandler.subscribe(System.nanoTime(), topicFilter, QoS.AT_LEAST_ONCE);
channel.runPendingTasks();
ArgumentCaptor<Long> longCaptor = ArgumentCaptor.forClass(Long.class);
verify(localDistService).match(anyLong(), eq(topicFilter), longCaptor.capture(), any());

transientSessionHandler.publish(s2cMessageList(topic, 2, QoS.AT_LEAST_ONCE),
Collections.singleton(new IMQTTTransientSession.MatchedTopicFilter(topicFilter, longCaptor.getValue())));
channel.runPendingTasks();

assertNotNull(channel.readOutbound());
assertNotNull(channel.readOutbound());
// deliberately never ack: both stay in flight, so the head is dropped while another entry remains

for (int i = 0; i < 6; i++) {
testTicker.advanceTimeBy(2, TimeUnit.SECONDS);
channel.advanceTimeBy(2, TimeUnit.SECONDS);
channel.runScheduledPendingTasks();
channel.runPendingTasks();
channel.flushOutbound();
}

// both in-flight messages have exceeded maxResendTimes and must be dropped
verify(eventCollector, times(2)).report(argThat(e ->
e instanceof QoS1Dropped d && d.reason() == DropReason.MaxRetried));
}
}