add prometheus instrumentation

internal/tasks/monthlyAggregate.go

@@ -6,6 +6,7 @@ import (
 	"log/slog"
 	"time"
 	"vctp/db"
+	"vctp/internal/metrics"
 	"vctp/internal/report"
 )
 
@@ -29,6 +30,7 @@ func (c *CronTask) AggregateMonthlySummary(ctx context.Context, month time.Time,
 }
 
 func (c *CronTask) aggregateMonthlySummary(ctx context.Context, targetMonth time.Time, force bool) error {
+	jobStart := time.Now()
 	if err := report.EnsureSnapshotRegistry(ctx, c.Database); err != nil {
 		return err
 	}
@@ -107,9 +109,12 @@ func (c *CronTask) aggregateMonthlySummary(ctx context.Context, targetMonth time
 
 	if err := c.generateReport(ctx, monthlyTable); err != nil {
 		c.Logger.Warn("failed to generate monthly report", "error", err, "table", monthlyTable)
+		metrics.RecordMonthlyAggregation(time.Since(jobStart), err)
+		return err
 	}
 
 	c.Logger.Debug("Finished monthly inventory aggregation", "summary_table", monthlyTable)
+	metrics.RecordMonthlyAggregation(time.Since(jobStart), nil)
 	return nil
 }