don't need negative events now

Author: duke8253

iocore/dns/DNS.cc

@@ -567,7 +567,6 @@ DNSHandler::startEvent(int /* event ATS_UNUSED */, Event *e)
       open_cons(nullptr); // use current target address.
       n_con = 1;
     }
-    e->ethread->schedule_every(this, -DNS_PERIOD);
 
     return EVENT_CONT;
   } else {
@@ -590,7 +589,6 @@ DNSHandler::startEvent_sdns(int /* event ATS_UNUSED */, Event *e)
   open_cons(&ip.sa, false, n_con);
   ++n_con; // TODO should n_con be zeroed?
 
-  e->schedule_every(-DNS_PERIOD);
   return EVENT_CONT;
 }
 
@@ -958,6 +956,10 @@ DNSHandler::mainEvent(int event, Event *e)
     write_dns(this);
   }
 
+  if (std::any_of(ns_down, ns_down + n_con, [](int f) { return f != 0; })) {
+    this_ethread()->schedule_at(this, DNS_PRIMARY_RETRY_PERIOD);
+  }
+
   return EVENT_CONT;
 }
 

iocore/dns/DNSConnection.cc

@@ -78,6 +78,14 @@ void
 DNSConnection::trigger()
 {
   handler->triggered.enqueue(this);
+
+  // Since the periodic check is removed, we need to call
+  // this when it's triggered by EVENTIO_DNS_CONNECTION.
+  // The handler should be pionting to DNSHandler::mainEvent.
+  // We can schedule an immediate event or call the handler
+  // directly, and since both arguments are not being used
+  // passing in 0 and nullptr will do the job.
+  handler->handleEvent(0, nullptr);
 }
 
 int