From 5978480b49c152e458055bb3a6b1b4ba9afa54e9 Mon Sep 17 00:00:00 2001
From: Paul Buetow <paul@buetow.org>
Date: Thu, 29 Jun 2023 09:55:23 +0300
Subject: add email-notification support

---
 internal/quorum/notify.go      | 12 +++----
 internal/quorum/quorum.go      | 73 ++++++++++++++++++++++++++----------------
 internal/quorum/quorum_test.go |  2 +-
 3 files changed, 52 insertions(+), 35 deletions(-)

(limited to 'internal')

diff --git a/internal/quorum/notify.go b/internal/quorum/notify.go
index b6e6b5d..7761b4d 100644
--- a/internal/quorum/notify.go
+++ b/internal/quorum/notify.go
@@ -17,7 +17,7 @@ func notify(conf config.Config, subject, body string) error {
 		return nil
 	}
 
-	log.Println("notify", subject, body)
+	log.Println("notify:", subject, body)
 
 	headers := map[string]string{
 		"From":         conf.EmailFrom,
@@ -40,11 +40,9 @@ func notify(conf config.Config, subject, body string) error {
 }
 
 func notifyError(conf config.Config, err error) {
-	if !notifyEnabled(conf) {
-		return
-	}
-
-	if err := notify(conf, fmt.Sprintf("GORUM: An error occured: %v", err), err.Error()); err != nil {
-		log.Println("error: ", err)
+	if notifyEnabled(conf) {
+		if err := notify(conf, fmt.Sprintf("GORUM: An error occured: %v", err), err.Error()); err != nil {
+			log.Println("error:", err)
+		}
 	}
 }
diff --git a/internal/quorum/quorum.go b/internal/quorum/quorum.go
index d33db56..bbdc640 100644
--- a/internal/quorum/quorum.go
+++ b/internal/quorum/quorum.go
@@ -42,7 +42,6 @@ func (quo Quorum) Start(ctx context.Context) <-chan vote.Vote {
 
 	interval := time.Second * time.Duration(quo.conf.LoopIntervalS)
 	if vote.Expiry <= interval {
-		// TODO: When to use log.Fatal and when to use panic?
 		log.Fatal("quorum: LoopIntervalS ", quo.conf.LoopIntervalS,
 			" should be less than the vote expiry of ", vote.Expiry)
 	}
@@ -50,23 +49,37 @@ func (quo Quorum) Start(ctx context.Context) <-chan vote.Vote {
 	go func() {
 		defer close(ch)
 
+		var (
+			myVote  vote.Vote
+			changed bool
+		)
+
 		for {
 			select {
 			case <-time.After(interval):
-				myVote, _ := quo.makeMyVote()
+				myVote, _ = quo.makeMyVote()
 				log.Println("quorum: made my vote:", myVote)
 				ch <- myVote
 			case v := <-quo.voteCh:
 				quo.vote(v)
-				if myVote, changed := quo.makeMyVote(); changed {
+				if myVote, changed = quo.makeMyVote(); changed {
 					log.Println("quorum: changed my vote:", myVote)
 					ch <- myVote
 				}
 			case <-ctx.Done():
 				return
 			}
-			if err := quo.persist(); err != nil {
+
+			scoresStr, err := quo.persist()
+			if err != nil {
 				log.Println("quorum:", err)
+				notifyError(quo.conf, err)
+				continue
+			}
+			if changed {
+				if err := notify(quo.conf, "GORUM: Quorum changed", scoresStr); err != nil {
+					log.Println("quorum:", err)
+				}
 			}
 		}
 	}()
@@ -109,26 +122,10 @@ func (quo Quorum) scores() (scores []Score) {
 	return
 }
 
-func (quo *Quorum) persist() error {
+func (quo *Quorum) str() string {
 	scores := quo.scores()
 	log.Println("quorum scores:", scores)
 
-	if _, err := os.Stat(quo.conf.StateDir); os.IsNotExist(err) {
-		if err := os.MkdirAll(quo.conf.StateDir, 0755); err != nil {
-			return err
-		}
-	}
-
-	stateFile := fmt.Sprintf("%s/scores", quo.conf.StateDir)
-	stateTmpFile := fmt.Sprintf("%s.tmp", stateFile)
-
-	// TODO: Also create a "is_leader" marker file in the fs!
-	fd, err := os.Create(stateTmpFile)
-	if err != nil {
-		return err
-	}
-	defer fd.Close()
-
 	var sb strings.Builder
 	for i, score := range scores {
 		sb.WriteString("At position ")
@@ -150,18 +147,40 @@ func (quo *Quorum) persist() error {
 		sb.WriteString("\n")
 	}
 
-	if _, err := fd.WriteString(sb.String()); err != nil {
-		return err
+	return sb.String()
+}
+
+func (quo *Quorum) persist() (string, error) {
+	scoresStr := quo.str()
+
+	if _, err := os.Stat(quo.conf.StateDir); os.IsNotExist(err) {
+		if err := os.MkdirAll(quo.conf.StateDir, 0755); err != nil {
+			return scoresStr, err
+		}
+	}
+
+	stateFile := fmt.Sprintf("%s/scores", quo.conf.StateDir)
+	stateTmpFile := fmt.Sprintf("%s.tmp", stateFile)
+
+	// TODO: Also create a "is_leader" marker file in the fs!
+	fd, err := os.Create(stateTmpFile)
+	if err != nil {
+		return scoresStr, err
+	}
+	defer fd.Close()
+
+	if _, err := fd.WriteString(scoresStr); err != nil {
+		return scoresStr, err
 	}
 
 	if err := fd.Sync(); err != nil {
-		return err
+		return scoresStr, err
 	}
-	return os.Rename(stateTmpFile, stateFile)
+	return scoresStr, os.Rename(stateTmpFile, stateFile)
 }
 
 func (quo *Quorum) makeMyVote() (vote.Vote, bool) {
-	newVote, err := quo.pruneVotes()
+	newVote, err := quo.expireOldVotes()
 	if err != nil {
 		log.Println("quorum:", err)
 		return quo.myVote, false
@@ -175,7 +194,7 @@ func (quo *Quorum) makeMyVote() (vote.Vote, bool) {
 	return quo.myVote, true
 }
 
-func (quo Quorum) pruneVotes() (vote.Vote, error) {
+func (quo Quorum) expireOldVotes() (vote.Vote, error) {
 	var expired []string
 	var live []string
 
diff --git a/internal/quorum/quorum_test.go b/internal/quorum/quorum_test.go
index fd51fb6..3ae87c6 100644
--- a/internal/quorum/quorum_test.go
+++ b/internal/quorum/quorum_test.go
@@ -134,7 +134,7 @@ func TestExpire(t *testing.T) {
 		t.Errorf("Expected to have two votes before expiry: %v", quo)
 	}
 
-	newVote, _ := quo.pruneVotes()
+	newVote, _ := quo.expireOldVotes()
 	if len(quo.votes) != 1 {
 		t.Errorf("Expected to have one vote after expiry: %v", quo)
 	}
-- 
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