feat: add exponential backoff retry strategy

Introduce a retry policy with exponential backoff and jitter for extractor and loader errors, with configurable max attempts and delay caps.

internal/app/custom_errors/loader.error.go

@@ -5,12 +5,13 @@ import (
 	"fmt"
 	"sync"
 
+	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/config"
 	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/models"
 )
 
 type LoaderError struct {
-	models.Batch
-	Msg string
+	Batch models.Batch
+	Msg   string
 }
 
 func (e *LoaderError) Error() string {
@@ -19,11 +20,11 @@ func (e *LoaderError) Error() string {
 
 func LoaderErrorHandler(
 	ctx context.Context,
-	maxRetryAttempts int,
+	retryConfig config.RetryConfig,
 	chErrorsIn <-chan LoaderError,
-	chChunksOut chan<- models.Batch,
+	chBatchesOut chan<- models.Batch,
 	chJobErrorsOut chan<- JobError,
-	wgActiveChunks *sync.WaitGroup,
+	wgActiveBatches *sync.WaitGroup,
 ) {
 	for {
 		if ctx.Err() != nil {
@@ -39,10 +40,11 @@ func LoaderErrorHandler(
 				return
 			}
 
-			if err.RetryCounter >= maxRetryAttempts {
+			if err.Batch.RetryCounter >= retryConfig.Attempts {
+				wgActiveBatches.Done()
 				jobError := JobError{
 					ShouldCancelJob: false,
-					Msg:             fmt.Sprintf("chunk %v reached max retries (%d)", err.Id, maxRetryAttempts),
+					Msg:             fmt.Sprintf("Batch %v reached max retries (%d)", err.Batch.Id, retryConfig.Attempts),
 					Prev:            &err,
 				}
 
@@ -52,17 +54,36 @@ func LoaderErrorHandler(
 					return
 				}
 
-				wgActiveChunks.Done()
 				continue
+			} else {
+				jobError := JobError{
+					ShouldCancelJob: false,
+					Msg:             fmt.Sprintf("Temporal error in batch %v (retries: %d)", err.Batch.Id, err.Batch.RetryCounter),
+					Prev:            &err,
+				}
+
+				select {
+				case chJobErrorsOut <- jobError:
+				case <-ctx.Done():
+					return
+				}
 			}
 
-			err.RetryCounter++
+			err.Batch.RetryCounter++
+			delay := computeBackoffDelay(
+				err.Batch.RetryCounter,
+				retryConfig.BaseDelayMs,
+				retryConfig.MaxDelayMs,
+				retryConfig.MaxJitterMs,
+			)
 
-			select {
-			case chChunksOut <- err.Batch:
-			case <-ctx.Done():
-				return
-			}
+			requeueWithBackoff(ctx, delay, func() {
+				select {
+				case chBatchesOut <- err.Batch:
+				case <-ctx.Done():
+					return
+				}
+			})
 		}
 	}
 }