Redis OSS configuration and limits
The Redis OSS engine provides a number of configuration parameters, some of which are modifiable in ElastiCache (Redis OSS) and some of which are not modifiable to provide stable performance and reliability.
Serverless caches
For serverless caches, parameter groups are not used and all Redis OSS configuration is not modifiable. The following Redis OSS parameters are in place:
| Name | Details | Description |
|---|---|---|
acl-pubsub-default |
|
Default pubsub channel permissions for ACL users on the cache. |
client-output-buffer-limit |
|
Normal clients have no buffer limit. PUB/SUB clients will be disconnected if they breach 32MiB backlog, or breach 8MiB backlog for 60s. |
client-query-buffer-limit |
1 GiB | The maximum size of a single client query buffer. Additionally, clients cannot issue a request with more than 4,000 arguments. |
cluster-allow-pubsubshard-when-down |
yes |
This allows the cache to serve pubsub traffic while the cache is partially down. |
cluster-allow-reads-when-down |
yes |
This allows the cache to serve read traffic while the cache is partially down. |
cluster-enabled |
yes |
All serverless caches are cluster mode enabled, which allows them to transparently partition their data across multiple backend shards. All slots are surfaced to clients as being owned by a single virtual node. |
cluster-require-full-coverage |
no |
When the keyspace is partially down (i.e. at least one hash slot is inaccessible), the cache will continue accepting queries for the part of the
keyspace that is still covered. The entire keyspace will always be "covered" by a single virtual node in cluster slots. |
lua-time-limit |
5000 |
The maximum execution time for a Lua script, in milliseconds,
before ElastiCache takes action to stop the script. If
|
maxclients |
65000 | The maximum number of clients that can be connected to the cache at one time. Further connections established may or may not succeed. |
maxmemory-policy |
volatile-lru |
Items with a TTL set are evicted following least-recently-used (LRU) estimation when a cache's memory limit is reached. |
notify-keyspace-events |
(an empty string) | Keyspace events are currently not supported on serverless caches. |
port |
Primary port: 6379 Read port: 6380 |
Serverless caches advertise two ports with the same hostname. The primary port allows writes and reads, whereas the read port allows lower-latency
eventually-consistent reads using the READONLY command. |
proto-max-bulk-len |
512 MiB | The maximum size of a single element request. |
timeout |
0 | Clients are not forcibly disconnected at a specific idle time, but they may be disconnected during steady-state for load balancing purposes. |
Additionally, the following limits are in place:
| Name | Details | Description |
|---|---|---|
| Key name length | 4 KiB | The maximum size for a single Redis OSS key or channel name. Clients referencing keys larger than this will receive an error. |
| Lua script size | 4 MiB | The maximum size of a single Redis OSS Lua script. Attempts to load a Lua script larger than this will receive an error. |
| Slot size | 32 GiB | The maximum size of a single Redis OSS hash slot. Clients trying to set more data than this on a single Redis OSS slot will trigger
the eviction policy on the slot, and if no keys are evictable, will receive an out of memory (OOM) error. |
Self-designed clusters
For self-designed clusters, see Redis OSS-specific parameters for the default values of configuration parameters and which are configurable. The default values are generally recommended unless you have a specific use case requiring them to be overridden.