lib/promscrape: properly detect IPv6 address for docker discovery

Previously service discovery was not able to discover IP address at IPv6 only networks.

 This commit adds fall-back for GlobalIPv6Address field at container
network.

Fixes https://github.com/VictoriaMetrics/VictoriaMetrics/issues/10965

docs/victoriametrics/changelog/CHANGELOG.md

@@ -45,6 +45,7 @@ See also [LTS releases](https://docs.victoriametrics.com/victoriametrics/lts-rel
 
 * BUGFIX: [MetricsQL](https://docs.victoriametrics.com/victoriametrics/metricsql/): properly drop data points filtered out by an inner [comparison operation](https://prometheus.io/docs/prometheus/latest/querying/operators/#comparison-binary-operators) when its result is used on the right side of another comparison. Previously, queries like `foo != (bar > 100)` could return unexpected results because filtered-out data points are represented internally as `NaN`, and `value != NaN` evaluates to `true`. Comparisons against explicitly present `NaN` values keep the previous behavior. See [#10018](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/10018). Thanks to @zasdaym for contribution.
 * BUGFIX: [vmagent](https://docs.victoriametrics.com/victoriametrics/vmagent/) and [vmsingle](https://docs.victoriametrics.com/victoriametrics/single-server-victoriametrics/): ignore HTTP proxy environment variables when scraping targets over Unix domain sockets. See [#11318](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/11318). Thanks to @lwmacct for contribution.
+ BUGFIX: [vmagent](https://docs.victoriametrics.com/victoriametrics/vmagent/) and [vmsingle](https://docs.victoriametrics.com/victoriametrics/single-server-victoriametrics/): properly assign scrape target IP address at IPv6-only networks for [docker_sd_configs](https://docs.victoriametrics.com/victoriametrics/sd_configs/#docker_sd_configs). See [#10965](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/10965).
 * BUGFIX: [vmalert](https://docs.victoriametrics.com/victoriametrics/vmalert/): fixed the display of rule state badges on the `Groups` page in the web UI. See [#11160](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/11160).
 * BUGFIX: [vmbackupmanager](https://docs.victoriametrics.com/victoriametrics/vmbackupmanager/): previously, `vmbackupmanager` was crashing on startup when it failed to restore backup state from remote storage, causing a crash loop. Now it logs the error and continues running, retrying the state restore before each scheduled backup. Added `vm_backup_errors_total{type="restoreState"}` metric to track backup state restore failures. See [#11217](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/11217).
 

lib/promscrape/discovery/docker/container.go

@@ -37,8 +37,9 @@ type containerNetworkSettings struct {
 }
 
 type containerNetwork struct {
-	IPAddress string
-	NetworkID string
+	GlobalIPv6Address string
+	IPAddress         string
+	NetworkID         string
 }
 
 func getContainersLabels(cfg *apiConfig) ([]*promutil.Labels, error) {
@@ -118,14 +119,18 @@ func addContainersLabels(containers []container, networkLabels map[string]*promu
 			networks = map[string]containerNetwork{firstNetworkMode: firstNetwork}
 		}
 		for _, n := range networks {
+			ipAddress := n.IPAddress
+			if len(ipAddress) == 0 {
+				ipAddress = n.GlobalIPv6Address
+			}
 			var added bool
 			for _, p := range c.Ports {
 				if p.Type != "tcp" {
 					continue
 				}
 				m := promutil.NewLabels(16)
-				m.Add("__address__", discoveryutil.JoinHostPort(n.IPAddress, p.PrivatePort))
-				m.Add("__meta_docker_network_ip", n.IPAddress)
+				m.Add("__address__", discoveryutil.JoinHostPort(ipAddress, p.PrivatePort))
+				m.Add("__meta_docker_network_ip", ipAddress)
 				m.Add("__meta_docker_port_private", strconv.Itoa(p.PrivatePort))
 				if p.PublicPort > 0 {
 					m.Add("__meta_docker_port_public", strconv.Itoa(p.PublicPort))
@@ -141,11 +146,11 @@ func addContainersLabels(containers []container, networkLabels map[string]*promu
 				// Use fallback port when no exposed ports are available or if all are non-TCP
 				addr := hostNetworkingHost
 				if c.HostConfig.NetworkMode != "host" {
-					addr = discoveryutil.JoinHostPort(n.IPAddress, defaultPort)
+					addr = discoveryutil.JoinHostPort(ipAddress, defaultPort)
 				}
 				m := promutil.NewLabels(16)
 				m.Add("__address__", addr)
-				m.Add("__meta_docker_network_ip", n.IPAddress)
+				m.Add("__meta_docker_network_ip", ipAddress)
 				addCommonLabels(m, c, networkLabels[n.NetworkID])
 				// Remove possible duplicate labels, which can appear after addCommonLabels() call
 				m.RemoveDuplicates()

lib/promscrape/discovery/docker/container_test.go

@@ -431,6 +431,96 @@ func TestAddContainerLabels(t *testing.T) {
 		}),
 	}
 	f(c, networkLabels, labelssExpected)
+
+	data = []byte(`[
+  {
+    "Name": "bridge",
+    "Id": "1dd8d1a8bef59943345c7231d7ce8268333ff5a8c5b3c94881e6b4742b447634",
+    "Created": "2021-03-18T14:36:04.290821903+08:00",
+    "Scope": "local",
+    "Driver": "bridge",
+    "EnableIPv6": true,
+    "IPAM": {
+      "Driver": "default",
+      "Options": null,
+      "Config": [
+        {
+          "Subnet": "fc00::/64",
+          "Gateway": "fc00::1"
+        }
+      ]
+    },
+    "Internal": false,
+    "Attachable": false,
+    "Ingress": false,
+    "ConfigFrom": {
+      "Network": ""
+    },
+    "ConfigOnly": false,
+    "Containers": {},
+    "Options": {
+      "com.docker.network.bridge.default_bridge": "true",
+      "com.docker.network.bridge.enable_icc": "true",
+      "com.docker.network.bridge.enable_ip_masquerade": "true",
+      "com.docker.network.bridge.host_binding_ipv4": "0.0.0.0",
+      "com.docker.network.bridge.name": "docker0",
+      "com.docker.network.driver.mtu": "1500"
+    },
+    "Labels": {}
+  }
+]`)
+	networks, err = parseNetworks(data)
+	if err != nil {
+		t.Fatalf("fail to parse networks: %v", err)
+	}
+	networkLabels = getNetworkLabelsByNetworkID(networks)
+
+	// NetworkMode != host
+	c = container{
+		ID:    "90bc3b31aa13da5c0b11af2e228d54b38428a84e25d4e249ae9e9c95e51a0700",
+		Names: []string{"/crow-server"},
+		Labels: map[string]string{
+			"com.docker.compose.config-hash":      "c9f0bd5bb31921f94cff367d819a30a0cc08d4399080897a6c5cd74b983156ec",
+			"com.docker.compose.container-number": "1",
+			"com.docker.compose.oneoff":           "False",
+			"com.docker.compose.project":          "crowserver",
+			"com.docker.compose.service":          "crow-server",
+			"com.docker.compose.version":          "1.11.2",
+		},
+		HostConfig: containerHostConfig{
+			NetworkMode: "bridge",
+		},
+		NetworkSettings: containerNetworkSettings{
+			Networks: map[string]containerNetwork{
+				"bridge": {
+					GlobalIPv6Address: "fc00::2",
+					NetworkID:         "1dd8d1a8bef59943345c7231d7ce8268333ff5a8c5b3c94881e6b4742b447634",
+				},
+			},
+		},
+	}
+	labelssExpected = []*promutil.Labels{
+		promutil.NewLabelsFromMap(map[string]string{
+			"__address__":                "[fc00::2]:8012",
+			"__meta_docker_container_id": "90bc3b31aa13da5c0b11af2e228d54b38428a84e25d4e249ae9e9c95e51a0700",
+			"__meta_docker_container_label_com_docker_compose_config_hash":      "c9f0bd5bb31921f94cff367d819a30a0cc08d4399080897a6c5cd74b983156ec",
+			"__meta_docker_container_label_com_docker_compose_container_number": "1",
+			"__meta_docker_container_label_com_docker_compose_oneoff":           "False",
+			"__meta_docker_container_label_com_docker_compose_project":          "crowserver",
+			"__meta_docker_container_label_com_docker_compose_service":          "crow-server",
+			"__meta_docker_container_label_com_docker_compose_version":          "1.11.2",
+			"__meta_docker_container_name":                                      "/crow-server",
+			"__meta_docker_container_network_mode":                              "bridge",
+			"__meta_docker_network_id":                                          "1dd8d1a8bef59943345c7231d7ce8268333ff5a8c5b3c94881e6b4742b447634",
+			"__meta_docker_network_ingress":                                     "false",
+			"__meta_docker_network_internal":                                    "false",
+			"__meta_docker_network_ip":                                          "fc00::2",
+			"__meta_docker_network_name":                                        "bridge",
+			"__meta_docker_network_scope":                                       "local",
+		}),
+	}
+	f(c, networkLabels, labelssExpected)
+
 }
 
 func TestDockerMultiNetworkLabels(t *testing.T) {