plugin/secondary: fix a bunch of things and tests (#1406)

Fix the error handling. Log when we have an error during any of the
transfer state. And if there isn't an error transfer the zones.

Also fix the tests in test/ so we, at least, check the initial transfer.

Update the docs to show more about how errors are handled.

Ref #1400

plugin/file/secondary.go

@@ -118,19 +118,6 @@ Restart:
 	retry := time.Second * time.Duration(z.Apex.SOA.Retry)
 	expire := time.Second * time.Duration(z.Apex.SOA.Expire)
 
-	if refresh < time.Hour {
-		refresh = time.Hour
-	}
-	if retry < time.Hour {
-		retry = time.Hour
-	}
-	if refresh > 24*time.Hour {
-		refresh = 24 * time.Hour
-	}
-	if retry > 12*time.Hour {
-		retry = 12 * time.Hour
-	}
-
 	refreshTicker := time.NewTicker(refresh)
 	retryTicker := time.NewTicker(retry)
 	expireTicker := time.NewTicker(expire)
@@ -151,7 +138,12 @@ Restart:
 			time.Sleep(jitter(2000)) // 2s randomize
 
 			ok, err := z.shouldTransfer()
-			if err != nil && ok {
+			if err != nil {
+				log.Printf("[WARNING] Failed retry check %s", err)
+				continue
+			}
+
+			if ok {
 				if err := z.TransferIn(); err != nil {
 					// transfer failed, leave retryActive true
 					break
@@ -169,8 +161,13 @@ Restart:
 			time.Sleep(jitter(5000)) // 5s randomize
 
 			ok, err := z.shouldTransfer()
-			retryActive = err != nil
-			if err != nil && ok {
+			if err != nil {
+				log.Printf("[WARNING] Failed refresh check %s", err)
+				retryActive = true
+				continue
+			}
+
+			if ok {
 				if err := z.TransferIn(); err != nil {
 					// transfer failed
 					retryActive = true

plugin/secondary/README.md

@@ -35,6 +35,10 @@ secondary [zones...] {
   normal authoritative serving you don't need *or* want to use this. **ADDRESS** can be an IP
   address, and IP:port or a string pointing to a file that is structured as /etc/resolv.conf.
 
+When a zone is due to be refreshed (Refresh timer fires) a random jitter of 5 seconds is
+applied, before fetching. In the case of retry this will be 2 seconds. If there are any errors
+during the transfer the transfer fails; this will be logged.
+
 ## Examples
 
 Transfer `example.org` from 10.0.1.1, and if that fails try 10.1.2.1.