Initial changes for DO gossip seed provider

protokube/pkg/gossip/do/BUILD.bazel

@@ -0,0 +1,11 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "go_default_library",
+    srcs = ["seeds.go"],
+    importpath = "k8s.io/kops/protokube/pkg/gossip/do",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//protokube/pkg/gossip:go_default_library"
+    ],
+)

protokube/pkg/gossip/do/seeds.go

@@ -0,0 +1,60 @@
+/*
+Copyright 2019 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package do
+
+import (
+	"fmt"
+	"context"
+	"k8s.io/klog"
+	"k8s.io/kops/pkg/resources/digitalocean"
+	"k8s.io/kops/protokube/pkg/gossip"
+)
+
+type SeedProvider struct {
+	cloud *digitalocean.Cloud
+	tag    string
+}
+
+var _ gossip.SeedProvider = &SeedProvider{}
+
+func (p *SeedProvider) GetSeeds() ([]string, error) {
+	var seeds []string
+
+	
+	droplets, _, err := p.cloud.Droplets().ListByTag(context.TODO(), p.tag, nil)
+
+	if err != nil {
+		return nil, fmt.Errorf("Droplets.ListByTag returned error: %v", err)
+	}
+
+	for _, droplet := range droplets {
+		ip, err := droplet.PrivateIPv4()
+		if err != nil {
+			klog.V(2).Infof("Appending a seed for cluster tag:%s, with ip=%s", p.tag, ip)
+			seeds = append(seeds, ip)
+		}
+	}
+
+	return seeds, nil
+}
+
+func NewSeedProvider(cloud *digitalocean.Cloud, tag string) (*SeedProvider, error) {
+	return &SeedProvider{
+		cloud:    cloud,
+		tag:    tag,
+	}, nil
+}

protokube/pkg/protokube/do_volume.go

@@ -31,12 +31,15 @@ import (
 
 	"k8s.io/kops/pkg/resources/digitalocean"
 	"k8s.io/kops/protokube/pkg/etcd"
+	"k8s.io/kops/protokube/pkg/gossip"
+	gossipdo "k8s.io/kops/protokube/pkg/gossip/do"
 )
 
 const (
 	dropletRegionMetadataURL     = "http://169.254.169.254/metadata/v1/region"
 	dropletNameMetadataURL       = "http://169.254.169.254/metadata/v1/hostname"
 	dropletIDMetadataURL         = "http://169.254.169.254/metadata/v1/id"
+	dropletIDMetadataTags        = "http://169.254.169.254/metadata/v1/tags"
 	dropletInternalIPMetadataURL = "http://169.254.169.254/metadata/v1/interfaces/private/0/ipv4/address"
 	localDevicePrefix            = "/dev/disk/by-id/scsi-0DO_Volume_"
 )
@@ -48,6 +51,7 @@ type DOVolumes struct {
 	region      string
 	dropletName string
 	dropletID   int
+	dropletTags []string
 }
 
 var _ Volumes = &DOVolumes{}
@@ -78,12 +82,18 @@ func NewDOVolumes(clusterID string) (*DOVolumes, error) {
 		return nil, fmt.Errorf("failed to initialize digitalocean cloud: %s", err)
 	}
 
+	dropletTags, err := getMetadataDropletTags()
+	if err != nil {
+		return nil, fmt.Errorf("failed to get droplet tags: %s", err)
+	}
+
 	return &DOVolumes{
 		Cloud:       cloud,
 		ClusterID:   clusterID,
 		dropletID:   dropletIDInt,
 		dropletName: dropletName,
 		region:      region,
+		dropletTags: dropletTags,
 	}, nil
 }
 
@@ -236,6 +246,17 @@ func getLocalDeviceName(vol *godo.Volume) string {
 	return localDevicePrefix + vol.Name
 }
 
+func (d *DOVolumes) GossipSeeds() (gossip.SeedProvider, error) {
+	for _, dropletTag := range d.dropletTags {
+        if strings.Contains(dropletTag, d.ClusterID) {
+			return gossipdo.NewSeedProvider(d.Cloud, dropletTag)
+        }
+	}
+	
+	
+	return nil, fmt.Errorf("could not determine a matching droplet tag for gossip seeding")
+}
+
 // GetDropletInternalIP gets the private IP of the droplet running this program
 // This function is exported so it can be called from protokube
 func GetDropletInternalIP() (net.IP, error) {
@@ -259,6 +280,13 @@ func getMetadataDropletID() (string, error) {
 	return getMetadata(dropletIDMetadataURL)
 }
 
+func getMetadataDropletTags() ([]string, error) {
+
+	tagString, error := getMetadata(dropletIDMetadataTags)
+	dropletTags := strings.Split(tagString,"\n")
+	return dropletTags, error
+}
+
 func getMetadata(url string) (string, error) {
 	resp, err := http.Get(url)
 	if err != nil {