When working with external APIs in your Kotlin applications, you might encounter transient errors, such as network timeouts or temporary server issues. Retrying failed API requests can improve user experience by automatically recovering from these temporary issues.
Understanding Retrying Strategies
Before we dig into the code, it's important to understand the different retry strategies:
- Immediate Retry: As soon as a request fails, another is attempted.
- Fixed Delay Retry: There is a fixed period between retries.
- Exponential Backoff: The time between retries increases exponentially.
Setting Up Retrofit in Kotlin
We will use Retrofit for making API requests in our Kotlin application. Ensure you have the necessary dependencies included in your build.gradle.kts file:
implementation("com.squareup.retrofit2:retrofit:2.9.0")
implementation("com.squareup.retrofit2:converter-gson:2.9.0")
Retrying with Interceptors
One way to implement retry logic is using an OkHttp Interceptor inside a Retrofit setup.
import okhttp3.Interceptor
import okhttp3.OkHttpClient
import retrofit2.Retrofit
import retrofit2.converter.gson.GsonConverterFactory
val retryInterceptor = Interceptor { chain ->
val request = chain.request()
var response = chain.proceed(request)
var retryCount = 0
val maxRetryCount = 3
while (!response.isSuccessful && retryCount < maxRetryCount) {
retryCount++
response = chain.proceed(request)
}
response
}
val client = OkHttpClient.Builder()
.addInterceptor(retryInterceptor)
.build()
val retrofit = Retrofit.Builder()
.baseUrl("https://api.example.com/")
.addConverterFactory(GsonConverterFactory.create())
.client(client)
.build()
Exponential Backoff Strategy
An exponential backoff strategy is more effective, especially in avoiding overwhelming an already struggling server.
val exponentialBackoffInterceptor = Interceptor { chain ->
val request = chain.request()
var response = chain.proceed(request)
var retryCount = 0
val maxRetryCount = 5
var backoffTime = 1000L // Start with 1 second
while (!response.isSuccessful && retryCount < maxRetryCount) {
Thread.sleep(backoffTime)
retryCount++
backoffTime *= 2 // Double the delay each time
response = chain.proceed(request)
}
response
}
val clientWithBackoff = OkHttpClient.Builder()
.addInterceptor(exponentialBackoffInterceptor)
.build()
val retryRetrofit = Retrofit.Builder()
.baseUrl("https://api.example.com/")
.addConverterFactory(GsonConverterFactory.create())
.client(clientWithBackoff)
.build()
In this setup, the retry interceptor waits double the time of the previous attempt before making a retry, helping reduce request bursts when issues occur.
Conclusion
Implementing retry logic in your Kotlin applications which interact with APIs makes them more resilient and user-friendly. Adjust the retry and backoff parameters based on your API's capacity and error nature. With properly implemented retry policies, you can handle temporary failures gracefully and enhance the robustness of your software.
