Merge #356: name the AMQP connection in its own log lines

Both connections were already named at newConnection() -- 'fleetd-reply-inbox' and
'fleetd-lead-mailbox' -- and neither name ever reached the log: 0 occurrences in
fleetd.out, and both connections logged under the same thread name
'[AMQP Connection 10.10.20.13:5672]'. So when one of the two died and never came
back, the log could not say which.

AmqpConnectionFailureLogger extends DefaultExceptionHandler and overrides only the
protected log(String, Throwable) sink that every handle* method calls virtually, so
the identity is added without changing any handler action.

My brief caused a defect here and the correction is the interesting part. I told the
worker the client 'currently uses ForgivingExceptionHandler', read off the log line
c.r.c.i.ForgivingExceptionHandler -- which names where the LOGGER FIELD is declared,
not the instance's class. javap on the jar shows ConnectionFactory's constructor does
'new DefaultExceptionHandler', and DefaultExceptionHandler extends StrictExceptionHandler
extends ForgivingExceptionHandler. The first version therefore extended the base and
silently dropped strict channel-closing on four listener/consumer paths. Now pinned by
a type assertion on both factories plus a behavioural test that handleConsumerException
still closes the channel once.

Verified on merge with a mutation the worker did not run: it mutated the parent class,
so I mutated the copied private-static isSocketClosedOrConnectionReset in the DANGEROUS
direction (always true => every failure logs at WARN and vanishes from the redeploy
gate's ERROR count). Caught: 'inbox failure line ==> expected: <ERROR> but was: <WARN>'.

Merged main in first; the auto-merge compiled. 1379 green, unpiped.

fleetd/src/main/java/dev/ltms/fleet/msg/AmqpReplyInbox.java

@@ -8,6 +8,7 @@ import com.rabbitmq.client.DeliverCallback;
 import com.rabbitmq.client.Recoverable;
 import com.rabbitmq.client.RecoveryListener;
 import com.rabbitmq.client.Return;
+import com.rabbitmq.client.impl.DefaultExceptionHandler;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -153,17 +154,22 @@ public final class AmqpReplyInbox implements ReplyInbox, AutoCloseable {
     /** As {@link #open(String)}, with an explicit consumer prefetch (CB-527: caps the held backlog per target). */
     public static AmqpReplyInbox open(String uri, int prefetch) {
         try {
-            ConnectionFactory factory = new ConnectionFactory();
-            factory.setUri(uri);
-            // Self-heal transient blips; topology recovery re-declares queues and re-attaches consumers.
-            factory.setAutomaticRecoveryEnabled(true);
-            factory.setTopologyRecoveryEnabled(true);
-            return new AmqpReplyInbox(factory.newConnection("fleetd-reply-inbox"), prefetch);
+            return new AmqpReplyInbox(connectionFactory(uri).newConnection(AmqpConnectionFailureLogger.REPLY_INBOX), prefetch);
         } catch (Exception e) {
             throw new IllegalStateException("cannot connect to AMQP broker at " + uri, e);
         }
     }
 
+    static ConnectionFactory connectionFactory(String uri) throws Exception {
+        ConnectionFactory factory = new ConnectionFactory();
+        factory.setUri(uri);
+        // Self-heal transient blips; topology recovery re-declares queues and re-attaches consumers.
+        factory.setAutomaticRecoveryEnabled(true);
+        factory.setTopologyRecoveryEnabled(true);
+        factory.setExceptionHandler(new AmqpConnectionFailureLogger(AmqpConnectionFailureLogger.REPLY_INBOX, log));
+        return factory;
+    }
+
     /** Wrap an already-open connection with {@link #DEFAULT_PREFETCH} (injection seam for the contract test). */
     AmqpReplyInbox(Connection connection) {
         this(connection, DEFAULT_PREFETCH);
@@ -571,3 +577,44 @@ public final class AmqpReplyInbox implements ReplyInbox, AutoCloseable {
         }
     }
 }
+
+/**
+ * Keeps RabbitMQ's forgiving exception behaviour while adding the connection identity that its
+ * default logger drops. Package-private so both AMQP connections use the same two names.
+ */
+final class AmqpConnectionFailureLogger extends DefaultExceptionHandler {
+
+    static final String REPLY_INBOX = "fleetd-reply-inbox";
+    static final String LEAD_MAILBOX = "fleetd-lead-mailbox";
+
+    private final String connectionName;
+    private final Logger logger;
+
+    AmqpConnectionFailureLogger(String connectionName, Logger logger) {
+        this.connectionName = connectionName;
+        this.logger = logger;
+    }
+
+    String connectionName() {
+        return connectionName;
+    }
+
+    @Override
+    protected void log(String message, Throwable cause) {
+        if (isSocketClosedOrConnectionReset(cause)) {
+            logger.warn("AMQP connection {}: {} (Exception message: {})", connectionName, message, cause.getMessage());
+        } else {
+            logger.error("AMQP connection {}: {}", connectionName, message, cause);
+        }
+    }
+
+    private static boolean isSocketClosedOrConnectionReset(Throwable cause) {
+        // Deliberate copy of ForgivingExceptionHandler's private static helper; check it on amqp-client upgrades.
+        if (!(cause instanceof IOException)) {
+            return false;
+        }
+        return "Connection reset".equals(cause.getMessage())
+                || "Socket closed".equals(cause.getMessage())
+                || "Connection reset by peer".equals(cause.getMessage());
+    }
+}

fleetd/src/main/java/dev/ltms/fleet/msg/LeadMailbox.java

@@ -122,17 +122,22 @@ public final class LeadMailbox implements LeadChannel, AutoCloseable {
     /** As {@link #open(String, String)}, with an explicit consumer prefetch. */
     public static LeadMailbox open(String uri, String selfCoordId, int prefetch) {
         try {
-            ConnectionFactory factory = new ConnectionFactory();
-            factory.setUri(uri);
-            // Self-heal transient blips; topology recovery re-declares the queue and re-attaches the consumer.
-            factory.setAutomaticRecoveryEnabled(true);
-            factory.setTopologyRecoveryEnabled(true);
-            return new LeadMailbox(factory.newConnection("fleetd-lead-mailbox"), selfCoordId, prefetch);
+            return new LeadMailbox(connectionFactory(uri).newConnection(AmqpConnectionFailureLogger.LEAD_MAILBOX), selfCoordId, prefetch);
         } catch (Exception e) {
             throw new IllegalStateException("cannot connect to AMQP coordination broker at " + uri, e);
         }
     }
 
+    static ConnectionFactory connectionFactory(String uri) throws Exception {
+        ConnectionFactory factory = new ConnectionFactory();
+        factory.setUri(uri);
+        // Self-heal transient blips; topology recovery re-declares queues and re-attaches consumers.
+        factory.setAutomaticRecoveryEnabled(true);
+        factory.setTopologyRecoveryEnabled(true);
+        factory.setExceptionHandler(new AmqpConnectionFailureLogger(AmqpConnectionFailureLogger.LEAD_MAILBOX, log));
+        return factory;
+    }
+
     /** Wrap an already-open connection with {@link #DEFAULT_PREFETCH} (injection seam for tests). */
     LeadMailbox(Connection connection, String selfCoordId) {
         this(connection, selfCoordId, DEFAULT_PREFETCH);

fleetd/src/test/java/dev/ltms/fleet/msg/AmqpConnectionFailureLoggerTest.java

@@ -0,0 +1,134 @@
+package dev.ltms.fleet.msg;
+
+import ch.qos.logback.classic.Level;
+import ch.qos.logback.classic.Logger;
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.core.read.ListAppender;
+import com.rabbitmq.client.Channel;
+import com.rabbitmq.client.ConnectionFactory;
+import com.rabbitmq.client.impl.DefaultExceptionHandler;
+import org.junit.jupiter.api.Test;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.lang.reflect.Proxy;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertInstanceOf;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class AmqpConnectionFailureLoggerTest {
+
+    @Test
+    void installedHandlersLogTheirOwnConnectionNamesAtErrorWithTheCause() throws Exception {
+        ConnectionFactory inboxFactory = AmqpReplyInbox.connectionFactory("amqp://127.0.0.1");
+        ConnectionFactory mailboxFactory = LeadMailbox.connectionFactory("amqp://127.0.0.1");
+
+        AmqpConnectionFailureLogger inboxHandler = installedStrictHandler(inboxFactory, "reply inbox");
+        AmqpConnectionFailureLogger mailboxHandler = installedStrictHandler(mailboxFactory, "lead mailbox");
+        assertEquals(AmqpConnectionFailureLogger.REPLY_INBOX, inboxHandler.connectionName());
+        assertEquals(AmqpConnectionFailureLogger.LEAD_MAILBOX, mailboxHandler.connectionName());
+
+        ListAppender<ILoggingEvent> inboxEvents = attach(AmqpReplyInbox.class);
+        ListAppender<ILoggingEvent> mailboxEvents = attach(LeadMailbox.class);
+        IllegalStateException inboxFailure = new IllegalStateException("inbox failure");
+        IllegalStateException mailboxFailure = new IllegalStateException("mailbox failure");
+        try {
+            inboxHandler.handleUnexpectedConnectionDriverException(null, inboxFailure);
+            mailboxHandler.handleConnectionRecoveryException(null, mailboxFailure);
+
+            assertError(inboxEvents, "AMQP connection fleetd-reply-inbox: An unexpected connection driver error occurred",
+                    inboxFailure, "inbox failure line");
+            assertError(mailboxEvents, "AMQP connection fleetd-lead-mailbox: Caught an exception during connection recovery!",
+                    mailboxFailure, "mailbox recovery line");
+        } finally {
+            detach(AmqpReplyInbox.class, inboxEvents);
+            detach(LeadMailbox.class, mailboxEvents);
+        }
+    }
+
+    @Test
+    void connectionResetKeepsForgivingHandlerWarningSemantics() {
+        AmqpConnectionFailureLogger handler = new AmqpConnectionFailureLogger(
+                AmqpConnectionFailureLogger.REPLY_INBOX, LoggerFactory.getLogger(AmqpReplyInbox.class));
+        ListAppender<ILoggingEvent> events = attach(AmqpReplyInbox.class);
+        try {
+            handler.handleUnexpectedConnectionDriverException(null, new IOException("Connection reset"));
+            assertEquals(1, events.list.size(), "the handler must still log a reset");
+            ILoggingEvent event = events.list.getFirst();
+            assertEquals(Level.WARN, event.getLevel(), "ForgivingExceptionHandler logs connection resets at WARN");
+            assertEquals("AMQP connection fleetd-reply-inbox: An unexpected connection driver error occurred "
+                            + "(Exception message: Connection reset)", event.getFormattedMessage());
+            assertTrue(event.getThrowableProxy() == null, "ForgivingExceptionHandler does not attach a reset stack trace");
+        } finally {
+            detach(AmqpReplyInbox.class, events);
+        }
+    }
+
+    @Test
+    void connectionNamesStayDistinct() {
+        assertNotEquals(AmqpConnectionFailureLogger.REPLY_INBOX, AmqpConnectionFailureLogger.LEAD_MAILBOX,
+                "reply-inbox and lead-mailbox failures must be distinguishable");
+    }
+
+    @Test
+    void strictConsumerExceptionStillClosesItsChannel() {
+        AtomicInteger closes = new AtomicInteger();
+        Channel channel = (Channel) Proxy.newProxyInstance(getClass().getClassLoader(), new Class<?>[] {Channel.class},
+                (_, method, _) -> switch (method.getName()) {
+                    case "close" -> {
+                        closes.incrementAndGet();
+                        yield null;
+                    }
+                    case "toString" -> "test-channel";
+                    default -> throw new UnsupportedOperationException(method.getName());
+                });
+        AmqpConnectionFailureLogger handler = new AmqpConnectionFailureLogger(
+                AmqpConnectionFailureLogger.REPLY_INBOX, LoggerFactory.getLogger(AmqpReplyInbox.class));
+
+        handler.handleConsumerException(channel, new IllegalStateException("consumer failed"), null, "tag", "handleDelivery");
+
+        assertEquals(1, closes.get(), "DefaultExceptionHandler must close a channel after a consumer exception");
+    }
+
+    @Test
+    void handlerOnlyChangesDefaultHandlerLogging() {
+        assertEquals(DefaultExceptionHandler.class,
+                AmqpConnectionFailureLogger.class.getSuperclass());
+        assertFalse(java.util.Arrays.stream(AmqpConnectionFailureLogger.class.getDeclaredMethods())
+                        .anyMatch(method -> method.getName().startsWith("handle")),
+                "all exception-handling methods must remain inherited from DefaultExceptionHandler");
+    }
+
+    private static ListAppender<ILoggingEvent> attach(Class<?> owner) {
+        Logger logger = (Logger) LoggerFactory.getLogger(owner);
+        logger.setLevel(Level.DEBUG);
+        ListAppender<ILoggingEvent> appender = new ListAppender<>();
+        appender.start();
+        logger.addAppender(appender);
+        return appender;
+    }
+
+    private static void detach(Class<?> owner, ListAppender<ILoggingEvent> appender) {
+        ((Logger) LoggerFactory.getLogger(owner)).detachAppender(appender);
+    }
+
+    private static AmqpConnectionFailureLogger installedStrictHandler(ConnectionFactory factory, String connection) {
+        assertInstanceOf(DefaultExceptionHandler.class, factory.getExceptionHandler(),
+                connection + " must keep DefaultExceptionHandler: replacing the strict handler with a forgiving one "
+                        + "changes when a channel is closed");
+        return assertInstanceOf(AmqpConnectionFailureLogger.class, factory.getExceptionHandler());
+    }
+
+    private static void assertError(ListAppender<ILoggingEvent> events, String message, Throwable cause, String name) {
+        assertEquals(1, events.list.size(), name);
+        ILoggingEvent event = events.list.getFirst();
+        assertEquals(Level.ERROR, event.getLevel(), name);
+        assertEquals(message, event.getFormattedMessage(), name);
+        assertEquals(cause.toString(), event.getThrowableProxy().getClassName() + ": "
+                + event.getThrowableProxy().getMessage(), name);
+    }
+}