blackbox: Introduce probe type

We're about to introduce a new probe type for HTTP-based pushes. As a
preparatory step, add a new probe type to the blackbox configuration
which allows the admin to discern between these types. For now, only
"fetch" probes are supported -- "push" probes will be added in a
subsequent commit. In order to maintain backwards compatibility with old
configurations, specifying no type will fall back to "fetch" probes.

3 files changed, 52 insertions, 9 deletions

diff --git a/internal/blackbox/blackbox.go b/internal/blackbox/blackbox.go
index 4dac46eee..e9259a78e 100644
--- a/internal/blackbox/blackbox.go
+++ b/internal/blackbox/blackbox.go
@@ -2,6 +2,7 @@ package blackbox
 
 import (
 	"context"
+	"fmt"
 	"net"
 	"time"
 
@@ -137,7 +138,25 @@ func (b Blackbox) Run() error {
 func (b Blackbox) runProbes() {
 	for ; ; time.Sleep(b.cfg.sleepDuration) {
 		for _, probe := range b.cfg.Probes {
-			b.doProbe(probe)
+			entry := log.WithFields(map[string]interface{}{
+				"probe": probe.Name,
+				"type":  probe.Type,
+			})
+
+			entry.Info("starting probe")
+
+			var err error
+			switch probe.Type {
+			case Fetch:
+				err = b.fetch(probe)
+			default:
+				err = fmt.Errorf("unsupported probe type: %q", probe.Type)
+			}
+			if err != nil {
+				entry.WithError(err).Error("probe failed")
+			}
+
+			entry.Info("finished probe")
 		}
 	}
 }
@@ -149,21 +168,15 @@ func servePrometheus(l net.Listener) error {
 	)
 }
 
-func (b Blackbox) doProbe(probe Probe) {
+func (b Blackbox) fetch(probe Probe) error {
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
 
-	entry := log.WithField("probe", probe.Name)
-	entry.Info("starting probe")
-
 	clone, err := stats.PerformHTTPClone(ctx, probe.URL, probe.User, probe.Password, false)
 	if err != nil {
-		entry.WithError(err).Error("probe failed")
-		return
+		return err
 	}
 
-	entry.Info("finished probe")
-
 	setGauge := func(gv *prometheus.GaugeVec, value float64) {
 		gv.WithLabelValues(probe.Name).Set(value)
 	}
@@ -171,4 +184,6 @@ func (b Blackbox) doProbe(probe Probe) {
 	b.fetchReferenceDiscoveryMetrics.measure(probe.Name, clone.ReferenceDiscovery)
 	b.httpPostMetrics.measure(probe.Name, &clone.FetchPack)
 	setGauge(b.wantedRefs, float64(clone.FetchPack.RefsWanted()))
+
+	return nil
 }
diff --git a/internal/blackbox/config.go b/internal/blackbox/config.go
index 6e8da380b..8f966c67d 100644
--- a/internal/blackbox/config.go
+++ b/internal/blackbox/config.go
@@ -24,11 +24,23 @@ type Config struct {
 	Probes []Probe `toml:"probe"`
 }
 
+// ProbeType is the type of the probe.
+type ProbeType string
+
+const (
+	// Fetch exercises the equivalent of git-fetch(1) with measurements for packfile negotiation
+	// and receiving the packfile.
+	Fetch = ProbeType("fetch")
+)
+
 // Probe is the configuration for a specific endpoint whose clone performance should be exercised.
 type Probe struct {
 	// Name is the name of the probe. This is used both for logging and for exported
 	// Prometheus metrics.
 	Name string `toml:"name"`
+	// Type is the type of the probe. See ProbeType for the supported types. Defaults to `Fetch`
+	// if no type was given.
+	Type ProbeType `toml:"type"`
 	// URL is the URL of the Git repository that should be probed. For now, only the
 	// HTTP transport is supported.
 	URL string `toml:"url"`
@@ -68,6 +80,13 @@ func ParseConfig(raw string) (Config, error) {
 			return Config{}, fmt.Errorf("all probes must have a 'name' attribute")
 		}
 
+		switch probe.Type {
+		case "", Fetch:
+			probe.Type = Fetch
+		default:
+			return Config{}, fmt.Errorf("unsupported probe type: %q", probe.Type)
+		}
+
 		parsedURL, err := url.Parse(probe.URL)
 		if err != nil {
 			return Config{}, err
diff --git a/internal/blackbox/config_test.go b/internal/blackbox/config_test.go
index 9e240761b..be11c89d5 100644
--- a/internal/blackbox/config_test.go
+++ b/internal/blackbox/config_test.go
@@ -49,9 +49,18 @@ func TestConfigParseFailures(t *testing.T) {
 			expectedErr: errors.New("missing prometheus_listen_addr"),
 		},
 		{
+			desc:        "invalid probe type",
+			in:          "prometheus_listen_addr = 'foo'\n[[probe]]\nname='foo'\nurl='http://foo/bar'\ntype='foo'",
+			expectedErr: errors.New("unsupported probe type: \"foo\""),
+		},
+		{
 			desc: "valid configuration",
 			in:   "prometheus_listen_addr = 'foo'\n[[probe]]\nname='foo'\nurl='http://foo/bar'\n",
 		},
+		{
+			desc: "valid configuration with explicit type",
+			in:   "prometheus_listen_addr = 'foo'\n[[probe]]\nname='foo'\nurl='http://foo/bar'\ntype='fetch'",
+		},
 	}
 
 	for _, tc := range testCases {