feat(warmup): add SdkWarmUp for CRaC and Lambda SnapStart priming

[joviegas]

Motivation and Context

Customers using Lambda SnapStart or CRaC (Coordinated Restore at Checkpoint) write their own priming code today to warm the SDK request path before a checkpoint. That code is non-obvious: the customer picks an operation, supplies dummy credentials, and suppresses the resulting errors.

SdkWarmUp.warmUp() moves that work into the SDK: it selects the operation for each service, supplies the credentials, and logs failures instead of throwing.

Addresses #5387. Related: #3801, #3236, #3737.

Modifications

Individuals PRs at the bottom.

Public API (sdk-core, software.amazon.awssdk.core.warmup):

@ThreadSafe
@SdkPublicApi
public final class SdkWarmUp {
    public static void warmUp();                                        // every client on the classpath
    public static void warmUp(Class<? extends SdkClient>... clients);   // the clients you name
}

Every service module on the classpath is warmed, including service modules added after this release.

Warm-up runs one synthetic operation per client against an in-memory canned-response HTTP client (dummy credentials, Region.US_EAST_1, endpointOverride(http://localhost)), exercising marshalling, signing, interceptors, and unmarshalling with no network I/O. It then sends one best-effort unauthenticated GET to the regional STS endpoint per HTTP client on the classpath, because DNS, TLS handshake, and certificate-chain paths need a real connection.

Usage

Lambda SnapStart. Lambda snapshots the JVM after the constructor completes, so call warmUp() there:

public class SampleLambdaHandler implements RequestHandler<Order, String> {

    public SampleLambdaHandler() {
        SdkWarmUp.warmUp();          // warms up all AWS SDK clients on the classpath
        // custom initialization code 
    }

    @Override
    public String handleRequest(Order order, Context context) {
        // handler code
    }
}

Standalone CRaC. Call warmUp() before the checkpoint:

public class MyApp implements Resource {

    public MyApp() {
        SdkWarmUp.warmUp();          // warms up all AWS SDK clients on the classpath
        Core.getGlobalContext().register(this);
    }

    @Override
    public void beforeCheckpoint(Context<? extends Resource> context) {
        // close clients and other open file descriptors
    }

    @Override
    public void afterRestore(Context<? extends Resource> context) {
        // recreate clients
    }
}

Warm specific clients when the classpath holds more service modules than the application calls:

SdkWarmUp.warmUp(DynamoDbClient.class, S3AsyncClient.class);

A sync client class warms the sync path and the sync HTTP clients on the classpath; an async client class warms the async path and the async HTTP clients.

Warm-up is opt-in and runs at most once per JVM. Ships in 2.52.0.

Testing

• Unit tests, and functional tests in the new test/warmup-tests module.
• JMH benchmarks for first-request latency and warm-up cost.

Screenshots (if appropriate)

Types of changes

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

License

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

Individual PRs

1. feat(sdk-core): Add SdkWarmUpProvider SPI and CannedResponseHttpClient for CRaC auto-priming- #7042
2. feat(sdk-core): add SdkWarmUp.prime() for CRaC auto-priming- #7056
3. feat(sdk-core): add sync HTTP-client warm-up to SdkWarmUp.prime() for CRaC priming- #7080
4. feat(codegen): generate empty SdkWarmUpProvider and META-INF/services registration per service- #7085
5. feat(sdk-core): add Async HTTP-client warm-up to SdkWarmUp.prime() for CRaC priming- #7092
6. feat(codegen): generate sync and async client instantiation in ServiceWarmUpProvider.warmUp()- #7101
7. Add overloaded menthod for SdkWarmUp.prime overloaded to accept speci…- #7130
8. feat(codegen): add WarmUpOperationSelector to pick the CRaC warm-up operation- #7135
9. Fix flaky NettyClientAlpnTest by retrying on port-bind race conditions- #7142
10. (feat:prime/crac) Invoke the selected warm-up operation in the generated SdkWarmUpProvider- #7159
11. feat(codegen): fill URI/endpoint-bound members for the CRaC warm-up call and warm sync/async clients independently- #7183
12. test(warmup): Add warm-up tests that auto-cover the generated provider of every service module- #7188
13. test(sdk-benchmarks): Add cold-start benchmarks for SdkWarmUp priming- #7207
14. perf(warmup): Warm HTTP clients at most once across targeted prime(ServiceClient.class...) call- #7212
15. Change mention of "crac" in namespace as "warmup" and change api name "prime" to "warmUp"- #7232
16. javadocs(warmup): Update SdkWarmUp Javadoc to detail service and HTTP client warm-up after surface review- #7235