Redis Specific Parameters
If you do not specify a parameter group for your Redis cluster,
then a default parameter group will be used (either default.redis2.6,
default.redis2.8, or default.redis3.2.
You cannot change the values of any parameters in the default parameter group;
however, you can create a custom parameter group and assign it to your cluster
at any time
as long as the values of conditionally modifiable parameters are the same in both
parameter groups.
Contents
- Redis 3.2.10 Parameter Changes
- Redis 3.2.6 Parameter Changes
- Redis 3.2.4 Parameter Changes
- Redis 2.8.24 (Enhanced) Added Parameters
- Redis 2.8.23 (Enhanced) Added Parameters
- Redis 2.8.22 (Enhanced) Added Parameters
- Redis 2.8.21 Added Parameters
- Redis 2.8.19 Added Parameters
- Redis 2.8.6 Added Parameters
- Redis 2.6.13 Parameters
- Redis Node-Type Specific Parameters
Note
Because the newer Redis versions provide a better and more stable user experience, Redis versions 2.6.13, 2.8.6, and 2.8.19 are deprecated when using the ElastiCache console. We recommend against using these Redis versions. If you need to use one of them, work with the AWS CLI or ElastiCache API.
For more information, see the following topics:
| AWS CLI | ElastiCache API | |
|---|---|---|
|
Create Cluster |
Creating a Cache Cluster (AWS CLI) This action cannot be used to create a replication group with cluster mode enabled. |
Creating a Cache Cluster (ElastiCache API) This action cannot be used to create a replication group with cluster mode enabled. |
|
Modify Cluster |
Modifying a Cache Cluster (AWS CLI) This action cannot be used to create a replication group with cluster mode enabled. |
Modifying a Cache Cluster (ElastiCache API) This action cannot be used to create a replication group with cluster mode enabled. |
|
Create Replication Group |
Creating a Redis (cluster mode disabled) Cluster with Replicas from Scratch (AWS CLI) Creating a Redis (cluster mode enabled) Cluster with Replicas from Scratch (AWS CLI) |
Creating a Redis (cluster mode disabled) Cluster with Replicas from Scratch (ElastiCache API) Creating a Redis (cluster mode enabled) Cluster with Replicas from Scratch (ElastiCache API) |
|
Modify Replication Group |
Modifying a Replication Group (AWS CLI) This action cannot be used to create a replication group with cluster mode enabled. |
Modifying a Replication Group (ElastiCache API) This action cannot be used to create a replication group with cluster mode enabled. |
Redis 3.2.10 Parameter Changes
Parameter group family: redis3.2
ElastiCache for Redis 3.2.10 there are no additional parameters supported.
Redis 3.2.6 Parameter Changes
Parameter group family: redis3.2
For Redis 3.2.6 there are no additional parameters supported.
Redis 3.2.4 Parameter Changes
Parameter group family: redis3.2
Beginning with Redis 3.2.4 there are two default parameter groups.
-
default.redis3.2– When running Redis 3.2.4, specify this parameter group or one derived from it, if you want to create a Redis (cluster mode disabled) replication group and still use the additional features of Redis 3.2.4. -
default.redis3.2.cluster.on– Specify this parameter group or one derived from it, when you want to create a Redis (cluster mode enabled) replication group.
New Parameters for Redis 3.2.4
Parameter group family: redis3.2
For Redis 3.2.4 the following additional parameters are supported.
| Name | Details | Description |
|---|---|---|
list-max-ziplist-size |
Default: -2 Type: integer Modifiable: No |
Lists are encoded in a special way to save space.
The number of entries allowed per internal list node can be specified
as a fixed maximum size or a maximum number of elements.
For a fixed maximum size, use -5 through -1, meaning:
|
list-compress-depth |
Default: 0 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
Lists may also be compressed.
Compress depth is the number of quicklist ziplist nodes from each side of
the list to exclude from compression.
The head and tail of the list are always uncompressed for fast push and pop
operations.
Settings are:
|
cluster-enabled |
Default: yes/no † Type: boolean Modifiable: No |
Indicates whether this is a Redis (cluster mode enabled) replication group in cluster mode (yes) or a Redis (cluster mode enabled) replication group in non-cluster mode (no). Redis (cluster mode enabled) replication groups in cluster mode can partition their data across up to 15 node groups. † Redis 3.2.x has two default parameter groups.
. |
cluster-require-full-coverage |
Default: no Type: boolean Modifiable: yes Changes Take Effect: Immediately |
When set to However, sometimes you want the subset of the cluster which is working
to continue to accept queries for the part of the key space that is still
covered. In order to do so, just set the |
hll-sparse-max-bytes |
Default: 3000 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
HyperLogLog sparse representation bytes limit. The limit includes the 16 byte header. When a HyperLogLog using the sparse representation crosses this limit, it is converted into the dense representation. A value greater than 16000 is not recommended, because at that point the dense representation is more memory efficient. We recommend a value of ~3000 in order to have the benefits of the space efficient encoding without slowing down PFADD too much, which is O(N) with the sparse encoding. The value can be raised to ~10000 when CPU is not a concern, but space is, and the data set is composed of many HyperLogLogs with cardinality in the 0 - 15000 range. |
reserved-memory-percent |
Default: 25 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
The percent of a node's memory reserved for nondata use. By default, the Redis data footprint grows until it consumes all of the node's memory. If this occurs, then node performance will likely suffer due to excessive memory paging. By reserving memory, you can set aside some of the available memory for non-Redis purposes to help reduce the amount of paging. This parameter is specific to ElastiCache, and is not part of the standard Redis distribution. For more information, see
|
Parameters Changed in Redis 3.2.4 (Enhanced)
Parameter group family: redis3.2
For Redis 3.2.4 the following parameters were changed.
| Name | Details | Change |
|---|---|---|
appendonly |
Default: off Modifiable: No |
If you want to upgrade from an earlier Redis version,
you must first turn |
appendfsync |
Default: off Modifiable: No |
If you want to upgrade from an earlier Redis version,
you must first turn |
repl-timeout |
Default: 60 Modifiable: No |
Is now unmodifiable with a default of 60. |
tcp-keepalive |
Default: 300 |
Default was 0. |
list-max-ziplist-entries |
Parameter is no longer available. |
|
list-max-ziplist-value |
Parameter is no longer available. |
Redis 2.8.24 (Enhanced) Added Parameters
Parameter group family: redis2.8
For Redis 2.8.24 there are no additional parameters supported.
Redis 2.8.23 (Enhanced) Added Parameters
Parameter group family: redis2.8
For Redis 2.8.23 the following additional parameter is supported.
| Name | Details | Description |
|---|---|---|
close-on-slave-write |
Default: yes Type: string (yes/no) Modifiable: Yes Changes Take Effect: Immediately |
If enabled, clients who attempt to write to a read-only replica will be disconnected. |
How close-on-slave-write works
The close-on-slave-write parameter is introduced by Amazon ElastiCache
to give you more control over how your cluster responds when a primary node and
a read replica node swap roles due to promoting a read replica to primary.
If the read-replica cluster is promoted to primary for any reason other than a Multi-AZ
enabled replication group failing over,
the client will continue trying to write to endpoint A.
Because endpoint A is now the endpoint for a read-replica, these writes will
fail.
This is the behavior for Redis prior to ElastiCache introducing close-on-slave-write
and the behavior if you disable close-on-slave-write.
With close-on-slave-write enabled,
any time a client attempts to write to a read-replica,
the client connection to the cluster is closed.
Your application logic should detect the disconnection,
check the DNS table,
and reconnect to the primary endpoint, which now would be endpoint B.
Why disable close-on-slave-write?
If disabling close-on-slave-write results in writes to the failing cluster,
why would you want to disable close-on-slave-write?
As previously mentioned,
with close-on-slave-write enabled,
any time a client attempts to write to a read-replica
the client connection to the cluster is closed.
Since establishing a new connection to the node takes time,
disconnecting and reconnecting as a result of a write request to the replica
would also impact the latency of read requests that were served through the same
connection,
until a new connection is established.
Therefore, if your application is especially read-heavy or very latency-sensitive,
you my prefer to keep your clients connected so as to not degrade read performance.
Redis 2.8.22 (Enhanced) Added Parameters
Parameter group family: redis2.8
For Redis 2.8.22 there are no additional parameters supported.
Important
-
Beginning with Redis version 2.8.22,
repl-backlog-sizeapplies to the primary cluster as well as to replica clusters. -
Beginning with Redis version 2.8.22, the
repl-timeoutparameter is not supported. If it is changed, ElastiCache will overwrite with the default (60s), as we do withappendonly.
The following parameters are no longer supported.
-
appendonly
-
appendfsync
-
repl-timeout
Redis 2.8.21 Added Parameters
Parameter group family: redis2.8
For Redis 2.8.21, there are no additional parameters supported.
Redis 2.8.19 Added Parameters
Parameter group family: redis2.8
For Redis 2.8.19 there are no additional parameters supported.
Redis 2.8.6 Added Parameters
Parameter group family: redis2.8
For Redis 2.8.6 the following additional parameters are supported.
| Name | Details | Description |
|---|---|---|
min-slaves-max-lag |
Default: 10 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
The number of seconds within which the primary node must receive a ping request from a read replica. If this amount of time passes and the primary does not receive a ping, then the replica is no longer considered available. If the number of available replicas drops below min-slaves-to-write, then the primary will stop accepting writes at that point. If either this parameter or min-slaves-to-write is 0, then the primary node will always accept writes requests, even if no replicas are available. |
min-slaves-to-write |
Default: 0 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
The minimum number of read replicas which must be available in order for the primary node to accept writes from clients. If the number of available replicas falls below this number, then the primary node will no longer accept write requests. If either this parameter or min-slaves-max-lag is 0, then the primary node will always accept writes requests, even if no replicas are available. |
notify-keyspace-events |
Default: (an empty string) Type: string Modifiable: Yes Changes Take Effect: Immediately |
The types of keyspace events that Redis can notify clients of. Each event type is represented by a single letter:
You can have any combination of these event types. For example, AKE means that Redis can publish notifications of all event types. Do not use any characters other than those listed above; attempts to do so will result in error messages. By default, this parameter is set to an empty string, meaning that keyspace event notification is disabled. |
repl-backlog-size |
Default: 1048576 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
The size, in bytes, of the primary node backlog buffer. The backlog is used for recording
updates to data at the primary node. When a read replica connects to
the primary, it attempts to perform a partial sync ( The minimum value for this parameter is 16384. Note Beginning with Redis 2.8.22, this parameter applies to the primary cluster as well as the read replicas. |
repl-backlog-ttl |
Default: 3600 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
The number of seconds that the primary node will retain the backlog buffer. Starting
from the
time the last replica node disconnected, the data in the backlog
will remain intact until If this parameter is set to 0, then the backlog buffer will never be released. |
repl-timeout |
Default: 60 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
Represents the timeout period, in seconds, for:
|
Redis 2.6.13 Parameters
Parameter group family: redis2.6
Redis 2.6.13 was the first version of Redis supported by ElastiCache. The following table shows the Redis 2.6.13 parameters that ElastiCache supports.
| Name | Details | Description |
|---|---|---|
activerehashing |
Default: yes Type: string (yes/no) Modifiable: At Creation |
Determines whether to enable Redis' active rehashing feature. The main hash table is rehashed ten times per second; each rehash operation consumes 1 millisecond of CPU time. This value is set when you create the parameter group. When assigning a new parameter group to a cluster, this value must be the same in both the old and new parameter groups. |
appendonly |
Default: no Type: string Modifiable: Yes Changes Take Effect: Immediately |
Enables or disables Redis' append only file feature (AOF). AOF captures any Redis commands that change data in the cache, and is used to recover from certain node failures. The default value is no, meaning AOF is turned off. Set this parameter to yes to enable AOF. For more information, see Mitigating Failures. Note Append Only Files (AOF) is not supported for
cache.t1.micro and cache.t2.* nodes.
For nodes of this type,
the Note For Multi-AZ replication groups, AOF is not allowed. |
appendfsync |
Default: everysec Type: string Modifiable: Yes Changes Take Effect: Immediately |
Controls how often the AOF output buffer is written to disk:
Important Some aspects value of this parameter changed in Redis version 3.2.4. See Parameters Changed in Redis 3.2.4 (Enhanced). |
client-output-buffer-limit-normal-hard-limit |
Default: 0 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
If a client's output buffer reaches the specified number of bytes, the client will be disconnected. The default is zero (no hard limit). |
client-output-buffer-limit-normal-soft-limit |
Default: 0 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
If a client's output buffer reaches the specified number of bytes, the client will
be
disconnected, but only if this condition persists for
client-output-buffer-limit-normal-soft-seconds.
The default is zero (no soft limit).
|
client-output-buffer-limit-normal-soft-seconds |
Default: 0 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
If a client's output buffer remains at
client-output-buffer-limit-normal-soft-limit bytes
for longer than this number of seconds, the client will be
disconnected. The default is zero (no time limit).
|
client-output-buffer-limit-pubsub-hard-limit |
Default: 33554432 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
For Redis publish/subscribe clients: If a client's output buffer reaches the specified number of bytes, the client will be disconnected. |
client-output-buffer-limit-pubsub-soft-limit |
Default: 8388608 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
For Redis publish/subscribe clients: If a client's output buffer reaches the
specified number of bytes, the client will be disconnected, but only if this
condition persists for
client-output-buffer-limit-pubsub-soft-seconds.
|
client-output-buffer-limit-pubsub-soft-seconds |
Default: 60 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
For Redis publish/subscribe clients: If a client's output buffer remains at
client-output-buffer-limit-pubsub-soft-limit bytes
for longer than this number of seconds, the client will be
disconnected.
|
client-output-buffer-limit-slave-hard-limit |
Default: For values see Redis Node-Type Specific Parameters Type: integer Modifiable: No |
For Redis read replicas: If a client's output buffer reaches the specified number of bytes, the client will be disconnected. |
client-output-buffer-limit-slave-soft-limit |
Default: For values see Redis Node-Type Specific Parameters Type: integer Modifiable: No |
For Redis read replicas: If a client's output buffer reaches the specified number
of
bytes, the client will be disconnected, but only if this condition
persists for client-output-buffer-limit-slave-soft-seconds.
|
client-output-buffer-limit-slave-soft-seconds |
Default: 60 Type: integer Modifiable: No |
For Redis read replicas: If a client's output buffer remains at
client-output-buffer-limit-slave-soft-limit bytes
for longer than this number of seconds, the client will be disconnected.
|
databases |
Default: 16 Type: integer Modifiable: At Creation |
The number of logical partitions the databases is split into. We recommend keeping this value low. This value is set when you create the parameter group. When assigning a new parameter group to a cluster, this value must be the same in both the old and new parameter groups. |
hash-max-ziplist-entries |
Default: 512 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
Determines the amount of memory used for hashes. Hashes with fewer than the specified number of entries are stored using a special encoding that saves space. |
hash-max-ziplist-value |
Default: 64 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
Determines the amount of memory used for hashes. Hashes with entries that are smaller than the specified number of bytes are stored using a special encoding that saves space. |
list-max-ziplist-entries |
Default: 512 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
Determines the amount of memory used for lists. Lists with fewer than the specified number of entries are stored using a special encoding that saves space. |
list-max-ziplist-value |
Default: 64 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
Determines the amount of memory used for lists. Lists with entries that are smaller than the specified number of bytes are stored using a special encoding that saves space. |
lua-time-limit |
Default: 5000 Type: integer Modifiable: No |
The maximum execution time for a Lua script, in milliseconds,
before ElastiCache takes action to stop the script.
If |
maxclients |
Default: 65000 Type: integer Modifiable: No |
The maximum number of clients that can be connected at one time. |
maxmemory-policy |
Default: volatile-lru Type: string Modifiable: Yes Changes Take Effect: Immediately |
The eviction policy for keys when maximum memory usage is reached.
Valid values are:
For more information, see Using Redis as an LRU cache. |
maxmemory-samples |
Default: 3 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
For least-recently-used (LRU) and time-to-live (TTL) calculations, this parameter represents the sample size of keys to check. By default, Redis chooses 3 keys and uses the one that was used least recently. |
reserved-memory |
Default: 0 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
The total memory, in bytes, reserved for non-data usage.
By default, the Redis node will grow until it consumes the node's
This parameter is specific to ElastiCache, and is not part of the standard Redis distribution. For more information, see
|
set-max-intset-entries |
Default: 512 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
Determines the amount of memory used for certain kinds of sets (strings that are integers in radix 10 in the range of 64 bit signed integers). Such sets with fewer than the specified number of entries are stored using a special encoding that saves space. |
slave-allow-chaining |
Default: no Type: string Modifiable: No |
Determines whether a read replica in Redis can have read replicas of its own. |
slowlog-log-slower-than |
Default: 10000 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
The maximum execution time, in microseconds, for commands to be logged by the Redis Slow Log feature. |
slowlog-max-len |
Default: 128 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
The maximum length of the Redis Slow Log. |
tcp-keepalive |
Default: 0 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
If this is set to a nonzero value (N), node clients are polled
every N seconds to ensure that they are still connected. With the
default setting of 0, no such polling occurs.
Important Some aspects of this parameter changed in Redis version 3.2.4. See Parameters Changed in Redis 3.2.4 (Enhanced). |
timeout |
Default: 0 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
The number of seconds a node waits before timing out.
Values are:
|
zset-max-ziplist-entries |
Default: 128 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
Determines the amount of memory used for sorted sets. Sorted sets with fewer than the specified number of elements are stored using a special encoding that saves space. |
zset-max-ziplist-value |
Default: 64 Type: integer Modifiable: Yes Changes Take Effect: Immediately |
Determines the amount of memory used for sorted sets. Sorted sets with entries that are smaller than the specified number of bytes are stored using a special encoding that saves space. |
Note
If you do not specify a parameter group for your Redis 2.6.13 cluster, then a
default parameter group (default.redis2.6) will be used. You
cannot change the values of any parameters in the default parameter group;
however, you can always create a custom parameter group and assign it to your
cluster at any time.
Redis Node-Type Specific Parameters
Although most parameters have a single value, some parameters have different
values depending on the node type used. The following table shows the default
values for the maxmemory,
client-output-buffer-limit-slave-hard-limit, and
client-output-buffer-limit-slave-soft-limit parameters for each node type.
The value of maxmemory is the maximum number of bytes available to
you for use, data and other uses, on the node.
Note
The maxmemory parameter cannot be modified.
| Node Type | maxmemory | client-output-buffer-limit-slave-hard-limit | client-output-buffer-limit-slave-soft-limit |
|---|---|---|---|
| cache.t1.micro | 142606336 | 14260633 | 14260633 |
| cache.t2.micro | 581959680 | 58195968 | 58195968 |
| cache.t2.small | 1665138688 | 166513868 | 166513868 |
| cache.t2.medium | 3461349376 | 346134937 | 346134937 |
| cache.m1.small | 943718400 | 943718400 | 943718400 |
| cache.m1.medium | 3093299200 | 309329920 | 309329920 |
| cache.m1.large | 7025459200 | 702545920 | 702545920 |
| cache.m1.xlarge | 14889779200 | 1488977920 | 1488977920 |
| cache.m2.xlarge | 17091788800 | 1709178880 | 1709178880 |
| cache.m2.2xlarge | 35022438400 | 3502243840 | 3502243840 |
| cache.m2.4xlarge | 70883737600 | 7088373760 | 7088373760 |
| cache.m3.medium | 2988441600 | 309329920 | 309329920 |
| cache.m3.large | 6501171200 | 650117120 | 650117120 |
| cache.m3.xlarge | 14260633600 | 1426063360 | 1426063360 |
| cache.m3.2xlarge | 29989273600 | 2998927360 | 2998927360 |
| cache.m4.large | 6892593152 | 689259315 | 689259315 |
| cache.m4.xlarge | 15328501760 | 1532850176 | 1532850176 |
| cache.m4.2xlarge | 31889126359 | 3188912636 | 3188912636 |
| cache.m4.4xlarge | 65257290629 | 6525729063 | 6525729063 |
| cache.m4.10xlarge | 166047614239 | 16604761424 | 16604761424 |
| cache.c1.xlarge | 6501171200 | 650117120 | 650117120 |
| cache.r3.large | 14470348800 | 1468006400 | 1468006400 |
| cache.r3.xlarge | 30513561600 | 3040870400 | 3040870400 |
| cache.r3.2xlarge | 62495129600 | 6081740800 | 6081740800 |
| cache.r3.4xlarge | 126458265600 | 12268339200 | 12268339200 |
| cache.r3.8xlarge | 254384537600 | 24536678400 | 24536678400 |
| cache.r4.large | 13201781556 | 1320178155 | 1320178155 |
| cache.r4.xlarge | 26898228839 | 2689822883 | 2689822883 |
| cache.r4.2xlarge | 54197537997 | 5419753799 | 5419753799 |
| cache.r4.4xlarge | 108858546586 | 10885854658 | 10885854658 |
| cache.r4.8xlarge | 218255432090 | 21825543209 | 21825543209 |
| cache.r4.16xlarge | 437021573120 | 43702157312 | 43702157312 |
Note
T1 instances do not support Multi-AZ with automatic failover.
T1 and T2 instances do not support Redis AOF.
All T2 instances are created in an Amazon Virtual Private Cloud (Amazon VPC).
T2 instances do not support Redis backup/restore.
T2 instances support Multi-AZ with automatic failover only when running Redis (cluster mode enabled).
