feat: add configuration parsing and job definitions

Add a YAML config schema for migration jobs (source/target schema, table, primary key, options) and parse it at startup.

cmd/go_migrate/extractor-error-handler.go

@@ -0,0 +1,102 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"sync"
+
+	"github.com/google/uuid"
+)
+
+type ExtractorError struct {
+	Batch
+	LastId    int64
+	HasLastId bool
+	Msg       string
+}
+
+func (e *ExtractorError) Error() string {
+	return e.Msg
+}
+
+const maxRetryAttempts = 3
+
+func extractorErrorHandler(
+	ctx context.Context,
+	chErrorsIn <-chan ExtractorError,
+	chBatchesOut chan<- Batch,
+	chJobErrorsOut chan<- JobError,
+	wgActiveBatches *sync.WaitGroup,
+) {
+	for {
+		if ctx.Err() != nil {
+			return
+		}
+
+		select {
+		case <-ctx.Done():
+			return
+
+		case err, ok := <-chErrorsIn:
+			if !ok {
+				return
+			}
+
+			if err.RetryCounter >= maxRetryAttempts {
+				jobError := JobError{
+					ShouldCancelJob: false,
+					Msg:             fmt.Sprintf("batch %v reached max retries (%d)", err.Id, maxRetryAttempts),
+					Prev:            &err,
+				}
+
+				select {
+				case chJobErrorsOut <- jobError:
+				case <-ctx.Done():
+					return
+				}
+
+				wgActiveBatches.Done()
+				continue
+			}
+
+			newBatch := err.Batch
+			newBatch.RetryCounter++
+
+			if err.HasLastId {
+				newBatch.ParentId = err.Id
+				newBatch.Id = uuid.New()
+				newBatch.LowerLimit = err.LastId
+				newBatch.IsLowerLimitInclusive = false
+			}
+
+			select {
+			case chBatchesOut <- newBatch:
+			case <-ctx.Done():
+				return
+			}
+		}
+	}
+}
+
+func ExtractorErrorFromLastRowMssql(lastRow UnknownRowValues, indexPrimaryKey int, batch *Batch, previousError error) ExtractorError {
+	lastIdRawValue := lastRow[indexPrimaryKey]
+
+	lastId, ok := ToInt64(lastIdRawValue)
+	if !ok {
+		currentBatch := *batch
+		currentBatch.RetryCounter = maxRetryAttempts
+		return ExtractorError{
+			Batch:     currentBatch,
+			HasLastId: true,
+			Msg:       fmt.Sprintf("Couldn't cast last id value as int: %s", previousError.Error()),
+		}
+
+	}
+
+	return ExtractorError{
+		Batch:     *batch,
+		HasLastId: true,
+		LastId:    lastId,
+		Msg:       previousError.Error(),
+	}
+}