www: Lazy load comment votes.

This diff removes the comment vote cache initialization that happened
with www startup. They are now lazy loaded into the cache when needed.

politeiawww/comments.go

@@ -26,31 +26,6 @@ type counters struct {
 	down uint64
 }
 
-// initCommentScores populates the comment scores cache.
-func (p *politeiawww) initCommentScores() error {
-	log.Tracef("initCommentScores")
-
-	// Fetch decred plugin inventory from cache
-	ir, err := p.decredInventory()
-	if err != nil {
-		return fmt.Errorf("decredInventory: %v", err)
-	}
-
-	// XXX this could be done much more efficiently since we
-	// already have all of the like comments in the inventory
-	// response, but re-using the updateCommentVotes function is
-	// simpler. This only gets run on startup so I'm not that
-	// worried about performance for right now.
-	for _, v := range ir.Comments {
-		_, err := p.updateCommentVotes(v.Token, v.CommentID)
-		if err != nil {
-			return fmt.Errorf("updateCommentVotes: %v", err)
-		}
-	}
-
-	return nil
-}
-
 // getComment retreives the specified comment from the cache then fills in
 // politeiawww specific data for the comment.
 func (p *politeiawww) getComment(token, commentID string) (*www.Comment, error) {
@@ -72,13 +47,9 @@ func (p *politeiawww) getComment(token, commentID string) (*www.Comment, error)
 	}
 
 	// Lookup comment votes
-	p.RLock()
-	defer p.RUnlock()
-
-	votes, ok := p.commentVotes[token+commentID]
-	if !ok {
-		log.Errorf("getComment: comment votes lookup failed for "+
-			"token:%v commentID:%v", token, commentID)
+	votes, err := p.getCommentVotes(token, commentID)
+	if err != nil {
+		return nil, err
 	}
 	c.ResultVotes = int64(votes.up - votes.down)
 	c.Upvotes = votes.up
@@ -87,6 +58,33 @@ func (p *politeiawww) getComment(token, commentID string) (*www.Comment, error)
 	return &c, nil
 }
 
+// getCommentVotes tries to get comment votes from the cache. If votes are
+// not stored, fetch them and update cache.
+//
+// This function must be called WITHOUT the lock held.
+func (p *politeiawww) getCommentVotes(token, commentID string) (counters, error) {
+	log.Tracef("getCommentVotes: %v %v", token, commentID)
+
+	// Check if comment votes is already cached
+	var votes counters
+	p.RLock()
+	vs, ok := p.commentVotes[token+commentID]
+	p.RUnlock()
+	votes = vs
+	// If not in cache, fetch comment votes and update cache
+	if !ok {
+		vsUpdated, err := p.updateCommentVotes(token, commentID)
+		if err != nil {
+			log.Errorf("getCommentVotes: comment votes update "+
+				"failed: token:%v commentID:%v", token, commentID)
+			return counters{}, err
+		}
+		votes = *vsUpdated
+	}
+
+	return votes, nil
+}
+
 // updateCommentVotes calculates the up/down votes for the specified comment,
 // updates the in-memory comment votes cache with these and returns them.
 func (p *politeiawww) updateCommentVotes(token, commentID string) (*counters, error) {

politeiawww/proposals.go

@@ -975,16 +975,10 @@ func (p *politeiawww) getPropComments(token string) ([]www.Comment, error) {
 		comments = append(comments, c)
 	}
 
-	// Fill in comment scores
-	p.RLock()
-	defer p.RUnlock()
-
 	for i, v := range comments {
-		votes, ok := p.commentVotes[v.Token+v.CommentID]
-		if !ok {
-			log.Errorf("getPropComments: comment votes lookup "+
-				"failed: token:%v commentID:%v pubKey:%v", v.Token,
-				v.CommentID, v.PublicKey)
+		votes, err := p.getCommentVotes(v.Token, v.CommentID)
+		if err != nil {
+			return nil, err
 		}
 		comments[i].ResultVotes = int64(votes.up - votes.down)
 		comments[i].Upvotes = votes.up

politeiawww/www.go

@@ -439,12 +439,6 @@ func _main() error {
 		return err
 	}
 
-	// Setup comment scores map
-	err = p.initCommentScores()
-	if err != nil {
-		return fmt.Errorf("initCommentScore: %v", err)
-	}
-
 	// Setup VoteResults cache table
 	log.Infof("Loading vote results cache table")
 	err = p.initVoteResults()