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# Retry Policies
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AWS-specific retry policies that extend the standard retry policy with AWS service-specific exception handling, providing intelligent retry logic for transient failures and service throttling.
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## Capabilities
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### AwsRetryPolicy
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The main retry policy class that implements AWS-specific retry logic with exponential backoff and jitter.
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```kotlin { .api }
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/**
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 * AWS-specific retry policy that extends StandardRetryPolicy with AWS service exception handling
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 */
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open class AwsRetryPolicy : StandardRetryPolicy() {
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    companion object {
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        /**
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         * The default retry policy instance used by AWS service clients
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         */
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        val Default: AwsRetryPolicy
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        internal val knownErrorTypes: Map<String, RetryErrorType>
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        internal val knownStatusCodes: Map<Int, RetryErrorType>
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    }
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    /**
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     * Evaluates AWS-specific exceptions to determine retry behavior
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     * @param ex The exception to evaluate
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     * @return RetryDirective indicating whether to retry, or null to use default behavior
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     */
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    protected override fun evaluateSpecificExceptions(ex: Throwable): RetryDirective?
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}
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```
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**Usage Examples:**
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```kotlin
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import aws.sdk.kotlin.runtime.http.retries.AwsRetryPolicy
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// Use the default AWS retry policy
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val retryPolicy = AwsRetryPolicy.Default
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// Create a custom retry policy (extending AwsRetryPolicy)
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class CustomAwsRetryPolicy : AwsRetryPolicy() {
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    protected override fun evaluateSpecificExceptions(ex: Throwable): RetryDirective? {
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        // Custom retry logic
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        return when (ex) {
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            is CustomServiceException -> RetryDirective.RetryError(RetryErrorType.Transient)
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            else -> super.evaluateSpecificExceptions(ex)
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        }
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    }
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}
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val customRetryPolicy = CustomAwsRetryPolicy()
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```
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## Integration with HTTP Client
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The retry policy integrates with the broader HTTP client infrastructure:
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```kotlin
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import aws.smithy.kotlin.runtime.http.request.HttpRequest
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import aws.smithy.kotlin.runtime.http.response.HttpResponse
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// Retry policies are typically configured at the service client level
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// and work with the HTTP engine to handle transient failures
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```
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## Known Error Types
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The AWS retry policy recognizes specific error codes and HTTP status codes for intelligent retry handling:
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### Throttling Errors
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```kotlin { .api }
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// Error codes that indicate throttling (should be retried with backoff)
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val throttlingErrors = mapOf(
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    "BandwidthLimitExceeded" to RetryErrorType.Throttling,
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    "EC2ThrottledException" to RetryErrorType.Throttling,
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    "LimitExceededException" to RetryErrorType.Throttling,
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    "PriorRequestNotComplete" to RetryErrorType.Throttling,
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    "ProvisionedThroughputExceededException" to RetryErrorType.Throttling,
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    "RequestLimitExceeded" to RetryErrorType.Throttling,
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    "RequestThrottled" to RetryErrorType.Throttling,
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    "RequestThrottledException" to RetryErrorType.Throttling,
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    "SlowDown" to RetryErrorType.Throttling,
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    "ThrottledException" to RetryErrorType.Throttling,
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    "Throttling" to RetryErrorType.Throttling,
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    "ThrottlingException" to RetryErrorType.Throttling,
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    "TooManyRequestsException" to RetryErrorType.Throttling,
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    "TransactionInProgressException" to RetryErrorType.Throttling
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)
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```
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### Transient Errors
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```kotlin { .api }
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// Error codes that indicate transient failures (should be retried)
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val transientErrors = mapOf(
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    "IDPCommunicationError" to RetryErrorType.Transient,
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    "RequestTimeout" to RetryErrorType.Transient,
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    "RequestTimeoutException" to RetryErrorType.Transient
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)
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```
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### HTTP Status Codes
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```kotlin { .api }
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// HTTP status codes that should trigger retries
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val retryableStatusCodes = mapOf(
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    500 to RetryErrorType.Transient, // Internal Server Error
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    502 to RetryErrorType.Transient, // Bad Gateway
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    503 to RetryErrorType.Transient, // Service Unavailable
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    504 to RetryErrorType.Transient  // Gateway Timeout
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)
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```
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## Configuration
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Retry policies can be configured with various parameters:
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- **Maximum Attempts**: Total number of retry attempts (including initial request)
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- **Base Delay**: Initial delay before first retry attempt
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- **Maximum Delay**: Cap on exponential backoff delay
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- **Jitter**: Randomization to prevent thundering herd problems
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- **Backoff Strategy**: Exponential, linear, or custom backoff algorithms