From 0c2c1d96f93e4b3fbcc8c9ce6d61133dc1ec022f Mon Sep 17 00:00:00 2001
From: Matthias Rampke <matthias@prometheus.io>
Date: Sun, 15 Sep 2024 09:55:11 +0000
Subject: [PATCH] Fix panic when parsing invalid lines

The line

```
|h|#consumer:Kafka::SharedConfigurationConsumer,topic:shared_configuration_update,partition:1,consumer_group:tc_rc_us
```

caused a panic because the line parsing _first_ splits by `:` and then failed to
find a `|` to split on.

Check that we get at least two "line parts" (i.e. splits around `|`) when we
expect them, and if not, gracefully reject the line instead of crashing.

Fixes #572.

Signed-off-by: Matthias Rampke <matthias@prometheus.io>
---
 pkg/line/line.go      | 11 ++++++++---
 pkg/line/line_test.go |  6 ++++++
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/pkg/line/line.go b/pkg/line/line.go
index 949a5ea..4abebca 100644
--- a/pkg/line/line.go
+++ b/pkg/line/line.go
@@ -211,7 +211,7 @@ func (p *Parser) LineToEvents(line string, sampleErrors prometheus.CounterVec, s
 	elements := strings.SplitN(line, ":", 2)
 	if len(elements) < 2 || len(elements[0]) == 0 || !utf8.ValidString(line) {
 		sampleErrors.WithLabelValues("malformed_line").Inc()
-		level.Debug(logger).Log("msg", "Bad line from StatsD", "line", line)
+		level.Debug(logger).Log("msg", "Bad line", "line", line)
 		return events
 	}
 
@@ -223,12 +223,17 @@ func (p *Parser) LineToEvents(line string, sampleErrors prometheus.CounterVec, s
 
 		// don't allow mixed tagging styles
 		sampleErrors.WithLabelValues("mixed_tagging_styles").Inc()
-		level.Debug(logger).Log("msg", "Bad line (multiple tagging styles) from StatsD", "line", line)
+		level.Debug(logger).Log("msg", "Bad line (multiple tagging styles)", "line", line)
 		return events
 	}
 
 	var samples []string
 	lineParts := strings.SplitN(elements[1], "|", 3)
+	if len(lineParts) < 2 {
+		sampleErrors.WithLabelValues("not_enough_parts_after_colon").Inc()
+		level.Debug(logger).Log("msg", "Bad line: not enough '|'-delimited parts after first ':'", "line", line)
+		return events
+	}
 	if strings.Contains(lineParts[0], ":") {
 		// handle DogStatsD extended aggregation
 		isValidAggType := false
@@ -251,7 +256,7 @@ func (p *Parser) LineToEvents(line string, sampleErrors prometheus.CounterVec, s
 			samples = aggLines
 		} else {
 			sampleErrors.WithLabelValues("invalid_extended_aggregate_type").Inc()
-			level.Debug(logger).Log("msg", "Bad line (invalid extended aggregate type) from StatsD", "line", line)
+			level.Debug(logger).Log("msg", "Bad line (invalid extended aggregate type)", "line", line)
 			return events
 		}
 	} else if usingDogStatsDTags {
diff --git a/pkg/line/line_test.go b/pkg/line/line_test.go
index 970320c..305d790 100644
--- a/pkg/line/line_test.go
+++ b/pkg/line/line_test.go
@@ -823,6 +823,12 @@ func TestLineToEvents(t *testing.T) {
 				},
 			},
 		},
+		"invalid event split over lines part 1": {
+			in: "karafka.consumer.consume.cpu_idle_second:  0.111090  -0.055903  -0.195390 (  2.419002)",
+		},
+		"invalid event split over lines part 2": {
+			in: "|h|#consumer:Kafka::SharedConfigurationConsumer,topic:shared_configuration_update,partition:1,consumer_group:tc_rc_us",
+		},
 	}
 
 	parser := NewParser()