Create and manage parameter groups

Parameter groups allow you to view and manage the parameters required for MemStore Redis OSS configuration according to the engine version in one place.
You can also manage the parameters of clusters connected to the parameter group collectively.

The parameter list and basic concepts provided by MemStore in KakaoCloud are compatible with Redis OSS. Changing parameters may affect the MemStore service, so it is recommended to review the appropriate parameters to be entered in advance.

Below is how to manage parameter groups in the MemStore service.

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• You can receive events related to parameter groups such as creation and modification through the Alert Center > Event Notifications feature.
  
• For a list of configurable events, refer to Cloud Trail > Key Concepts. For event notification settings, refer to the Alert Center > Create and Manage Notification Policies guide.

View parameter group list

You can view the list of parameter groups, including default and custom groups, provided by KakaoCloud MemStore.

1. Go to KakaoCloud Console > Data Store > MemStore menu.

2. Click the Parameter Group menu and select the Custom group/Default group tab according to the type of parameter group to view.

3. Navigate to the Parameter Group menu that matches the selected tab.

   Item	Description
   Name	Name of the parameter group
   Cluster mode	Indicates whether cluster mode is enabled
   Family	MemStore family engine version compatible with the parameter group
   Number of connected clusters	Number of clusters connected to this group - A warning icon is displayed if there is an issue with the parameter application status of the connected cluster
   Description	Description of the parameter group
   More	Available only for custom groups - Modify: Modify parameters - Copy: Create a new parameter group with the same parameters as this group - Reset to default: Reset the group's parameters to the initial values set at the time of creation - Rollback: Revert the parameter group to the previous values. Rollback is not possible if there are no modifications or if it has already been rolled back - Delete: Delete the parameter group

View parameter group details

You can view detailed information about the MemStore parameter group.

1. Go to KakaoCloud Console > Data Store > MemStore menu.
2. Click the Parameter Group menu and select the Custom group/Default group tab according to the type of parameter group to view.
3. Navigate to the Parameter Group menu that matches the selected tab and select the parameter group to view detailed information.

Tab: Parameters

Item	Description
Name	Parameter name
Value	Value of the parameter
Type	Type of the parameter - Some Dynamic parameters require session refresh for global application
Data format	Data format of the parameter
Editable status	Not editable, Editable, Editable (Modified) - Only Editable parameters can be modified, and modified parameters are displayed as Editable (Modified)

Tab: Connected clusters

Item	Description
Name	Cluster name
Status	Cluster status
Parameter application status	Status of parameter application. For more details, refer to Parameter application status
Engine version	Redis OSS engine version of the cluster
Node type	Instance type for cluster configuration
Cluster mode	Indicates whether cluster mode is enabled, Enabled, Disabled
High availability	Indicates whether high availability is enabled, Enabled, Disabled
[Retry] button	Available when the parameter application status is Error-Sync or Suspended. Retry parameter application to clusters connected to the parameter group.

Tab: Recent events

View key events related to the parameter group that occurred in the last 7 days.

Item	Description
Time	Time the event occurred
Name	Event name
Content	Event content, results, cluster names where events occurred, etc.

• Parameter group, recent event types

Parameter group type	Event name	Description
Common group	Apply Parameter Group	Triggered when a parameter group application request is received
	Apply Parameter Group Failed	Triggered when the parameter group application operation to a cluster is completed but fails
	Apply Parameter Group Complete	Triggered when the parameter group application operation is completed for all clusters
	Apply Parameter Group To Cluster	Triggered when starting the application of the parameter group to a cluster
	Apply Parameter Group To Cluster Failed	Triggered when the application of the parameter group to a cluster fails
	Apply Parameter Group To Cluster Complete	Triggered when the parameter group is successfully applied to a specific cluster
Custom	Create Parameter Group	Triggered when a parameter group creation request is received
	Update Parameter Group	Triggered when a parameter group modification request is received
	Update Parameters	Triggered when a parameter value modification request is received
	Reset Parameters	Triggered when a parameter reset request is received
	Rollback Parameters	Triggered when a request to roll back to a previous parameter value is received

Create parameter group

1. Go to KakaoCloud Console > Data Store > MemStore menu.

2. Click the Parameter Group menu and select the Custom group tab.

3. In the Custom group tab, click the icon > Create Parameter Group.

4. In the Create Parameter Group page, enter the required information. Parameter values can be modified after the parameter group is created.

   Item	Category	Description
   Basic settings	Parameter group name	Name of the parameter group - The same name cannot be used within the same project
   	Description (optional)	Additional description for the parameter group, up to 100 characters
   Parameter group settings	Family	MemStore family engine version of the parameter group
   	Cluster mode	Indicates whether cluster mode is enabled
   	Default parameter group	Select the default parameter group provided for that engine version
   Parameters		Initial parameter values of the parameter group

Modify parameter group

Custom parameter groups can be modified after the group is created. Only parameters with Editable status can be modified. Modified parameters are displayed as Editable (Modified).

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• Some Dynamic parameters require session refresh for global application.
• If the parameter application status of a connected cluster is Pending or Applying, you cannot modify the parameters.
• In the parameter group modification page, the selected checkboxes remain even if you navigate through the list of editable parameters.

caution

• Modifying certain parameters may affect MemStore service operations. For more details, refer to Parameters to be careful when modifying.
• If issues arise after modifying parameters, it is recommended to copy the parameter group for backup and then proceed with Retry/Rollback/Reset.

1. Go to KakaoCloud Console > Data Store > MemStore menu.

2. Click the Parameter Group menu and select the Custom group tab.

3. Select the parameter group to be modified, then click the [More] icon > Modify.

4. Modify the necessary information in the Modify Parameter Group page.

   Item	Category	Description
   Basic information	Parameter group name	Name of the parameter group
   	Description (optional)	Additional description for the parameter group, up to 100 characters
   Editable parameters		List of editable parameters within the parameter group - Modified parameters are displayed as Editable (Modified)

5. If multiple clusters are connected to the parameter group, you can select the parameter application method.
   Apply all: Apply the modified parameters to all clusters simultaneously.
   Sequential apply: Apply the modified parameters sequentially to clusters.

Parameters to be careful when modifying

When modifying parameter values in a custom parameter group, modifying certain parameters may affect MemStore service operations. Please refer to the following details for more information.

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repl-backlog

• The buffer temporarily stores data to be sent to the replica node for partial synchronization if the primary and replica nodes are disconnected due to a network interruption.
  
• If a network interruption occurs, the primary node accumulates data for synchronization in the backlog. When the replica reconnects, partial synchronization (psync) is attempted using the data stored in the backlog.
  
• The primary node maintains backlog data only for a certain period (repl-backlog-ttl) after the last disconnection from the replica node, after which the backlog buffer is released. After the backlog buffer is released, if the replica node reconnects, a full sync is performed for data synchronization.
• Related parameters: repl-backlog-size, repl-backlog-ttl

client-output-buffer-limit-normal-hard-limit

Type	Input range	Description	Possible issues
integer	0~	Upper limit of client output buffer memory usage Setting to 0 means no limit.	If the client output buffer memory reaches this parameter value, the client connection is disconnected. Setting the value too low may cause the MemStore service to fail to provision. It is recommended to set a sufficient value or the default value (0) considering the workload.

client-output-buffer-limit-normal-soft-limit

Type	Input range	Description	Possible issues
integer	0~	Threshold for client output buffer memory usage Allowed for a certain period (client-output-buffer-limit-normal-soft-seconds). Setting to 0 means no threshold.	If the client output buffer memory usage exceeds the parameter value for longer than the threshold time, the client connection is disconnected. Setting the value too low may cause the MemStore service to fail to provision. It is recommended to set a sufficient value or the default value (0) considering the workload.

client-output-buffer-limit-normal-soft-seconds

Type	Input range	Description	Possible issues
integer	0~2147483647	Time allowed for the client output buffer to reach the set threshold value (seconds) Setting to 0 means no time limit.	If the client output buffer memory usage exceeds the threshold value (client-output-buffer-limit-normal-soft-limit) for longer than this parameter value, the client connection is disconnected. Setting the value too low may cause the MemStore service to fail to provision. It is recommended to set a sufficient value or the default value (0) considering the workload.

min-replicas-max-lag

Type	Input range	Description	Possible issues
integer	0~2147483647	Maximum ping response delay time for replica nodes allowed by the primary node.	If the primary node does not receive pings within the set time, the replica is considered unavailable until it reconnects. It is recommended to set a reasonable value considering service stability.

min-replicas-to-write

Type	Input range	Description	Possible issues
integer	0~2147483647	Minimum number of replicas the primary node must maintain to accept write requests.	The primary node needs a minimum number of replica nodes set in min-replicas-to-write to process write requests. If the number of replica nodes is not secured as set in the parameter, write operations on the primary node are rejected. *Example: min-replicas-to-write: 5 is set, but the cluster has only two replica nodes primary.memstore:6379> SET hello memstore(error) NOREPLICAS Not enough good replicas to write.

repl-backlog-size

Type	Input range	Description	Possible issues
integer	16384~	Size of the backlog buffer for the primary node to synchronize data with replica nodes	If the replication lag between the primary and replica nodes is greater than the backlog size set by this parameter, a full sync occurs. If set lower than the workload requirements, frequent full syncs may occur, affecting service performance or temporarily reducing service availability. It is recommended to set a sufficient value considering the workload.

repl-backlog-ttl

Type	Input range	Description	Possible issues
integer	0~2147483647	Period for which the primary node retains the backlog buffer for synchronization with replica nodes Setting to 0 means the backlog buffer is never released.	After the set time, the backlog data on the primary node is released, and a full sync is performed to replicate data to the replica node. Setting the value too low may cause frequent full syncs, affecting service performance or temporarily reducing service availability. It is recommended to set a sufficient value considering the workload.

maxclients

Type	Input range	Description	Possible issues
integer	100~65000	Maximum number of clients that can connect to a node	If set lower than the workload requirements, clients may fail to connect, and the node may be unable to pass health checks, causing failover. It is recommended to set a sufficient value considering the node type and workload.

Copy parameter group

Custom parameter groups provide a copy feature that can be used for backup. Copy the selected parameter group to create a new parameter group.

1. Go to KakaoCloud Console > Data Store > MemStore menu.
2. Click the Parameter Group menu and select the Custom group tab.
3. Select the parameter group to be copied, then click the [More] icon > Copy.
4. In the popup, check the input information and click the [OK] button.
5. Verify the copied parameter group in the Custom group tab.

Reset parameter group to default

Custom parameter groups provide a feature to reset parameters back to the initial values. Initial values are the default values provided by the selected engine version at the time of group creation. Resetting to default values attempts to apply the parameter changes to all connected clusters.

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• If the parameter application status of a connected cluster is Pending or Applying, you cannot reset the parameters to the default values.

1. Go to KakaoCloud Console > Data Store > MemStore menu.
2. Click the Parameter Group menu and select the Custom group tab.
3. Select the parameter group to be reset to default values, then click the [More] icon > Reset parameters to default values.
4. In the popup, review the instructions and click the [OK] button.
   If multiple clusters are connected to the parameter group, you can select the parameter application method.
   Apply all: Apply the modified parameters to all clusters simultaneously.
   Sequential apply: Apply the modified parameters sequentially to clusters. The parameter application status for pending clusters is displayed as Pending.
5. If there are connected clusters, check the parameter application status to ensure that the reset has been successfully applied to each cluster.

Roll back parameter group

Custom parameter groups provide a rollback feature that allows you to revert the parameter values to their previous state after modifications. This feature is available only when there is a modification history just before attempting the rollback.

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• If the parameter application status of a connected cluster is Pending or Applying, the parameter group cannot be rolled back.
• After rollback, you cannot revert to an earlier modification history, as the parameters have already been changed to the most recent modification state. If you modify the parameters again after rollback, a new modification history is created, allowing rollback again.

1. Go to KakaoCloud Console > Data Store > MemStore menu.
2. Click the Parameter Group menu and select the Custom group tab.
3. Select the parameter group to be rolled back, then click the [More] icon > Rollback.
4. In the popup, review the instructions and click the [OK] button.
5. If there are connected clusters, check the parameter application status to ensure that the rollback has been successfully applied to each cluster.

Delete parameter group

You can delete a custom parameter group if it is no longer needed.

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• Default parameter groups cannot be deleted.
• Parameter groups cannot be deleted if they are connected to a cluster.

1. Go to KakaoCloud Console > Data Store > MemStore menu.
2. Click the Parameter Group menu and select the Custom group tab.
3. Select the parameter group to be deleted, then click the [More] icon > Delete.
4. In the popup, enter the required information and click the [OK] button.
5. Verify that the parameter group has been deleted in the Custom group tab.

Retry parameter application

If the parameter application status of a connected instance is not In-Sync but Error-Sync or Suspended, you can retry the parameter application.
For more details on parameter application status, refer to Parameter application status.

1. Go to KakaoCloud Console > Data Store > MemStore menu.
2. Click the Parameter Group menu and select the Custom group tab.
3. Navigate to the Parameter Group menu that matches the selected tab and select the parameter group to view detailed information.
4. Go to the Connected cluster tab.
5. Click the [Retry] button for the instance to be retried.