From df402e885d4fe461b9bfef78ade52077b7bde26d Mon Sep 17 00:00:00 2001
From: Leandro Piccilli <piccilli@gmail.com>
Date: Tue, 14 Feb 2017 00:56:48 +0100
Subject: [PATCH] Check if tag value is empty before allocation

closes #2390
closes #2404
---
 CHANGELOG.md                             |  1 +
 metric/metric.go                         |  7 ++++++-
 metric/metric_test.go                    | 23 +++++++++++++++++++++++
 plugins/inputs/prometheus/parser_test.go |  8 +++-----
 plugins/parsers/nagios/parser_test.go    |  2 +-
 5 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2aaf94adbfbe8..a49f5e8f8a50b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -61,6 +61,7 @@ be deprecated eventually.
 - [#2341](https://github.com/influxdata/telegraf/issues/2341): telegraf swallowing panics in --test mode.
 - [#2358](https://github.com/influxdata/telegraf/pull/2358): Create pidfile with 644 permissions & defer file deletion.
 - [#2282](https://github.com/influxdata/telegraf/issues/2282): Reloading telegraf freezes prometheus output.
+- [#2390](https://github.com/influxdata/telegraf/issues/2390): Empty tag value causes error on InfluxDB output.
 
 ## v1.2.1 [2017-02-01]
 
diff --git a/metric/metric.go b/metric/metric.go
index 0a2ca41b6e282..edf3b77949d70 100644
--- a/metric/metric.go
+++ b/metric/metric.go
@@ -44,13 +44,18 @@ func New(
 	// pre-allocate exact size of the tags slice
 	taglen := 0
 	for k, v := range tags {
-		// TODO check that length of tag key & value are > 0
+		if len(k) == 0 || len(v) == 0 {
+			continue
+		}
 		taglen += 2 + len(escape(k, "tagkey")) + len(escape(v, "tagval"))
 	}
 	m.tags = make([]byte, taglen)
 
 	i := 0
 	for k, v := range tags {
+		if len(k) == 0 || len(v) == 0 {
+			continue
+		}
 		m.tags[i] = ','
 		i++
 		i += copy(m.tags[i:], escape(k, "tagkey"))
diff --git a/metric/metric_test.go b/metric/metric_test.go
index f133a507ca129..dd231f8c46a6f 100644
--- a/metric/metric_test.go
+++ b/metric/metric_test.go
@@ -625,3 +625,26 @@ func TestNewMetricFailNaN(t *testing.T) {
 	_, err := New("cpu", tags, fields, now)
 	assert.NoError(t, err)
 }
+
+func TestEmptyTagValueOrKey(t *testing.T) {
+	now := time.Now()
+
+	tags := map[string]string{
+		"host":     "localhost",
+		"emptytag": "",
+		"":         "valuewithoutkey",
+	}
+	fields := map[string]interface{}{
+		"usage_idle": float64(99),
+	}
+	m, err := New("cpu", tags, fields, now)
+
+	assert.True(t, m.HasTag("host"))
+	assert.False(t, m.HasTag("emptytag"))
+	assert.Equal(t,
+		fmt.Sprintf("cpu,host=localhost usage_idle=99 %d\n", now.UnixNano()),
+		m.String())
+
+	assert.NoError(t, err)
+
+}
diff --git a/plugins/inputs/prometheus/parser_test.go b/plugins/inputs/prometheus/parser_test.go
index fcd32ad43bbd7..4f2a8516f4b31 100644
--- a/plugins/inputs/prometheus/parser_test.go
+++ b/plugins/inputs/prometheus/parser_test.go
@@ -111,11 +111,9 @@ func TestParseValidPrometheus(t *testing.T) {
 		"gauge": float64(1),
 	}, metrics[0].Fields())
 	assert.Equal(t, map[string]string{
-		"osVersion":        "CentOS Linux 7 (Core)",
-		"dockerVersion":    "1.8.2",
-		"kernelVersion":    "3.10.0-229.20.1.el7.x86_64",
-		"cadvisorRevision": "",
-		"cadvisorVersion":  "",
+		"osVersion":     "CentOS Linux 7 (Core)",
+		"dockerVersion": "1.8.2",
+		"kernelVersion": "3.10.0-229.20.1.el7.x86_64",
 	}, metrics[0].Tags())
 
 	// Counter value
diff --git a/plugins/parsers/nagios/parser_test.go b/plugins/parsers/nagios/parser_test.go
index ee21ea1174ca4..b1e3d6fddc58c 100644
--- a/plugins/parsers/nagios/parser_test.go
+++ b/plugins/parsers/nagios/parser_test.go
@@ -67,7 +67,7 @@ func TestParseValidOutput(t *testing.T) {
 	assert.Equal(t, map[string]interface{}{
 		"value": float64(0.008457),
 	}, metrics[0].Fields())
-	assert.Equal(t, map[string]string{"unit": ""}, metrics[0].Tags())
+	assert.Equal(t, map[string]string{}, metrics[0].Tags())
 }
 
 func TestParseInvalidOutput(t *testing.T) {