remote_storage: use S3 SDK's adaptive retry policy (#5813)

## Problem

Currently, we aren't doing any explicit slowdown in response to 429
responses. Recently, as we hit remote storage a bit harder (pageserver
does more ListObjectsv2 requests than it used to since #5580 ), we're
seeing storms of 429 responses that may be the result of not just doing
too may requests, but continuing to do those extra requests without
backing off any more than our usual backoff::exponential.

## Summary of changes

Switch from AWS's "Standard" retry policy to "Adaptive" -- docs describe
this as experimental but it has been around for a long time. The main
difference between Standard and Adaptive is that Adaptive rate-limits
the client in response to feedback from the server, which is meant to
avoid scenarios where the client would otherwise repeatedly hit
throttling responses.

Cargo.lock

@@ -4064,6 +4064,7 @@ dependencies = [
  "aws-config",
  "aws-credential-types",
  "aws-sdk-s3",
+ "aws-smithy-async",
  "aws-smithy-http",
  "aws-types",
  "azure_core",

Cargo.toml

@@ -48,6 +48,7 @@ async-trait = "0.1"
 aws-config = { version = "0.56", default-features = false, features=["rustls"] }
 aws-sdk-s3 = "0.29"
 aws-smithy-http = "0.56"
+aws-smithy-async = { version = "0.56", default-features = false, features=["rt-tokio"] }
 aws-credential-types = "0.56"
 aws-types = "0.56"
 axum = { version = "0.6.20", features = ["ws"] }

libs/remote_storage/Cargo.toml

@@ -8,6 +8,7 @@ license.workspace = true
 anyhow.workspace = true
 async-trait.workspace = true
 once_cell.workspace = true
+aws-smithy-async.workspace = true
 aws-smithy-http.workspace = true
 aws-types.workspace = true
 aws-config.workspace = true

libs/remote_storage/src/s3_bucket.rs

@@ -4,23 +4,27 @@
 //! allowing multiple api users to independently work with the same S3 bucket, if
 //! their bucket prefixes are both specified and different.
 
-use std::borrow::Cow;
+use std::{borrow::Cow, sync::Arc};
 
 use anyhow::Context;
 use aws_config::{
     environment::credentials::EnvironmentVariableCredentialsProvider,
-    imds::credentials::ImdsCredentialsProvider, meta::credentials::CredentialsProviderChain,
-    provider_config::ProviderConfig, web_identity_token::WebIdentityTokenCredentialsProvider,
+    imds::credentials::ImdsCredentialsProvider,
+    meta::credentials::CredentialsProviderChain,
+    provider_config::ProviderConfig,
+    retry::{RetryConfigBuilder, RetryMode},
+    web_identity_token::WebIdentityTokenCredentialsProvider,
 };
 use aws_credential_types::cache::CredentialsCache;
 use aws_sdk_s3::{
-    config::{Config, Region},
+    config::{AsyncSleep, Config, Region, SharedAsyncSleep},
     error::SdkError,
     operation::get_object::GetObjectError,
     primitives::ByteStream,
     types::{Delete, ObjectIdentifier},
     Client,
 };
+use aws_smithy_async::rt::sleep::TokioSleep;
 use aws_smithy_http::body::SdkBody;
 use hyper::Body;
 use scopeguard::ScopeGuard;
@@ -83,10 +87,23 @@ impl S3Bucket {
             .or_else("imds", ImdsCredentialsProvider::builder().build())
         };
 
+        // AWS SDK requires us to specify how the RetryConfig should sleep when it wants to back off
+        let sleep_impl: Arc<dyn AsyncSleep> = Arc::new(TokioSleep::new());
+
+        // We do our own retries (see [`backoff::retry`]).  However, for the AWS SDK to enable rate limiting in response to throttling
+        // responses (e.g. 429 on too many ListObjectsv2 requests), we must provide a retry config.  We set it to use at most one
+        // attempt, and enable 'Adaptive' mode, which causes rate limiting to be enabled.
+        let mut retry_config = RetryConfigBuilder::new();
+        retry_config
+            .set_max_attempts(Some(1))
+            .set_mode(Some(RetryMode::Adaptive));
+
         let mut config_builder = Config::builder()
             .region(region)
             .credentials_cache(CredentialsCache::lazy())
-            .credentials_provider(credentials_provider);
+            .credentials_provider(credentials_provider)
+            .sleep_impl(SharedAsyncSleep::from(sleep_impl))
+            .retry_config(retry_config.build());
 
         if let Some(custom_endpoint) = aws_config.endpoint.clone() {
             config_builder = config_builder