From: Johannes Visintini <github@joker234.de>
Date: Thu, 17 Jan 2019 10:00:43 +0000 (+0100)
Subject: Implemented Last-Modified HTTP header metric (#407)
X-Git-Url: https://vcs.fsf.org/?a=commitdiff_plain;h=844641a4704570c718fb96d990255a34290236d6;p=blackbox_exporter.git

Implemented Last-Modified HTTP header metric (#407)

This feature returns a probe_http_last_modified metric with the content
of the Last-Modified HTTP response header, if it is set by the server.

Signed-off-by: Johannes Visintini <johannes.visintini@uni-heidelberg.de>
---

diff --git a/prober/http.go b/prober/http.go
index ed58b96..9aa6104 100644
--- a/prober/http.go
+++ b/prober/http.go
@@ -172,6 +172,11 @@ func ProbeHTTP(ctx context.Context, target string, module config.Module, registr
 			Name: "probe_failed_due_to_regex",
 			Help: "Indicates if probe failed due to regex",
 		})
+
+		probeHTTPLastModified = prometheus.NewGauge(prometheus.GaugeOpts{
+			Name: "probe_http_last_modified_timestamp_seconds",
+			Help: "Returns the Last-Modified HTTP response header in unixtime",
+		})
 	)
 
 	for _, lv := range []string{"resolve", "connect", "tls", "processing", "transfer"} {
@@ -337,6 +342,12 @@ func ProbeHTTP(ctx context.Context, target string, module config.Module, registr
 		// At this point body is fully read and we can write end time.
 		tt.current.end = time.Now()
 
+		// Check if there is a Last-Modified HTTP response header.
+		if t, err := http.ParseTime(resp.Header.Get("Last-Modified")); err == nil {
+			registry.MustRegister(probeHTTPLastModified)
+			probeHTTPLastModified.Set(float64(t.Unix()))
+		}
+
 		var httpVersionNumber float64
 		httpVersionNumber, err = strconv.ParseFloat(strings.TrimPrefix(resp.Proto, "HTTP/"), 64)
 		if err != nil {