From 5130d37632dda8994579aa7926c573e6578e5c46 Mon Sep 17 00:00:00 2001
From: Nathan Coad <nathan@thecoads.com>
Date: Wed, 14 Jan 2026 10:27:24 +1100
Subject: [PATCH] ensure we dont collect hourly snapshot too soon after startup

---
 internal/report/snapshots.go         | 32 ++++++++++++++++++++++++++++
 internal/tasks/inventorySnapshots.go | 30 ++++++++++++++++++++------
 internal/tasks/tasks.go              |  9 ++++----
 main.go                              |  9 ++++----
 4 files changed, 66 insertions(+), 14 deletions(-)

diff --git a/internal/report/snapshots.go b/internal/report/snapshots.go
index a543c02..b417782 100644
--- a/internal/report/snapshots.go
+++ b/internal/report/snapshots.go
@@ -361,6 +361,38 @@ ORDER BY snapshot_time ASC, table_name ASC
 	return records, rows.Err()
 }
 
+func LatestSnapshotTime(ctx context.Context, database db.Database, snapshotType string) (time.Time, error) {
+	dbConn := database.DB()
+	driver := strings.ToLower(dbConn.DriverName())
+
+	var maxTime sql.NullInt64
+	switch driver {
+	case "sqlite":
+		if err := dbConn.GetContext(ctx, &maxTime, `
+SELECT MAX(snapshot_time)
+FROM snapshot_registry
+WHERE snapshot_type = ?
+`, snapshotType); err != nil {
+			return time.Time{}, err
+		}
+	case "pgx", "postgres":
+		if err := dbConn.GetContext(ctx, &maxTime, `
+SELECT MAX(snapshot_time)
+FROM snapshot_registry
+WHERE snapshot_type = $1
+`, snapshotType); err != nil {
+			return time.Time{}, err
+		}
+	default:
+		return time.Time{}, fmt.Errorf("unsupported driver for listing snapshots: %s", driver)
+	}
+
+	if !maxTime.Valid || maxTime.Int64 <= 0 {
+		return time.Time{}, nil
+	}
+	return time.Unix(maxTime.Int64, 0), nil
+}
+
 func FormatSnapshotLabel(snapshotType string, snapshotTime time.Time, tableName string) string {
 	switch snapshotType {
 	case "hourly":
diff --git a/internal/tasks/inventorySnapshots.go b/internal/tasks/inventorySnapshots.go
index e55a31d..42fd5e4 100644
--- a/internal/tasks/inventorySnapshots.go
+++ b/internal/tasks/inventorySnapshots.go
@@ -51,6 +51,30 @@ func (c *CronTask) RunVcenterSnapshotHourly(ctx context.Context, logger *slog.Lo
 		logger.Info("Hourly snapshot job finished", "duration", time.Since(startedAt))
 	}()
 	startTime := time.Now()
+
+	// reload settings in case vcenter list has changed
+	c.Settings.ReadYMLSettings()
+
+	if c.FirstHourlySnapshotCheck {
+		if err := report.EnsureSnapshotRegistry(ctx, c.Database); err != nil {
+			return err
+		}
+		lastSnapshot, err := report.LatestSnapshotTime(ctx, c.Database, "hourly")
+		if err != nil {
+			return err
+		}
+		minIntervalSeconds := intWithDefault(c.Settings.Values.Settings.VcenterInventorySnapshotSeconds, 3600)
+		if !lastSnapshot.IsZero() && startTime.Sub(lastSnapshot) < time.Duration(minIntervalSeconds)*time.Second {
+			c.Logger.Info("Skipping hourly snapshot, last snapshot too recent",
+				"last_snapshot", lastSnapshot,
+				"min_interval_seconds", minIntervalSeconds,
+			)
+			c.FirstHourlySnapshotCheck = false
+			return nil
+		}
+		c.FirstHourlySnapshotCheck = false
+	}
+
 	tableName, err := hourlyInventoryTableName(startTime)
 	if err != nil {
 		return err
@@ -60,16 +84,10 @@ func (c *CronTask) RunVcenterSnapshotHourly(ctx context.Context, logger *slog.Lo
 	if err := ensureDailyInventoryTable(ctx, dbConn, tableName); err != nil {
 		return err
 	}
-	if err := report.EnsureSnapshotRegistry(ctx, c.Database); err != nil {
-		return err
-	}
 	if err := report.RegisterSnapshot(ctx, c.Database, "hourly", tableName, startTime); err != nil {
 		c.Logger.Warn("failed to register hourly snapshot", "error", err, "table", tableName)
 	}
 
-	// reload settings in case vcenter list has changed
-	c.Settings.ReadYMLSettings()
-
 	var wg sync.WaitGroup
 	var errCount int64
 	concurrencyLimit := c.Settings.Values.Settings.HourlySnapshotConcurrency
diff --git a/internal/tasks/tasks.go b/internal/tasks/tasks.go
index 4aa3c9d..1dd807e 100644
--- a/internal/tasks/tasks.go
+++ b/internal/tasks/tasks.go
@@ -9,8 +9,9 @@ import (
 
 // CronTask stores runtime information to be used by tasks
 type CronTask struct {
-	Logger   *slog.Logger
-	Database db.Database
-	Settings *settings.Settings
-	VcCreds  *vcenter.VcenterLogin
+	Logger                   *slog.Logger
+	Database                 db.Database
+	Settings                 *settings.Settings
+	VcCreds                  *vcenter.VcenterLogin
+	FirstHourlySnapshotCheck bool
 }
diff --git a/main.go b/main.go
index ff9e45e..1342541 100644
--- a/main.go
+++ b/main.go
@@ -161,10 +161,11 @@ func main() {
 
 	// Pass useful information to the cron jobs
 	ct := &tasks.CronTask{
-		Logger:   logger,
-		Database: database,
-		Settings: s,
-		VcCreds:  &creds,
+		Logger:                   logger,
+		Database:                 database,
+		Settings:                 s,
+		VcCreds:                  &creds,
+		FirstHourlySnapshotCheck: true,
 	}
 
 	/*