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fix(sessiondict): defer kick out of the registry compute block and guard remove by live register — fixes #304 #311

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fix(sessiondict): defer kick out of the registry compute block and guard remove by live register — fixes #304 #311

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a847906
fix(sessiondict): defer kick out of the registry compute block and gu…
ImDanXie Sep 25, 2026
0002a11
test(sessiondict): regression tests for re-entrant kick and delayed t…
ImDanXie Sep 25, 2026
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31 changes: 27 additions & 4 deletions ...sion-dict-server/src/main/java/org/apache/bifromq/sessiondict/server/SessionRegistry.java
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Original file line number Diff line number Diff line change
Expand Up @@ -37,9 +37,11 @@
import java.util.TreeMap;
import java.util.concurrent.ConcurrentSkipListMap;
import java.util.concurrent.atomic.AtomicInteger;
import lombok.extern.slf4j.Slf4j;
import org.apache.bifromq.sessiondict.rpc.proto.ServerRedirection;
import org.apache.bifromq.type.ClientInfo;

@Slf4j
class SessionRegistry implements ISessionRegistry {
private static final ServerRedirection NO_MOVE =
ServerRedirection.newBuilder().setType(ServerRedirection.Type.NO_MOVE).build();
Expand All @@ -56,6 +58,13 @@ class SessionRegistry implements ISessionRegistry {
public void add(ClientInfo sessionOwner, ISessionRegister register) {
String tenantId = sessionOwner.getTenantId();
MqttClientKey clientKey = MqttClientKey.from(sessionOwner);
// The kick callback synchronously calls back into remove() on the same thread (the kicked
// register unregisters itself from its Quit path), and ConcurrentHashMap.compute must not
// be re-entered for the same key — the nested remove could delete the mapping this add
// has just installed, losing the new session from the dictionary. Collect the kick and
// perform it only after leaving the compute block.
ISessionRegister[] kickedRegister = new ISessionRegister[1];
ClientInfo[] kickedOwner = new ClientInfo[1];
tenantSessions.compute(tenantId, (k, v) -> {
if (v == null) {
v = new ConcurrentSkipListMap<>(ClientKeyComparator);
Expand All @@ -69,9 +78,10 @@ public void add(ClientInfo sessionOwner, ISessionRegister register) {
if (!prevSessionOwner.equals(sessionOwner)) {
ISessionRegister prevSessionRegister = clientRegisterMap.remove(prevSessionOwner);
clientRegisterMap.put(sessionOwner, register);
// kick previous session owner
// kick previous session owner after leaving the compute block
assert prevSessionRegister != null;
prevSessionRegister.kick(tenantId, prevSessionOwner, sessionOwner, NO_MOVE);
kickedRegister[0] = prevSessionRegister;
kickedOwner[0] = prevSessionOwner;
if (isPersistent(sessionOwner) && !isPersistent(prevSessionOwner)) {
// kicked by a persistent session
SessionCounter sessionCounter = sessionCounters.get(tenantId);
Expand All @@ -83,7 +93,8 @@ public void add(ClientInfo sessionOwner, ISessionRegister register) {
} else {
ISessionRegister prevSessionRegister = clientRegisterMap.put(sessionOwner, register);
if (prevSessionRegister != null && prevSessionRegister != register) {
prevSessionRegister.kick(tenantId, prevSessionOwner, sessionOwner, NO_MOVE);
kickedRegister[0] = prevSessionRegister;
kickedOwner[0] = prevSessionOwner;
}
}
// ignore duplicated add
Expand All @@ -98,14 +109,26 @@ public void add(ClientInfo sessionOwner, ISessionRegister register) {
}
return v;
});
if (kickedRegister[0] != null) {
try {
kickedRegister[0].kick(tenantId, kickedOwner[0], sessionOwner, NO_MOVE);
} catch (RuntimeException e) {
// best-effort notification: the previous register's stream may already be closed
log.debug("Kicked session register ignored exception: {}", e.getMessage());
}
}
}

@Override
public void remove(ClientInfo sessionOwner, ISessionRegister register) {
String tenantId = sessionOwner.getTenantId();
MqttClientKey clientKey = MqttClientKey.from(sessionOwner);
tenantSessions.computeIfPresent(tenantId, (k, v) -> {
boolean s1 = v.remove(clientKey, sessionOwner);
// Only drop the dict entry if the register being removed is still the live one —
// after a same-owner takeover the old register's (possibly delayed) teardown must
// not delete the mapping installed by the new register, nor drift the counters.
boolean s1 = register == clientRegisterMap.get(sessionOwner)
&& v.remove(clientKey, sessionOwner);
boolean s2 = clientRegisterMap.remove(sessionOwner, register);
if (s1) {
SessionCounter sessionCounter = sessionCounters.get(tenantId);
Expand Down
111 changes: 111 additions & 0 deletions ...-dict-server/src/test/java/org/apache/bifromq/sessiondict/server/SessionRegistryTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -218,6 +218,117 @@ public void testTransientKicksPersistent() {
assertGaugeValue(tenantId1, MqttLivePersistentSessionGauge, 0.0);
}

@Test
public void testKickCallbackReenteringRemoveKeepsNewSession() {
// The real register's kick() synchronously unregisters itself via regListener,
// which calls remove() back on the same thread — the compute block must not be
// re-entered, and the new session must survive in the dictionary.
ISessionRegister registerMock1 = Mockito.mock(ISessionRegister.class);
ISessionRegister registerMock2 = Mockito.mock(ISessionRegister.class);

ClientInfo sessionOwner1 = ClientInfo.newBuilder()
.setTenantId(tenantId1)
.putMetadata(MQTT_USER_ID_KEY, "user1")
.putMetadata(MQTT_CLIENT_ID_KEY, "client1")
.putMetadata(MQTT_CLIENT_SESSION_TYPE, MQTT_CLIENT_SESSION_TYPE_T_VALUE)
.putMetadata(MQTT_CHANNEL_ID_KEY, "channel1")
.build();

ClientInfo sessionOwner2 = ClientInfo.newBuilder()
.setTenantId(tenantId1)
.putMetadata(MQTT_USER_ID_KEY, "user1")
.putMetadata(MQTT_CLIENT_ID_KEY, "client1")
.putMetadata(MQTT_CLIENT_SESSION_TYPE, MQTT_CLIENT_SESSION_TYPE_T_VALUE)
.putMetadata(MQTT_CHANNEL_ID_KEY, "channel2")
.build();

Mockito.doAnswer(invocation -> {
sessionRegistry.remove(sessionOwner1, registerMock1);
return null;
}).when(registerMock1).kick(org.mockito.ArgumentMatchers.any(),
org.mockito.ArgumentMatchers.any(), org.mockito.ArgumentMatchers.any(),
org.mockito.ArgumentMatchers.any());

sessionRegistry.add(sessionOwner1, registerMock1);
sessionRegistry.add(sessionOwner2, registerMock2);

Mockito.verify(registerMock1).kick(eq(tenantId1), eq(sessionOwner1), eq(sessionOwner2),
eq(ServerRedirection.newBuilder().setType(ServerRedirection.Type.NO_MOVE).build()));

Optional<ClientInfo> retrieved = sessionRegistry.get(tenantId1, "user1", "client1");
assertTrue(retrieved.isPresent());
assertEquals(sessionOwner2, retrieved.get());
assertGaugeValue(tenantId1, MqttConnectionGauge, 1.0);
}

@Test
public void testReAddSameOwnerWithReenteringKickKeepsNewSession() {
// Same owner re-registered with a different register: the nested remove() from the
// kick callback used to delete the mapping this add had just installed, silently
// losing the session from the dictionary (subsequent kill could not find it).
ISessionRegister registerMock1 = Mockito.mock(ISessionRegister.class);
ISessionRegister registerMock2 = Mockito.mock(ISessionRegister.class);

ClientInfo sessionOwner = ClientInfo.newBuilder()
.setTenantId(tenantId1)
.putMetadata(MQTT_USER_ID_KEY, "user1")
.putMetadata(MQTT_CLIENT_ID_KEY, "client1")
.putMetadata(MQTT_CLIENT_SESSION_TYPE, MQTT_CLIENT_SESSION_TYPE_T_VALUE)
.putMetadata(MQTT_CHANNEL_ID_KEY, "channel1")
.build();

Mockito.doAnswer(invocation -> {
sessionRegistry.remove(sessionOwner, registerMock1);
return null;
}).when(registerMock1).kick(org.mockito.ArgumentMatchers.any(),
org.mockito.ArgumentMatchers.any(), org.mockito.ArgumentMatchers.any(),
org.mockito.ArgumentMatchers.any());

sessionRegistry.add(sessionOwner, registerMock1);
sessionRegistry.add(sessionOwner, registerMock2);

Mockito.verify(registerMock1).kick(eq(tenantId1), eq(sessionOwner), eq(sessionOwner),
eq(ServerRedirection.newBuilder().setType(ServerRedirection.Type.NO_MOVE).build()));

Optional<ClientInfo> retrieved = sessionRegistry.get(tenantId1, "user1", "client1");
assertTrue(retrieved.isPresent());
assertEquals(sessionOwner, retrieved.get());
assertGaugeValue(tenantId1, MqttConnectionGauge, 1.0);
}

@Test
public void testDelayedTeardownOfTakenOverRegisterKeepsNewSession() {
// Production sequence after a same-owner takeover: the old register's stream is closed
// by the client only after it receives the Quit, so the old register's teardown
// (remove) can land well after the new register has been added. The remove must not
// delete the dictionary entry installed by the new register, nor drift the counters.
ISessionRegister registerMock1 = Mockito.mock(ISessionRegister.class);
ISessionRegister registerMock2 = Mockito.mock(ISessionRegister.class);

ClientInfo sessionOwner = ClientInfo.newBuilder()
.setTenantId(tenantId1)
.putMetadata(MQTT_USER_ID_KEY, "user1")
.putMetadata(MQTT_CLIENT_ID_KEY, "client1")
.putMetadata(MQTT_CLIENT_SESSION_TYPE, MQTT_CLIENT_SESSION_TYPE_T_VALUE)
.putMetadata(MQTT_CHANNEL_ID_KEY, "channel1")
.build();

sessionRegistry.add(sessionOwner, registerMock1);
sessionRegistry.add(sessionOwner, registerMock2); // takeover, kicks registerMock1

// delayed teardown of the OLD register (what doFinally does when its stream closes)
sessionRegistry.remove(sessionOwner, registerMock1);

Optional<ClientInfo> retrieved = sessionRegistry.get(tenantId1, "user1", "client1");
assertTrue(retrieved.isPresent());
assertEquals(sessionOwner, retrieved.get());
assertGaugeValue(tenantId1, MqttConnectionGauge, 1.0);

// teardown of the LIVE register still removes the entry
sessionRegistry.remove(sessionOwner, registerMock2);
assertTrue(sessionRegistry.get(tenantId1, "user1", "client1").isEmpty());
}

@Test
public void testRemoveSession() {
ISessionRegister registerMock = Mockito.mock(ISessionRegister.class);
Expand Down