Adding RedisCluster client to support Redis Cluster Mode (#1660)

Co-authored-by: Chayim <chayim@users.noreply.github.com>
Co-authored-by: Anas <anas.el.amraoui@live.com>

1 files changed, 102 insertions, 0 deletions

diff --git a/redis/exceptions.py b/redis/exceptions.py
index 91eb3c7..eb6ecc2 100644
--- a/redis/exceptions.py
+++ b/redis/exceptions.py
@@ -84,3 +84,105 @@ class AuthenticationWrongNumberOfArgsError(ResponseError):
     were sent to the AUTH command
     """
     pass
+
+
+class RedisClusterException(Exception):
+    """
+    Base exception for the RedisCluster client
+    """
+    pass
+
+
+class ClusterError(RedisError):
+    """
+    Cluster errors occurred multiple times, resulting in an exhaustion of the
+    command execution TTL
+    """
+    pass
+
+
+class ClusterDownError(ClusterError, ResponseError):
+    """
+    Error indicated CLUSTERDOWN error received from cluster.
+    By default Redis Cluster nodes stop accepting queries if they detect there
+    is at least a hash slot uncovered (no available node is serving it).
+    This way if the cluster is partially down (for example a range of hash
+    slots are no longer covered) the entire cluster eventually becomes
+    unavailable. It automatically returns available as soon as all the slots
+    are covered again.
+    """
+    def __init__(self, resp):
+        self.args = (resp,)
+        self.message = resp
+
+
+class AskError(ResponseError):
+    """
+    Error indicated ASK error received from cluster.
+    When a slot is set as MIGRATING, the node will accept all queries that
+    pertain to this hash slot, but only if the key in question exists,
+    otherwise the query is forwarded using a -ASK redirection to the node that
+    is target of the migration.
+    src node: MIGRATING to dst node
+        get > ASK error
+        ask dst node > ASKING command
+    dst node: IMPORTING from src node
+        asking command only affects next command
+        any op will be allowed after asking command
+    """
+
+    def __init__(self, resp):
+        """should only redirect to master node"""
+        self.args = (resp,)
+        self.message = resp
+        slot_id, new_node = resp.split(' ')
+        host, port = new_node.rsplit(':', 1)
+        self.slot_id = int(slot_id)
+        self.node_addr = self.host, self.port = host, int(port)
+
+
+class TryAgainError(ResponseError):
+    """
+    Error indicated TRYAGAIN error received from cluster.
+    Operations on keys that don't exist or are - during resharding - split
+    between the source and destination nodes, will generate a -TRYAGAIN error.
+    """
+    def __init__(self, *args, **kwargs):
+        pass
+
+
+class ClusterCrossSlotError(ResponseError):
+    """
+    Error indicated CROSSSLOT error received from cluster.
+    A CROSSSLOT error is generated when keys in a request don't hash to the
+    same slot.
+    """
+    message = "Keys in request don't hash to the same slot"
+
+
+class MovedError(AskError):
+    """
+    Error indicated MOVED error received from cluster.
+    A request sent to a node that doesn't serve this key will be replayed with
+    a MOVED error that points to the correct node.
+    """
+    pass
+
+
+class MasterDownError(ClusterDownError):
+    """
+    Error indicated MASTERDOWN error received from cluster.
+    Link with MASTER is down and replica-serve-stale-data is set to 'no'.
+    """
+    pass
+
+
+class SlotNotCoveredError(RedisClusterException):
+    """
+    This error only happens in the case where the connection pool will try to
+    fetch what node that is covered by a given slot.
+
+    If this error is raised the client should drop the current node layout and
+    attempt to reconnect and refresh the node layout again
+    """
+    pass