Pass maxConcurrency to CRT (#3742)

Author: zoewangg

.changes/next-release/bugfix-AWSCRTbasedS3Client-18fdc58.json

@@ -0,0 +1,6 @@
+{
+    "type": "bugfix",
+    "category": "AWS CRT-based S3 Client",
+    "contributor": "",
+    "description": "Fix an issue where maxConcurrency configured by the user on the builder was not honored."
+}

services/s3/src/main/java/software/amazon/awssdk/services/s3/S3CrtAsyncClientBuilder.java

@@ -88,12 +88,15 @@ public interface S3CrtAsyncClientBuilder extends SdkBuilder<S3CrtAsyncClientBuil
      *
      * <p>
      * Whether the transfer manager can achieve the configured target throughput depends on various factors such as the network
-     * bandwidth of the environment and the configured {@link #maxConcurrency}.
+     * bandwidth of the environment and whether {@link #maxConcurrency} is configured.
      *
      * <p>
-     * By default, it is 10 Gbps. If users want to transfer as fast as possible, it's recommended to set it to the maximum network
-     * bandwidth on the host that the application is running on. For EC2 instances, you can find network bandwidth for a specific
+     * By default, it is 10 gigabits per second. If users want to transfer as fast as possible, it's recommended to set it to the
+     * maximum network bandwidth on the host that the application is running on. For EC2 instances, you can find network
+     * bandwidth for a specific
      * instance type in <a href="https://aws.amazon.com/ec2/instance-types/">Amazon EC2 instance type page</a>.
+     * If you are running into out of file descriptors error, consider using {@link #maxConcurrency(Integer)} to limit the
+     * number of connections.
      *
      * @param targetThroughputInGbps the target throughput in Gbps
      * @return this builder for method chaining.

services/s3/src/main/java/software/amazon/awssdk/services/s3/internal/crt/S3CrtAsyncHttpClient.java

@@ -70,6 +70,7 @@ private S3CrtAsyncHttpClient(Builder builder) {
                                  .withClientBootstrap(s3NativeClientConfiguration.clientBootstrap())
                                  .withPartSize(s3NativeClientConfiguration.partSizeBytes())
                                  .withComputeContentMd5(false)
+                                 .withMaxConnections(s3NativeClientConfiguration.maxConcurrency())
                                  .withThroughputTargetGbps(s3NativeClientConfiguration.targetThroughputInGbps())
                                  .withInitialReadWindowSize(initialWindowSize)
                                  .withReadBackpressureEnabled(true);