Introduce "EndpointDiscoveryFailedException", which is thrown when an operation requires endpoint discovery, but endpoint discovery fails.

codegen/src/main/java/software/amazon/awssdk/codegen/poet/endpointdiscovery/EndpointDiscoveryAsyncCacheLoaderGenerator.java

@@ -27,6 +27,7 @@
 import com.squareup.javapoet.TypeSpec;
 import java.time.Instant;
 import java.time.temporal.ChronoUnit;
+import java.util.List;
 import java.util.concurrent.CompletableFuture;
 import software.amazon.awssdk.annotations.SdkInternalApi;
 import software.amazon.awssdk.codegen.emitters.GeneratorTaskParams;
@@ -38,6 +39,7 @@
 import software.amazon.awssdk.core.endpointdiscovery.EndpointDiscoveryCacheLoader;
 import software.amazon.awssdk.core.endpointdiscovery.EndpointDiscoveryEndpoint;
 import software.amazon.awssdk.core.endpointdiscovery.EndpointDiscoveryRequest;
+import software.amazon.awssdk.utils.Validate;
 
 public class EndpointDiscoveryAsyncCacheLoaderGenerator implements ClassSpec {
 
@@ -100,12 +102,15 @@ private MethodSpec discoverEndpoint(OperationModel opModel) {
                                                      .returns(returnType);
 
         if (!opModel.getInputShape().isHasHeaderMember()) {
+            ClassName endpointClass = poetExtensions.getModelClass("Endpoint");
             methodBuilder.addCode("return $L.$L($L.builder().build()).thenApply(r -> {",
                                   CLIENT_FIELD,
                                   opModel.getMethodName(),
                                   poetExtensions.getModelClass(opModel.getInputShape().getC2jName()))
-                         .addStatement("$T endpoint = r.endpoints().get(0)",
-                                       poetExtensions.getModelClass("Endpoint"))
+                         .addStatement("$T<$T> endpoints = r.endpoints()", List.class, endpointClass)
+                         .addStatement("$T.notEmpty(endpoints, \"Endpoints returned by service for endpoint discovery must "
+                                       + "not be empty.\")", Validate.class)
+                         .addStatement("$T endpoint = endpoints.get(0)", endpointClass)
                          .addStatement("return $T.builder().endpoint(toUri(endpoint.address(), $L.defaultEndpoint()))" +
                                        ".expirationTime($T.now().plus(endpoint.cachePeriodInMinutes(), $T.MINUTES)).build()",
                                        EndpointDiscoveryEndpoint.class,

codegen/src/main/java/software/amazon/awssdk/codegen/poet/endpointdiscovery/EndpointDiscoveryCacheLoaderGenerator.java

@@ -27,6 +27,7 @@
 import com.squareup.javapoet.TypeSpec;
 import java.time.Instant;
 import java.time.temporal.ChronoUnit;
+import java.util.List;
 import java.util.concurrent.CompletableFuture;
 import software.amazon.awssdk.annotations.SdkInternalApi;
 import software.amazon.awssdk.codegen.emitters.GeneratorTaskParams;
@@ -38,6 +39,7 @@
 import software.amazon.awssdk.core.endpointdiscovery.EndpointDiscoveryCacheLoader;
 import software.amazon.awssdk.core.endpointdiscovery.EndpointDiscoveryEndpoint;
 import software.amazon.awssdk.core.endpointdiscovery.EndpointDiscoveryRequest;
+import software.amazon.awssdk.utils.Validate;
 
 public class EndpointDiscoveryCacheLoaderGenerator implements ClassSpec {
 
@@ -101,14 +103,18 @@ private MethodSpec discoverEndpoint(OperationModel opModel) {
                                                      .returns(returnType);
 
         if (!opModel.getInputShape().isHasHeaderMember()) {
+            ClassName endpointClass = poetExtensions.getModelClass("Endpoint");
             methodBuilder.addCode("return $T.supplyAsync(() -> {", CompletableFuture.class)
                          .addStatement("$T response = $L.$L($L.builder().build())",
                                        poetExtensions.getModelClass(opModel.getOutputShape().getC2jName()),
                                        CLIENT_FIELD,
                                        opModel.getMethodName(),
                                        poetExtensions.getModelClass(opModel.getInputShape().getC2jName()))
-                         .addStatement("$T endpoint = response.endpoints().get(0)",
-                                       poetExtensions.getModelClass("Endpoint"))
+                         .addStatement("$T<$T> endpoints = response.endpoints()", List.class, endpointClass)
+                         .addStatement("$T.notEmpty(endpoints, \"Endpoints returned by service for endpoint discovery must "
+                                       + "not be empty.\")", Validate.class)
+                         .addStatement("$T endpoint = endpoints.get(0)",
+                                       endpointClass)
                          .addStatement("return $T.builder().endpoint(toUri(endpoint.address(), $L.defaultEndpoint()))" +
                                        ".expirationTime($T.now().plus(endpoint.cachePeriodInMinutes(), $T.MINUTES)).build()",
                                        EndpointDiscoveryEndpoint.class,

codegen/src/test/resources/software/amazon/awssdk/codegen/poet/endpointdiscovery/test-async-cache-loader.java

@@ -2,13 +2,15 @@
 
 import java.time.Instant;
 import java.time.temporal.ChronoUnit;
+import java.util.List;
 import java.util.concurrent.CompletableFuture;
 import software.amazon.awssdk.annotations.Generated;
 import software.amazon.awssdk.annotations.SdkInternalApi;
 import software.amazon.awssdk.core.endpointdiscovery.EndpointDiscoveryCacheLoader;
 import software.amazon.awssdk.core.endpointdiscovery.EndpointDiscoveryEndpoint;
 import software.amazon.awssdk.core.endpointdiscovery.EndpointDiscoveryRequest;
 import software.amazon.awssdk.services.endpointdiscoverytest.model.Endpoint;
+import software.amazon.awssdk.utils.Validate;
 
 @SdkInternalApi
 @Generated("software.amazon.awssdk:codegen")
@@ -26,14 +28,17 @@ public static EndpointDiscoveryTestAsyncEndpointDiscoveryCacheLoader create(Endp
     @Override
     public CompletableFuture<EndpointDiscoveryEndpoint> discoverEndpoint(EndpointDiscoveryRequest endpointDiscoveryRequest) {
         return client.describeEndpoints(
-                software.amazon.awssdk.services.endpointdiscoverytest.model.DescribeEndpointsRequest.builder().build())
-                .thenApply(
-                        r -> {
-                            Endpoint endpoint = r.endpoints().get(0);
-                            return EndpointDiscoveryEndpoint.builder()
-                                    .endpoint(toUri(endpoint.address(), endpointDiscoveryRequest.defaultEndpoint()))
-                                    .expirationTime(Instant.now().plus(endpoint.cachePeriodInMinutes(), ChronoUnit.MINUTES))
-                                    .build();
-                        });
+            software.amazon.awssdk.services.endpointdiscoverytest.model.DescribeEndpointsRequest.builder().build())
+                     .thenApply(
+                         r -> {
+                             List<Endpoint> endpoints = r.endpoints();
+                             Validate.notEmpty(endpoints,
+                                               "Endpoints returned by service for endpoint discovery must not be empty.");
+                             Endpoint endpoint = endpoints.get(0);
+                             return EndpointDiscoveryEndpoint.builder()
+                                                             .endpoint(toUri(endpoint.address(), endpointDiscoveryRequest.defaultEndpoint()))
+                                                             .expirationTime(Instant.now().plus(endpoint.cachePeriodInMinutes(), ChronoUnit.MINUTES))
+                                                             .build();
+                         });
     }
 }

codegen/src/test/resources/software/amazon/awssdk/codegen/poet/endpointdiscovery/test-sync-cache-loader.java

@@ -2,6 +2,7 @@
 
 import java.time.Instant;
 import java.time.temporal.ChronoUnit;
+import java.util.List;
 import java.util.concurrent.CompletableFuture;
 import software.amazon.awssdk.annotations.Generated;
 import software.amazon.awssdk.annotations.SdkInternalApi;
@@ -10,6 +11,7 @@
 import software.amazon.awssdk.core.endpointdiscovery.EndpointDiscoveryRequest;
 import software.amazon.awssdk.services.endpointdiscoverytest.model.DescribeEndpointsResponse;
 import software.amazon.awssdk.services.endpointdiscoverytest.model.Endpoint;
+import software.amazon.awssdk.utils.Validate;
 
 @SdkInternalApi
 @Generated("software.amazon.awssdk:codegen")
@@ -28,12 +30,14 @@ public static EndpointDiscoveryTestEndpointDiscoveryCacheLoader create(EndpointD
     public CompletableFuture<EndpointDiscoveryEndpoint> discoverEndpoint(EndpointDiscoveryRequest endpointDiscoveryRequest) {
         return CompletableFuture.supplyAsync(() -> {
             DescribeEndpointsResponse response = client
-                    .describeEndpoints(software.amazon.awssdk.services.endpointdiscoverytest.model.DescribeEndpointsRequest
-                            .builder().build());
-            Endpoint endpoint = response.endpoints().get(0);
+                .describeEndpoints(software.amazon.awssdk.services.endpointdiscoverytest.model.DescribeEndpointsRequest
+                                       .builder().build());
+            List<Endpoint> endpoints = response.endpoints();
+            Validate.notEmpty(endpoints, "Endpoints returned by service for endpoint discovery must not be empty.");
+            Endpoint endpoint = endpoints.get(0);
             return EndpointDiscoveryEndpoint.builder()
-                    .endpoint(toUri(endpoint.address(), endpointDiscoveryRequest.defaultEndpoint()))
-                    .expirationTime(Instant.now().plus(endpoint.cachePeriodInMinutes(), ChronoUnit.MINUTES)).build();
+                                            .endpoint(toUri(endpoint.address(), endpointDiscoveryRequest.defaultEndpoint()))
+                                            .expirationTime(Instant.now().plus(endpoint.cachePeriodInMinutes(), ChronoUnit.MINUTES)).build();
         });
     }
 }

core/sdk-core/src/main/java/software/amazon/awssdk/core/endpointdiscovery/EndpointDiscoveryCacheLoader.java

@@ -18,10 +18,10 @@
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.util.concurrent.CompletableFuture;
-import software.amazon.awssdk.annotations.SdkInternalApi;
+import software.amazon.awssdk.annotations.SdkProtectedApi;
 import software.amazon.awssdk.core.exception.SdkClientException;
 
-@SdkInternalApi
+@SdkProtectedApi
 public interface EndpointDiscoveryCacheLoader {
     CompletableFuture<EndpointDiscoveryEndpoint> discoverEndpoint(EndpointDiscoveryRequest endpointDiscoveryRequest);
 

core/sdk-core/src/main/java/software/amazon/awssdk/core/endpointdiscovery/EndpointDiscoveryFailedException.java

@@ -0,0 +1,88 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. 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.
+ * A copy of the License is located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ * or in the "license" file accompanying this file. This file 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 software.amazon.awssdk.core.endpointdiscovery;
+
+import software.amazon.awssdk.annotations.SdkPublicApi;
+import software.amazon.awssdk.core.exception.SdkClientException;
+import software.amazon.awssdk.utils.Validate;
+
+/**
+ * This exception is thrown when the SDK was unable to retrieve an endpoint from AWS. The cause describes what specific part of
+ * the endpoint discovery process failed.
+ */
+@SdkPublicApi
+public class EndpointDiscoveryFailedException extends SdkClientException {
+
+    private static final long serialVersionUID = 1L;
+
+    private EndpointDiscoveryFailedException(Builder b) {
+        super(b);
+        Validate.paramNotNull(b.cause(), "cause");
+    }
+
+    public static Builder builder() {
+        return new BuilderImpl();
+    }
+
+    public static EndpointDiscoveryFailedException create(Throwable cause) {
+        return builder().message("Failed when retrieving a required endpoint from AWS.")
+                        .cause(cause)
+                        .build();
+    }
+
+    @Override
+    public Builder toBuilder() {
+        return new BuilderImpl(this);
+    }
+
+    public interface Builder extends SdkClientException.Builder {
+        @Override
+        Builder message(String message);
+
+        @Override
+        Builder cause(Throwable cause);
+
+        @Override
+        EndpointDiscoveryFailedException build();
+    }
+
+    protected static final class BuilderImpl extends SdkClientException.BuilderImpl implements Builder {
+
+        protected BuilderImpl() {
+        }
+
+        protected BuilderImpl(EndpointDiscoveryFailedException ex) {
+            super(ex);
+        }
+
+        @Override
+        public Builder message(String message) {
+            this.message = message;
+            return this;
+        }
+
+        @Override
+        public Builder cause(Throwable cause) {
+            this.cause = cause;
+            return this;
+        }
+
+        @Override
+        public EndpointDiscoveryFailedException build() {
+            return new EndpointDiscoveryFailedException(this);
+        }
+    }
+}

core/sdk-core/src/main/java/software/amazon/awssdk/core/endpointdiscovery/EndpointDiscoveryRefreshCache.java

@@ -20,14 +20,11 @@
 import java.util.Map;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ExecutionException;
 import software.amazon.awssdk.annotations.SdkProtectedApi;
-import software.amazon.awssdk.utils.Logger;
 
 @SdkProtectedApi
 public final class EndpointDiscoveryRefreshCache {
-
-    private static final Logger log = Logger.loggerFor(EndpointDiscoveryRefreshCache.class);
-
     private final Map<String, EndpointDiscoveryEndpoint> cache = new ConcurrentHashMap<>();
 
     private final EndpointDiscoveryCacheLoader client;
@@ -63,7 +60,7 @@ public URI get(String accessKey, EndpointDiscoveryRequest request) {
 
         if (endpoint == null) {
             if (request.required()) {
-                return cache.computeIfAbsent(key, k -> discoverEndpoint(request).join()).endpoint();
+                return cache.computeIfAbsent(key, k -> getAndJoin(request)).endpoint();
             } else {
                 EndpointDiscoveryEndpoint tempEndpoint = EndpointDiscoveryEndpoint.builder()
                                                                                   .endpoint(request.defaultEndpoint())
@@ -90,6 +87,17 @@ public URI get(String accessKey, EndpointDiscoveryRequest request) {
         return endpoint.endpoint();
     }
 
+    private EndpointDiscoveryEndpoint getAndJoin(EndpointDiscoveryRequest request) {
+        try {
+            return discoverEndpoint(request).get();
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+            throw EndpointDiscoveryFailedException.create(e);
+        } catch (ExecutionException e) {
+            throw EndpointDiscoveryFailedException.create(e.getCause());
+        }
+    }
+
     private void refreshCacheAsync(EndpointDiscoveryRequest request, String key) {
         discoverEndpoint(request).thenApply(v -> cache.put(key, v));
     }