m/pkg/logtree: implement concise stringification
This adds a new method on LogEntry: ConciseString(). It's designed to
be used in cases where we want to display the log line on some
limited-width (and likely non-interactive) log console, like TTY
consoles in Metropolis.
This is a bit too Metropolis-specific to my liking (we hardcode some
logic related to the layout of root.role.*), but it'll do for now.
Change-Id: I1079b8b19a3c304fcc5077ce6b4c69887a34d7ae
Reviewed-on: https://review.monogon.dev/c/monogon/+/1359
Reviewed-by: Leopold Schabel <leo@monogon.tech>
Tested-by: Jenkins CI
diff --git a/metropolis/pkg/logtree/logtree_entry.go b/metropolis/pkg/logtree/logtree_entry.go
index 442d456..a020910 100644
--- a/metropolis/pkg/logtree/logtree_entry.go
+++ b/metropolis/pkg/logtree/logtree_entry.go
@@ -20,6 +20,8 @@
"fmt"
"strings"
+ "github.com/mitchellh/go-wordwrap"
+
"source.monogon.dev/metropolis/pkg/logbuffer"
apb "source.monogon.dev/metropolis/proto/api"
)
@@ -57,6 +59,116 @@
return "INVALID"
}
+// ConciseString returns a concise representation of this log entry for
+// constrained environments, like TTY consoles.
+//
+// The output format is as follows:
+//
+// shortened dn I Hello there
+// some component W Something went wrong
+// shortened dn I Goodbye there
+// external stuff R I am en external process using raw logging.
+//
+// The above output is the result of calling ConciseString on three different
+// LogEntries.
+//
+// If maxWidth is greater than zero, word wrapping will be applied. For example,
+// with maxWidth set to 40:
+//
+// shortened I Hello there
+// some component W Something went wrong and here are the very long details that
+// | describe this particular issue: according to all known laws of
+// | aviation, there is no way a bee should be able to fly.
+// shortened dn I Goodbye there
+// external stuff R I am en external process using raw logging.
+//
+// The above output is also the result of calling ConciseString on three
+// different LogEntries.
+//
+// Multi-line log entries will emit 'continuation' lines (with '|') in the same
+// way as word wrapping does. That means that even with word wrapping disabled,
+// the result of this function might be multiline.
+//
+// The width of the first column (the 'shortened DN' column) is automatically
+// selected based on maxWidth. If maxWidth is less than 60, the column will be
+// omitted. For example, with maxWidth set to 20:
+//
+// I Hello there
+// W Something went wrong and here are the very long details that
+// | describe this particular issue: according to all known laws of
+// | aviation, there is no way a bee should be able to fly.
+// I Goodbye there
+// R I am en external process using raw logging.
+//
+// The given `dict` implements simple replacement rules for shortening the DN
+// parts of a log entry's DN. Some rules are hardcoded for Metropolis' DN tree.
+// If no extra shortening rules should be applied, dict can be set to ni// The
+// given `dict` implements simple replacement rules for shortening the DN parts
+// of a log entry's DN. Some rules are hardcoded for Metropolis' DN tree. If no
+// extra shortening rules should be applied, dict can be set to nil.
+func (l *LogEntry) ConciseString(dict ShortenDictionary, maxWidth int) string {
+ // Decide on a dnWidth.
+ dnWidth := 0
+ switch {
+ case maxWidth >= 80:
+ dnWidth = 20
+ case maxWidth >= 60:
+ dnWidth = 16
+ case maxWidth <= 0:
+ // No word wrapping.
+ dnWidth = 20
+ }
+
+ // Compute shortened DN, if needed.
+ sh := ""
+ if dnWidth > 0 {
+ sh = l.DN.Shorten(dict, dnWidth)
+ sh = fmt.Sprintf("%*s ", dnWidth, sh)
+ }
+
+ // Prefix of the first line emitted.
+ var prefix string
+ switch {
+ case l.Leveled != nil:
+ prefix = sh + string(l.Leveled.Severity()) + " "
+ case l.Raw != nil:
+ prefix = sh + "R "
+ }
+ // Prefix of rest of lines emitted.
+ continuationPrefix := strings.Repeat(" ", len(sh)) + "| "
+
+ // Collect lines based on the type of LogEntry.
+ var lines []string
+ collect := func(message string) {
+ if maxWidth > 0 {
+ message = wordwrap.WrapString(message, uint(maxWidth-len(prefix)))
+ }
+ for _, m2 := range strings.Split(message, "\n") {
+ if len(m2) == 0 {
+ continue
+ }
+ if len(lines) == 0 {
+ lines = append(lines, prefix+m2)
+ } else {
+ lines = append(lines, continuationPrefix+m2)
+ }
+ }
+ }
+ switch {
+ case l.Leveled != nil:
+ _, messages := l.Leveled.Strings()
+ for _, m := range messages {
+ collect(m)
+ }
+ case l.Raw != nil:
+ collect(l.Raw.String())
+ default:
+ return ""
+ }
+
+ return strings.Join(lines, "\n")
+}
+
// Strings returns the canonical representation of this payload split into a
// prefix and all lines that were contained in the original message. This is
// meant to be displayed to the user by showing the prefix before each line,