Adds the possibility to vary the template of tablet debug urls.

go/vt/discovery/healthcheck.go

@@ -39,6 +39,7 @@ package discovery
 import (
 	"bytes"
 	"encoding/json"
+	"flag"
 	"fmt"
 	"html/template"
 	"net/http"
@@ -47,9 +48,8 @@ import (
 	"sync"
 	"time"
 
-	"golang.org/x/net/context"
-
 	"github.com/golang/protobuf/proto"
+	"golang.org/x/net/context"
 	"vitess.io/vitess/go/netutil"
 	"vitess.io/vitess/go/stats"
 	"vitess.io/vitess/go/vt/grpcclient"
@@ -67,6 +67,8 @@ var (
 	hcErrorCounters          = stats.NewCountersWithMultiLabels("HealthcheckErrors", "Healthcheck Errors", []string{"Keyspace", "ShardName", "TabletType"})
 	hcMasterPromotedCounters = stats.NewCountersWithMultiLabels("HealthcheckMasterPromoted", "Master promoted in keyspace/shard name because of health check errors", []string{"Keyspace", "ShardName"})
 	healthcheckOnce          sync.Once
+	tabletURLTemplateString  = flag.String("tablet_url_template", "http://{{.GetTabletHostPort}}", "format string describing debug tablet url formatting. See the Go code for getTabletDebugURL() how to customize this.")
+	tabletURLTemplate        *template.Template
 )
 
 // See the documentation for NewHealthCheck below for an explanation of these parameters.
@@ -117,6 +119,20 @@ const (
 `
 )
 
+func init() {
+	loadTabletURLTemplate()
+}
+
+// loadTabletURLTemplate loads or reloads the URL template.
+// Should only be used independently for testing.
+func loadTabletURLTemplate() {
+	tabletURLTemplate = template.New("")
+	_, err := tabletURLTemplate.Parse(*tabletURLTemplateString)
+	if err != nil {
+		log.Exitf("error parsing template: %v", err)
+	}
+}
+
 // HealthCheckStatsListener is the listener to receive health check stats update.
 type HealthCheckStatsListener interface {
 	// StatsUpdate is called when:
@@ -187,6 +203,44 @@ func (e *TabletStats) DeepEqual(f *TabletStats) bool {
 			(e.LastError != nil && f.LastError != nil && e.LastError.Error() == f.LastError.Error()))
 }
 
+// GetTabletHostPort formats a tablet host port address.
+func (e TabletStats) GetTabletHostPort() string {
+	vtPort := e.Tablet.PortMap["vt"]
+	return netutil.JoinHostPort(e.Tablet.Hostname, vtPort)
+}
+
+// GetHostNameLevel returns the specified hostname level. If the level does not exist it will pick the closest level.
+// This seems unused but can be utilized by certain url formatting templates. See getTabletDebugURL for more details.
+func (e TabletStats) GetHostNameLevel(level int) string {
+	chunkedHostname := strings.Split(e.Tablet.Hostname, ".")
+
+	if level < 0 {
+		return chunkedHostname[0]
+	} else if level >= len(chunkedHostname) {
+		return chunkedHostname[len(chunkedHostname)-1]
+	} else {
+		return chunkedHostname[level]
+	}
+}
+
+// getTabletDebugURL formats a debug url to the tablet.
+// It uses a format string that can be passed into the app to format
+// the debug URL to accommodate different network setups. It applies
+// the html/template string defined to a TabletStats object. The
+// format string can refer to members and functions of TabletStats
+// like a regular html/template string.
+//
+// For instance given a tablet with hostname:port of host.dc.domain:22
+// could be configured as follows:
+// http://{{.GetTabletHostPort}} -> http://host.dc.domain:22
+// https://{{.Tablet.Hostname}} -> https://host.dc.domain
+// https://{{.GetHostNameLevel 0}}.bastion.corp -> https://host.bastion.corp
+func (e TabletStats) getTabletDebugURL() string {
+	var buffer bytes.Buffer
+	tabletURLTemplate.Execute(&buffer, e)
+	return buffer.String()
+}
+
 // HealthCheck defines the interface of health checking module.
 // The goal of this object is to maintain a StreamHealth RPC
 // to a lot of tablets. Tablets are added / removed by calling the
@@ -737,7 +791,6 @@ func (tcs *TabletsCacheStatus) StatusAsHTML() template.HTML {
 		sort.Sort(tcs.TabletsStats)
 	}
 	for _, ts := range tcs.TabletsStats {
-		vtPort := ts.Tablet.PortMap["vt"]
 		color := "green"
 		extra := ""
 		if ts.LastError != nil {
@@ -755,11 +808,10 @@ func (tcs *TabletsCacheStatus) StatusAsHTML() template.HTML {
 			extra = fmt.Sprintf(" (RepLag: %v)", ts.Stats.SecondsBehindMaster)
 		}
 		name := ts.Name
-		addr := netutil.JoinHostPort(ts.Tablet.Hostname, vtPort)
 		if name == "" {
-			name = addr
+			name = ts.GetTabletHostPort()
 		}
-		tLinks = append(tLinks, fmt.Sprintf(`<a href="http://%s" style="color:%v">%v</a>%v`, addr, color, name, extra))
+		tLinks = append(tLinks, fmt.Sprintf(`<a href="%s" style="color:%v">%v</a>%v`, ts.getTabletDebugURL(), color, name, extra))
 	}
 	return template.HTML(strings.Join(tLinks, "<br>"))
 }

go/vt/discovery/healthcheck_test.go

@@ -23,6 +23,8 @@ import (
 	"html/template"
 	"io"
 	"reflect"
+	"strings"
+	"sync"
 	"testing"
 	"time"
 
@@ -35,9 +37,6 @@ import (
 	"vitess.io/vitess/go/vt/vttablet/queryservice/fakes"
 	"vitess.io/vitess/go/vt/vttablet/tabletconn"
 
-	"strings"
-	"sync"
-
 	querypb "vitess.io/vitess/go/vt/proto/query"
 	topodatapb "vitess.io/vitess/go/vt/proto/topodata"
 )
@@ -573,6 +572,42 @@ func TestTemplate(t *testing.T) {
 	}
 }
 
+func TestDebugURLFormatting(t *testing.T) {
+	flag.Set("tablet_url_template", "https://{{.GetHostNameLevel 0}}.bastion.{{.Tablet.Alias.Cell}}.corp")
+	loadTabletURLTemplate()
+
+	tablet := topo.NewTablet(0, "cell", "host.dc.domain")
+	ts := []*TabletStats{
+		{
+			Key:     "a",
+			Tablet:  tablet,
+			Target:  &querypb.Target{Keyspace: "k", Shard: "s", TabletType: topodatapb.TabletType_REPLICA},
+			Up:      true,
+			Serving: false,
+			Stats:   &querypb.RealtimeStats{SecondsBehindMaster: 1, CpuUsage: 0.3},
+			TabletExternallyReparentedTimestamp: 0,
+		},
+	}
+	tcs := &TabletsCacheStatus{
+		Cell:         "cell",
+		Target:       &querypb.Target{Keyspace: "k", Shard: "s", TabletType: topodatapb.TabletType_REPLICA},
+		TabletsStats: ts,
+	}
+	templ := template.New("").Funcs(status.StatusFuncs)
+	templ, err := templ.Parse(HealthCheckTemplate)
+	if err != nil {
+		t.Fatalf("error parsing template: %v", err)
+	}
+	wr := &bytes.Buffer{}
+	if err := templ.Execute(wr, []*TabletsCacheStatus{tcs}); err != nil {
+		t.Fatalf("error executing template: %v", err)
+	}
+	expectedURL := `"https://host.bastion.cell.corp"`
+	if !strings.Contains(wr.String(), expectedURL) {
+		t.Fatalf("output missing formatted URL, expectedURL: %s , output: %s", expectedURL, wr.String())
+	}
+}
+
 type listener struct {
 	output chan *TabletStats
 }