How to configure connection pool (max connections) in S3 client?

[shunjiad]

I’m using the aws-sdk-s3 crate and would like to configure the connection pool settings, specifically to set a maximum number of connections for the S3 client. However, I couldn’t find clear documentation on how to adjust this.

• Is there a way to configure the connection pool size (max connections) when initializing an S3 client?
• If so, what are the recommended approaches or settings to control connection reuse efficiently?
• Does the SDK provide built-in options for this, or do I need to customize the underlying hyper client?

Any guidance or examples would be greatly appreciated. Thanks!

[landonxjames]

There is currently no way to configure this via the SDK. Hyper does offer some configurations for the connection pool (ex: this), but seemingly not one for max connections. You would have to construct your own Hyper client and provide it to the SDK to use it.

[shunjiad]

Thanks for the help. But I cannot pass the custom hyper client to the SdkConfig.

error[E0277]: the trait bound `hyper_util::client::legacy::Client<HttpConnector, _>: HttpClient` is not satisfied
   --> src/main.rs:165:22
    |
165 |         .http_client(hyper_client)
    |          ----------- ^^^^^^^^^^^^ the trait `HttpClient` is not implemented for `hyper_util::client::legacy::Client<HttpConnector, _>`
    |          |
    |          required by a bound introduced by this call
    |
    = help: the trait `HttpClient` is implemented for `SharedHttpClient`
note: required by a bound in `ConfigLoader::http_client`
    |
399 |         pub fn http_client(mut self, http_client: impl HttpClient + 'static) -> Self {
    |                                                        ^^^^^^^^^^ required by this bound in `ConfigLoader::http_client`

[landonxjames]

As the error says, you will need to implement the HttpClient trait for the client you constructed. You can see an example of that in our codebase here: https://github.com/smithy-lang/smithy-rs/blob/94dbe3b0f658fe2c69bdfbefba06cd3ecde2a668/rust-runtime/aws-smithy-http-client/src/hyper_legacy.rs#L438