Cache sticky endpoint channels

dialogue-clients/src/main/java/com/palantir/dialogue/clients/ReloadingClientFactory.java

@@ -48,6 +48,7 @@
 import com.palantir.dialogue.core.DialogueChannel;
 import com.palantir.dialogue.core.DialogueDnsResolver;
 import com.palantir.dialogue.core.StickyEndpointChannels;
+import com.palantir.dialogue.core.StickyEndpointChannelsFactory;
 import com.palantir.dialogue.core.TargetUri;
 import com.palantir.dialogue.hc5.ApacheHttpClientChannels;
 import com.palantir.logsafe.Preconditions;
@@ -300,7 +301,7 @@ public StickyChannelFactory2 getStickyChannels2(String serviceName) {
         return new StickyChannelFactory2() {
             @Override
             public Channel getStickyChannel() {
-                return internalDialogueChannel.get().stickyChannels().get();
+                return internalDialogueChannel.get().stickyChannel();
             }
 
             @Override
@@ -504,9 +505,10 @@ public String toString() {
                     + exceptionSupplier.get().getMessage() + '}';
         }
 
+        @Unsafe
         @Override
-        public Supplier<Channel> stickyChannels() {
-            return () -> this;
+        public Channel stickyChannel() {
+            return this;
         }
 
         @Override
@@ -516,9 +518,7 @@ public EndpointChannel endpoint(Endpoint _endpoint) {
     }
 
     /* Abstracts away DialogueChannel so that we can handle no-service/no-uri case in #getInternalDialogueChannel. */
-    private interface InternalDialogueChannel extends Channel, EndpointChannelFactory {
-        Supplier<Channel> stickyChannels();
-    }
+    private interface InternalDialogueChannel extends Channel, EndpointChannelFactory, StickyEndpointChannelsFactory {}
 
     private static final class InternalDialogueChannelFromDialogueChannel implements InternalDialogueChannel {
 
@@ -539,8 +539,8 @@ public EndpointChannel endpoint(Endpoint endpoint) {
         }
 
         @Override
-        public Supplier<Channel> stickyChannels() {
-            return dialogueChannel.stickyChannels();
+        public Channel stickyChannel() {
+            return dialogueChannel.stickyChannel();
         }
     }
 

dialogue-core/src/main/java/com/palantir/dialogue/core/CachingEndpointChannelFactory.java

@@ -0,0 +1,47 @@
+/*
+ * (c) Copyright 2026 Palantir Technologies Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.palantir.dialogue.core;
+
+import com.github.benmanes.caffeine.cache.Caffeine;
+import com.github.benmanes.caffeine.cache.LoadingCache;
+import com.palantir.dialogue.Endpoint;
+import com.palantir.dialogue.EndpointChannel;
+import com.palantir.dialogue.EndpointChannelFactory;
+
+final class CachingEndpointChannelFactory implements EndpointChannelFactory {
+
+    private final LoadingCache<Endpoint, EndpointChannel> cache;
+    private final EndpointChannelFactory delegate;
+
+    CachingEndpointChannelFactory(EndpointChannelFactory delegate, int maxEndpointCacheSize) {
+        this.delegate = delegate;
+        this.cache = Caffeine.newBuilder()
+                .maximumSize(maxEndpointCacheSize)
+                .weakValues()
+                .build(delegate::endpoint);
+    }
+
+    @Override
+    public EndpointChannel endpoint(Endpoint endpoint) {
+        return cache.get(endpoint);
+    }
+
+    @Override
+    public String toString() {
+        return "CachingEndpointChannelFactory{" + delegate + '}';
+    }
+}

dialogue-core/src/main/java/com/palantir/dialogue/core/Config.java

@@ -79,6 +79,12 @@ default int maxQueueSize() {
         return 100_000;
     }
 
+    /** Maximum number of cached endpoint channels. Values {@code <= 0} disable caching. */
+    @Value.Default
+    default int maxEndpointCacheSize() {
+        return 1_000;
+    }
+
     OptionalInt overrideSingleHostIndex();
 
     @Value.Default

dialogue-core/src/main/java/com/palantir/dialogue/core/DialogueChannel.java

@@ -31,6 +31,7 @@
 import com.palantir.dialogue.EndpointChannelFactory;
 import com.palantir.dialogue.Request;
 import com.palantir.dialogue.Response;
+import com.palantir.dialogue.core.DialogueChannelFactory.ChannelArgs;
 import com.palantir.logsafe.Preconditions;
 import com.palantir.logsafe.Safe;
 import com.palantir.logsafe.SafeArg;
@@ -49,16 +50,17 @@
 import java.util.function.Function;
 import java.util.function.Supplier;
 
-public final class DialogueChannel implements Channel, EndpointChannelFactory {
+public final class DialogueChannel implements Channel, EndpointChannelFactory, StickyEndpointChannelsFactory {
     private static final SafeLogger log = SafeLoggerFactory.get(DialogueChannel.class);
     private final EndpointChannelFactory delegate;
     private final Config cf;
-    private final Supplier<Channel> stickyChannelSupplier;
+    private final StickyEndpointChannelsFactory stickyEndpointChannelsFactory;
 
-    private DialogueChannel(Config cf, EndpointChannelFactory delegate, Supplier<Channel> stickyChannelSupplier) {
+    private DialogueChannel(
+            Config cf, EndpointChannelFactory delegate, StickyEndpointChannelsFactory stickyEndpointChannelsFactory) {
         this.cf = cf;
         this.delegate = delegate;
-        this.stickyChannelSupplier = stickyChannelSupplier;
+        this.stickyEndpointChannelsFactory = stickyEndpointChannelsFactory;
     }
 
     @Override
@@ -71,8 +73,17 @@ public EndpointChannel endpoint(Endpoint endpoint) {
         return delegate.endpoint(endpoint);
     }
 
+    /**
+     * @deprecated use {@link #stickyChannel()}
+     */
+    @Deprecated
     public Supplier<Channel> stickyChannels() {
-        return stickyChannelSupplier;
+        return () -> stickyChannel();
+    }
+
+    @Override
+    public Channel stickyChannel() {
+        return stickyEndpointChannelsFactory.stickyChannel();
     }
 
     public static Builder builder() {
@@ -219,8 +230,7 @@ public LimitedChannel apply(List<TargetUri> targetUris) {
 
             Channel multiHostQueuedChannel = QueuedChannel.create(cf, stickyValidationChannel);
             EndpointChannelFactory channelFactory = createEndpointChannelFactory(multiHostQueuedChannel, cf);
-
-            Supplier<Channel> stickyChannelSupplier =
+            StickyEndpointChannelsFactory stickyEndpointChannelsFactory =
                     StickyEndpointChannels2.create(cf, stickyValidationChannel, channelFactory);
 
             Meter createMeter = clientMetrics
@@ -230,7 +240,7 @@ public LimitedChannel apply(List<TargetUri> targetUris) {
                     .build();
             createMeter.mark();
 
-            return new DialogueChannel(cf, channelFactory, stickyChannelSupplier);
+            return new DialogueChannel(cf, channelFactory, stickyEndpointChannelsFactory);
         }
 
         private static ImmutableList<LimitedChannel> createHostChannels(
@@ -241,7 +251,7 @@ private static ImmutableList<LimitedChannel> createHostChannels(
                         cf.overrideSingleHostIndex().orElse(uriIndex);
                 TargetUri targetUri = targetUris.get(uriIndex);
                 Channel channel = cf.channelFactory()
-                        .create(DialogueChannelFactory.ChannelArgs.builder()
+                        .create(ChannelArgs.builder()
                                 .uri(targetUri.uri())
                                 .uriIndexForInstrumentation(uriIndexForInstrumentation)
                                 .resolvedAddress(targetUri.resolvedAddress())

dialogue-core/src/main/java/com/palantir/dialogue/core/StickyEndpointChannels2.java

@@ -33,28 +33,34 @@
 import javax.annotation.concurrent.ThreadSafe;
 import org.jspecify.annotations.Nullable;
 
-final class StickyEndpointChannels2 implements Supplier<Channel> {
+final class StickyEndpointChannels2 implements StickyEndpointChannelsFactory {
 
-    private final Supplier<EndpointChannelFactory> delegate;
+    private final Supplier<Channel> queueOverrideSupplier;
+    private final EndpointChannelFactory delegate;
 
-    StickyEndpointChannels2(Supplier<EndpointChannelFactory> endpointChannelFactory) {
+    StickyEndpointChannels2(Supplier<Channel> queueOverrideSupplier, EndpointChannelFactory endpointChannelFactory) {
+        this.queueOverrideSupplier = queueOverrideSupplier;
         this.delegate = endpointChannelFactory;
     }
 
     @Override
-    public Channel get() {
-        return new StickyChannel2(delegate.get());
+    public Channel stickyChannel() {
+        return new StickyChannel2(queueOverrideSupplier, delegate);
     }
 
     @Override
     public String toString() {
         return "StickyEndpointChannels2{" + delegate + "}";
     }
 
-    static Supplier<Channel> create(Config cf, LimitedChannel nodeSelectionChannel, EndpointChannelFactory delegate) {
+    static StickyEndpointChannelsFactory create(
+            Config cf, LimitedChannel nodeSelectionChannel, EndpointChannelFactory delegate) {
         Supplier<Channel> queueOverrideSupplier = new QueueOverrideSupplier(cf, nodeSelectionChannel);
-        return new StickyEndpointChannels2(
-                new StickyEndpointChannels2EndpointFactorySupplier(queueOverrideSupplier, delegate));
+        int maxEndpointCacheSize = cf.maxEndpointCacheSize();
+        EndpointChannelFactory channelFactory = (maxEndpointCacheSize <= 0)
+                ? delegate
+                : new CachingEndpointChannelFactory(delegate, maxEndpointCacheSize);
+        return new StickyEndpointChannels2(queueOverrideSupplier, channelFactory);
     }
 
     private static final class QueueOverrideSupplier implements Supplier<Channel> {
@@ -81,43 +87,25 @@ public Channel get() {
         }
     }
 
-    private static final class StickyEndpointChannels2EndpointFactorySupplier
-            implements Supplier<EndpointChannelFactory> {
-
-        private final Supplier<Channel> queueOverrideSupplier;
-        private final EndpointChannelFactory delegate;
-
-        StickyEndpointChannels2EndpointFactorySupplier(
-                Supplier<Channel> queueOverrideSupplier, EndpointChannelFactory delegate) {
-            this.queueOverrideSupplier = queueOverrideSupplier;
-            this.delegate = delegate;
-        }
-
-        @Override
-        public EndpointChannelFactory get() {
-            Channel queueOverride = queueOverrideSupplier.get();
-            return endpoint -> {
-                EndpointChannel endpointChannel = delegate.endpoint(endpoint);
-                return (EndpointChannel) request -> {
-                    QueueAttachments.setQueueOverride(request, queueOverride);
-                    return endpointChannel.execute(request);
-                };
-            };
-        }
-    }
-
-    private static final class StickyChannel2 implements EndpointChannelFactory, Channel {
+    private static final class StickyChannel2 implements Channel, EndpointChannelFactory {
 
+        private final Channel queueOverride;
         private final EndpointChannelFactory channelFactory;
         private final StickyRouter router = new StickyRouter();
 
-        private StickyChannel2(EndpointChannelFactory channelFactory) {
+        private StickyChannel2(Supplier<Channel> queueOverrideSupplier, EndpointChannelFactory channelFactory) {
+            this.queueOverride = queueOverrideSupplier.get();
             this.channelFactory = channelFactory;
         }
 
         @Override
         public EndpointChannel endpoint(Endpoint endpoint) {
-            return new StickyEndpointChannel(router, channelFactory.endpoint(endpoint));
+            EndpointChannel endpointChannel = channelFactory.endpoint(endpoint);
+            EndpointChannel endpointWithQueueOverride = innerRequest -> {
+                QueueAttachments.setQueueOverride(innerRequest, queueOverride);
+                return endpointChannel.execute(innerRequest);
+            };
+            return request -> router.execute(request, endpointWithQueueOverride);
         }
 
         @Override
@@ -240,24 +228,4 @@ private static ListenableFuture<Response> executeWithStickyTarget(
             return endpointChannel.execute(request);
         }
     }
-
-    private static final class StickyEndpointChannel implements EndpointChannel {
-        private final StickyRouter stickyRouter;
-        private final EndpointChannel delegate;
-
-        StickyEndpointChannel(StickyRouter stickyRouter, EndpointChannel delegate) {
-            this.stickyRouter = stickyRouter;
-            this.delegate = delegate;
-        }
-
-        @Override
-        public ListenableFuture<Response> execute(Request request) {
-            return stickyRouter.execute(request, delegate);
-        }
-
-        @Override
-        public String toString() {
-            return "StickyEndpointChannel{delegate=" + delegate + '}';
-        }
-    }
 }

dialogue-core/src/main/java/com/palantir/dialogue/core/StickyEndpointChannelsFactory.java

@@ -0,0 +1,23 @@
+/*
+ * (c) Copyright 2025 Palantir Technologies Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.palantir.dialogue.core;
+
+import com.palantir.dialogue.Channel;
+
+public interface StickyEndpointChannelsFactory {
+    Channel stickyChannel();
+}