From 00f02b5fbc344e2fd11d7f0914a15d50f6194fd8 Mon Sep 17 00:00:00 2001
From: Richard Scothern <richard.scothern@gmail.com>
Date: Fri, 23 Oct 2015 15:25:42 -0700
Subject: [PATCH] Buffer writing the scheduler entry state to disk by
 periodically checking for changes to the entries index and saving it to the
 filesystem.

Signed-off-by: Richard Scothern <richard.scothern@gmail.com>
---
 docs/proxy/scheduler/scheduler.go | 45 ++++++++++++++++++++++++++-----
 1 file changed, 38 insertions(+), 7 deletions(-)

diff --git a/docs/proxy/scheduler/scheduler.go b/docs/proxy/scheduler/scheduler.go
index 6af777cc4..e91920a1d 100644
--- a/docs/proxy/scheduler/scheduler.go
+++ b/docs/proxy/scheduler/scheduler.go
@@ -16,6 +16,7 @@ type expiryFunc func(string) error
 const (
 	entryTypeBlob = iota
 	entryTypeManifest
+	indexSaveFrequency = 5 * time.Second
 )
 
 // schedulerEntry represents an entry in the scheduler
@@ -36,6 +37,8 @@ func New(ctx context.Context, driver driver.StorageDriver, path string) *TTLExpi
 		pathToStateFile: path,
 		ctx:             ctx,
 		stopped:         true,
+		doneChan:        make(chan struct{}),
+		saveTimer:       time.NewTicker(indexSaveFrequency),
 	}
 }
 
@@ -54,6 +57,10 @@ type TTLExpirationScheduler struct {
 
 	onBlobExpire     expiryFunc
 	onManifestExpire expiryFunc
+
+	indexDirty bool
+	saveTimer  *time.Ticker
+	doneChan   chan struct{}
 }
 
 // OnBlobExpire is called when a scheduled blob's TTL expires
@@ -119,6 +126,31 @@ func (ttles *TTLExpirationScheduler) Start() error {
 		entry.timer = ttles.startTimer(entry, entry.Expiry.Sub(time.Now()))
 	}
 
+	// Start a ticker to periodically save the entries index
+
+	go func() {
+		for {
+			select {
+			case <-ttles.saveTimer.C:
+				if !ttles.indexDirty {
+					continue
+				}
+
+				ttles.Lock()
+				err := ttles.writeState()
+				if err != nil {
+					context.GetLogger(ttles.ctx).Errorf("Error writing scheduler state: %s", err)
+				} else {
+					ttles.indexDirty = false
+				}
+				ttles.Unlock()
+
+			case <-ttles.doneChan:
+				return
+			}
+		}
+	}()
+
 	return nil
 }
 
@@ -134,10 +166,7 @@ func (ttles *TTLExpirationScheduler) add(key string, ttl time.Duration, eType in
 	}
 	ttles.entries[key] = entry
 	entry.timer = ttles.startTimer(entry, ttl)
-
-	if err := ttles.writeState(); err != nil {
-		context.GetLogger(ttles.ctx).Errorf("Error writing scheduler state: %s", err)
-	}
+	ttles.indexDirty = true
 }
 
 func (ttles *TTLExpirationScheduler) startTimer(entry *schedulerEntry, ttl time.Duration) *time.Timer {
@@ -163,9 +192,7 @@ func (ttles *TTLExpirationScheduler) startTimer(entry *schedulerEntry, ttl time.
 		}
 
 		delete(ttles.entries, entry.Key)
-		if err := ttles.writeState(); err != nil {
-			context.GetLogger(ttles.ctx).Errorf("Error writing scheduler state: %s", err)
-		}
+		ttles.indexDirty = true
 	})
 }
 
@@ -181,6 +208,9 @@ func (ttles *TTLExpirationScheduler) Stop() {
 	for _, entry := range ttles.entries {
 		entry.timer.Stop()
 	}
+
+	close(ttles.doneChan)
+	ttles.saveTimer.Stop()
 	ttles.stopped = true
 }
 
@@ -194,6 +224,7 @@ func (ttles *TTLExpirationScheduler) writeState() error {
 	if err != nil {
 		return err
 	}
+
 	return nil
 }