Exponential backoff for request client, rebased. Updated license to

2015, cleaned more //[a-z] comments. Added in support for Environment
variable gaurds over the backcoff w/ default NoBackoff. Rebased.

pkg/client/unversioned/restclient_test.go

@@ -19,8 +19,11 @@ package unversioned
 import (
 	"net/http"
 	"net/http/httptest"
+	"net/url"
+	"os"
 	"reflect"
 	"testing"
+	"time"
 
 	"k8s.io/kubernetes/pkg/api/testapi"
 	"k8s.io/kubernetes/pkg/api/unversioned"
@@ -139,3 +142,39 @@ func TestDoRequestCreated(t *testing.T) {
 	}
 	fakeHandler.ValidateRequest(t, "/"+testapi.Default.Version()+"/test", "GET", nil)
 }
+
+func TestCreateBackoffManager(t *testing.T) {
+
+	theUrl, _ := url.Parse("http://localhost")
+
+	// 1 second base backoff + duration of 2 seconds -> exponential backoff for requests.
+	os.Setenv(envBackoffBase, "1")
+	os.Setenv(envBackoffDuration, "2")
+	backoff := readExpBackoffConfig()
+	backoff.UpdateBackoff(theUrl, nil, 500)
+	backoff.UpdateBackoff(theUrl, nil, 500)
+	if backoff.CalculateBackoff(theUrl)/time.Second != 2 {
+		t.Errorf("Backoff env not working.")
+	}
+
+	// 0 duration -> no backoff.
+	os.Setenv(envBackoffBase, "1")
+	os.Setenv(envBackoffDuration, "0")
+	backoff.UpdateBackoff(theUrl, nil, 500)
+	backoff.UpdateBackoff(theUrl, nil, 500)
+	backoff = readExpBackoffConfig()
+	if backoff.CalculateBackoff(theUrl)/time.Second != 0 {
+		t.Errorf("Zero backoff duration, but backoff still occuring.")
+	}
+
+	// No env -> No backoff.
+	os.Setenv(envBackoffBase, "")
+	os.Setenv(envBackoffDuration, "")
+	backoff = readExpBackoffConfig()
+	backoff.UpdateBackoff(theUrl, nil, 500)
+	backoff.UpdateBackoff(theUrl, nil, 500)
+	if backoff.CalculateBackoff(theUrl)/time.Second != 0 {
+		t.Errorf("Backoff should have been 0.")
+	}
+
+}