refactor: implement extractor retry logic and streamline extractor interface

internal/app/etl/extractors/consumer.go

@@ -0,0 +1,94 @@
+package extractors
+
+import (
+	"context"
+	"errors"
+	"slices"
+	"strings"
+	"sync"
+	"sync/atomic"
+
+	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/config"
+	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/custom_errors"
+	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/etl"
+	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/models"
+)
+
+func Consume(
+	ctx context.Context,
+	extractor etl.Extractor,
+	tableInfo config.SourceTableInfo,
+	columns []models.ColumnType,
+	batchSize int,
+	chPartitionsIn <-chan models.Partition,
+	chBatchesOut chan<- models.Batch,
+	chErrorsOut chan<- custom_errors.JobError,
+	wgActivePartitions *sync.WaitGroup,
+	rowsRead *int64,
+) {
+	indexPrimaryKey := slices.IndexFunc(columns, func(col models.ColumnType) bool {
+		return strings.EqualFold(col.Name(), tableInfo.PrimaryKey)
+	})
+
+	if indexPrimaryKey == -1 {
+		select {
+		case <-ctx.Done():
+			return
+		case chErrorsOut <- custom_errors.JobError{
+			ShouldCancelJob: true,
+			Msg:             "Primary key not found in provided columns",
+		}:
+		}
+		return
+	}
+
+	for {
+		if ctx.Err() != nil {
+			return
+		}
+
+		select {
+		case <-ctx.Done():
+			return
+		case partition, ok := <-chPartitionsIn:
+			if !ok {
+				return
+			}
+
+			rowsReadResult, err := extractWithRetries(
+				ctx,
+				extractor,
+				tableInfo,
+				columns,
+				batchSize,
+				partition,
+				indexPrimaryKey,
+				chBatchesOut,
+			)
+			wgActivePartitions.Done()
+
+			if rowsReadResult > 0 {
+				atomic.AddInt64(rowsRead, int64(rowsReadResult))
+			}
+
+			if err != nil {
+				var jobError *custom_errors.JobError
+				if errors.As(err, &jobError) {
+					select {
+					case <-ctx.Done():
+						return
+					case chErrorsOut <- *jobError:
+					}
+				} else {
+					select {
+					case <-ctx.Done():
+						return
+					case chErrorsOut <- custom_errors.JobError{ShouldCancelJob: false, Msg: err.Error(), Prev: err}:
+					}
+				}
+
+				continue
+			}
+		}
+	}
+}