make sure temp file(s) are closed during defrag

[ghouscht]

Bug report criteria

• This bug report is not security related, security issues should be disclosed privately via etcd maintainers.
• This is not a support request or question, support requests or questions should be raised in the etcd discussion forums.
• You have read the etcd bug reporting guidelines.
• Existing open issues along with etcd frequently asked questions have been checked and this is not a duplicate.

What happened?

Some temp file(s) (

etcd/server/storage/backend/backend.go

Line 487 in bd88963

temp, err := os.CreateTemp(dir, "db.tmp.*")

) might not be closed during defrag. See discussion #18822 (comment) for more details.

[ghouscht]

/assign

Will take care of this.

[ghouscht]

Apparently if everything works as expected the temp file is closed:

• tmpdb.Close (*bbolt.DB) is called here:

  etcd/server/storage/backend/backend.go

  Line 532 in 7b70b5f

  err = tmpdb.Close()

  (which also closes the file descriptor of the db file)
• because of

  etcd/server/storage/backend/backend.go

  Lines 495 to 497 in 7b70b5f

  	options.OpenFile = func(_ string, _ int, _ os.FileMode) (file *os.File, err error) {
  	return temp, nil
  	}

  the temporary file isn't opened again, so calling tmpdb.Close also closes the temp file descriptor

Probably in one of the error cases this doesn't happen. Need to check.

[ghouscht]

This is done. All PRs, including the ones for the backports to 3.4 and 3.5 have been merged.