feat(sdk-core): add sync HTTP-client warm-up to SdkWarmUp.prime() for CRaC priming

core/sdk-core/src/main/java/software/amazon/awssdk/core/crac/SdkWarmUp.java

@@ -19,6 +19,7 @@
 import software.amazon.awssdk.annotations.SdkPublicApi;
 import software.amazon.awssdk.annotations.ThreadSafe;
 import software.amazon.awssdk.core.internal.crac.ClasspathWarmUpInvoker;
+import software.amazon.awssdk.core.internal.http.loader.ClasspathHttpWarmupInvoker;
 
 /**
  * Entry point for warming up SDK service request paths before a Coordinated Restore at Checkpoint (CRaC)
@@ -66,6 +67,7 @@ public static void prime() {
             }
             // Set primed only after invokeAll() succeeds, so a failed run leaves primed false and a later call retries.
             ClasspathWarmUpInvoker.create().invokeAll();
+            ClasspathHttpWarmupInvoker.create().invokeAll();
             primed = true;
         }
     }

core/sdk-core/src/main/java/software/amazon/awssdk/core/internal/crac/ClasspathWarmUpInvoker.java

@@ -15,13 +15,10 @@
 
 package software.amazon.awssdk.core.internal.crac;
 
-import java.util.Iterator;
-import java.util.ServiceConfigurationError;
 import java.util.ServiceLoader;
 import software.amazon.awssdk.annotations.SdkInternalApi;
 import software.amazon.awssdk.annotations.SdkTestInternalApi;
 import software.amazon.awssdk.core.crac.SdkWarmUpProvider;
-import software.amazon.awssdk.utils.Logger;
 
 /**
  * {@link WarmUpInvoker} implementation that uses {@link ServiceLoader} to find {@link SdkWarmUpProvider}
@@ -30,8 +27,6 @@
 @SdkInternalApi
 public final class ClasspathWarmUpInvoker implements WarmUpInvoker {
 
-    private static final Logger log = Logger.loggerFor(ClasspathWarmUpInvoker.class);
-
     private final WarmUpServiceLoader serviceLoader;
 
     @SdkTestInternalApi
@@ -41,30 +36,7 @@ public final class ClasspathWarmUpInvoker implements WarmUpInvoker {
 
     @Override
     public void invokeAll() {
-        Iterator<SdkWarmUpProvider> iterator = serviceLoader.loadProviders();
-        boolean invokedAny = false;
-
-        while (iterator.hasNext()) {
-            SdkWarmUpProvider provider;
-            try {
-                provider = iterator.next();
-            } catch (ServiceConfigurationError e) {
-                // next() has already advanced past the bad provider, so it is safe to continue to the next one.
-                log.warn(() -> "Skipping an SdkWarmUpProvider that could not be loaded.", e);
-                continue;
-            }
-
-            invokedAny = true;
-            try {
-                provider.warmUp();
-            } catch (RuntimeException e) {
-                log.warn(() -> "An SdkWarmUpProvider failed during warmUp() and was skipped.", e);
-            }
-        }
-
-        if (!invokedAny) {
-            log.debug(() -> "No SdkWarmUpProvider implementations were discovered on the classpath.");
-        }
+        WarmUpDiscovery.forEachDiscovered(serviceLoader.loadProviders(), SdkWarmUpProvider::warmUp);
     }
 
     /**

core/sdk-core/src/main/java/software/amazon/awssdk/core/internal/crac/RegionEndpointResolver.java

@@ -0,0 +1,91 @@
+/*
+ * 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.internal.crac;
+
+import java.net.URI;
+import java.util.Optional;
+import software.amazon.awssdk.annotations.SdkInternalApi;
+import software.amazon.awssdk.core.SdkSystemSetting;
+import software.amazon.awssdk.utils.OptionalUtils;
+import software.amazon.awssdk.utils.StringUtils;
+import software.amazon.awssdk.utils.SystemSetting;
+import software.amazon.awssdk.utils.http.SdkHttpUtils;
+import software.amazon.awssdk.utils.internal.SystemSettingUtils;
+
+/**
+ * Resolves the regional STS endpoint ({@code https://sts.<region>.amazonaws.com/}) used by the CRaC HTTP-client warm-up.
+ *
+ * <p>The region is taken from the first of: {@link SdkSystemSetting#AWS_REGION} (the {@code aws.region} system property or
+ * {@code AWS_REGION} environment variable), the {@code AWS_DEFAULT_REGION} environment variable, or {@value #DEFAULT_REGION}.
+ *
+ * <p>Only system properties and environment variables are read. The full SDK region-resolution chain (IMDS, profile file) is
+ * avoided during priming because those add network or filesystem calls that may fail or time out. The endpoint host always
+ * uses the {@code amazonaws.com} suffix, which is incorrect for the China, GovCloud, and ISO partitions; in those partitions
+ * the warm-up request simply fails and is ignored, since it is best-effort.
+ */
+@SdkInternalApi
+public final class RegionEndpointResolver {
+
+    static final String DEFAULT_REGION = "us-east-1";
+
+    private RegionEndpointResolver() {
+    }
+
+    public static RegionEndpointResolver create() {
+        return new RegionEndpointResolver();
+    }
+
+    /**
+     * @return the regional STS endpoint URI for the resolved region; never null.
+     */
+    public URI stsEndpoint() {
+        // URL-encode the region before putting it in the host, same as Region.of(String).
+        return URI.create("https://sts." + SdkHttpUtils.urlEncode(resolveRegion()) + ".amazonaws.com/");
+    }
+
+    private String resolveRegion() {
+        Optional<String> awsRegion = trimmed(SdkSystemSetting.AWS_REGION.getStringValue());
+        return OptionalUtils.firstPresent(awsRegion, RegionEndpointResolver::awsDefaultRegion)
+                            .orElse(DEFAULT_REGION);
+    }
+
+    private static Optional<String> awsDefaultRegion() {
+        return trimmed(SystemSettingUtils.resolveEnvironmentVariable(new AwsDefaultRegionEnvVar()));
+    }
+
+    private static Optional<String> trimmed(Optional<String> value) {
+        // trimToNull returns null for blank/empty input, so Optional.map collapses those to an empty Optional.
+        return value.map(StringUtils::trimToNull);
+    }
+
+    // AWS_DEFAULT_REGION is an environment-variable-only fallback with no system-property equivalent.
+    private static final class AwsDefaultRegionEnvVar implements SystemSetting {
+        @Override
+        public String property() {
+            return null;
+        }
+
+        @Override
+        public String environmentVariable() {
+            return "AWS_DEFAULT_REGION";
+        }
+
+        @Override
+        public String defaultValue() {
+            return null;
+        }
+    }
+}

core/sdk-core/src/main/java/software/amazon/awssdk/core/internal/crac/WarmUpDiscovery.java

@@ -0,0 +1,66 @@
+/*
+ * 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.internal.crac;
+
+import java.util.Iterator;
+import java.util.ServiceConfigurationError;
+import java.util.function.Consumer;
+import software.amazon.awssdk.annotations.SdkInternalApi;
+import software.amazon.awssdk.utils.Logger;
+
+/**
+ * Shared best-effort {@link java.util.ServiceLoader} iteration for the CRaC warm-up paths.
+ */
+@SdkInternalApi
+public final class WarmUpDiscovery {
+
+    private static final Logger log = Logger.loggerFor(WarmUpDiscovery.class);
+
+    private WarmUpDiscovery() {
+    }
+
+    /**
+     * Applies {@code action} to every discovered element, skipping (and logging at warn) any element that fails to load or
+     * whose action throws, so the rest still run. Logs at debug when nothing is discovered.
+     */
+    public static <T> void forEachDiscovered(Iterator<T> iterator, Consumer<T> action) {
+        boolean discoveredAny = false;
+        while (iterator.hasNext()) {
+            T element;
+            try {
+                element = iterator.next();
+            } catch (ServiceConfigurationError e) {
+                // next() has already advanced past the bad element, so it is safe to continue to the next one.
+                log.warn(() -> "Skipping a warm-up task that could not be loaded.", e);
+                continue;
+            }
+
+            discoveredAny = true;
+            T discovered = element;
+            try {
+                action.accept(discovered);
+            } catch (RuntimeException | LinkageError e) {
+                // LinkageError because a discovered element can fail to link (missing deps/native lib, failed static init),
+                // which is an Error, not an Exception. Skip it to keep warm-up best-effort; fatal Errors still propagate.
+                log.warn(() -> "Warm-up failed for " + discovered.getClass().getName() + " and was skipped.", e);
+            }
+        }
+
+        if (!discoveredAny) {
+            log.debug(() -> "No warm-up tasks were discovered on the classpath.");
+        }
+    }
+}

core/sdk-core/src/main/java/software/amazon/awssdk/core/internal/crac/WarmUpRequest.java

@@ -0,0 +1,71 @@
+/*
+ * 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.internal.crac;
+
+import java.net.URI;
+import java.util.Optional;
+import software.amazon.awssdk.annotations.SdkInternalApi;
+import software.amazon.awssdk.http.ContentStreamProvider;
+import software.amazon.awssdk.http.SdkHttpMethod;
+import software.amazon.awssdk.http.SdkHttpRequest;
+
+/**
+ * Describes the request the CRaC warm-up sends to the resolved endpoint, and converts it to an {@link SdkHttpRequest} bound to
+ * that endpoint. The request is never signed and needs no credentials; only its execution (DNS, TLS, request/response I/O)
+ * matters for JIT priming.
+ */
+@SdkInternalApi
+public final class WarmUpRequest {
+
+    private final SdkHttpMethod method;
+    private final String body;
+    private final String contentType;
+
+    private WarmUpRequest(SdkHttpMethod method, String body, String contentType) {
+        this.method = method;
+        this.body = body;
+        this.contentType = contentType;
+    }
+
+    /**
+     * A bare {@code GET} to the endpoint, with no body. Warms DNS, the TLS handshake, and certificate-chain validation, which
+     * are the dominant cold-start costs and are shared across all services and operations.
+     */
+    public static WarmUpRequest get() {
+        return new WarmUpRequest(SdkHttpMethod.GET, null, null);
+    }
+
+    /**
+     * @retusrn this request as an {@link SdkHttpRequest} targeting {@code endpoint}.
+     */
+    public SdkHttpRequest toHttpRequest(URI endpoint) {
+        SdkHttpRequest.Builder builder = SdkHttpRequest.builder()
+                                                       .method(method)
+                                                       .uri(endpoint);
+        if (body != null) {
+            builder.putHeader("Content-Type", contentType)
+                   .putHeader("Content-Length", String.valueOf(body.getBytes(java.nio.charset.StandardCharsets.UTF_8).length));
+        }
+        return builder.build();
+    }
+
+    /**
+     * @return the request body stream provider, or empty if this request has no body.
+     */
+    public Optional<ContentStreamProvider> contentStreamProvider() {
+        return body == null ? Optional.empty() : Optional.of(ContentStreamProvider.fromUtf8String(body));
+    }
+}

core/sdk-core/src/main/java/software/amazon/awssdk/core/internal/http/loader/ClasspathHttpWarmupInvoker.java

@@ -0,0 +1,49 @@
+/*
+ * 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.internal.http.loader;
+
+import java.util.Collections;
+import java.util.List;
+import software.amazon.awssdk.annotations.SdkInternalApi;
+import software.amazon.awssdk.annotations.SdkTestInternalApi;
+
+/**
+ * {@link HttpWarmupInvoker} that owns the set of {@link HttpClientWarmer}s and invokes each.
+ */
+@SdkInternalApi
+public final class ClasspathHttpWarmupInvoker implements HttpWarmupInvoker {
+
+    private final List<HttpClientWarmer> warmers;
+
+    @SdkTestInternalApi
+    ClasspathHttpWarmupInvoker(List<HttpClientWarmer> warmers) {
+        this.warmers = warmers;
+    }
+
+    /**
+     * @return an invoker over the HTTP-client warmers on the classpath.
+     */
+    public static HttpWarmupInvoker create() {
+        return new ClasspathHttpWarmupInvoker(Collections.singletonList(SyncHttpClientWarmer.create()));
+    }
+
+    @Override
+    public void invokeAll() {
+        for (HttpClientWarmer warmer : warmers) {
+            warmer.warmAll();
+        }
+    }
+}

core/sdk-core/src/main/java/software/amazon/awssdk/core/internal/http/loader/HttpClientWarmer.java

@@ -0,0 +1,30 @@
+/*
+ * 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.internal.http.loader;
+
+import software.amazon.awssdk.annotations.SdkInternalApi;
+
+/**
+ * Warms the sync or async HTTP clients on the classpath for CRaC priming.
+ */
+@SdkInternalApi
+public interface HttpClientWarmer {
+
+    /**
+     * Warms every HTTP client found on the classpath. Best-effort; never throws.
+     */
+    void warmAll();
+}