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.
63 lines
1.6 KiB
Go
63 lines
1.6 KiB
Go
package logger
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import (
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"log/slog"
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slogjournal "github.com/systemd/slog-journal"
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)
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// newJournalHandler returns a slog.Handler that delivers records to the
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// systemd journal using the native protocol. It returns nil when stderr
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// is not connected to journald, in which case the caller falls back to
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// the stderr text handler.
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func newJournalHandler(opts *slog.HandlerOptions) slog.Handler {
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if !stderrIsJournal() {
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return nil
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}
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h, err := slogjournal.NewHandler(&slogjournal.Options{
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Level: opts.Level,
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ReplaceAttr: journalReplaceAttr,
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ReplaceGroup: sanitizeJournalKey,
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})
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if err != nil {
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return nil
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}
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return h
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}
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// journalReplaceAttr sanitizes slog attribute keys so they satisfy the
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// journal's ^[A-Z_][A-Z0-9_]*$ constraint. Without this, otherwise
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// valid attributes from third-party handlers (e.g. the trace_id/span_id
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// injected by slogtraceid) are silently dropped by the journal.
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func journalReplaceAttr(groups []string, a slog.Attr) slog.Attr {
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a.Key = sanitizeJournalKey(a.Key)
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return a
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}
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// sanitizeJournalKey maps an arbitrary string to a journal-legal key:
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// upper-cases ASCII letters, replaces everything outside [A-Z0-9_] with
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// '_', and prefixes '_' if the first byte is a digit.
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func sanitizeJournalKey(k string) string {
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if k == "" {
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return k
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}
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b := make([]byte, 0, len(k)+1)
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for i := 0; i < len(k); i++ {
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c := k[i]
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switch {
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case c >= 'A' && c <= 'Z', c == '_':
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b = append(b, c)
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case c >= 'a' && c <= 'z':
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b = append(b, c-'a'+'A')
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case c >= '0' && c <= '9':
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if i == 0 {
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b = append(b, '_')
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}
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b = append(b, c)
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default:
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b = append(b, '_')
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}
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}
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return string(b)
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}
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