Instead of Exception, catch only RedisError

Tighten up and target our `try`/`except` blocks in our distributed
algorithms.  `RedisError` is the base exception class for all exceptions
raised by redis-py.

https://github.com/andymccurdy/redis-py/blob/1a41cfd95a53a95b078084d8627be6b6fba3bb71/redis/exceptions.py#L4-L5

pottery/nextid.py

@@ -23,6 +23,7 @@
 from typing import cast
 
 from redis import Redis
+from redis import RedisError
 from redis.client import Script
 from typing_extensions import Final
 
@@ -138,7 +139,7 @@ def __current_id(self) -> int:
             for future in concurrent.futures.as_completed(futures):
                 try:
                     current_ids.append(int(future.result()))
-                except Exception as error:
+                except RedisError as error:
                     _logger.error(error, exc_info=True)
         num_masters_gotten = len(current_ids)
         if num_masters_gotten < len(self.masters) // 2 + 1:
@@ -161,7 +162,7 @@ def __current_id(self, value: int) -> None:
             for future in concurrent.futures.as_completed(futures):
                 try:
                     num_masters_set += future.result() == value
-                except Exception as error:
+                except RedisError as error:
                     _logger.error(error, exc_info=True)
         if num_masters_set < len(self.masters) // 2 + 1:
             raise QuorumNotAchieved(self.masters, self.key)

pottery/redlock.py

@@ -36,6 +36,7 @@
 from typing import cast
 
 from redis import Redis
+from redis import RedisError
 from redis.client import Script
 from typing_extensions import Final
 
@@ -254,7 +255,7 @@ def __acquire_masters(self) -> bool:
             for future in concurrent.futures.as_completed(futures):
                 try:
                     num_masters_acquired += future.result()
-                except Exception as error:  # pragma: no cover
+                except RedisError as error:  # pragma: no cover
                     _logger.error(error, exc_info=True)
             quorum = num_masters_acquired >= len(self.masters) // 2 + 1
             elapsed = timer.elapsed() - self.__drift()
@@ -359,7 +360,7 @@ def locked(self) -> int:
             for future in concurrent.futures.as_completed(futures):
                 try:
                     ttls.append(future.result())
-                except Exception as error:  # pragma: no cover
+                except RedisError as error:  # pragma: no cover
                     _logger.error(error, exc_info=True)
             num_masters_acquired = sum(1 for ttl in ttls if ttl > 0)
             quorum = num_masters_acquired >= len(self.masters) // 2 + 1
@@ -401,7 +402,7 @@ def extend(self) -> None:
                 for future in concurrent.futures.as_completed(futures):
                     try:
                         num_masters_extended += future.result()
-                    except Exception as error:  # pragma: no cover
+                    except RedisError as error:  # pragma: no cover
                         _logger.error(error, exc_info=True)
             quorum = num_masters_extended >= len(self.masters) // 2 + 1
             self._extension_num += quorum
@@ -431,7 +432,7 @@ def release(self) -> None:
             for future in concurrent.futures.as_completed(futures):
                 try:
                     num_masters_released += future.result()
-                except Exception as error:  # pragma: no cover
+                except RedisError as error:  # pragma: no cover
                     _logger.error(error, exc_info=True)
         quorum = num_masters_released >= len(self.masters) // 2 + 1
         if not quorum: