Hi there -
I’m trying to solve a bug in the backrest UI for restic, where Windows backups take 50% longer when run under backrest than when invoked directly on the CLI.
The program works by invoking restic and parsing its stdout status messages. I suspect there is some kind of IO issues causing the slowdown on Windows, but so far I’ve been unable to track it down or isolate the cause.
I decided to change tacks today and create a Benchmark function to invoke the restic backup wrapping code, to at least save some iteration time. However, when running under go test I get a very bizarre Access Denied error and I’m wondering if anyone has ideas:
Process STDOUT:
{"message_type":"status","percent_done":0,"total_files":1,"total_bytes":10737418240,"current_files":["/C/backrest/1162000510/10G-data4135267563"]}
{"message_type":"status","seconds_remaining":4661,"percent_done":0.00006117867305874825,"total_files":1,"total_bytes":10737418240,"bytes_done":656901,"current_files":["/C/backrest/1162000510/10G-data4135267563"]}
{"message_type":"status","seconds_remaining":1862,"percent_done":0.0001660994254052639,"total_files":1,"total_bytes":10737418240,"bytes_done":1783479,"current_files":["/C/backrest/1162000510/10G-data4135267563"]}
{"message_type":"status","seconds_remaining":1917,"percent_done":0.0001660994254052639,"total_files":1,"total_bytes":10737418240,"bytes_done":1783479,"current_files":["/C/backrest/1162000510/10G-data4135267563"]}
{"message_type":"error","error":{},"during":"archival","item":""}
{"message_type":"error","error":{},"during":"archival","item":""}
{"message_type":"error","error":{},"during":"archival","item":""}
{"message_type":"error","error":{},"during":"archival","item":""}
{"message_type":"status","seconds_remaining":2030,"percent_done":0.0001660994254052639,"total_files":1,"total_bytes":10737418240,"bytes_done":1783479,"error_count":4}
Fatal: unable to save snapshot: Access is denied.
When I look at the created temporary directories, the repository was init’d successfully and every use has full permission over the directory and its parent.
The internet suggested antivirus can interfere, but I disabled Real-Time Protection in Windows Defender and I’m still having issues. Does anyone have any ideas what might be going on?
Here’s my test code:
func BenchmarkResticBackup(b *testing.B) {
for i := 0; i < b.N; i++ {
// stop the timer during test setup
b.StopTimer()
repo, err := os.MkdirTemp("C:\\backrest", "")
if err != nil {
b.Fatalf("failed to create temp dir: %v", err)
}
b.Logf("repo: %s", repo)
// create a new repo with cache disabled for testing
binPath, err := resticinstaller.FindOrInstallResticBinary()
if err != nil {
b.Fatalf("find restic binary: %v", err)
}
r := NewRepo(binPath, repo, WithFlags("--no-cache"), WithEnv("RESTIC_PASSWORD=test"))
if err := r.Init(context.Background()); err != nil {
b.Fatalf("failed to init repo: %v", err)
}
// create 10G of test data
dir, err := os.MkdirTemp("C:\\backrest", "")
if err != nil {
b.Fatalf("failed to create temp dir: %v", err)
}
b.Logf("dir: %s", dir)
f, err := os.CreateTemp(dir, "10G-data")
if err != nil {
b.Fatalf("failed to create file: %v", err)
}
// generate and write 10G of data from random
rr := io.LimitReader(rand.Reader, 10*1024*1024*1024)
if _, err := io.Copy(f, rr); err != nil {
b.Fatalf("failed to write 10G of data: %v", err)
}
f.Close()
// make sure permissions are set openly
if err := RecursiveChmod(dir, 0777); err != nil {
b.Fatalf("failed to set permissions: %v", err)
}
if err := RecursiveChmod(repo, 0777); err != nil {
b.Fatalf("failed to set permissions: %v", err)
}
// start the timer and perform a backup
b.StartTimer()
_, err = r.Backup(context.Background(), []string{dir}, func(event *BackupProgressEntry) {
b.Logf("backup event: %v", event)
})
if err != nil {
b.Fatalf("unexpected error: %v", err)
}
// delete test data
if err := os.RemoveAll(dir); err != nil {
b.Fatalf("failed to remove test data: %v", err)
}
if err := os.RemoveAll(repo); err != nil {
b.Fatalf("failed to remove repo: %v", err)
}
}
}