return tenants in http header

Author: yuchen-db

cmd/thanos/receive.go

@@ -7,7 +7,7 @@ import (
 	"context"
 	"fmt"
 	"net"
-  "net/http"
+	"net/http"
 	"os"
 	"path"
 	"strconv"
@@ -325,8 +325,12 @@ func runReceive(
 			httpserver.WithTLSConfig(*conf.httpTLSConfig),
 		)
 		srv.Handle("/-/downscale", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-			n := dbs.GetTenantsLen()
+			tenants := dbs.GetTenants()
+			n := len(tenants)
 			w.Header().Set("Tenant-Count", strconv.Itoa(n))
+			for _, tname := range tenants {
+				w.Header().Add("Tenants", tname)
+			}
 			if n > 0 {
 				w.WriteHeader(http.StatusTooEarly)
 			} else {

pkg/receive/multitsdb.go

@@ -122,10 +122,14 @@ func NewMultiTSDB(
 	return mt
 }
 
-func (t *MultiTSDB) GetTenantsLen() int {
+func (t *MultiTSDB) GetTenants() []string {
 	t.mtx.RLock()
+	tenants := make([]string, 0, len(t.tenants))
+	for tname := range t.tenants {
+		tenants = append(tenants, tname)
+	}
 	defer t.mtx.RUnlock()
-	return len(t.tenants)
+	return tenants
 }
 
 type localClient struct {