reconnect: Add ability to do a number of retries without backoff.

This is aimed at an upcoming database clustering implementation, where it's
desirable to try all of the cluster members quickly before backing off to
retry them again in sequence.

Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: Russell Bryant <russell@ovn.org>
Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: Justin Pettit <jpettit@ovn.org>

1 files changed, 35 insertions, 18 deletions

diff --git a/python/ovs/reconnect.py b/python/ovs/reconnect.py
index ec52ebb7a..34cc76987 100644
--- a/python/ovs/reconnect.py
+++ b/python/ovs/reconnect.py
@@ -154,6 +154,7 @@ class Reconnect(object):
         self.last_connected = None
         self.last_disconnected = None
         self.max_tries = None
+        self.backoff_free_tries = 0
 
         self.creation_time = now
         self.n_attempted_connections = 0
@@ -242,6 +243,12 @@ class Reconnect(object):
             self.backoff > self.max_backoff):
                 self.backoff = self.max_backoff
 
+    def set_backoff_free_tries(self, backoff_free_tries):
+        """Sets the number of connection attempts that will be made without
+        backoff to 'backoff_free_tries'.  Values 0 and 1 both
+        represent a single attempt."""
+        self.backoff_free_tries = backoff_free_tries
+
     def set_probe_interval(self, probe_interval):
         """Sets the "probe interval" to 'probe_interval', in milliseconds.  If
         this is zero, it disables the connection keepalive feature.  If it is
@@ -337,7 +344,7 @@ class Reconnect(object):
                 else:
                     self.info_level("%s: error listening for connections"
                                     % self.name)
-            else:
+            elif self.backoff < self.max_backoff:
                 if self.passive:
                     type_ = "listen"
                 else:
@@ -352,8 +359,15 @@ class Reconnect(object):
             if (self.state in (Reconnect.Active, Reconnect.Idle)):
                 self.last_disconnected = now
 
+            if not self.__may_retry():
+                self._transition(now, Reconnect.Void)
+                return
+
             # Back off
-            if (self.state in (Reconnect.Active, Reconnect.Idle) and
+            if self.backoff_free_tries > 1:
+                self.backoff_free_tries -= 1
+                self.backoff = 0
+            elif (self.state in (Reconnect.Active, Reconnect.Idle) and
                 (self.last_activity - self.last_connected >= self.backoff or
                  self.passive)):
                 if self.passive:
@@ -363,23 +377,26 @@ class Reconnect(object):
             else:
                 if self.backoff < self.min_backoff:
                     self.backoff = self.min_backoff
-                elif self.backoff >= self.max_backoff / 2:
-                    self.backoff = self.max_backoff
-                else:
+                elif self.backoff < self.max_backoff / 2:
                     self.backoff *= 2
-
-                if self.passive:
-                    self.info_level("%s: waiting %.3g seconds before trying "
-                                    "to listen again"
-                                    % (self.name, self.backoff / 1000.0))
+                    if self.passive:
+                        action = "trying to listen again"
+                    else:
+                        action = "reconnect"
+                    self.info_level("%s: waiting %.3g seconds before %s"
+                                    % (self.name, self.backoff / 1000.0,
+                                       action))
                 else:
-                    self.info_level("%s: waiting %.3g seconds before reconnect"
-                                    % (self.name, self.backoff / 1000.0))
-
-            if self.__may_retry():
-                self._transition(now, Reconnect.Backoff)
-            else:
-                self._transition(now, Reconnect.Void)
+                    if self.backoff < self.max_backoff:
+                        if self.passive:
+                            action = "try to listen"
+                        else:
+                            action = "reconnect"
+                        self.info_level("%s: continuing to %s in the "
+                                        "background but suppressing further "
+                                        "logging" % (self.name, action))
+                    self.backoff = self.max_backoff
+            self._transition(now, Reconnect.Backoff)
 
     def connecting(self, now):
         """Tell this FSM that a connection or listening attempt is in progress.
@@ -390,7 +407,7 @@ class Reconnect(object):
         if self.state != Reconnect.ConnectInProgress:
             if self.passive:
                 self.info_level("%s: listening..." % self.name)
-            else:
+            elif self.backoff < self.max_backoff:
                 self.info_level("%s: connecting..." % self.name)
             self._transition(now, Reconnect.ConnectInProgress)