metricsreader, elect: read metrics from zone leader (#611)

Author: djshow832

lib/config/label.go

@@ -0,0 +1,17 @@
+// Copyright 2024 PingCAP, Inc.
+// SPDX-License-Identifier: Apache-2.0
+
+package config
+
+const (
+	// LocationLabelName indicates the label name that decides the location of TiProxy and backends.
+	// We use `zone` because the follower read in TiDB also uses `zone` to decide location.
+	LocationLabelName = "zone"
+)
+
+func (cfg *Config) GetLocation() string {
+	if len(cfg.Labels) == 0 {
+		return ""
+	}
+	return cfg.Labels[LocationLabelName]
+}

lib/config/proxy.go

@@ -13,7 +13,6 @@ import (
 
 	"github.com/BurntSushi/toml"
 	"github.com/pingcap/tiproxy/lib/util/errors"
-	"github.com/pingcap/tiproxy/lib/util/sys"
 )
 
 var (
@@ -224,8 +223,17 @@ func (cfg *Config) GetIPPort() (ip, port, statusPort string, err error) {
 		// reporting a non unicast IP makes no sense, try to find one
 		// loopback/linklocal-unicast are not global unicast IP, but are valid local unicast IP
 		if pip := net.ParseIP(ip); ip == "" || pip.Equal(net.IPv4bcast) || pip.IsUnspecified() || pip.IsMulticast() {
-			if v := sys.GetGlobalUnicastIP(); v != "" {
-				ip = v
+			if addrs, err := net.InterfaceAddrs(); err == nil {
+				for _, address := range addrs {
+					if ipnet, ok := address.(*net.IPNet); ok && ipnet.IP.IsGlobalUnicast() {
+						ipStr := ipnet.IP.String()
+						// filter virtual IP
+						if !strings.HasPrefix(cfg.HA.VirtualIP, ipStr) {
+							ip = ipStr
+							break
+						}
+					}
+				}
 			}
 		}
 	}

pkg/balance/factor/mock_test.go

@@ -14,7 +14,6 @@ import (
 	"github.com/pingcap/tiproxy/pkg/balance/observer"
 	"github.com/pingcap/tiproxy/pkg/balance/policy"
 	"github.com/prometheus/common/model"
-	clientv3 "go.etcd.io/etcd/client/v3"
 )
 
 var _ policy.BackendCtx = (*mockBackend)(nil)
@@ -103,7 +102,7 @@ func newMockMetricsReader() *mockMetricsReader {
 	}
 }
 
-func (mmr *mockMetricsReader) Start(ctx context.Context, etcdCli *clientv3.Client) error {
+func (mmr *mockMetricsReader) Start(ctx context.Context) error {
 	return nil
 }
 
@@ -117,6 +116,10 @@ func (mmr *mockMetricsReader) GetQueryResult(key string) metricsreader.QueryResu
 	return mmr.qrs[key]
 }
 
+func (mmr *mockMetricsReader) GetBackendMetrics() []byte {
+	return nil
+}
+
 func (mmr *mockMetricsReader) Close() {
 }