query: add onmaxtries config option

OnMaxTries config gives the caller access to the peer's address once a
maximum number of retries have been attempted. This config helps meet
the needs of different callers as some may use the address to
immediately disconnect the peer vs others that may choose to try again.

Author: kcalvinalvin

query/workmanager.go

@@ -94,6 +94,11 @@ type Config struct {
 	// make this configurable to easily mock the worker used during tests.
 	NewWorker func(Peer) Worker
 
+	// OnMaxTries gives the caller access to the Peer object once a maximum
+	// number of retries have been attempted. The caller can then access the
+	// Peer's address and can choose to punish the peer accordingly.
+	OnMaxTries func(Peer)
+
 	// Ranking is used to rank the connected peers when determining who to
 	// give work to.
 	Ranking PeerRanking
@@ -381,6 +386,14 @@ Loop:
 					log.Debugf("Canceled batch %v",
 						batchNum)
 
+					// Since we've reached this query's
+					// maximum number of retries, now is the
+					// time to call the OnMaxTries callback
+					// function if it isn't nil.
+					if w.cfg.OnMaxTries != nil {
+						w.cfg.OnMaxTries(result.peer)
+					}
+
 					continue Loop
 				}