bitflicker64 commented on code in PR #3130:
URL: https://github.com/apache/hugegraph/pull/3130#discussion_r3774892838


##########
hugegraph-store/hg-store-client/src/main/java/org/apache/hugegraph/store/client/grpc/AbstractGrpcClient.java:
##########
@@ -169,6 +193,224 @@ protected AbstractStub setStubOption(AbstractStub value) {
                             config.getGrpcMaxOutboundMessageSize());
     }
 
+    private static boolean usesChannels(HgPair<ManagedChannel, ?>[] pairs,
+                                        ManagedChannel[] channels) {
+        if (pairs == null || pairs.length != channels.length) {
+            return false;
+        }
+        for (int i = 0; i < pairs.length; i++) {
+            HgPair<ManagedChannel, ?> pair = pairs[i];
+            if (pair == null || pair.getKey() != channels[i]) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    private void refreshChannelsIfAddressChanged(String target) {
+        if (!this.shouldRefreshChannels(target)) {
+            return;
+        }
+
+        ReentrantLock refreshLock = refreshLocks.computeIfAbsent(target,
+                                                                 key -> new 
ReentrantLock());
+        if (!refreshLock.tryLock()) {
+            return;
+        }
+
+        try {
+            if (!this.shouldRefreshChannels(target)) {
+                return;
+            }
+
+            String resolvedTarget = this.resolveTarget(target);
+            this.postponeNextRefresh(target);
+            if (resolvedTarget.isEmpty()) {
+                return;
+            }
+
+            ManagedChannel[] staleChannels = channels.get(target);
+            String previousTarget = resolvedTargets.get(target);
+            if (previousTarget == null && staleChannels == null) {
+                resolvedTargets.put(target, resolvedTarget);
+                return;
+            }
+            if (resolvedTarget.equals(previousTarget)) {
+                return;
+            }
+            if (staleChannels == null) {
+                resolvedTargets.put(target, resolvedTarget);
+                return;
+            }
+
+            ManagedChannel[] replacementChannels;
+            try {
+                replacementChannels = this.createChannels(target);
+            } catch (RuntimeException ignored) {
+                return;
+            }
+
+            boolean replaced = false;
+            synchronized (channels) {
+                if (channels.get(target) == staleChannels) {
+                    channels.put(target, replacementChannels);
+                    resolvedTargets.put(target, resolvedTarget);
+                    replaced = true;
+                }
+            }
+
+            if (replaced) {
+                this.retireChannels(staleChannels);
+            } else {
+                this.retireChannels(replacementChannels);
+            }
+        } finally {
+            refreshLock.unlock();
+        }
+    }
+
+    private boolean shouldRefreshChannels(String target) {
+        AtomicLong nextResolution = nextResolutions.computeIfAbsent(target,
+                                                                    key -> new 
AtomicLong());
+        return System.nanoTime() - nextResolution.get() >= 0L;
+    }
+
+    private void postponeNextRefresh(String target) {
+        long interval = Math.max(0L, this.channelRefreshIntervalNanos());
+        nextResolutions.computeIfAbsent(target, key -> new AtomicLong())
+                       .set(System.nanoTime() + interval);
+    }
+
+    protected long channelRefreshIntervalNanos() {
+        return DEFAULT_CHANNEL_REFRESH_INTERVAL_NANOS;
+    }
+
+    protected long channelDrainTimeoutNanos() {
+        return TimeUnit.SECONDS.toNanos(config.getGrpcTimeoutSeconds());
+    }
+
+    private ManagedChannel[] createChannels(String target) {
+        ManagedChannel[] value = new ManagedChannel[concurrency];
+        CountDownLatch latch = new CountDownLatch(concurrency);
+        AtomicReference<RuntimeException> failure = new AtomicReference<>();
+        for (int i = 0; i < concurrency; i++) {
+            int fi = i;
+            executor.execute(() -> {
+                try {
+                    value[fi] = createChannel(target);
+                } catch (Exception e) {
+                    failure.compareAndSet(null, new RuntimeException(e));
+                } finally {
+                    latch.countDown();
+                }
+            });
+        }
+
+        InterruptedException interruption = null;
+        while (latch.getCount() > 0L) {
+            try {
+                latch.await();
+            } catch (InterruptedException e) {
+                interruption = e;
+            }
+        }
+
+        if (failure.get() != null || interruption != null) {
+            forceTerminateChannels(value);
+        }
+        if (interruption != null) {
+            Thread.currentThread().interrupt();
+            throw new RuntimeException(interruption);
+        }
+        if (failure.get() != null) {
+            throw failure.get();
+        }
+        return value;
+    }
+
+    private void retireChannels(ManagedChannel[] retiredChannels) {
+        Arrays.stream(retiredChannels)
+              .filter(channel -> channel != null && !channel.isShutdown())
+              .forEach(ManagedChannel::shutdown);
+
+        long timeout = Math.max(0L, this.channelDrainTimeoutNanos());
+        CHANNEL_CLEANUP_EXECUTOR.schedule(
+                () -> forceTerminateChannels(retiredChannels), timeout,
+                TimeUnit.NANOSECONDS);
+    }
+
+    private void forceTerminateChannels(ManagedChannel[] retiredChannels) {
+        for (ManagedChannel channel : retiredChannels) {
+            if (channel != null && !channel.isTerminated()) {
+                channel.shutdownNow();
+            }
+        }
+    }
+
+    private static String targetHost(String target) {
+        if (target == null || target.isEmpty()) {
+            return "";
+        }
+
+        String endpoint = target;
+        if (target.startsWith("dns://")) {
+            endpoint = target.substring("dns://".length());
+            while (endpoint.startsWith("/")) {
+                endpoint = endpoint.substring(1);
+            }
+            int pathStart = endpoint.indexOf('/');
+            if (pathStart >= 0) {
+                endpoint = endpoint.substring(pathStart + 1);
+            }
+        } else if (target.contains("://")) {
+            return "";
+        }
+
+        return endpointHost(endpoint);
+    }
+
+    private static String endpointHost(String endpoint) {
+        if (endpoint == null || endpoint.isEmpty()) {
+            return "";
+        }
+
+        if (endpoint.charAt(0) == '[') {
+            int hostEnd = endpoint.indexOf(']');
+            if (hostEnd <= 1) {
+                return "";
+            }
+            return endpoint.substring(1, hostEnd);
+        }
+
+        int lastColon = endpoint.lastIndexOf(':');
+        if (lastColon < 0) {
+            return endpoint;
+        }
+        if (endpoint.indexOf(':') != lastColon) {
+            return endpoint;
+        }
+        return endpoint.substring(0, lastColon);
+    }
+
+    protected InetAddress[] resolveHost(String host) throws 
UnknownHostException {
+        return InetAddress.getAllByName(host);
+    }
+
+    protected String resolveTarget(String target) {
+        String host = targetHost(target);
+        if (host.isEmpty()) {
+            return "";
+        }
+        try {
+            return Arrays.stream(this.resolveHost(host))

Review Comment:
   Final exact-head confirmation on `bdd8df11`: both cold initialization and 
DNS refresh remain behind bounded prestarted trusted executors, so a denied 
Gremlin caller performs neither DNS/socket work nor thread creation. The 
focused Java 11 suite passes 37/37, including the real restricted-caller cold 
and refresh paths. The final concurrency review and Design Audit found no 
blocker.



##########
hugegraph-store/hg-store-client/src/main/java/org/apache/hugegraph/store/client/grpc/AbstractGrpcClient.java:
##########
@@ -169,6 +193,224 @@ protected AbstractStub setStubOption(AbstractStub value) {
                             config.getGrpcMaxOutboundMessageSize());
     }
 
+    private static boolean usesChannels(HgPair<ManagedChannel, ?>[] pairs,
+                                        ManagedChannel[] channels) {
+        if (pairs == null || pairs.length != channels.length) {
+            return false;
+        }
+        for (int i = 0; i < pairs.length; i++) {
+            HgPair<ManagedChannel, ?> pair = pairs[i];
+            if (pair == null || pair.getKey() != channels[i]) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    private void refreshChannelsIfAddressChanged(String target) {
+        if (!this.shouldRefreshChannels(target)) {
+            return;
+        }
+
+        ReentrantLock refreshLock = refreshLocks.computeIfAbsent(target,
+                                                                 key -> new 
ReentrantLock());
+        if (!refreshLock.tryLock()) {
+            return;
+        }
+
+        try {
+            if (!this.shouldRefreshChannels(target)) {
+                return;
+            }
+
+            String resolvedTarget = this.resolveTarget(target);
+            this.postponeNextRefresh(target);
+            if (resolvedTarget.isEmpty()) {
+                return;
+            }
+
+            ManagedChannel[] staleChannels = channels.get(target);
+            String previousTarget = resolvedTargets.get(target);
+            if (previousTarget == null && staleChannels == null) {
+                resolvedTargets.put(target, resolvedTarget);
+                return;
+            }
+            if (resolvedTarget.equals(previousTarget)) {
+                return;
+            }
+            if (staleChannels == null) {
+                resolvedTargets.put(target, resolvedTarget);
+                return;
+            }
+
+            ManagedChannel[] replacementChannels;
+            try {
+                replacementChannels = this.createChannels(target);
+            } catch (RuntimeException ignored) {
+                return;
+            }
+
+            boolean replaced = false;
+            synchronized (channels) {
+                if (channels.get(target) == staleChannels) {
+                    channels.put(target, replacementChannels);
+                    resolvedTargets.put(target, resolvedTarget);
+                    replaced = true;
+                }
+            }
+
+            if (replaced) {
+                this.retireChannels(staleChannels);

Review Comment:
   Final exact-head confirmation on `bdd8df11`: QueryV2 still delegates through 
guarded `getAsyncStub(target)`, directly injected test channels are closed on 
replacement, and ordinary QueryV2 clients participate in inherited lifecycle 
cleanup. The focused Java 11 suite passes 37/37; JaCoCo records the changed 
injected-channel cleanup lines as covered (`mi=0`). No blocker remained in 
independent API/failure review or the Design Audit.



##########
hugegraph-store/hg-store-client/src/main/java/org/apache/hugegraph/store/client/grpc/AbstractGrpcClient.java:
##########
@@ -169,6 +201,289 @@ protected AbstractStub setStubOption(AbstractStub value) {
                             config.getGrpcMaxOutboundMessageSize());
     }
 
+    private static boolean usesChannels(HgPair<ManagedChannel, ?>[] pairs,
+                                        ManagedChannel[] channels) {
+        if (pairs == null || pairs.length != channels.length) {
+            return false;
+        }
+        for (int i = 0; i < pairs.length; i++) {
+            HgPair<ManagedChannel, ?> pair = pairs[i];
+            if (pair == null || pair.getKey() != channels[i]) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    /**
+     * Submits a refresh for the target unless one is already in flight or the 
refresh interval
+     * has not elapsed. Returns the in-flight refresh, or null when none is 
running.
+     */
+    private CompletableFuture<Void> triggerChannelRefresh(String target) {
+        CompletableFuture<Void> inFlight = refreshTasks.get(target);
+        if (inFlight != null) {
+            return inFlight;
+        }
+        if (!this.shouldRefreshChannels(target)) {
+            return null;
+        }
+
+        CompletableFuture<Void> refresh = new CompletableFuture<>();
+        CompletableFuture<Void> running = refreshTasks.putIfAbsent(target, 
refresh);
+        if (running != null) {
+            return running;
+        }
+
+        // Throttle before submitting, so that a failing resolver cannot be 
retried in a loop.
+        this.postponeNextRefresh(target);
+        try {
+            this.submitChannelRefresh(() -> {
+                try {
+                    this.refreshChannelsIfAddressChanged(target);
+                } catch (Throwable e) {
+                    // The executor discards what a task throws, so report it 
here.
+                    log.warn("Failed to refresh channels of target {}", 
target, e);
+                } finally {
+                    this.completeRefresh(target, refresh);
+                }
+            });
+        } catch (Throwable e) {
+            // Includes a thread creation denied on this thread; never leave 
the entry behind.
+            log.warn("Failed to submit a channel refresh for target {}", 
target, e);
+            this.completeRefresh(target, refresh);
+        }
+        return refresh;
+    }
+
+    private void completeRefresh(String target, CompletableFuture<Void> 
refresh) {
+        /*
+         * Throttle from completion as well as from submission: a resolver 
that is slow rather
+         * than failing can outlast its own interval, which would let every 
later call queue
+         * another lookup behind it.
+         */
+        this.postponeNextRefresh(target);
+        refreshTasks.remove(target, refresh);
+        refresh.complete(null);
+    }
+
+    private void submitChannelRefresh(Runnable task) {
+        CHANNEL_MAINTENANCE_EXECUTOR.execute(task);
+    }
+
+    private void awaitInitialResolution(CompletableFuture<Void> refresh) {
+        if (refresh == null) {
+            return;
+        }
+        try {
+            refresh.get(Math.max(0L, this.initialResolutionTimeoutNanos()),
+                        TimeUnit.NANOSECONDS);
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+        } catch (Exception ignored) {
+            // A slow or failing resolver must not delay the first pool any 
further.
+        }
+    }
+
+    /**
+     * Runs on a maintenance thread, never on a request thread. At most one 
runs per target at a
+     * time — that comes from the refreshTasks entry, not from the size of the 
executor. Replaces
+     * the target's pool when its resolved address set has changed, publishing 
the replacement
+     * before retiring the previous pool.
+     */
+    private void refreshChannelsIfAddressChanged(String target) {
+        String resolvedTarget = this.resolveTarget(target);
+        if (resolvedTarget.isEmpty()) {
+            return;
+        }
+
+        ManagedChannel[] staleChannels = channels.get(target);
+        String previousTarget = resolvedTargets.get(target);
+        if (resolvedTarget.equals(previousTarget)) {
+            return;
+        }
+        if (staleChannels == null) {
+            /*
+             * Nothing to replace yet. Recording the address here is what lets 
the common path
+             * build its first pool already knowing the address, instead of 
rebuilding it.
+             */
+            resolvedTargets.put(target, resolvedTarget);
+            return;
+        }
+
+        ManagedChannel[] replacementChannels;
+        try {
+            replacementChannels = this.createChannels(target);
+        } catch (RuntimeException e) {
+            // Keep serving from the last healthy pool.
+            log.warn("Failed to create replacement channels of target {}, " +
+                     "keeping the current pool", target, e);
+            return;
+        }
+
+        boolean replaced = false;
+        synchronized (channels) {
+            if (channels.get(target) == staleChannels) {
+                channels.put(target, replacementChannels);
+                resolvedTargets.put(target, resolvedTarget);
+                replaced = true;
+            }
+        }
+        if (replaced) {
+            log.info("Replaced the channel pool of target {}, address changed 
from {} to {}",
+                     target, previousTarget, resolvedTarget);
+        }
+
+        this.retireChannels(replaced ? staleChannels : replacementChannels);
+    }
+
+    private boolean shouldRefreshChannels(String target) {
+        AtomicLong nextResolution = nextResolutions.computeIfAbsent(target,
+                                                                    key -> new 
AtomicLong());
+        return System.nanoTime() - nextResolution.get() >= 0L;

Review Comment:
   Final exact-head confirmation on `bdd8df11`: first-run state remains 
explicit (`null` deadline), and deadline evaluation still uses overflow-safe 
signed subtraction. Negative-origin and `Long.MAX_VALUE`/`Long.MIN_VALUE` 
wraparound regressions remain in the 37/37 passing Java 11 focused suite. No 
blocker remained in the final reviews or Design Audit.



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