improve detection of .NET log severities

level.go

@@ -85,20 +85,33 @@ func GuessLevel(line string) Level {
 		for _, sf := range subfields {
 			sf = strings.TrimLeft(strings.ToLower(sf), "\"[(<'")
 			sf = strings.TrimPrefix(sf, "level=")
-			if len(sf) < 4 {
-				continue
-			}
-			switch sf[:4] {
-			case "debu":
-				return LevelDebug
-			case "info", "noti":
-				return LevelInfo
-			case "warn":
-				return LevelWarning
-			case "erro":
-				return LevelError
-			case "crit", "fata":
-				return LevelCritical
+
+			if l := len(sf); l == 3 {
+				switch sf {
+				case "dbg", "trc":
+					return LevelDebug
+				case "inf":
+					return LevelInfo
+				case "wrn":
+					return LevelWarning
+				case "err":
+					return LevelError
+				case "ftl":
+					return LevelCritical
+				}
+			} else if l >= 4 {
+				switch sf[:4] {
+				case "debu":
+					return LevelDebug
+				case "info", "noti":
+					return LevelInfo
+				case "warn":
+					return LevelWarning
+				case "erro":
+					return LevelError
+				case "crit", "fata":
+					return LevelCritical
+				}
 			}
 		}
 	}

level_test.go

@@ -29,4 +29,11 @@ func TestGuessLevel(t *testing.T) {
 	assert.Equal(t, LevelDebug, GuessLevel(`[2020-06-25 17:35:37,609][DEBUG][action.search            ] [srv] [tweets-100][6]`))
 	assert.Equal(t, LevelError, GuessLevel(`[2023-10-12T09:56:53.393595+00:00] otel-php.ERROR: Export failure {"exception":"[object] (RuntimeException(code: 0): Export retry limit exceeded at /var/www/vendor/open-telemetry/sdk/Common/Export/Http/PsrTransport.php:114)","source":"OpenTelemetry\\Contrib\\Otlp\\SpanExporter"} []`))
 	assert.Equal(t, LevelWarning, GuessLevel(`2023.10.12 13:58:41.168802 [ 847 ] {} <Warning> TCPHandler: Using deprecated interserver protocol because the client is too old. Consider upgrading all nodes in cluster.`))
+
+	assert.Equal(t, LevelDebug, GuessLevel("[06:23:18 DBG] message"))
+	assert.Equal(t, LevelInfo, GuessLevel("[06:23:18 INF] message"))
+	assert.Equal(t, LevelWarning, GuessLevel("[06:23:18 WRN] message"))
+	assert.Equal(t, LevelError, GuessLevel("[06:23:18 ERR] message"))
+	assert.Equal(t, LevelCritical, GuessLevel("[06:23:18 FTL] message"))
+
 }