Move to blocking client, towards virtual threads

Rather than build everything from the bottom up around the complexity
of CompletableFutures and Flows, migrating to a blocking approach and
remove the async client and async methods. We will move towards more
virtual threads-based approaches, and increase the minimum Java version.

The server has not yet been updated, and we should look at possible
ways to implement blocking/queue style event streams if possible.

This change also requires us to bump the minimum version from
Java 17 to 21.

Author: mtdowling

README.md

@@ -35,7 +35,7 @@ and building services. These examples can be used as a template for a new projec
 ## Usage
 
 > [!WARNING]
-> Smithy-Java only supports **Java 17** or later. Older Java versions are not supported.
+> Smithy-Java only supports **Java 21** or later. Older Java versions are not supported.
 
 ### Codegen (Gradle)
 

auth-api/src/main/java/software/amazon/smithy/java/auth/api/NullSigner.java

@@ -5,7 +5,6 @@
 
 package software.amazon.smithy.java.auth.api;
 
-import java.util.concurrent.CompletableFuture;
 import software.amazon.smithy.java.auth.api.identity.Identity;
 import software.amazon.smithy.java.context.Context;
 
@@ -31,7 +30,7 @@ private NullSigner() {}
      * @return the request as-is.
      */
     @Override
-    public CompletableFuture<Object> sign(Object request, Identity identity, Context properties) {
-        return CompletableFuture.completedFuture(request);
+    public Object sign(Object request, Identity identity, Context properties) {
+        return request;
     }
 }

auth-api/src/main/java/software/amazon/smithy/java/auth/api/Signer.java

@@ -5,7 +5,6 @@
 
 package software.amazon.smithy.java.auth.api;
 
-import java.util.concurrent.CompletableFuture;
 import software.amazon.smithy.java.auth.api.identity.Identity;
 import software.amazon.smithy.java.context.Context;
 
@@ -25,7 +24,7 @@ public interface Signer<RequestT, IdentityT extends Identity> extends AutoClosea
      * @param properties Signing properties.
      * @return the signed request.
      */
-    CompletableFuture<RequestT> sign(RequestT request, IdentityT identity, Context properties);
+    RequestT sign(RequestT request, IdentityT identity, Context properties);
 
     @SuppressWarnings("unchecked")
     static <RequestT, IdentityT extends Identity> Signer<RequestT, IdentityT> nullSigner() {

auth-api/src/main/java/software/amazon/smithy/java/auth/api/identity/IdentityResolver.java

@@ -6,7 +6,6 @@
 package software.amazon.smithy.java.auth.api.identity;
 
 import java.util.List;
-import java.util.concurrent.CompletableFuture;
 import software.amazon.smithy.java.context.Context;
 
 /**
@@ -20,9 +19,9 @@ public interface IdentityResolver<IdentityT extends Identity> {
      * error string. Unexpected errors like malformed input or networking errors are allowed to throw exceptions.
      *
      * @param requestProperties The request properties used to resolve an Identity.
-     * @return a CompletableFuture for the resolved identity result.
+     * @return the resolved identity result.
      */
-    CompletableFuture<IdentityResult<IdentityT>> resolveIdentity(Context requestProperties);
+    IdentityResult<IdentityT> resolveIdentity(Context requestProperties);
 
     /**
      * Retrieve the class of the identity resolved by this identity resolver.
@@ -42,7 +41,8 @@ static <I extends Identity> IdentityResolver<I> chain(List<IdentityResolver<I>>
     }
 
     /**
-     * Create an implementation of {@link IdentityResolver} that returns a specific, pre-defined instance of {@link Identity}.
+     * Create an implementation of {@link IdentityResolver} that returns a specific, pre-defined instance of
+     * {@link Identity}.
      */
     static <I extends Identity> IdentityResolver<I> of(I identity) {
         return new StaticIdentityResolver<>(identity);

auth-api/src/main/java/software/amazon/smithy/java/auth/api/identity/IdentityResolverChain.java

@@ -8,7 +8,6 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Objects;
-import java.util.concurrent.CompletableFuture;
 import software.amazon.smithy.java.context.Context;
 
 final class IdentityResolverChain<IdentityT extends Identity> implements IdentityResolver<IdentityT> {
@@ -29,35 +28,15 @@ public Class<IdentityT> identityType() {
     }
 
     @Override
-    public CompletableFuture<IdentityResult<IdentityT>> resolveIdentity(Context requestProperties) {
+    public IdentityResult<IdentityT> resolveIdentity(Context requestProperties) {
         List<IdentityResult<?>> errors = new ArrayList<>();
-        return executeChain(resolvers.get(0), requestProperties, errors, 0);
-    }
-
-    private CompletableFuture<IdentityResult<IdentityT>> executeChain(
-            IdentityResolver<IdentityT> resolver,
-            Context requestProperties,
-            List<IdentityResult<?>> errors,
-            int idx
-    ) {
-        var result = resolver.resolveIdentity(requestProperties);
-        if (idx + 1 < resolvers.size()) {
-            var nextResolver = resolvers.get(idx + 1);
-            return result.thenCompose(ir -> {
-                if (ir.error() != null) {
-                    errors.add(ir);
-                    return executeChain(nextResolver, requestProperties, errors, idx + 1);
-                }
-                return CompletableFuture.completedFuture(ir);
-            });
-        }
-
-        return result.thenApply(ir -> {
-            if (ir.error() != null) {
-                errors.add(ir);
-                return IdentityResult.ofError(IdentityResolverChain.class, "Attempted resolvers: " + errors);
+        for (IdentityResolver<IdentityT> resolver : resolvers) {
+            IdentityResult<IdentityT> result = resolver.resolveIdentity(requestProperties);
+            if (result.error() == null) {
+                return result;
             }
-            return ir;
-        });
+            errors.add(result);
+        }
+        return IdentityResult.ofError(IdentityResolverChain.class, "Attempted resolvers: " + errors);
     }
 }

auth-api/src/main/java/software/amazon/smithy/java/auth/api/identity/StaticIdentityResolver.java

@@ -6,21 +6,20 @@
 package software.amazon.smithy.java.auth.api.identity;
 
 import java.util.Objects;
-import java.util.concurrent.CompletableFuture;
 import software.amazon.smithy.java.context.Context;
 
 final class StaticIdentityResolver<IdentityT extends Identity> implements IdentityResolver<IdentityT> {
 
     private final IdentityT identity;
-    private final CompletableFuture<IdentityResult<IdentityT>> result;
+    private final IdentityResult<IdentityT> result;
 
     public StaticIdentityResolver(IdentityT identity) {
         this.identity = Objects.requireNonNull(identity);
-        this.result = CompletableFuture.completedFuture(IdentityResult.of(identity));
+        this.result = IdentityResult.of(identity);
     }
 
     @Override
-    public CompletableFuture<IdentityResult<IdentityT>> resolveIdentity(Context requestProperties) {
+    public IdentityResult<IdentityT> resolveIdentity(Context requestProperties) {
         return result;
     }
 

aws/aws-event-streams/src/main/java/software/amazon/smithy/java/aws/events/RpcEventStreamsUtil.java

@@ -32,7 +32,8 @@ public static Flow.Publisher<ByteBuffer> bodyForEventStreaming(
         return EventStreamFrameEncodingProcessor.create(eventStream, eventStreamEncodingFactory, input);
     }
 
-    public static <O extends SerializableStruct> CompletableFuture<O> deserializeResponse(
+    // TODO: Make more synchronous
+    public static <O extends SerializableStruct> O deserializeResponse(
             EventDecoderFactory<AwsEventFrame> eventDecoderFactory,
             DataStream bodyDataStream
     ) {
@@ -63,7 +64,7 @@ public void onComplete() {
             }
         });
 
-        return result;
+        return result.join();
     }
 
     private static Schema streamingMember(Schema schema) {

aws/aws-sigv4/src/jmh/java/software/amazon/smithy/java/aws/client/auth/scheme/sigv4/SigV4SignerTrials.java

@@ -5,14 +5,12 @@
 
 package software.amazon.smithy.java.aws.client.auth.scheme.sigv4;
 
-import java.io.IOException;
 import java.net.URI;
 import java.nio.charset.StandardCharsets;
 import java.security.Security;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
-import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
 import org.openjdk.jmh.annotations.Benchmark;
 import org.openjdk.jmh.annotations.BenchmarkMode;
@@ -110,9 +108,9 @@ public void setup() throws Exception {
     }
 
     @Benchmark
-    public void sign() throws IOException, ExecutionException, InterruptedException {
+    public void sign() {
         if (!skipTest) {
-            signer.sign(request, TEST_IDENTITY, TEST_PROPERTIES).get();
+            signer.sign(request, TEST_IDENTITY, TEST_PROPERTIES);
         } else {
             System.out.println("Skipping benchmark on Windows");
         }

aws/aws-sigv4/src/main/java/software/amazon/smithy/java/aws/client/auth/scheme/sigv4/SigV4Signer.java

@@ -22,7 +22,6 @@
 import java.util.Set;
 import java.util.SortedMap;
 import java.util.TreeMap;
-import java.util.concurrent.CompletableFuture;
 import javax.crypto.Mac;
 import javax.crypto.spec.SecretKeySpec;
 import software.amazon.smithy.java.auth.api.Signer;
@@ -98,11 +97,7 @@ public void close() {
     }
 
     @Override
-    public CompletableFuture<HttpRequest> sign(
-            HttpRequest request,
-            AwsCredentialsIdentity identity,
-            Context properties
-    ) {
+    public HttpRequest sign(HttpRequest request, AwsCredentialsIdentity identity, Context properties) {
         var region = properties.expect(SigV4Settings.REGION);
         var name = properties.expect(SigV4Settings.SIGNING_NAME);
         var clock = properties.getOrDefault(SigV4Settings.CLOCK, Clock.systemUTC());
@@ -111,32 +106,31 @@ public CompletableFuture<HttpRequest> sign(
         // TODO: Support chunk encoding
         // TODO: support UNSIGNED
 
-        return getPayloadHash(request.body()).thenApply(payloadHash -> {
-            var signedHeaders = createSignedHeaders(
-                    request.method(),
-                    request.uri(),
-                    request.headers(),
-                    payloadHash,
-                    region,
-                    name,
-                    clock.instant(),
-                    identity.accessKeyId(),
-                    identity.secretAccessKey(),
-                    identity.sessionToken(),
-                    !request.body().hasKnownLength());
-            // Don't let the cached buffers grow too large.
-            var sb = signingResources.sb;
-            if (sb.length() > BUFFER_SIZE) {
-                sb.setLength(BUFFER_SIZE);
-                sb.trimToSize();
-            }
-            sb.setLength(0);
-            return request.toBuilder().headers(HttpHeaders.of(signedHeaders)).build();
-        });
+        var payloadHash = getPayloadHash(request.body());
+        var signedHeaders = createSignedHeaders(
+                request.method(),
+                request.uri(),
+                request.headers(),
+                payloadHash,
+                region,
+                name,
+                clock.instant(),
+                identity.accessKeyId(),
+                identity.secretAccessKey(),
+                identity.sessionToken(),
+                !request.body().hasKnownLength());
+        // Don't let the cached buffers grow too large.
+        var sb = signingResources.sb;
+        if (sb.length() > BUFFER_SIZE) {
+            sb.setLength(BUFFER_SIZE);
+            sb.trimToSize();
+        }
+        sb.setLength(0);
+        return request.toBuilder().headers(HttpHeaders.of(signedHeaders)).build();
     }
 
-    private CompletableFuture<String> getPayloadHash(DataStream dataStream) {
-        return dataStream.asByteBuffer().thenApply(this::hexHash);
+    private String getPayloadHash(DataStream dataStream) {
+        return hexHash(dataStream.waitForByteBuffer());
     }
 
     private String hexHash(ByteBuffer bytes) {

aws/aws-sigv4/src/test/java/software/amazon/smithy/java/aws/client/auth/scheme/sigv4/SigV4TestRunner.java

@@ -159,7 +159,7 @@ private static HttpRequest parseRequest(String fileName) {
         Result createResult(
                 Signer<HttpRequest, AwsCredentialsIdentity> signer
         ) throws ExecutionException, InterruptedException {
-            var signedRequest = signer.sign(request, context.identity, context.properties).get();
+            var signedRequest = signer.sign(request, context.identity, context.properties);
             boolean isValid = signedRequest.headers().equals(expected.headers())
                     && signedRequest.uri().equals(expected.uri())
                     && signedRequest.method().equals(expected.method());