refactor: implement Consume method in GenericLoader; enhance error handling in ProcessBatch

cmd/go_migrate/process.go

@@ -20,6 +20,8 @@ import (
 	"golang.org/x/sync/errgroup"
 )
 
+const jobErrorsChannelSize int = 100
+
 func buildTruncateQuery(targetDbType, schema, table, truncateMethod string) string {
 	if truncateMethod == "DELETE" {
 		if targetDbType == "postgres" {
@@ -110,11 +112,11 @@ func processMigrationJob(
 		log.Error("Unexpected error calculating batch ranges: ", err)
 	}
 
-	chJobErrors := make(chan custom_errors.JobError, job.ExtractorQueueSize)
+	chJobErrors := make(chan custom_errors.JobError, jobErrorsChannelSize)
 	chLoadersErrors := make(chan custom_errors.LoaderError, job.ExtractorQueueSize)
 	chPartitions := make(chan models.Partition, job.ExtractorQueueSize)
 	chBatchesRaw := make(chan models.Batch, job.ExtractorQueueSize)
-	chBatchesTransformed := make(chan models.Batch, job.ExtractorQueueSize)
+	chBatchesTransformed := make(chan models.Batch, job.TransformerQueueSize)
 
 	var wgActivePartitions sync.WaitGroup
 	var wgActiveBatches sync.WaitGroup

internal/app/etl/loaders/consume.go

@@ -0,0 +1,63 @@
+package loaders
+
+import (
+	"context"
+	"errors"
+	"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/models"
+)
+
+func (gl *GenericLoader) Consume(
+	ctx context.Context,
+	tableInfo config.TargetTableInfo,
+	columns []models.ColumnType,
+	retryConfig config.RetryConfig,
+	chBatchesIn <-chan models.Batch,
+	chErrorsOut chan<- custom_errors.JobError,
+	wgActiveBatches *sync.WaitGroup,
+	rowsLoaded *int64,
+) {
+	colNames := mapSlice(columns, func(col models.ColumnType) string {
+		return col.Name()
+	})
+
+	for {
+		if ctx.Err() != nil {
+			return
+		}
+
+		select {
+		case <-ctx.Done():
+			return
+		case batch, ok := <-chBatchesIn:
+			if !ok {
+				return
+			}
+
+			processedRows, err := gl.ProcessBatch(ctx, tableInfo, colNames, batch)
+			wgActiveBatches.Done()
+
+			if err != nil {
+				if jobError, ok := errors.AsType[*custom_errors.JobError](err); ok {
+					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}:
+					}
+				}
+			} else {
+				atomic.AddInt64(rowsLoaded, int64(processedRows))
+			}
+		}
+	}
+}

internal/app/etl/loaders/main.go

@@ -38,8 +38,7 @@ func (gl *GenericLoader) ProcessBatch(
 	)
 
 	if err != nil {
-		var pgErr *pgconn.PgError
-		if errors.As(err, &pgErr) {
+		if pgErr, ok := errors.AsType[*pgconn.PgError](err); ok {
 			if pgErr.Code == "23505" {
 				return 0, &custom_errors.JobError{
 					ShouldCancelJob: true,