From 414e14f82699ebfd2c6a9f0254bd8ec4a321f89e Mon Sep 17 00:00:00 2001
From: Justin Li <jli.justinli@gmail.com>
Date: Thu, 17 Jul 2014 01:45:14 -0400
Subject: [PATCH] Remove a small file, and add comments

---
 backend/noop/driver.go |  2 +-
 tracker/routines.go    | 30 ----------------------------
 tracker/tracker.go     | 44 +++++++++++++++++++++++++++++++++++++++---
 3 files changed, 42 insertions(+), 34 deletions(-)
 delete mode 100644 tracker/routines.go

diff --git a/backend/noop/driver.go b/backend/noop/driver.go
index 04750e8..8fba995 100644
--- a/backend/noop/driver.go
+++ b/backend/noop/driver.go
@@ -7,8 +7,8 @@
 package noop
 
 import (
-	"github.com/chihaya/chihaya/config"
 	"github.com/chihaya/chihaya/backend"
+	"github.com/chihaya/chihaya/config"
 	"github.com/chihaya/chihaya/tracker/models"
 )
 
diff --git a/tracker/routines.go b/tracker/routines.go
deleted file mode 100644
index 4c5dd53..0000000
--- a/tracker/routines.go
+++ /dev/null
@@ -1,30 +0,0 @@
-// Copyright 2014 The Chihaya Authors. All rights reserved.
-// Use of this source code is governed by the BSD 2-Clause license,
-// which can be found in the LICENSE file.
-
-package tracker
-
-import (
-	"time"
-
-	"github.com/golang/glog"
-)
-
-func PurgeInactivePeers(p Pool, purgeEmptyTorrents bool, threshold, interval time.Duration) {
-	for _ = range time.NewTicker(interval).C {
-		before := time.Now().Add(-threshold)
-		glog.V(0).Infof("Purging peers with no announces since %s", before)
-
-		conn, err := p.Get()
-
-		if err != nil {
-			glog.Error("Unable to get connection for a routine")
-			continue
-		}
-
-		err = conn.PurgeInactivePeers(purgeEmptyTorrents, before)
-		if err != nil {
-			glog.Errorf("Error purging torrents: %s", err)
-		}
-	}
-}
diff --git a/tracker/tracker.go b/tracker/tracker.go
index 5a715a4..5f47fee 100644
--- a/tracker/tracker.go
+++ b/tracker/tracker.go
@@ -7,17 +7,25 @@
 package tracker
 
 import (
-	"github.com/chihaya/chihaya/config"
+	"time"
+
+	"github.com/golang/glog"
+
 	"github.com/chihaya/chihaya/backend"
+	"github.com/chihaya/chihaya/config"
 	"github.com/chihaya/chihaya/tracker/models"
 )
 
+// Tracker represents the logic necessary to service BitTorrent announces,
+// independently of the underlying data transports used.
 type Tracker struct {
 	cfg     *config.Config
 	Pool    Pool
 	backend backend.Conn
 }
 
+// New creates a new Tracker, and opens any necessary connections.
+// Maintenance routines are automatically spawned in the background.
 func New(cfg *config.Config) (*Tracker, error) {
 	pool, err := Open(&cfg.Tracker)
 	if err != nil {
@@ -29,7 +37,7 @@ func New(cfg *config.Config) (*Tracker, error) {
 		return nil, err
 	}
 
-	go PurgeInactivePeers(
+	go purgeInactivePeers(
 		pool,
 		cfg.PurgeInactiveTorrents,
 		cfg.Announce.Duration*2,
@@ -43,8 +51,38 @@ func New(cfg *config.Config) (*Tracker, error) {
 	}, nil
 }
 
+// Writer serializes a tracker's responses, and is implemented for each
+// response transport used by the tracker.
+//
+// Note, data passed into any of these functions will not contain sensitive
+// information, so it may be passed back the client freely.
 type Writer interface {
-	WriteError(error) error
+	WriteError(err error) error
 	WriteAnnounce(*models.AnnounceResponse) error
 	WriteScrape(*models.ScrapeResponse) error
 }
+
+// purgeInactivePeers periodically walks the torrent database and removes
+// peers that haven't announced recently.
+//
+// The default interval is 2x the announce interval, which gives delayed
+// peers a chance to stay alive, while ensuring the majority of responses
+// contain active peers.
+func purgeInactivePeers(p Pool, purgeEmptyTorrents bool, threshold, interval time.Duration) {
+	for _ = range time.NewTicker(interval).C {
+		before := time.Now().Add(-threshold)
+		glog.V(0).Infof("Purging peers with no announces since %s", before)
+
+		conn, err := p.Get()
+
+		if err != nil {
+			glog.Error("Unable to get connection for a routine")
+			continue
+		}
+
+		err = conn.PurgeInactivePeers(purgeEmptyTorrents, before)
+		if err != nil {
+			glog.Errorf("Error purging torrents: %s", err)
+		}
+	}
+}