Make default region and credential loading lazy.

.changes/next-release/bugfix-AWSSDKforJavav2-d33383e.json

@@ -0,0 +1,5 @@
+{
+    "category": "AWS SDK for Java v2", 
+    "type": "bugfix", 
+    "description": "Defer all errors raised when creating `ProfileCredentialsProvider` to the `resolveCredentials()` call."
+}

.changes/next-release/feature-AWSSDKforJavav2-63c04be.json

@@ -0,0 +1,5 @@
+{
+    "category": "AWS SDK for Java v2", 
+    "type": "feature", 
+    "description": "Never initialize the default credentials provider chain if credentials are always specified in the client builder."
+}

.changes/next-release/feature-AWSSDKforJavav2-6c062f1.json

@@ -0,0 +1,5 @@
+{
+    "category": "AWS SDK for Java v2", 
+    "type": "feature", 
+    "description": "Never initialie the default region provider chain if the region is always specified in the client builder."
+}

core/auth/src/main/java/software/amazon/awssdk/auth/credentials/DefaultCredentialsProvider.java

@@ -16,6 +16,7 @@
 package software.amazon.awssdk.auth.credentials;
 
 import software.amazon.awssdk.annotations.SdkPublicApi;
+import software.amazon.awssdk.auth.credentials.internal.LazyAwsCredentialsProvider;
 import software.amazon.awssdk.utils.SdkAutoCloseable;
 import software.amazon.awssdk.utils.ToString;
 
@@ -41,7 +42,7 @@ public final class DefaultCredentialsProvider implements AwsCredentialsProvider,
 
     private static final DefaultCredentialsProvider DEFAULT_CREDENTIALS_PROVIDER = new DefaultCredentialsProvider(builder());
 
-    private final AwsCredentialsProviderChain providerChain;
+    private final LazyAwsCredentialsProvider providerChain;
 
     /**
      * @see #builder()
@@ -61,23 +62,28 @@ public static DefaultCredentialsProvider create() {
     /**
      * Create the default credential chain using the configuration in the provided builder.
      */
-    private static AwsCredentialsProviderChain createChain(Builder builder) {
-        AwsCredentialsProvider[] credentialsProviders = new AwsCredentialsProvider[] {
-            SystemPropertyCredentialsProvider.create(),
-            EnvironmentVariableCredentialsProvider.create(),
-            ProfileCredentialsProvider.create(),
-            ContainerCredentialsProvider.builder()
-                                        .asyncCredentialUpdateEnabled(builder.asyncCredentialUpdateEnabled)
-                                            .build(),
-            InstanceProfileCredentialsProvider.builder()
-                                              .asyncCredentialUpdateEnabled(builder.asyncCredentialUpdateEnabled)
-                                                  .build()
-        };
-
-        return AwsCredentialsProviderChain.builder()
-                                          .reuseLastProviderEnabled(builder.reuseLastProviderEnabled)
-                                          .credentialsProviders(credentialsProviders)
-                                          .build();
+    private static LazyAwsCredentialsProvider createChain(Builder builder) {
+        boolean asyncCredentialUpdateEnabled = builder.asyncCredentialUpdateEnabled;
+        boolean reuseLastProviderEnabled = builder.reuseLastProviderEnabled;
+
+        return LazyAwsCredentialsProvider.create(() -> {
+            AwsCredentialsProvider[] credentialsProviders = new AwsCredentialsProvider[] {
+                    SystemPropertyCredentialsProvider.create(),
+                    EnvironmentVariableCredentialsProvider.create(),
+                    ProfileCredentialsProvider.create(),
+                    ContainerCredentialsProvider.builder()
+                                                .asyncCredentialUpdateEnabled(asyncCredentialUpdateEnabled)
+                                                .build(),
+                    InstanceProfileCredentialsProvider.builder()
+                                                      .asyncCredentialUpdateEnabled(asyncCredentialUpdateEnabled)
+                                                      .build()
+            };
+
+            return AwsCredentialsProviderChain.builder()
+                                              .reuseLastProviderEnabled(reuseLastProviderEnabled)
+                                              .credentialsProviders(credentialsProviders)
+                                              .build();
+        });
     }
 
     /**

core/auth/src/main/java/software/amazon/awssdk/auth/credentials/ProfileCredentialsProvider.java

@@ -52,28 +52,47 @@ public final class ProfileCredentialsProvider implements AwsCredentialsProvider,
      * @see #builder()
      */
     private ProfileCredentialsProvider(BuilderImpl builder) {
-        this.profileName = builder.profileName != null ? builder.profileName
-                                                       : ProfileFileSystemSetting.AWS_PROFILE.getStringValueOrThrow();
-
-        // Load the profiles file
-        this.profileFile = Optional.ofNullable(builder.profileFile)
-                                   .orElseGet(builder.defaultProfileFileLoader);
-
-        // Load the profile and credentials provider
-        this.credentialsProvider = profileFile.profile(profileName)
-                                              .flatMap(p -> new ProfileCredentialsUtils(p, profileFile::profile)
-                                                  .credentialsProvider())
-                                              .orElse(null);
-
-        // If we couldn't load the credentials provider for some reason, save an exception describing why. This exception will
-        // only be raised on calls to getCredentials. We don't want to raise an exception here because it may be expected (eg. in
-        // the default credential chain).
-        if (credentialsProvider == null) {
-            String loadError = String.format("Profile file contained no credentials for profile '%s': %s",
-                                             profileName, profileFile);
-            this.loadException = SdkClientException.builder().message(loadError).build();
+        AwsCredentialsProvider credentialsProvider = null;
+        RuntimeException loadException = null;
+        ProfileFile profileFile = null;
+        String profileName = null;
+
+        try {
+            profileName = builder.profileName != null ? builder.profileName
+                                                      : ProfileFileSystemSetting.AWS_PROFILE.getStringValueOrThrow();
+
+            // Load the profiles file
+            profileFile = Optional.ofNullable(builder.profileFile)
+                                  .orElseGet(builder.defaultProfileFileLoader);
+
+            // Load the profile and credentials provider
+            String finalProfileName = profileName;
+            ProfileFile finalProfileFile = profileFile;
+            credentialsProvider =
+                    profileFile.profile(profileName)
+                               .flatMap(p -> new ProfileCredentialsUtils(p, finalProfileFile::profile).credentialsProvider())
+                               .orElseThrow(() -> {
+                                   String errorMessage = String.format("Profile file contained no credentials for " +
+                                                                       "profile '%s': %s", finalProfileName, finalProfileFile);
+                                   return SdkClientException.builder().message(errorMessage).build();
+                               });
+        } catch (RuntimeException e) {
+            // If we couldn't load the credentials provider for some reason, save an exception describing why. This exception
+            // will only be raised on calls to getCredentials. We don't want to raise an exception here because it may be
+            // expected (eg. in the default credential chain).
+            loadException = e;
+        }
+
+        if (loadException != null) {
+            this.loadException = loadException;
+            this.credentialsProvider = null;
+            this.profileFile = null;
+            this.profileName = null;
         } else {
             this.loadException = null;
+            this.credentialsProvider = credentialsProvider;
+            this.profileFile = profileFile;
+            this.profileName = profileName;
         }
     }
 

core/auth/src/main/java/software/amazon/awssdk/auth/credentials/internal/LazyAwsCredentialsProvider.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2010-2019 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.auth.credentials.internal;
+
+import java.util.function.Supplier;
+import software.amazon.awssdk.annotations.SdkInternalApi;
+import software.amazon.awssdk.auth.credentials.AwsCredentials;
+import software.amazon.awssdk.auth.credentials.AwsCredentialsProvider;
+import software.amazon.awssdk.utils.IoUtils;
+import software.amazon.awssdk.utils.SdkAutoCloseable;
+import software.amazon.awssdk.utils.ToString;
+
+/**
+ * A wrapper for {@link AwsCredentialsProvider} that defers creation of the underlying provider until the first time the
+ * {@link AwsCredentialsProvider#resolveCredentials()} method is invoked.
+ */
+@SdkInternalApi
+public class LazyAwsCredentialsProvider implements AwsCredentialsProvider, SdkAutoCloseable {
+    private final Supplier<AwsCredentialsProvider> delegateConstructor;
+    private volatile AwsCredentialsProvider delegate;
+
+    private LazyAwsCredentialsProvider(Supplier<AwsCredentialsProvider> delegateConstructor) {
+        this.delegateConstructor = delegateConstructor;
+    }
+
+    public static LazyAwsCredentialsProvider create(Supplier<AwsCredentialsProvider> delegateConstructor) {
+        return new LazyAwsCredentialsProvider(delegateConstructor);
+    }
+
+    @Override
+    public AwsCredentials resolveCredentials() {
+        if (delegate == null) {
+            synchronized (this) {
+                if (delegate == null) {
+                    delegate = delegateConstructor.get();
+                }
+            }
+        }
+        return delegate.resolveCredentials();
+    }
+
+    @Override
+    public void close() {
+        IoUtils.closeIfCloseable(delegate, null);
+    }
+
+    @Override
+    public String toString() {
+        return ToString.builder("LazyAwsCredentialsProvider")
+                       .add("delegateConstructor", delegateConstructor)
+                       .add("delegate", delegate)
+                       .build();
+    }
+}

core/auth/src/test/java/software/amazon/awssdk/auth/credentials/ProfileCredentialsProviderTest.java

@@ -27,6 +27,16 @@
  * Verify functionality of {@link ProfileCredentialsProvider}.
  */
 public class ProfileCredentialsProviderTest {
+    @Test
+    public void missingCredentialsFileThrowsExceptionInGetCredentials() {
+        ProfileCredentialsProvider provider =
+                new ProfileCredentialsProvider.BuilderImpl()
+                        .defaultProfileFileLoader(() -> { throw new IllegalStateException(); })
+                        .build();
+
+        assertThatThrownBy(provider::resolveCredentials).isInstanceOf(IllegalStateException.class);
+    }
+
     @Test
     public void missingProfileFileThrowsExceptionInGetCredentials() {
         ProfileCredentialsProvider provider =

core/auth/src/test/java/software/amazon/awssdk/auth/credentials/internal/LazyAwsCredentialsProviderTest.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2010-2019 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.auth.credentials.internal;
+
+import java.util.function.Supplier;
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.Mockito;
+import software.amazon.awssdk.auth.credentials.AwsCredentialsProvider;
+
+public class LazyAwsCredentialsProviderTest {
+    @SuppressWarnings("unchecked")
+    private Supplier<AwsCredentialsProvider> credentialsConstructor = Mockito.mock(Supplier.class);
+
+    private AwsCredentialsProvider credentials = Mockito.mock(AwsCredentialsProvider.class);
+
+    @Before
+    public void reset() {
+        Mockito.reset(credentials, credentialsConstructor);
+        Mockito.when(credentialsConstructor.get()).thenReturn(credentials);
+    }
+
+    @Test
+    public void creationDoesntInvokeSupplier() {
+        LazyAwsCredentialsProvider.create(credentialsConstructor);
+        Mockito.verifyZeroInteractions(credentialsConstructor);
+    }
+
+    @Test
+    public void resolveCredentialsInvokesSupplierExactlyOnce() {
+        LazyAwsCredentialsProvider credentialsProvider = LazyAwsCredentialsProvider.create(credentialsConstructor);
+        credentialsProvider.resolveCredentials();
+        credentialsProvider.resolveCredentials();
+
+        Mockito.verify(credentialsConstructor, Mockito.times(1)).get();
+        Mockito.verify(credentials, Mockito.times(2)).resolveCredentials();
+    }
+}

core/aws-core/src/main/java/software/amazon/awssdk/awscore/client/builder/AwsDefaultClientBuilder.java

@@ -35,6 +35,7 @@
 import software.amazon.awssdk.regions.ServiceMetadata;
 import software.amazon.awssdk.regions.providers.AwsRegionProvider;
 import software.amazon.awssdk.regions.providers.DefaultAwsRegionProviderChain;
+import software.amazon.awssdk.regions.providers.LazyAwsRegionProvider;
 import software.amazon.awssdk.utils.AttributeMap;
 
 /**
@@ -60,7 +61,8 @@ public abstract class AwsDefaultClientBuilder<BuilderT extends AwsClientBuilder<
     extends SdkDefaultClientBuilder<BuilderT, ClientT>
     implements AwsClientBuilder<BuilderT, ClientT> {
     private static final String DEFAULT_ENDPOINT_PROTOCOL = "https";
-    private static final AwsRegionProvider DEFAULT_REGION_PROVIDER = new DefaultAwsRegionProviderChain();
+    private static final AwsRegionProvider DEFAULT_REGION_PROVIDER =
+            new LazyAwsRegionProvider(DefaultAwsRegionProviderChain::new);
 
     protected AwsDefaultClientBuilder() {
         super();

core/regions/src/main/java/software/amazon/awssdk/regions/providers/LazyAwsRegionProvider.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2010-2019 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.regions.providers;
+
+import java.util.function.Supplier;
+import software.amazon.awssdk.annotations.SdkProtectedApi;
+import software.amazon.awssdk.regions.Region;
+import software.amazon.awssdk.utils.ToString;
+
+/**
+ * A wrapper for {@link AwsRegionProvider} that defers creation of the underlying provider until the first time the
+ * {@link AwsRegionProvider#getRegion()} method is invoked.
+ */
+@SdkProtectedApi
+public class LazyAwsRegionProvider implements AwsRegionProvider {
+    private final Supplier<AwsRegionProvider> delegateConstructor;
+    private volatile AwsRegionProvider delegate;
+
+    public LazyAwsRegionProvider(Supplier<AwsRegionProvider> delegateConstructor) {
+        this.delegateConstructor = delegateConstructor;
+    }
+
+    @Override
+    public Region getRegion() {
+        if (delegate == null) {
+            synchronized (this) {
+                if (delegate == null) {
+                    delegate = delegateConstructor.get();
+                }
+            }
+        }
+        return delegate.getRegion();
+    }
+
+    @Override
+    public String toString() {
+        return ToString.builder("LazyAwsRegionProvider")
+                       .add("delegateConstructor", delegateConstructor)
+                       .add("delegate", delegate)
+                       .build();
+    }
+}