Previews: refactor (#47728)

* #44449: return standard thumb service even if auth setup fails

* #44449: remove dashboardPreviewsScheduler feature flag

* #44449: externalize dashboardPreviews config

* #44449: disable previews by default

* #44449: rename logger

* #44449: dashboardPreviewsAdmin feature requires dev mode

* #44449: retrigger CII

pkg/setting/setting_dashboard_previews.go

@@ -0,0 +1,31 @@
+package setting
+
+import (
+	"time"
+
+	"gopkg.in/ini.v1"
+)
+
+type DashboardPreviewsSettings struct {
+	SchedulerInterval time.Duration
+	MaxCrawlDuration  time.Duration
+	RenderingTimeout  time.Duration
+	CrawlThreadCount  uint32
+}
+
+func readDashboardPreviewsSettings(iniFile *ini.File) DashboardPreviewsSettings {
+	maxThreadCount := uint32(20)
+
+	s := DashboardPreviewsSettings{}
+
+	previewsCrawlerSection := iniFile.Section("dashboard_previews.crawler")
+	s.CrawlThreadCount = uint32(previewsCrawlerSection.Key("thread_count").MustUint(6))
+	if s.CrawlThreadCount > maxThreadCount {
+		s.CrawlThreadCount = maxThreadCount
+	}
+
+	s.SchedulerInterval = previewsCrawlerSection.Key("scheduler_interval").MustDuration(12 * time.Hour)
+	s.MaxCrawlDuration = previewsCrawlerSection.Key("max_crawl_duration").MustDuration(1 * time.Hour)
+	s.RenderingTimeout = previewsCrawlerSection.Key("rendering_timeout").MustDuration(20 * time.Second)
+	return s
+}