Creating a Custom Parameter Template for a DCS Instance

System default parameter templates vary by Redis version and instance type. A system default parameter template contains default instance parameter configurations. Parameter templates can be customized for parameter configurations, and can be selected in instance creation.

This section describes how to create and modify a custom parameter template on the DCS console.

Procedure

Log in to the DCS console.
Click in the upper left corner of the management console and select the region where your instance is located.
In the navigation pane, choose Parameter Templates.
Click the Default Templates or Custom Templates tab to create a template based on a default template or an existing custom template.
- If you select Default Templates, click Customize in the Operation column of the row containing the desired cache engine version.
- If you select Custom Templates, click Copy in the Operation column in the row containing the desired custom template.
Specify Template Name and Description.

The template name can contain 4 to 64 characters and must start with a letter or digit. Only letters, digits, hyphens (-), underscores (_), and periods (.) are allowed. The description can be empty.
Select Modifiable parameters.

Currently, you can enter a keyword in the search box to search for a parameter by parameter name.

In the row that contains the parameter to be modified, enter a value in the Assigned Value column.

Table 1 describes the parameters. In most cases, default values are retained.

**Table 1** DCS Redis instance configuration parameters
Parameter	Description	Exception Scenario	Value Range	Default Value
active-expire-num	Number of randomly checked keys in regular expired key deletions. Enlarging this parameter may increase CPU usage or command latency in a short period of time. Lessening this parameter may increase expired keys in the memory.	-	1–1000	20
timeout	The maximum amount of time (in seconds) a connection between a client and the DCS instance can be allowed to remain idle before the connection is terminated. The value 0 indicates that the parameter is disabled. That is, the client is not disconnected when it is idle.	-	0–7200 Unit: second	0
appendfsync	Controls how often fsync() transfers cached data to the disk. Note that some OSs will perform a complete data transfer but some others only make a "best-effort" attempt.	Single-node instances do not have this parameter.	no: fsync() is never called. The OS will flush data when it is ready. This mode offers the highest performance. always: fsync() is called after every write to the AOF. This mode is very slow, but also very safe. everysec: fsync() is called once per second. This mode provides a compromise between safety and performance.	no
appendonly	Indicates whether to log each modification of the instance. By default, data is written to disks asynchronously in Redis. If this function is disabled, recently-generated data might be lost in the event of a power failure.	Single-node instances do not have this parameter.	yes: Logs are enabled, that is, persistence is enabled. no: Logs are disabled, that is, persistence is disabled. only-replica: Enable persistence only on replica nodes.	yes
client-output-buffer-limit-slave-soft-seconds	When the client-output-buffer-slave-soft-limit parameter is exceeded for more than the value of this parameter, the server drops the connection. The smaller the value, the easier the disconnection.	-	0–60 Unit: second	60
client-output-buffer-slave-hard-limit	Hard limit on the output buffer of replica clients. Once the output buffer exceeds the hard limit, the client is immediately disconnected. The smaller the value, the easier the disconnection.	-	0–17,179,869,184 Unit: byte	1,717,986,918
client-output-buffer-slave-soft-limit	Soft limit on the output buffer of replica clients. Once the output buffer exceeds the soft limit and continuously remains above the limit for the time specified by the client-output-buffer-limit-slave-soft-seconds parameter, the client is disconnected. The smaller the value, the easier the disconnection.	-	0–17,179,869,184 Unit: byte	1,717,986,918
maxmemory-policy	The policy applied when the maxmemory limit is reached. 8 values are available.	-	volatile-lru: Evict keys by trying to remove the less recently used (LRU) keys first, but only among keys that have an expire set. allkeys-lru: Evict keys by trying to remove the LRU keys first. volatile-random: Evict keys randomly, but only among keys that have an expire set. allkeys-random: Evict keys randomly. volatile-ttl: Evict keys with an expire set, and try to evict keys with a shorter time to live (TTL) first. noeviction: Do not delete any keys and only return errors when the memory limit was reached. volatile-lfu: Evict keys by trying to remove the less frequently used (LFU) keys first, but only among keys that have an expire set. allkeys-lfu: Evict keys by trying to remove the LFU keys first. For details about eviction policies, see the Redis official website.	volatile-lru
lua-time-limit	Maximum time allowed for executing a Lua script.	-	100–5,000 Unit: millisecond	5,000
master-read-only	Sets the instance to be read-only. All write operations will fail.	Proxy Cluster instances do not have this parameter.	yes no	no
maxclients	The maximum number of clients allowed to be concurrently connected to a DCS instance. The larger the value, the more costly the connection to the server, which affects the server performance and increases the command latency. An excessively small value may constrain the server performance. This parameter specifies the maximum number of connections on a single node (single shard). Cluster: Maximum connections per node = Maximum connections of the instance/Shard quantity Single-node and master/standby: Maximum connections on a single node = Maximum connections of the instance	Read/Write splitting instances do not support this parameter.	1000–50,000	10,000
proto-max-bulk-len	Maximum size of a single element request. Set this parameter to be greater than the customer request length. Otherwise, the request cannot be executed.	-	1,048,576–536,870,912 Unit: byte	536,870,912
repl-backlog-size	The replication backlog size. The backlog is a buffer that accumulates replica data when replicas are disconnected from the master. When a replica reconnects, a partial synchronization is performed to synchronize the data that was missed while replicas were disconnected.	-	16,384–1,073,741,824 Unit: byte	1,048,576
repl-backlog-ttl	The amount of time, in seconds, before the backlog buffer is released, starting from the last a replica was disconnected. The value 0 indicates that the backlog is never released.	-	0–604,800 Unit: second	3,600
repl-timeout	Replication timeout.	Single-node instances do not have this parameter.	30–3,600 Unit: second	60
hash-max-ziplist-entries	The maximum number of hashes that can be encoded using ziplist, a data structure optimized to reduce memory use.	-	1–10,000	512
hash-max-ziplist-value	The largest value allowed for a hash encoded using ziplist, a special data structure optimized for memory use.	-	1–10,000	64
set-max-intset-entries	When a set is composed entirely of strings and number of integer elements is less than this parameter value, the set is encoded using intset, a data structure optimized for memory use.	-	1–10,000	512
zset-max-ziplist-entries	The maximum number of sorted sets that can be encoded using ziplist, a data structure optimized to reduce memory use.	-	1–10,000	128
zset-max-ziplist-value	The largest value allowed for a sorted set encoded using ziplist, a special data structure optimized for memory use.	-	1–10,000	64
latency-monitor-threshold	The minimum amount of latency that will be logged as latency spikes If this parameter is set to 0, latency monitoring is disabled. If this parameter is set to a value greater than 0, all events blocking the server for a time greater than the configured value will be logged. To obtain statistics data, and configure and enable latency monitoring, run the LATENCY command. NOTE: The latency-monitor-threshold parameter is usually used for fault location. After locating faults based on the latency information collected, change the value of latency-monitor-threshold to 0 to avoid unnecessary latency.	Proxy Cluster instances do not have this parameter.	0–86,400,000 Unit: millisecond	0
notify-keyspace-events	Controls which keyspace events notifications are enabled for. If this parameter is configured, the Redis Pub/Sub feature will allow clients to receive an event notification when a Redis data set is modified. This parameter is disabled only when it is left blank.	Proxy Cluster instances do not have this parameter.	A combination of different values can be used to enable notifications for multiple event types. Possible values include: K: Keyspace events, published with the __keyspace@__ prefix E: Keyevent events, published with __keyevent@__ prefix g: Generic commands (non-type specific) such as DEL, EXPIRE, and RENAME $: String commands l: List commands s: Set commands h: Hash commands z: Sorted set commands x: Expired events (events generated every time a key expires) e: Evicted events (events generated when a key is evicted from maxmemory) A: an alias for "g$lshzxe" The parameter value must contain either K or E. A cannot be used together with any of the characters in "g$lshzxe". For example, the value Kl means that Redis will notify Pub/Sub clients about keyspace events and list commands. The value AKE means Redis will notify Pub/Sub clients about all events.	Ex
slowlog-log-slower-than	Slow queries cover scheduled commands whose execution is delayed. slowlog-log-slower-than is the maximum time allowed for command execution. If this threshold is exceeded, Redis will record the query.	-	0–1,000,000 Unit: microsecond	10,000
slowlog-max-len	The maximum allowed number of slow queries that can be logged. Slow query log consumes memory, but you can reclaim this memory by running the SLOWLOG RESET command.	-	0–1000	128
auto-kill-timeout-lua-process	When this parameter is enabled, processes running the lua script are killed when their execution times out. However, scripts with write operations are not killed, but their nodes automatically restart (if persistence has been enabled for the instance) without saving the write operations.	Single-node instances and DCS Redis 3.0 instances do not have this parameter.	yes: enabled no: disabled	no
dispatch-pubsub-to-fixed-shard	This parameter specifies whether pub/sub channels are on the shard of slot 0. When this parameter is enabled, the pub/sub processing logic is consistent with that of single-node instances. You are advised to enable this parameter if you do not depend heavily on pub/sub. If you depend heavily on pub/sub, use the default configuration to allocate subscriptions to all shards.	Only Proxy Cluster instances have this parameter.	yes: Enable this parameter to allocate subscription channels to the shard of slot 0. no: Disable this parameter to allocate channels to the shard of each channel-hashed slot.	no
readonly-lua-route-to-slave-enabled	If enabled, read-only Lua scripts of read-only users are executed and routed to the standby node.	Only read/write splitting instances support this parameter.	yes: enabled no: disabled	no
cluster-sentinel-enabled	To support Sentinels for the instance.	Only Proxy Cluster instances have this parameter.	yes: enabled no: disabled	no
scan-support-wr-split	The SCAN command is executed on the master node when this parameter is disabled, or is executed on the standby node otherwise. Enabling this parameter relieves SCAN commands on the master node. But newly written data in the master node may not be synchronized to replicas in time.	Only Proxy Cluster instances have this parameter. Proxy Cluster instances created earlier may not support this parameter. In this case, contact customer service to upgrade instances.	yes: enabled no: disabled	no

The default values and value ranges of the maxclients, reserved-memory-percent, client-output-buffer-slave-soft-limit, and client-output-buffer-slave-hard-limit parameters are related to the instance specifications. Therefore, these parameters are not displayed in the parameter template.
For more information about the parameters described in Table 1, visit https://redis.io/topics/memory-optimization.

Click OK.

Modifying or Deleting Custom Templates

Log in to the DCS console.
Click in the upper left corner of the management console and select the region where your instance is located.
In the navigation pane, choose Parameter Templates.
Choose the Custom Templates tab.
To edit a custom parameter template, use either of the following ways:
- Locate the row containing the desired template and click Edit in the Operation column.
  1. Change the name or modify the description.
  2. In the Parameters area, select Modifiable parameters. In the row containing the desired parameter, enter a value in the Assigned Value column. Table 1 describes the parameters. In most cases, retain the default values.
  3. Click OK.
- Click the name of a custom template.
  1. Select Modifiable parameters. Enter a keyword in the search box to search for a parameter by its name.
  2. Click Modify.
  3. In the row containing the desired parameter, enter a value in the Assigned Value column. Table 1 describes the parameters. In most cases, retain the default values.
  4. Click Save.
To delete custom templates, click Delete in the Operation column on the right of the templates to be deleted.

Click Yes.