Retrieval: Make it possible to relabel query params

This only allows relabelling the first value
for a given parameter, this should be sufficient in practice.

Godeps/Godeps.json

@@ -44,23 +44,19 @@
 		},
 		{
 			"ImportPath": "github.com/prometheus/client_golang/extraction",
-			"Comment": "0.7.0",
+			"Rev": "3a499bf7fc46bc58337ce612d0cbb29c550b8118"
-			"Rev": "6dbab8106ed3ed77359ac85d9cf08e30290df864"
 		},
 		{
 			"ImportPath": "github.com/prometheus/client_golang/model",
-			"Comment": "0.7.0",
+			"Rev": "3a499bf7fc46bc58337ce612d0cbb29c550b8118"
-			"Rev": "6dbab8106ed3ed77359ac85d9cf08e30290df864"
 		},
 		{
 			"ImportPath": "github.com/prometheus/client_golang/prometheus",
-			"Comment": "0.7.0",
+			"Rev": "3a499bf7fc46bc58337ce612d0cbb29c550b8118"
-			"Rev": "6dbab8106ed3ed77359ac85d9cf08e30290df864"
 		},
 		{
 			"ImportPath": "github.com/prometheus/client_golang/text",
-			"Comment": "0.7.0",
+			"Rev": "3a499bf7fc46bc58337ce612d0cbb29c550b8118"
-			"Rev": "6dbab8106ed3ed77359ac85d9cf08e30290df864"
 		},
 		{
 			"ImportPath": "github.com/prometheus/client_model/go",

Godeps/_workspace/src/github.com/prometheus/client_golang/model/labelname.go

@@ -46,6 +46,10 @@ const (
 	// will not be attached to time series.
 	MetaLabelPrefix = "__meta_"
 
+	// ParamLabelPrefix is a prefix for labels that provide URL parameters
+	// used to scrape a target.
+	ParamLabelPrefix = "__param_"
+
 	// JobLabel is the label name indicating the job from which a timeseries
 	// was scraped.
 	JobLabel LabelName = "job"

retrieval/target.go

@@ -197,10 +197,24 @@ func (t *Target) Update(cfg *config.ScrapeConfig, baseLabels, metaLabels clientm
 
 	t.url.Scheme = cfg.Scheme
 	t.url.Path = string(baseLabels[clientmodel.MetricsPathLabel])
+	params := url.Values{}
+	for k, v := range cfg.Params {
+		params[k] = make([]string, len(v))
+		copy(params[k], v)
+	}
+	for k, v := range baseLabels {
+		if strings.HasPrefix(string(k), clientmodel.ParamLabelPrefix) {
+			if len(params[string(k[len(clientmodel.ParamLabelPrefix):])]) > 0 {
+				params[string(k[len(clientmodel.ParamLabelPrefix):])][0] = string(v)
+			} else {
+				params[string(k[len(clientmodel.ParamLabelPrefix):])] = []string{string(v)}
+			}
+		}
+	}
+	t.url.RawQuery = params.Encode()
 	if cfg.BasicAuth != nil {
 		t.url.User = url.UserPassword(cfg.BasicAuth.Username, cfg.BasicAuth.Password)
 	}
-	t.url.RawQuery = cfg.Params.Encode()
 
 	t.scrapeInterval = time.Duration(cfg.ScrapeInterval)
 	t.deadline = time.Duration(cfg.ScrapeTimeout)

retrieval/target_test.go

@@ -390,6 +390,49 @@ func BenchmarkScrape(b *testing.B) {
 	}
 }
 
+func TestURLParams(t *testing.T) {
+	server := httptest.NewServer(
+		http.HandlerFunc(
+			func(w http.ResponseWriter, r *http.Request) {
+				w.Header().Set("Content-Type", `text/plain; version=0.0.4`)
+				w.Write([]byte{})
+				r.ParseForm()
+				if r.Form["foo"][0] != "bar" {
+					t.Fatalf("URL parameter 'foo' had unexpected first value '%v'", r.Form["foo"][0])
+				}
+				if r.Form["foo"][1] != "baz" {
+					t.Fatalf("URL parameter 'foo' had unexpected second value '%v'", r.Form["foo"][1])
+				}
+			},
+		),
+	)
+	defer server.Close()
+	serverURL, err := url.Parse(server.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	target := NewTarget(
+		&config.ScrapeConfig{
+			JobName:        "test_job1",
+			ScrapeInterval: config.Duration(1 * time.Minute),
+			ScrapeTimeout:  config.Duration(1 * time.Second),
+			Scheme:         serverURL.Scheme,
+			Params: url.Values{
+				"foo": []string{"bar", "baz"},
+			},
+		},
+		clientmodel.LabelSet{
+			clientmodel.AddressLabel: clientmodel.LabelValue(serverURL.Host),
+			"__param_foo":            "bar",
+		},
+		nil)
+	app := &collectResultAppender{}
+	if err = target.scrape(app); err != nil {
+		t.Fatal(err)
+	}
+}
+
 func newTestTarget(targetURL string, deadline time.Duration, baseLabels clientmodel.LabelSet) *Target {
 	t := &Target{
 		url: &url.URL{

retrieval/targetmanager.go

@@ -329,6 +329,11 @@ func (tm *TargetManager) targetsFromGroup(tg *config.TargetGroup, cfg *config.Sc
 			}
 			labels[clientmodel.AddressLabel] = clientmodel.LabelValue(addr)
 		}
+		for k, v := range cfg.Params {
+			if len(v) > 0 {
+				labels[clientmodel.LabelName(clientmodel.ParamLabelPrefix+k)] = clientmodel.LabelValue(v[0])
+			}
+		}
 		// Copy labels into the labelset for the target if they are not
 		// set already. Apply the labelsets in order of decreasing precedence.
 		labelsets := []clientmodel.LabelSet{

retrieval/targetmanager_test.go

@@ -14,6 +14,7 @@
 package retrieval
 
 import (
+	"net/url"
 	"reflect"
 	"regexp"
 	"testing"
@@ -157,12 +158,25 @@ func TestTargetManagerConfigUpdate(t *testing.T) {
 	testJob1 := &config.ScrapeConfig{
 		JobName:        "test_job1",
 		ScrapeInterval: config.Duration(1 * time.Minute),
+		Params: url.Values{
+			"testParam": []string{"paramValue", "secondValue"},
+		},
 		TargetGroups: []*config.TargetGroup{{
 			Targets: []clientmodel.LabelSet{
 				{clientmodel.AddressLabel: "example.org:80"},
 				{clientmodel.AddressLabel: "example.com:80"},
 			},
 		}},
+		RelabelConfigs: []*config.RelabelConfig{
+			{
+				// Copy out the URL parameter.
+				SourceLabels: clientmodel.LabelNames{"__param_testParam"},
+				Regex:        &config.Regexp{*regexp.MustCompile("^(.*)$")},
+				TargetLabel:  "testParam",
+				Replacement:  "$1",
+				Action:       config.RelabelReplace,
+			},
+		},
 	}
 	testJob2 := &config.ScrapeConfig{
 		JobName:        "test_job2",
@@ -226,24 +240,24 @@ func TestTargetManagerConfigUpdate(t *testing.T) {
 			scrapeConfigs: []*config.ScrapeConfig{testJob1},
 			expected: map[string][]clientmodel.LabelSet{
 				"test_job1:static:0": {
-					{clientmodel.JobLabel: "test_job1", clientmodel.InstanceLabel: "example.org:80"},
+					{clientmodel.JobLabel: "test_job1", clientmodel.InstanceLabel: "example.org:80", "testParam": "paramValue"},
-					{clientmodel.JobLabel: "test_job1", clientmodel.InstanceLabel: "example.com:80"},
+					{clientmodel.JobLabel: "test_job1", clientmodel.InstanceLabel: "example.com:80", "testParam": "paramValue"},
 				},
 			},
 		}, {
 			scrapeConfigs: []*config.ScrapeConfig{testJob1},
 			expected: map[string][]clientmodel.LabelSet{
 				"test_job1:static:0": {
-					{clientmodel.JobLabel: "test_job1", clientmodel.InstanceLabel: "example.org:80"},
+					{clientmodel.JobLabel: "test_job1", clientmodel.InstanceLabel: "example.org:80", "testParam": "paramValue"},
-					{clientmodel.JobLabel: "test_job1", clientmodel.InstanceLabel: "example.com:80"},
+					{clientmodel.JobLabel: "test_job1", clientmodel.InstanceLabel: "example.com:80", "testParam": "paramValue"},
 				},
 			},
 		}, {
 			scrapeConfigs: []*config.ScrapeConfig{testJob1, testJob2},
 			expected: map[string][]clientmodel.LabelSet{
 				"test_job1:static:0": {
-					{clientmodel.JobLabel: "test_job1", clientmodel.InstanceLabel: "example.org:80"},
+					{clientmodel.JobLabel: "test_job1", clientmodel.InstanceLabel: "example.org:80", "testParam": "paramValue"},
-					{clientmodel.JobLabel: "test_job1", clientmodel.InstanceLabel: "example.com:80"},
+					{clientmodel.JobLabel: "test_job1", clientmodel.InstanceLabel: "example.com:80", "testParam": "paramValue"},
 				},
 				"test_job2:static:0": {
 					{clientmodel.JobLabel: "test_job2", clientmodel.InstanceLabel: "example.org:8080", "foo": "bar", "new": "ox-ba"},