moby/daemon/logger/loggerutils/file_unix.go
Cory Snider 49aa66b597 daemon/logger: rotate log files, never truncate
Truncating the current log file while a reader is still reading through
it results in log lines getting missed. In contrast, rotating the file
allows readers who have the file open can continue to read from it
undisturbed. Rotating frees up the file name for the logger to create a
new file in its place. This remains true even when max-file=1; the
current log file is "rotated" from its name without giving it a new one.

On POSIXy filesystem APIs, rotating the last file is straightforward:
unlink()ing a file name immediately deletes the name from the filesystem
and makes it available for reuse, even if processes have the file open
at the time. Windows on the other hand only makes the name available
for reuse once the file itself is deleted, which only happens when no
processes have it open. To reuse the file name while the file is still
in use, the file needs to be renamed. So that's what we have to do:
rotate the file to a temporary name before marking it for deletion.

Signed-off-by: Cory Snider <csnider@mirantis.com>
2022-05-19 15:22:22 -04:00

18 lines
317 B
Go

//go:build !windows
// +build !windows
package loggerutils
import "os"
func openFile(name string, flag int, perm os.FileMode) (*os.File, error) {
return os.OpenFile(name, flag, perm)
}
func open(name string) (*os.File, error) {
return os.Open(name)
}
func unlink(name string) error {
return os.Remove(name)
}