Prototype voter

.golangci.yaml

@@ -36,3 +36,9 @@ linters:
     - thelper
     - varcheck
     - varnamelen
+linters-settings:
+  tagliatelle:
+    case:
+      use-field-name: true
+      rules:
+        json: goCamel

go.mod

@@ -5,6 +5,7 @@ go 1.20
 require (
 	github.com/dchest/uniuri v1.2.0
 	github.com/go-resty/resty/v2 v2.7.0
+	github.com/samber/lo v1.38.1
 	github.com/stretchr/testify v1.8.4
 	go.uber.org/goleak v1.2.1
 )
@@ -13,6 +14,7 @@ require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/kr/text v0.2.0 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	golang.org/x/exp v0.0.0-20220303212507-bbda1eaf7a17 // indirect
 	golang.org/x/net v0.0.0-20211029224645-99673261e6eb // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -10,10 +10,14 @@ github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
 github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/samber/lo v1.38.1 h1:j2XEAqXKb09Am4ebOg31SpvzUTTs6EN3VfgeLUhPdXM=
+github.com/samber/lo v1.38.1/go.mod h1:+m/ZKRl6ClXCE2Lgf3MsQlWfh4bn1bz6CXEOxnEXnEA=
 github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 go.uber.org/goleak v1.2.1 h1:NBol2c7O1ZokfZ0LEU9K6Whx/KnwvepVetCUhtKja4A=
 go.uber.org/goleak v1.2.1/go.mod h1:qlT2yGI9QafXHhZZLxlSuNsMw3FFLxBr+tBRlmO1xH4=
+golang.org/x/exp v0.0.0-20220303212507-bbda1eaf7a17 h1:3MTrJm4PyNL9NBqvYDSj3DHl46qQakyfqfWo4jgfaEM=
+golang.org/x/exp v0.0.0-20220303212507-bbda1eaf7a17/go.mod h1:lgLbSvA5ygNOMpwM/9anMpWVlVJ7Z+cHWq/eFuinpGE=
 golang.org/x/net v0.0.0-20211029224645-99673261e6eb h1:pirldcYWx7rx7kE5r+9WsOXPXK0+WH5+uZ7uPmJ44uM=
 golang.org/x/net v0.0.0-20211029224645-99673261e6eb/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=

voter.go

@@ -1,57 +1,127 @@
 package elect
 
 import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/json"
+	"fmt"
+	"log"
 	"time"
 
 	"github.com/dchest/uniuri"
 	"github.com/go-resty/resty/v2"
+	"github.com/samber/lo"
 )
 
 type Voter struct {
 	client     *resty.Client
-	instanceID string
-	signingKey string
+	signingKey []byte
 	update     chan<- time.Duration
+	done       <-chan bool
+	vote       vote
+}
+
+type vote struct {
+	VoterID             string `json:"voterID"`
+	LastSeenCandidateID string `json:"lastSeenCandidateID"`
+	NumPollsSinceChange int    `json:"numPollsSinceChange"`
+}
+
+type voteResponse struct {
+	CandidateID string `json:"candidateID"`
 }
 
 func NewVoter(url string, signingKey string) *Voter {
-	update := make(chan time.Duration) // intentionally 0-capacity
+	update := make(chan time.Duration)
+	done := make(chan bool)
 
 	v := &Voter{
 		client: resty.New().
+			SetCloseConnection(true).
 			SetBaseURL(url),
-		instanceID: uniuri.New(),
-		signingKey: signingKey,
+		signingKey: []byte(signingKey),
 		update:     update,
+		done:       done,
+		vote: vote{
+			VoterID: uniuri.New(),
+		},
 	}
 
-	go v.loop(update)
+	go v.loop(update, done)
 
 	return v
 }
 
 func (v *Voter) Stop() {
 	close(v.update)
+	<-v.done
 }
 
-func (v *Voter) loop(update <-chan time.Duration) {
+func (v *Voter) loop(update <-chan time.Duration, done chan<- bool) {
 	t := time.NewTicker(5 * time.Second)
 	defer t.Stop()
+	defer close(done)
 
 	for {
+		if !v.poll(update, t) {
+			break
+		}
+	}
+}
+
+func (v *Voter) poll(update <-chan time.Duration, t *time.Ticker) bool {
+	t2 := &time.Timer{}
+
+	if v.vote.NumPollsSinceChange < 10 {
+		t2 = time.NewTimer(100 * time.Millisecond)
+	}
+
 	select {
+	case <-t2.C:
+		v.sendVote()
+
 	case <-t.C:
-			v.vote()
+		v.sendVote()
 
 	case period, ok := <-update:
 		if !ok {
-				return
+			return false
 		}
 
 		t.Reset(period)
 	}
-	}
+
+	return true
 }
 
-func (v *Voter) vote() {
+func (v *Voter) sendVote() {
+	js := lo.Must(json.Marshal(v.vote))
+
+	genMAC := hmac.New(sha256.New, v.signingKey)
+	genMAC.Write(js)
+	mac := fmt.Sprintf("%x", genMAC.Sum(nil))
+
+	vr := &voteResponse{}
+
+	resp, err := v.client.R().
+		SetHeader("Signature", mac).
+		SetBody(js).
+		SetResult(vr).
+		Post("_vote")
+	if err != nil {
+		log.Printf("_vote response: %s", err)
+		return
+	}
+
+	if resp.IsError() {
+		log.Printf("_vote response: [%d] %s\n%s", resp.StatusCode(), resp.Status(), resp.String())
+		return
+	}
+
+	if vr.CandidateID == v.vote.LastSeenCandidateID {
+		v.vote.NumPollsSinceChange++
+	} else {
+		v.vote.LastSeenCandidateID = vr.CandidateID
+		v.vote.NumPollsSinceChange = 0
+	}
 }

voter_test.go

@@ -2,6 +2,7 @@ package elect_test
 
 import (
 	"testing"
+	"time"
 
 	"github.com/gopatchy/elect"
 	"github.com/stretchr/testify/require"
@@ -10,8 +11,10 @@ import (
 func TestNew(t *testing.T) {
 	t.Parallel()
 
-	v := elect.NewVoter("[::1]:1234", "abc123")
+	v := elect.NewVoter("https://[::1]:1234", "abc123")
 	require.NotNil(t, v)
 
+	time.Sleep(1 * time.Second)
+
 	defer v.Stop()
 }