create db links if not exist for all configured repos

internal/cache/cache.go

@@ -6,6 +6,7 @@ import (
 	"net"
 	"net/http"
 	"os"
+	"path/filepath"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -59,6 +60,10 @@ func NewCache(cacheRoot string, mirrorURLs []string, mirroredRepos []string) (*C
 		return nil, err
 	}
 
+	if err := checkSymLinks(cr, mirroredRepos); err != nil {
+		return nil, err
+	}
+
 	return &Cache{
 		cfg: cfg,
 		cr:  cr,
@@ -80,3 +85,21 @@ type UpstreamError struct {
 func (e *UpstreamError) Error() string {
 	return fmt.Sprintf("upstream returned %d", e.StatusCode)
 }
+
+func checkSymLinks(cr *os.Root, repos []string) error {
+	for _, repo := range repos {
+		dirPath := filepath.Join(repo, "os/x86_64")
+		if err := cr.MkdirAll(dirPath, 0750); err != nil {
+			return err
+		}
+		lnPath := filepath.Join(dirPath, repo+".db")
+		srcPath := filepath.Join(dirPath, repo+".db.tar.gz")
+		if _, err := cr.Lstat(lnPath); err == nil {
+			continue // link exists
+		}
+		if err := cr.Symlink(srcPath, lnPath); err != nil {
+			return err
+		}
+	}
+	return nil
+}