feat(sdk-core): add sync HTTP-client warm-up to SdkWarmUp.prime() for CRaC priming by joviegas · Pull Request #7080 · aws/aws-sdk-java-v2

joviegas · 2026-06-26T00:08:45Z

Motivation and Context

This change adds the second half of the hybrid priming approach: one real GET per sync HTTP client on the classpath, so that network path is JIT-compiled into the CRaC snapshot. It also adds the region/endpoint resolution shared with the future async warm-up.

Modifications

SdkWarmUp.prime() now runs the per-service providers and then the HTTP-client warm-up, both inside the existing idempotency guard. The HTTP-client warm-up is best-effort: a network failure during init is logged and swallowed so the rest of priming completes.

New internal types in sdk-core:

RegionEndpointResolver (internal.crac): resolves the region from the aws.region system property or AWS_REGION environment variable, falling back to us-east-1, and builds https://sts.<region>.amazonaws.com/. It reads only system properties and environment variables, avoiding the SDK region-resolution chain (IMDS, profile file) during priming. The region is validated with HostnameValidator; a value that is not a valid hostname component is rejected and the default region is used, so a malformed region cannot alter the endpoint host. AWS_DEFAULT_REGION is not consulted, matching how the SDK resolves a region from system settings for endpoints.
SyncHttpClientWarmer (internal.http.loader): discovers every sync SdkHttpService through the existing package-private SdkServiceLoader, builds each client, sends the warm-up GET, drains the response body, and closes the client.
WarmUpDiscovery: the discover-and-iterate loop shared by the per-service and HTTP-client warm-up. It skips an element that fails to load or run, including LinkageError (a client jar present without its transitive dependencies), so one broken element does not stop the others.
HttpClientWarmer interface plus HttpWarmupInvoker / ClasspathHttpWarmupInvoker: prime() calls one invoker that owns the set of warmers. The async warmer is added to that set later without changing SdkWarmUp or SyncHttpClientWarmer.

Tests for the warm-up against every sync HTTP client live in a new test/warmup-tests module rather than in each client module, avoiding the sdk-core -> apache-client -> http-client-tests -> sdk-core cyclic dependency.

Testing

Added Junits test

Screenshots (if appropriate)

Types of changes

Bug fix (non-breaking change which fixes an issue)
[x ] New feature (non-breaking change which adds functionality)

License

I confirm that this pull request can be released under the Apache 2 license

… CRaC priming

joviegas · 2026-06-26T17:15:51Z

+public class Apache5HttpClientWarmUpTest {
+
+    @Rule
+    public WireMockRule mockServer = new WireMockRule(0);


We have a test for each HTTP client instead of a shared suite in test/http-client-tests. A shared suite there would create a cyclic dependency, because sdk-core has test dependencies on apache-client and netty-nio-client (sdk-core -> apache-client -> http-client-tests -> sdk-core). I filed JAVA-9020 to refactor this on master; once fixed, these tests can move to test/http-client-tests as a single SyncHttpClientWarmUpTestSuite shared across all HTTP clients.

A separate centralized package would be great, but maybe we can have a dedicated test package for testing CRaC components instead of using http-client-tests

joviegas · 2026-06-26T17:16:21Z

        <version>${awsjavasdk.version}</version>
        <scope>test</scope>
    </dependency>
+    <dependency>


Same as https://github.com/aws/aws-sdk-java-v2/pull/7080/changes#r3482981849

dagnir · 2026-06-26T19:57:04Z

+    }
+
+    // AWS_DEFAULT_REGION is an environment-variable-only fallback with no system-property equivalent.
+    private static final class AwsDefaultRegionEnvVar implements SystemSetting {


AFAIK, we don't use AWS_DEFAULT_REGION for determining endpoints in the SDK (only DefaultsMode). Should we leave this out?

removed it now

dagnir · 2026-06-26T20:06:20Z

+     */
+    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/");


might benefit from using

aws-sdk-java-v2/utils/src/main/java/software/amazon/awssdk/utils/HostnameValidator.java

Lines 31 to 33 in 8a6a76c

public static void validateHostnameCompliant(String hostnameComponent, String paramName, String object) {

validateHostnameCompliant(hostnameComponent, paramName, object, DEFAULT_HOSTNAME_COMPLIANT_PATTERN);

}

alternatively, build using the URI constructor will also validate it for correctness

Good call, adopted HostnameValidator. The region is now validated with validateHostnameCompliant; if it isn't a valid hostname component, we log and fall back to us-east-1 rather than propagate the exception, since endpoint resolution runs inside the best-effort warm-up and must not break priming.

dagnir · 2026-06-26T20:20:52Z

+    private final String body;
+    private final String contentType;


The ctor is private; are these necessary?

Good catch, they weren't necessary. The class started as a small spec (method/body/content-type) intended to be shared by the sync and async warmers, but once the warm-up settled on a simple GET those fields were always null. I've removed WarmUpRequest entirely.

dagnir · 2026-06-26T20:23:51Z

+ * Resolves the regional STS endpoint ({@code https://sts.<region>.amazonaws.com/}) used by the CRaC HTTP-client warm-up.
+ *


Is this class intended to resolve other service endpoints in the future?

No. It is specific to whichever single service we pick for the warm-up (currently STS). It always returns one endpoint for that hardcoded service. If we later switch the warm-up to another service (e.g. DynamoDB), this class would build that endpoint instead. Renamed stsEndpoint() to endpoint() to reflect that.

dagnir · 2026-06-26T20:25:49Z

+ * matters for JIT priming.
+ */
+@SdkInternalApi
+public final class WarmUpRequest {


Not really sure about the usefulness of this class. Does it make more sense to just have a utility class/factory just creates the HttpExecuteRequest directly?

removed now

dagnir · 2026-06-26T20:31:48Z

+public class Apache5HttpClientWarmUpTest {
+
+    @Rule
+    public WireMockRule mockServer = new WireMockRule(0);


A separate centralized package would be great, but maybe we can have a dedicated test package for testing CRaC components instead of using http-client-tests

…/crac_warmup_orchestration_partB

github-actions · 2026-06-30T03:53:59Z

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joviegas requested a review from a team as a code owner June 26, 2026 00:08

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

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… CRaC priming

joviegas force-pushed the joviegas/crac_warmup_orchestration_partB branch 2 times, most recently from e4dfbde to 5b172b4 Compare June 26, 2026 15:17

Updated tests

82c723b

joviegas force-pushed the joviegas/crac_warmup_orchestration_partB branch from 5b172b4 to 82c723b Compare June 26, 2026 15:29

restructure test and comments

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joviegas force-pushed the joviegas/crac_warmup_orchestration_partB branch 2 times, most recently from bbf82e3 to 44b6b00 Compare June 26, 2026 16:43

joviegas commented Jun 26, 2026

View reviewed changes

Fixed checkstyle issues

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joviegas force-pushed the joviegas/crac_warmup_orchestration_partB branch from 44b6b00 to 2f5b864 Compare June 26, 2026 18:26

dagnir reviewed Jun 26, 2026

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joviegas force-pushed the joviegas/crac_warmup_orchestration_partB branch 3 times, most recently from 7421ffc to b4e9f64 Compare June 29, 2026 20:00

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joviegas force-pushed the joviegas/crac_warmup_orchestration_partB branch from b4e9f64 to 072736d Compare June 29, 2026 20:14

dagnir approved these changes Jun 29, 2026

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joviegas and others added 3 commits June 29, 2026 15:13

Update test for blank input

9d6a9d5

Update before and after conditions in test

131e157

Merge branch 'feature/master/crac_auto_priming_support' into joviegas…

af69a6a

…/crac_warmup_orchestration_partB

joviegas merged commit 70fb508 into feature/master/crac_auto_priming_support Jun 30, 2026
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github-actions Bot locked as resolved and limited conversation to collaborators Jun 30, 2026

	public static void validateHostnameCompliant(String hostnameComponent, String paramName, String object) {
	validateHostnameCompliant(hostnameComponent, paramName, object, DEFAULT_HOSTNAME_COMPLIANT_PATTERN);
	}

		* Resolves the regional STS endpoint ({@code https://sts.<region>.amazonaws.com/}) used by the CRaC HTTP-client warm-up.
		*

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joviegas commented Jun 26, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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joviegas commented Jun 26, 2026 •

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