From 4dde940244c1d5108ddacd7a67c6a4ec4b186f68 Mon Sep 17 00:00:00 2001
From: Kyryl Sablin <kyryl.sablin@schibsted.com>
Date: Thu, 1 Nov 2018 15:22:02 +0100
Subject: [PATCH] add wildcard label name

Signed-off-by: Kyryl Sablin <kyryl.sablin@schibsted.com>
---
 model/labels.go      | 8 +++++++-
 model/labels_test.go | 8 ++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/model/labels.go b/model/labels.go
index 41051a01..3394283b 100644
--- a/model/labels.go
+++ b/model/labels.go
@@ -78,12 +78,15 @@ const (
 	// QuantileLabel is used for the label that defines the quantile in a
 	// summary.
 	QuantileLabel = "quantile"
+
+	// Used in some configurations to define that all labels should be used.
+	WildcardLabel = "*"
 )
 
 // LabelNameRE is a regular expression matching valid label names. Note that the
 // IsValid method of LabelName performs the same check but faster than a match
 // with this regular expression.
-var LabelNameRE = regexp.MustCompile("^[a-zA-Z_][a-zA-Z0-9_]*$")
+var LabelNameRE = regexp.MustCompile("^\\*$|^[a-zA-Z_][a-zA-Z0-9_]*$")
 
 // A LabelName is a key for a LabelSet or Metric.  It has a value associated
 // therewith.
@@ -96,6 +99,9 @@ func (ln LabelName) IsValid() bool {
 	if len(ln) == 0 {
 		return false
 	}
+	if len(ln) == 1 && ln[0] == '*' {
+		return true
+	}
 	for i, b := range ln {
 		if !((b >= 'a' && b <= 'z') || (b >= 'A' && b <= 'Z') || b == '_' || (b >= '0' && b <= '9' && i > 0)) {
 			return false
diff --git a/model/labels_test.go b/model/labels_test.go
index e8df28ff..a9354035 100644
--- a/model/labels_test.go
+++ b/model/labels_test.go
@@ -127,6 +127,14 @@ func TestLabelNameIsValid(t *testing.T) {
 			ln:    "colon:in:the:middle",
 			valid: false,
 		},
+		{
+			ln:    "*",
+			valid: true,
+		},
+		{
+			ln:    "a*",
+			valid: false,
+		},
 	}
 
 	for _, s := range scenarios {