Ask Bjørn Hansen
d8b9cddfb8
When stderr is connected to journald, switch from the plain text handler to the native journal protocol via github.com/systemd/slog-journal. Each record now carries PRIORITY, MESSAGE, and slog attributes as structured fields, so journalctl -p and LogLevelMax= in unit files filter by severity instead of dropping everything at once. Detection follows systemd.exec(5): parse JOURNAL_STREAM as <dev>:<ino> and fstat(2) stderr to confirm the match, guarding against processes that inherit the env var but have stderr redirected elsewhere. The fstat path is Linux-only; other platforms fall through to the existing text handler. Also honour DEBUG_INVOCATION by raising stderr to Debug level, matching the behaviour of systemd.service(5) RestartMode=debug.
42 lines
1.1 KiB
Go
42 lines
1.1 KiB
Go
//go:build linux
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package logger
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import (
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"os"
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"strconv"
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"strings"
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"syscall"
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)
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// stderrIsJournal reports whether os.Stderr is currently connected to
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// the systemd journal. systemd.exec(5) sets JOURNAL_STREAM to
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// "<dev>:<inode>" of the journal stream at service start. Detection
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// must fstat(2) the actual stderr and compare — a child process may
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// redirect stderr while inheriting the env var, so presence of the
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// variable alone is not sufficient.
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func stderrIsJournal() bool {
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dev, ino, ok := parseJournalStream(os.Getenv("JOURNAL_STREAM"))
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if !ok {
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return false
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}
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var st syscall.Stat_t
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if err := syscall.Fstat(int(os.Stderr.Fd()), &st); err != nil {
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return false
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}
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return uint64(st.Dev) == dev && uint64(st.Ino) == ino
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}
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func parseJournalStream(v string) (dev, ino uint64, ok bool) {
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sep := strings.IndexByte(v, ':')
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if sep <= 0 || sep == len(v)-1 {
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return 0, 0, false
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}
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d, err1 := strconv.ParseUint(v[:sep], 10, 64)
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n, err2 := strconv.ParseUint(v[sep+1:], 10, 64)
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if err1 != nil || err2 != nil {
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return 0, 0, false
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}
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return d, n, true
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}
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