Better control variance docs

doc.go

@@ -71,7 +71,7 @@ Per-request, in-memory cache: fetch the same key twice, the second request is se
 
 Intelligent multi support: running GetMulti correctly fetches from memory, then memcache, then the datastore; each tier only sends keys off to the next one if they were missing.
 
-Memcache variance: Goon limits the length of the memcache requests to minimize outliers
+Memcache control variance: long memcache requests are cancelled.
 
 Transactions use a separate context, but locally cache any results on success.
 
@@ -125,31 +125,14 @@ goon:
 	g := &Group{Id: 1}
 	err := n.Get(g)
 
-Memcache variance:
-	Put:
-		MemcachePutTimeoutThreshold is the number of bytes at which the memcache timeout uses the large setting.
-		MemcachePutTimeoutSmall is the amount of time to wait during memcache Put operations before aborting them and using the datastore.
-		MemcachePutTimeoutLarge is the amount of time to wait for large memcache Put requests.
+Memcache Control Variance
 
-	Get:
-		MemcacheGetTimeout is the amount of time to wait for all memcache Get requests
+Memcache is generally fast. When it is slow, goon will timeout the memcache
+requests and proceed to use the datastore directly. The memcache put and
+get timeout variables determine how long to wait for various kinds of
+requests. The default settings were determined experimentally and should
+provide reasonable defaults for most applications.
 
-	Notes:
-		The default settings are in effect and used by goon but if you are seeing too many memcache timeout errors in your logs, you may want to bump up the times.
-		Conversely, if you're using github.com/mjibson/appstats and are seeing Memcache requests finishing routinely before the default values you can bump them down.
-		Finally, if these are not good default values as thought, please open an issue.
-
-	To change defaults:
-		package myapp
-
-		import (
-			"github.com/mjibson/goon"
-			"time"
-		)
-
-		func init() {
-			goon.MemcachePutTimeoutThreshold = 1024 * 50 // 50k
-			goon.MemcachePutTimeoutSmall = time.Millisecond * 10
-		}
+See: http://talks.golang.org/2013/highperf.slide#23
 */
 package goon

goon.go

@@ -31,18 +31,19 @@ import (
 var (
 	// LogErrors issues appengine.Context.Errorf on any error.
 	LogErrors = true
+
 	// MemcachePutTimeoutThreshold is the number of bytes at which the memcache
 	// timeout uses the large setting.
-	MemcachePutTimeoutThreshold = 1024 * 50 // 50K bytes
+	MemcachePutTimeoutThreshold = 1024 * 50
 	// MemcachePutTimeoutSmall is the amount of time to wait during memcache
 	// Put operations before aborting them and using the datastore.
 	MemcachePutTimeoutSmall = time.Millisecond * 5
 	// MemcachePutTimeoutLarge is the amount of time to wait for large memcache
 	// Put requests.
 	MemcachePutTimeoutLarge = time.Millisecond * 15
 	// MemcacheGetTimeout is the amount of time to wait for all memcache Get
-	// requests
-	MemcacheGetTimeout = time.Millisecond * 10 // the Duration that we'll wait for memcache.Get
+	// requests.
+	MemcacheGetTimeout = time.Millisecond * 10
 )
 
 // Goon holds the app engine context and the request memory cache.