cmd/coordinator: save CPU by not validating recent .tar.gz snapshots
We were burning a fair bit of CPU here.
Updates golang/go#12671
Change-Id: Iba16e1caa80a1f0b7330098209acaf6d46ce048f
Reviewed-on: https://go-review.googlesource.com/17130
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/cmd/coordinator/coordinator.go b/cmd/coordinator/coordinator.go
index 6ed78cc..bcd0112 100644
--- a/cmd/coordinator/coordinator.go
+++ b/cmd/coordinator/coordinator.go
@@ -1483,17 +1483,30 @@
return nil
}
+var timeSnapshotCorruptionFixed = time.Date(2015, time.November, 1, 0, 0, 0, 0, nil)
+
// snapshotExists reports whether the snapshot exists and isn't corrupt.
// Unfortunately we put some corrupt ones in for awhile, so this check is
// now more paranoid than it used to be.
func (br *builderRev) snapshotExists() bool {
- // TODO(bradfitz): clean up the repo and revert this to what
- // it was before, maybe based on the date of the file. The old
- // code was just:
- // resp, err := http.Head(br.snapshotURL())
- // return err == nil && resp.StatusCode == http.StatusOK
+ resp, err := http.Head(br.snapshotURL())
+ if err != nil || resp.StatusCode != http.StatusOK {
+ return false
+ }
- resp, err := http.Get(br.snapshotURL())
+ // If the snapshot is newer than the point at which we fixed writing
+ // potentially-truncated snapshots to GCS, then stop right here.
+ // See history in golang.org/issue/12671
+ lastMod, err := http.ParseTime(resp.Header.Get("Last-Modified"))
+ if err == nil && lastMod.After(timeSnapshotCorruptionFixed) {
+ log.Printf("Snapshot exists for %v (without truncate checks)", br)
+ return true
+ }
+
+ // Otherwise, if the snapshot is too old, verify it.
+ // This path is slow.
+ // TODO(bradfitz): delete this in 6 months or so? (around 2016-06-01)
+ resp, err = http.Get(br.snapshotURL())
if err != nil {
return false
}
