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Retrying network requests in case of failure
Devrath edited this page Jun 15, 2021
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1 revision
- Demonstrates the usage of higher-order functions together with coroutines.
- The higher-order function retry() retries a certain suspending operation for a given amount of times.
- It uses an exponential backoff for retries, which means that the delay between retries increases exponentially.
- The behavior of the Mock API is defined in a way that it responses with 2 unsuccessful responses followed by a successful response.
class RetryNetworkRequestViewModel(
private val api: MockApi = mockApi()
) : BaseViewModel<UiState>() {
fun performNetworkRequest() {
uiState.value = UiState.Loading
viewModelScope.launch {
val numberOfRetries = 2
try {
retry(times = numberOfRetries) {
val recentVersions = api.getRecentAndroidVersions()
uiState.value = UiState.Success(recentVersions)
}
} catch (e: Exception) {
uiState.value = UiState.Error("Network Request failed")
}
}
}
// retry with exponential backoff
// inspired by https://stackoverflow.com/questions/46872242/how-to-exponential-backoff-retry-on-kotlin-coroutines
private suspend fun <T> retry(
times: Int,
initialDelayMillis: Long = 100,
maxDelayMillis: Long = 1000,
factor: Double = 2.0,
block: suspend () -> T
): T {
var currentDelay = initialDelayMillis
repeat(times) {
try {
return block()
} catch (exception: Exception) {
Timber.e(exception)
}
delay(currentDelay)
currentDelay = (currentDelay * factor).toLong().coerceAtMost(maxDelayMillis)
}
return block() // last attempt
}
}