redis/redis-py · error · SlotNotCoveredError

{len(uncovered)} shard channel(s) left unreconciled; slot(s)

Error message

{len(uncovered)} shard channel(s) left unreconciled; slot(s) not covered by the cluster: {uncovered!r}

What it means

Error "{len(uncovered)} shard channel(s) left unreconciled; slot(s) not covered by the cluster: {uncovered!r}" thrown in redis/redis-py.

Source

Thrown at redis/cluster.py:3338

                        e,
                    )
                    if first_migrate_error is None:
                        first_migrate_error = e
                    continue
            # Garbage-collect per-node pubsubs that no longer hold any
            # subscription so their connections are released.
            for name, pubsub in list(self.node_pubsub_mapping.items()):
                if not pubsub.subscribed:
                    try:
                        pubsub.reset()
                    except Exception:
                        pass
                    self.node_pubsub_mapping.pop(name, None)
        if uncovered:
            # Surface the uncovered channels so the caller (and observer
            # notification path) knows reconciliation was incomplete. All
            # coverable siblings have already been migrated above.
            raise SlotNotCoveredError(
                f"{len(uncovered)} shard channel(s) left unreconciled; "
                f"slot(s) not covered by the cluster: {uncovered!r}"
            )
        if first_migrate_error is not None and not made_progress:
            # Every migration attempted in this pass failed transiently and
            # nothing else made progress. Re-raise the first caught error
            # (typically the root cause; later failures are often downstream
            # symptoms of the same unreachable node) so the worker's done-
            # callback surfaces a single representative failure through the
            # same logger channel used for SlotNotCoveredError. Per-channel
            # WARNINGs above preserve the full forensic detail.
            raise first_migrate_error

    def _migrate_shard_channel(self, channel, handler, old_name, new_node):
        # Detach from the old per-node pubsub, best-effort: the old node may
        # already be unreachable during migration / failover.
        if old_name and old_name in self.node_pubsub_mapping:
            old_pubsub = self.node_pubsub_mapping[old_name]

View on GitHub (pinned to da03cdc7e8)

When it happens

Trigger: Thrown at redis/cluster.py:3338 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of redis/redis-py@da03cdc7e8 (2026-08-04). Data as JSON: /data/errors/471d16fc9519f7e8.json. Report an issue: GitHub.