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Elastic MapReduce

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Custom Scaling Configuration

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最終更新日: 2026-10-09 15:25:43
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Basic Settings

In the Basic Settings section, you can set the number of scale-out and scale-in nodes of the custom scaling feature, configure the elastic resource type, and configure whether auto scaling supports graceful scale-in. You can also view the number of elastic node resources in the current cluster and release elastic instances with one click.
Parameter
Description
Minimum Number of Nodes
Minimum number of task nodes retained for auto scaling in the cluster when the automatic scale-in policy is triggered.
Maximum Number of Nodes
Maximum number of task nodes retained for auto scaling in the cluster when the automatic scale-out policy is triggered. The cumulative number of nodes scaled out by one or more specifications cannot exceed the maximum number of nodes.
Release All
One-click removal of all nodes scaled out by auto scaling, without affecting nodes not scaled out by auto scaling.
Release Spot Instances
One-click removal of only the spot instance nodes scaled out by auto scaling, without affecting non-spot instance resource nodes.
Release Pay-As-You-Go Instances
One-click removal of the pay-as-you-go instance nodes scaled out by auto scaling, without affecting pay-as-you-go nodes not scaled out by auto scaling.
Global Switch of Graceful Scale-In
Disabled by default, which means the graceful scale-in policy is disabled in any scale-in rule. After it is enabled, the graceful scale-in policy takes effect when graceful scale-in and a single rule are enabled at the same time.
Resource Type
The HOST resource type supports pay-as-you-go and spot instance billing modes, while POD resources support the pay-as-you-go billing mode only and can only be used to deploy the NodeManager role of YARN.
Attention
When the resource type is switched, the corresponding scaling specifications and node selection policy are switched and take effect accordingly.

Scaling Specification Management

A scaling specification specifies the node specifications and node payment policies for scale-out through custom scaling. To keep cluster load changes linear, it is recommended to keep the CPU and memory of the scaling specifications as consistent as possible.
Node selection policy: Two policies are supported: Pay-As-You-Go and Spot Instance First.
Pay-As-You-Go: When a scale-out rule is triggered, pay-as-you-go nodes are all added to supplement computing power.
Spot Instance First: When a scale-out rule is triggered, spot instances are added preferentially to supplement computing power. When spot instance resources are insufficient, pay-as-you-go resources are used to make up the computing power. Minimum Proportion of Pay-As-You-Go Nodes: Guarantees the minimum proportion of pay-as-you-go nodes in the total number of nodes scaled out each time.
Example:
If 10 nodes are scaled out at a time and the minimum proportion of pay-as-you-go nodes is 20%, at least two pay-as-you-go nodes will be supplemented when the scale-out rule is triggered, and the remaining eight nodes will be supplemented by spot instances. When the spot instance resources are fewer than eight nodes, pay-as-you-go node resources are used to make up the difference.
Nodes in a scaling specification support adding, deleting, modifying, and querying, and the priority of a scaling specification can be adjusted as needed. Rules are prioritized from high to low (1 > 2 > 3 > 4 > 5).
Attention:
If "Resource type: POD" is preset in basic settings, the node payment policy only supports pay-as-you-go billing.

Scaling Rule Management

A scaling rule is a business policy that configures the trigger conditions of scale-out and scale-in actions and the number of changed nodes. Two scaling policies are supported: load-based scaling and time-based scaling. Select an appropriate policy based on business requirements to set scaling rules. Mixed elastic rule settings of time-based scaling and load-based scaling are also supported. Rules are triggered in the principle of "first triggered, first executed; simultaneous triggers are executed by rule priority".

Setting Load-based Scaling

When the peaks and troughs of cluster computing cannot be accurately estimated, load-based scaling can be used for policy configuration to ensure that important jobs are completed on time. The load is mainly based on the metric statistics rules preset for YARN or Trino, and task nodes are automatically adjusted when preset conditions are triggered.
Attention:
For details on cluster queue load metrics, see Queue Load Metric Mapping.
Click Add Rule. On the create rule page, select By Load for the policy type and configure the rule as follows:

Configuration Item
Description
Rule Type
Scale-out and scale-in.
Policy Type
By Load
Rule Name
Name of the scaling rule. In a cluster, scaling rule names (including scale-out and scale-in rule names) must be unique.
Validity Period
The load-based scaling rule is triggered only within the validity period. No Limit is selected for the time range by default, and custom time periods are supported for configuring load-based scaling rules.
Load Type
YARN or Trino load metrics are supported. Trino load-based scaling is supported only by clusters of EMR-V2.7.0 and EMR-V3.40 or later that have the Trino component deployed.
Statistical Rule
Set trigger thresholds for single or multiple rules based on the selected cluster load metrics. Up to five statistical rules can be set, and rule statistics by subqueue is supported.
Rule: specifies the queue and load metrics, and sets conditional rules for the trigger threshold.
Statistical period: Within a statistical period, it counts as one trigger when the selected load metric reaches the trigger threshold according to the selected aggregation dimension (average, maximum, or minimum). Three statistical periods are currently supported: 300 seconds, 600 seconds, and 900 seconds.
Repetition count: The number of times the load metric reaches the threshold after aggregation. The elastic scaling action of the cluster is triggered after this count is reached.
Scale-Out/Scale-In Method
Three methods are supported: node, memory, and number of cores. Only non-zero integers are accepted as input values for all three methods. When the method is number of cores or memory, the system will calculate the number of nodes to be scaled out based on maximum computing power, and the system will calculate the minimum number of nodes to be removed while ensuring business continuity, scaling in in reverse chronological order and ensuring that at least one node is scaled in.
Scale-Out Service
Scale-out components inherit the cluster-level configuration by default, and scaled-out nodes belong to the default configuration group of the node type. To adjust the scale-out component configuration, you can specify configuration settings.
Node Label
By default, when this parameter is left empty, scaled-out resources are marked with the default label. Once configured, scaled-out resources will be marked with the specified label.
Resource Replenishment Retry
During peak order placement, automatic scale-out may result in the actual number of scale-out machines failing to reach the elastic target quantity due to resource contention. When the resource replenishment retry policy is enabled and the configured scaling specification resources are sufficient, the system will automatically retry resource requests until the target quantity is achieved or approached. If automatic scale-out frequently falls short of expectations due to insufficient resources, you can enable this configuration. Note that enabling retries may extend the automatic scale-out time. Pay attention to the impact of the policy adjustment on your business.
Cooldown Period
Interval between the successful execution of the current rule and the start of the next auto scaling action (the cooldown period ranges from 0 to 43200 seconds).
Graceful Scale-In
After graceful scale-in mode is enabled, if a node is running a task when the scale-in action is triggered, the node will not be released immediately but waits for the task to complete within a custom time period before being scaled in. If the task is not completed when the custom time period ends, the node will still be scaled in.

Setting Time-based Scaling

When cluster computing has obvious peaks and troughs within a certain period, time-based scaling can be used for policy configuration to ensure that important jobs are completed on time. A time-based scaling policy can add or remove task nodes at fixed time periods every day, every week, or every month. Click Add Rule. On the create rule page, select By Time for the policy type and configure the rule as follows:
Configuration Item
Description
Rule Type
Scale-out and scale-in.
Policy Type
By Time
Rule Name
Name of the scaling rule. In a cluster, scaling rule names (including scale-out and scale-in rule names) must be unique.
Execution Type
Execute once: The scaling action is triggered at a specific time, accurate to the minute.
Repeat: The scaling action is triggered at each specified time period or at a specific time. Daily, Weekly, and Monthly are supported.
Execution time: The specific time to perform the scaling action each day.
Rule validity period: The validity period range for triggering a single repeated rule.
Scale-Out/Scale-In Method
Three methods are supported: node, memory, and number of cores. Only non-zero integers are accepted as input values for all three methods. When the method is number of cores or memory, the system will calculate the number of nodes to be scaled out based on maximum computing power, and the system will calculate the minimum number of nodes to be removed while ensuring business continuity, scaling in in reverse chronological order and ensuring that at least one node is scaled in.
Scale-Out Service
Scale-out components inherit the cluster-level configuration by default, and scaled-out nodes belong to the default configuration group of the node type. To adjust the scale-out component configuration, you can specify configuration settings.
Node Label
By default, when this parameter is left empty, scaled-out resources are marked with the default label. Once configured, scaled-out resources will be marked with the specified label.
Resource Replenishment Retry
During peak order placement, automatic scale-out may result in the actual number of scale-out machines failing to reach the elastic target quantity due to resource contention. When the resource replenishment retry policy is enabled and the configured scaling specification resources are sufficient, the system will automatically retry resource requests until the target quantity is achieved or approached. If automatic scale-out frequently falls short of expectations due to insufficient resources, you can enable this configuration. Note that enabling retries may extend the automatic scale-out time. Pay attention to the impact of the policy adjustment on your business.
Retry Expiration Time
Elastic scaling may fail to execute at the specified time for various reasons. By setting the retry expiration time, the system retries execution at regular intervals within the time range until the scaling is executed when the conditions are met.
Cooldown Period
Interval between the successful execution of the current rule and the start of the next auto scaling action (the cooldown period ranges from 0 to 43200 seconds).
Scheduled Termination
Specifies the usage duration of scaled-out resources, so that the current batch of nodes is not affected when scale-in rules are triggered. No Limit is selected by default, and a custom termination duration is supported. Enter an integer in the range of 1 to 24 hours.
Usage scenario: Suitable when computing power needs to be supplemented during fixed periods and maintained within one day, and other scale-in rules do not affect this batch of resources.
Graceful Scale-In
After graceful scale-in mode is enabled, if a node is running a task when the scale-in action is triggered, the node will not be released immediately but waits for the task to complete within a custom time period before being scaled in. If the task is not completed when the custom time period ends, the node will still be scaled in.


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