TorManager: Add delay before subsequent new identity retries

The request can be retried immediately after the first
new identity, but if we do more new identities, we have to wait
for at least 6 seconds before doing the request, otherwise
it won't be done on a new ip based on my experiments.

Potential issue: If after getting third new identity, request
takes > 12 seconds (since timeout is 15) and returns 429, then the
Tor Manager will let it do a 4th try instead of giving up (meaning
request is taking forever from user's perspective).
Should be a very rare occurence however.

Signed-off-by: Jesús <heckyel@hyperbola.info>

youtube/util.py

@@ -61,7 +61,9 @@ connection_pool = urllib3.PoolManager(cert_reqs='CERT_REQUIRED')
 
 class TorManager:
     MAX_TRIES = 3
-    COOLDOWN_TIME = 5
+    # Remember the 6-sec wait times, so make cooldown be two of those
+    # (otherwise it will retry forever if 429s never end)
+    COOLDOWN_TIME = 12
 
     def __init__(self):
         self.old_tor_connection_pool = None
@@ -99,6 +101,12 @@ class TorManager:
 
     def new_identity(self, time_failed_request_started):
         '''return error, or None if no error and the identity is fresh'''
+
+        # The overall pattern at maximum (always returning 429) will be
+        # R N (0) R N (6) R N (6) R | (12) R N (0) R N (6) ...
+        # where R is a request, N is a new identity, (x) is a wait time of
+        # x sec, and | is where we give up and display an error to the user.
+
         print('new_identity: new_identity called')
         # blocks if another greenlet currently has the lock
         self.new_identity_lock.acquire()
@@ -133,9 +141,18 @@ class TorManager:
                 traceback.print_exc()
                 return 'Failed to connect to Tor control port.'
             finally:
+                original_try_num = self.try_num
                 self.try_num += 1
                 if self.try_num > self.MAX_TRIES:
                     self.try_num = 1
+
+            # If we do the request right after second new identity it won't
+            # be a new IP, based on experiments.
+            # Not necessary after first new identity
+            if original_try_num > 1:
+                print('Sleeping for 6 seconds before retrying request')
+                time.sleep(6)   # experimentally determined minimum
+
             return None
         finally:
             self.new_identity_lock.release()