Make caser a local varialbe, not a global one.

The cases.Caser returned by calling cases.Title *cannot* be shared among
goroutines. This might happen when Prometheus tries to scrape multiple
targets at the same time. From the docs:

A Caser may be stateful and should therefore not be shared between
goroutines.

Fixes: #922

Signed-off-by: Marcelo E. Magallon <marcelo.magallon@grafana.com>

diff --git a/prober/http.go b/prober/http.go
index 54f40998f968210d34219b1a71f21e8e4dde55fc..99d38a2bf592281448d80ff8bcef1f831ab35eb7 100644 (file)
--- a/prober/http.go
+++ b/prober/http.go
@@ -46,8 +46,6 @@ import (
        "github.com/prometheus/blackbox_exporter/config"
 )
 
-var caser = cases.Title(language.Und)
-
 func matchRegularExpressions(reader io.Reader, httpConfig config.HTTPProbe, logger log.Logger) bool {
        body, err := ioutil.ReadAll(reader)
        if err != nil {
@@ -342,6 +340,16 @@ func ProbeHTTP(ctx context.Context, target string, module config.Module, registr
                return false
        }
 
+       // Do not move the following variable to global scope. The cases.Caser returned by
+       // calling cases.Title *cannot* be shared among goroutines. This might happen when
+       // Prometheus tries to scrape multiple targets at the same time. From the docs:
+       //
+       // A Caser may be stateful and should therefore not be shared between goroutines.
+       //
+       // Issue: https://github.com/prometheus/blackbox_exporter/issues/922
+
+       caser := cases.Title(language.Und)
+
        httpClientConfig := module.HTTP.HTTPClientConfig
        if len(httpClientConfig.TLSConfig.ServerName) == 0 {
                // If there is no `server_name` in tls_config, use

diff --git a/prober/http_test.go b/prober/http_test.go
index dc5b65bbd09879f22698efa256f7a2352a4c56c2..cd277618aa33b4158661ebae5365d4f97f4fa6d5 100644 (file)
--- a/prober/http_test.go
+++ b/prober/http_test.go
@@ -35,6 +35,8 @@ import (
        "github.com/go-kit/log"
        "github.com/prometheus/client_golang/prometheus"
        pconfig "github.com/prometheus/common/config"
+       "golang.org/x/text/cases"
+       "golang.org/x/text/language"
 
        "github.com/prometheus/blackbox_exporter/config"
 )
@@ -1068,6 +1070,7 @@ func TestHTTPHeaders(t *testing.T) {
                "Accept-Language": "en-US",
        }
        ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+               caser := cases.Title(language.Und)
                for key, value := range headers {
                        if caser.String(key) == "Host" {
                                if r.Host != value {