Smart configuration defaults

Configure this functionality by using the following:

defaults_mode - shared AWS config file setting

AWS_DEFAULTS_MODE - environment variable

aws.defaultsMode - JVM system property: Java/Kotlin only

With this setting, you can choose a mode that aligns with your application architecture, which then provides optimized default values for your application. If an AWS SDK setting has a value explicitly set, then that value always takes precedence. If an AWS SDK setting does not have a value explicitly set, and defaults_mode is not equal to legacy, then this feature can provide different default values for various settings optimized for your application. Settings may include the following: HTTP communication settings, retry behavior, service Regional endpoint settings, and, potentially, any SDK-related configuration. Customers who use this feature can get new configuration defaults tailored to common usage scenarios. If your defaults_mode is not equal to legacy, we recommend performing tests of your application when you upgrade the SDK, because the default values provided might change as best practices evolve.

Default value: legacy

Note: New major versions of SDKs will default to standard.

Valid values:

• legacy – Provides default settings that vary by SDK and existed before establishment of defaults_mode.

• standard – Provides the latest recommended default values that should be safe to run in most scenarios.

• in-region – Builds on the standard mode and includes optimization tailored for applications that call AWS services from within the same AWS Region.

• cross-region – Builds on the standard mode and includes optimization tailored for applications that call AWS services in a different Region.

• mobile – Builds on the standard mode and includes optimization tailored for mobile applications.

• auto – Builds on the standard mode and includes experimental features. The SDK attempts to discover the runtime environment to determine the appropriate settings automatically. The auto detection is heuristics-based and does not provide 100% accuracy. If the runtime environment can't be determined, standard mode is used. The auto detection might query instance metadata, which might introduce latency. If startup latency is critical to your application, we recommend choosing an explicit defaults_mode instead.

Example of setting this value in the config file:

[default]
defaults_mode = standard

The following parameters might be optimized based on the selection of defaults_mode:

• retryMode – Specifies how the SDK attempts retries. See Retry behavior.

• stsRegionalEndpoints – Specifies how the SDK determines the AWS service endpoint that it uses to talk to the AWS Security Token Service (AWS STS). See AWS STS Regional endpoints.

• s3UsEast1RegionalEndpoints – Specifies how the SDK determines the AWS service endpoint that it uses to talk to the Amazon S3 for the us-east-1 Region.

• connectTimeoutInMillis – After making an initial connection attempt on a socket, the amount of time before timing out. If the client does not receive a completion of the connect handshake, the client gives up and fails the operation.

• tlsNegotiationTimeoutInMillis – The maximum amount of time that a TLS handshake can take from the time the CLIENT HELLO message is sent to the time the client and server have fully negotiated ciphers and exchanged keys.