redis-clustering

Name: redis-clustering
Author: redis

739installs22forks

How to install redis-clustering?

redis/agent-skills/redis-clustering

$npx -y skills add redis/agent-skills --skill redis-clustering

Installs into the current project.

Summary

Redis Cluster and replication guidance covering hash tags for multi-key operations, avoiding CROSSSLOT errors, and reading from replicas to scale read-heavy workloads. Use when designing keys for a sharded Redis Cluster, debugging CROSSSLOT errors on MGET / SDIFF / pipelines, con

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SKILL.md

1	# Redis Clustering
2
3	Guidance for designing keys and routing reads in a sharded Redis Cluster (and in standalone primary/replica replication). Covers the two failure modes that bite most new cluster users: `CROSSSLOT` errors on multi-key operations, and overloading primaries with read traffic.
4
5	## When to apply
6
7	- Designing keys for a Redis Cluster deployment.
8	- Debugging a `CROSSSLOT` error on `MGET`, `SDIFF`, transactions, or pipelines.
9	- Implementing transactions / Lua scripts that touch multiple keys.
10	- Scaling out read traffic without adding shards.
11
12	## 1. Hash tags for multi-key operations
13
14	Redis Cluster distributes keys across 16,384 slots by hashing the key name. Any command that touches multiple keys (`MGET`, `SDIFF`, `SUNIONSTORE`, transactions, pipelines, Lua scripts with multiple `KEYS[]`) requires all keys to live on the same slot — otherwise the server returns a `CROSSSLOT` error.
15
16	Hash tags force this: the part between `{` and `}` is the only thing hashed for slot assignment, so two keys sharing a hash tag always land together.
17
18	```python
19	# Same slot — multi-key ops work
20	redis.set("{user:1001}:profile", "...")
21	redis.set("{user:1001}:settings", "...")
22	redis.lmove("{user:1001}:pending", "{user:1001}:processed", "LEFT", "RIGHT")
23	```
24
25	```python
26	# Different keys, no hash tag — CROSSSLOT on multi-key commands in cluster mode
27	redis.set("user:1001:profile", "...")
28	redis.set("user:1001:settings", "...")
29	pipe = redis.pipeline()
30	pipe.get("user:1001:profile")
31	pipe.get("user:1001:settings")
32	pipe.execute() # CROSSSLOT error in cluster
33	```
34
35	Rules of thumb:
36
37	- Use a tag scoped to the meaningful entity, e.g. `{user:1001}`. Avoid bare `{1001}` — unrelated namespaces (`purchase:{1001}`, `employee:{1001}`) would all collide on the same slot.
38	- Only tag where you actually need multi-key ops. Tagging everything creates hotspots and defeats the point of sharding.
39	- A single-key command on a hash-tagged key works fine, so adding tags later is incremental — but renaming keys in production is painful, so plan tagging up front for entities you'll group.
40
41	See [references/hash-tags.md](references/hash-tags.md).
42
43	## 2. Read replicas for read-heavy workloads
44
45	If reads dominate writes, route them to replicas to free primary capacity. Works both in Redis Cluster (each shard has 1+ replica) and in standalone primary/replica replication.
46
47	```python
48	# Redis Cluster: enable replica reads on the client
49	from redis.cluster import RedisCluster
50
51	rc = RedisCluster(host="localhost", port=6379, read_from_replicas=True)
52	rc.set("key", "value") # → primary
53	value = rc.get("key") # → may be served by a replica
54	```
55
56	For non-cluster setups, point two clients at the right nodes:
57
58	```python
59	primary = Redis(host="primary-host", port=6379)
60	replica = Redis(host="replica-host", port=6379)
61	primary.set("key", "value")
62	value = replica.get("key")
63	```
64
65	The trade-off is consistency: replicas are eventually consistent. Don't read your own writes from a replica; don't use replica reads for anything that requires strict freshness (financial balances, idempotency state). Good fits: cache layers, analytics, dashboards, recommendation feeds.
66
67	See [references/read-replicas.md](references/read-replicas.md).
68
69	## References
70
71	- [Redis Cluster spec — hash tags](https://redis.io/docs/latest/operate/oss_and_stack/reference/cluster-spec/#hash-tags)
72	- [Redis: multi-key operations in cluster](https://redis.io/docs/latest/operate/rs/databases/durability-ha/clustering/#multikey-operations)
73	- [Redis: Replication](https://redis.io/docs/latest/operate/oss_and_stack/management/replication/)

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Type

redis-clustering

739installs22forks

View on GitHub

How to install redis-clustering?

redis/agent-skills/redis-clustering

$npx -y skills add redis/agent-skills --skill redis-clustering

Installs into the current project.

Summary

Files · 1

View on GitHub

SKILL.md

1	# Redis Clustering
2
3	Guidance for designing keys and routing reads in a sharded Redis Cluster (and in standalone primary/replica replication). Covers the two failure modes that bite most new cluster users: `CROSSSLOT` errors on multi-key operations, and overloading primaries with read traffic.
4
5	## When to apply
6
7	- Designing keys for a Redis Cluster deployment.
8	- Debugging a `CROSSSLOT` error on `MGET`, `SDIFF`, transactions, or pipelines.
9	- Implementing transactions / Lua scripts that touch multiple keys.
10	- Scaling out read traffic without adding shards.
11
12	## 1. Hash tags for multi-key operations
13
14	Redis Cluster distributes keys across 16,384 slots by hashing the key name. Any command that touches multiple keys (`MGET`, `SDIFF`, `SUNIONSTORE`, transactions, pipelines, Lua scripts with multiple `KEYS[]`) requires all keys to live on the same slot — otherwise the server returns a `CROSSSLOT` error.
15
16	Hash tags force this: the part between `{` and `}` is the only thing hashed for slot assignment, so two keys sharing a hash tag always land together.
17
18	```python
19	# Same slot — multi-key ops work
20	redis.set("{user:1001}:profile", "...")
21	redis.set("{user:1001}:settings", "...")
22	redis.lmove("{user:1001}:pending", "{user:1001}:processed", "LEFT", "RIGHT")
23	```
24
25	```python
26	# Different keys, no hash tag — CROSSSLOT on multi-key commands in cluster mode
27	redis.set("user:1001:profile", "...")
28	redis.set("user:1001:settings", "...")
29	pipe = redis.pipeline()
30	pipe.get("user:1001:profile")
31	pipe.get("user:1001:settings")
32	pipe.execute() # CROSSSLOT error in cluster
33	```
34
35	Rules of thumb:
36
37	- Use a tag scoped to the meaningful entity, e.g. `{user:1001}`. Avoid bare `{1001}` — unrelated namespaces (`purchase:{1001}`, `employee:{1001}`) would all collide on the same slot.
38	- Only tag where you actually need multi-key ops. Tagging everything creates hotspots and defeats the point of sharding.
39	- A single-key command on a hash-tagged key works fine, so adding tags later is incremental — but renaming keys in production is painful, so plan tagging up front for entities you'll group.
40
41	See [references/hash-tags.md](references/hash-tags.md).
42
43	## 2. Read replicas for read-heavy workloads
44
45	If reads dominate writes, route them to replicas to free primary capacity. Works both in Redis Cluster (each shard has 1+ replica) and in standalone primary/replica replication.
46
47	```python
48	# Redis Cluster: enable replica reads on the client
49	from redis.cluster import RedisCluster
50
51	rc = RedisCluster(host="localhost", port=6379, read_from_replicas=True)
52	rc.set("key", "value") # → primary
53	value = rc.get("key") # → may be served by a replica
54	```
55
56	For non-cluster setups, point two clients at the right nodes:
57
58	```python
59	primary = Redis(host="primary-host", port=6379)
60	replica = Redis(host="replica-host", port=6379)
61	primary.set("key", "value")
62	value = replica.get("key")
63	```
64
65	The trade-off is consistency: replicas are eventually consistent. Don't read your own writes from a replica; don't use replica reads for anything that requires strict freshness (financial balances, idempotency state). Good fits: cache layers, analytics, dashboards, recommendation feeds.
66
67	See [references/read-replicas.md](references/read-replicas.md).
68
69	## References
70
71	- [Redis Cluster spec — hash tags](https://redis.io/docs/latest/operate/oss_and_stack/reference/cluster-spec/#hash-tags)
72	- [Redis: multi-key operations in cluster](https://redis.io/docs/latest/operate/rs/databases/durability-ha/clustering/#multikey-operations)
73	- [Redis: Replication](https://redis.io/docs/latest/operate/oss_and_stack/management/replication/)

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6 picks

Type