removed newly added syncs from the provider queue and updated its doc…

…umentation

queue/queue.go

@@ -14,11 +14,11 @@ import (
 
 var log = logging.Logger("provider.queue")
 
-// Queue provides a durable, FIFO interface to the datastore for storing cids
+// Queue provides a best-effort durability, FIFO interface to the datastore for storing cids
 //
-// Durability just means that cids in the process of being provided when a
-// crash or shutdown occurs will still be in the queue when the node is
-// brought back online.
+// Best-effort durability just means that cids in the process of being provided when a
+// crash or shutdown occurs may be in the queue when the node is brought back online
+// depending on whether the underlying datastore has synchronous or asynchronous writes.
 type Queue struct {
 	// used to differentiate queues in datastore
 	// e.g. provider vs reprovider
@@ -102,12 +102,6 @@ func (q *Queue) work() {
 							log.Errorf("error deleting queue entry with key (%s), due to error (%s), stopping provider", head.Key, err)
 							return
 						}
-
-						if err := q.ds.Sync(k); err != nil {
-							log.Errorf("error syncing deletion of queue entry with key (%s), due to error (%s), stopping provider", head.Key, err)
-							continue
-						}
-
 						continue
 					}
 				} else {
@@ -130,25 +124,13 @@ func (q *Queue) work() {
 					log.Errorf("Failed to enqueue cid: %s", err)
 					continue
 				}
-
-				if err := q.ds.Sync(k); err != nil {
-					log.Errorf("Failed to sync enqueuing cid: %s", err)
-					continue
-				}
-
 			case dequeue <- c:
 				err := q.ds.Delete(k)
 
 				if err != nil {
 					log.Errorf("Failed to delete queued cid %s with key %s: %s", c, k, err)
 					continue
 				}
-
-				if err := q.ds.Sync(k); err != nil {
-					log.Errorf("Failed to sync deleted queued cid %s with key %s: %s", c, k, err)
-					continue
-				}
-
 				c = cid.Undef
 			case <-q.ctx.Done():
 				return