What are the default values for NettyNioAsyncHttpClient maxConcurrency, maxPendingConnectionAcquires, and connectionAcquisitionTimeout?

[ashwinsangem]

Question

I'm experiencing connection acquisition timeouts in production and would like to understand the default values for NettyNioAsyncHttpClient configuration parameters to better tune my application.

Specifically, what are the default values for:

• maxConcurrency()
• maxPendingConnectionAcquires()
• connectionAcquisitionTimeout()

Production Issue

I'm encountering this error in my materializer application:

software.amazon.awssdk.core.exception.SdkClientException: Unable to execute HTTP request: Acquire operation took longer than the configured maximum time. This indicates that a request cannot get a connection from the pool within the specified maximum time. This can be due to high request rate.
Caused by: java.util.concurrent.TimeoutException: Acquire operation took longer than 10000 milliseconds.

The error suggests the acquire timeout is 10 seconds, but I'd like to confirm the official defaults for all parameters.

Current Configuration

I'm currently using explicit configuration to avoid relying on defaults:

NettyNioAsyncHttpClient.builder()
  .readTimeout(Duration.ofSeconds(60))
  .maxConcurrency(100)
  .maxPendingConnectionAcquires(1000)
  .connectionAcquisitionTimeout(Duration.ofSeconds(30))

Documentation Gap

The HTTP Configuration Netty documentation or the source file doesn't explicitly list the default values for these parameters. It would be helpful to have these documented for better application tuning.

Use Case

My application has a component that processes data and uploads to S3. It needs to handle:

• High throughput with multiple concurrent S3 operations
• Resilient connection handling for production environments
• Predictable resource usage

Understanding the defaults would help me make informed decisions about whether to use explicit configuration or rely on SDK defaults.

Request

Could you please provide the official default values for these parameters? If they're documented somewhere I missed, a pointer to the documentation would be appreciated.

Thank you!

[debora-ito]

Yes this is a little hard to find, sometimes the default values are mentioned in the HTTP client Javadoc but it's not consistent.

The default values are:

• maxConcurrency(): 50
• maxPendingConnectionAcquires(): 10000
• connectionAcquisitionTimeout(): 10 seconds

See the code where the defaults are set here.