unified-storage: setup ring to shard requests (#103783)

* Updates the instrumentation_server service to use mux instead of the builtin router, and have it store the router in the module server: this is so we can register the /ring endpoint to check the status of the ring
* Create a new Ring service that depends on the instrumentation server and declares it as a dependency for the storage server
* Create standalone MemberlistKV service for Ring service to use
* Update the storage server Search and GetStats handler to distribute requests if applicable

pkg/server/memberlist.go

@@ -0,0 +1,53 @@
+package server
+
+import (
+	"github.com/grafana/dskit/dns"
+	"github.com/grafana/dskit/flagext"
+	"github.com/grafana/dskit/kv"
+	"github.com/grafana/dskit/kv/codec"
+	"github.com/grafana/dskit/kv/memberlist"
+	"github.com/grafana/dskit/ring"
+	"github.com/grafana/dskit/services"
+	"github.com/grafana/grafana/pkg/infra/log"
+	"github.com/grafana/grafana/pkg/setting"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+func (ms *ModuleServer) initMemberlistKV() (services.Service, error) {
+	logger := log.New("memberlist")
+
+	dnsProviderReg := prometheus.WrapRegistererWithPrefix(
+		"grafana",
+		prometheus.WrapRegistererWith(
+			prometheus.Labels{"component": "memberlist"},
+			ms.registerer,
+		),
+	)
+	dnsProvider := dns.NewProvider(logger, dnsProviderReg, dns.GolangResolverType)
+
+	KVStore := kv.Config{Store: "memberlist"}
+
+	memberlistKVsvc := memberlist.NewKVInitService(toMemberlistConfig(ms.cfg), logger, dnsProvider, ms.registerer)
+	KVStore.MemberlistKV = memberlistKVsvc.GetMemberlistKV
+
+	ms.MemberlistKVConfig = KVStore
+
+	return memberlistKVsvc, nil
+}
+
+func toMemberlistConfig(cfg *setting.Cfg) *memberlist.KVConfig {
+	memberlistKVcfg := &memberlist.KVConfig{}
+	flagext.DefaultValues(memberlistKVcfg)
+	memberlistKVcfg.Codecs = []codec.Codec{
+		ring.GetCodec(),
+	}
+	if cfg.MemberlistBindAddr != "" {
+		memberlistKVcfg.TCPTransport.BindAddrs = []string{cfg.MemberlistBindAddr}
+	}
+	if cfg.MemberlistAdvertiseAddr != "" {
+		memberlistKVcfg.AdvertiseAddr = cfg.MemberlistAdvertiseAddr
+	}
+	memberlistKVcfg.JoinMembers = []string{cfg.MemberlistJoinMember}
+
+	return memberlistKVcfg
+}