Method: regionAutoscalers.list

Retrieves a list of autoscalers contained within the specified region.

HTTP request


The URL uses gRPC Transcoding syntax.

Path parameters



Project ID for this request.



Name of the region scoping this request.

Query parameters


integer (uint32 format)

The maximum number of results per page that should be returned. If the number of available results is larger than maxResults, Compute Engine returns a nextPageToken that can be used to get the next page of results in subsequent list requests. Acceptable values are 0 to 500, inclusive. (Default: 500)



Specifies a page token to use. Set pageToken to the nextPageToken returned by a previous list request to get the next page of results.



A filter expression that filters resources listed in the response. The expression must specify the field name, a comparison operator, and the value that you want to use for filtering. The value must be a string, a number, or a boolean. The comparison operator must be either =, !=, >, or <.

For example, if you are filtering Compute Engine instances, you can exclude instances named example-instance by specifying name != example-instance.

You can also filter nested fields. For example, you could specify scheduling.automaticRestart = false to include instances only if they are not scheduled for automatic restarts. You can use filtering on nested fields to filter based on resource labels.

To filter on multiple expressions, provide each separate expression within parentheses. For example:

(scheduling.automaticRestart = true)
(cpuPlatform = "Intel Skylake")

By default, each expression is an AND expression. However, you can include AND and OR expressions explicitly. For example:

(cpuPlatform = "Intel Skylake") OR
(cpuPlatform = "Intel Broadwell") AND
(scheduling.automaticRestart = true)


Sorts list results by a certain order. By default, results are returned in alphanumerical order based on the resource name.

You can also sort results in descending order based on the creation timestamp using orderBy="creationTimestamp desc". This sorts results based on the creationTimestamp field in reverse chronological order (newest result first). Use this to sort resources like operations so that the newest operation is returned first.

Currently, only sorting by name or creationTimestamp desc is supported.



Opt-in for partial success behavior which provides partial results in case of failure. The default value is false.

Request body

The request body must be empty.

Response body

If successful, the response body contains data with the following structure:

JSON representation
  "id": string,
  "items": [
      "id": string,
      "creationTimestamp": string,
      "name": string,
      "description": string,
      "target": string,
      "autoscalingPolicy": {
        "minNumReplicas": integer,
        "maxNumReplicas": integer,
        "scaleInControl": {
          "maxScaledInReplicas": {
            "fixed": integer,
            "percent": integer,
            "calculated": integer
          "timeWindowSec": integer
        "coolDownPeriodSec": integer,
        "cpuUtilization": {
          "utilizationTarget": number
        "customMetricUtilizations": [
            "metric": string,
            "filter": string,
            "utilizationTarget": number,
            "singleInstanceAssignment": number,
            "utilizationTargetType": enum
        "loadBalancingUtilization": {
          "utilizationTarget": number
        "mode": enum
      "zone": string,
      "region": string,
      "selfLink": string,
      "status": enum,
      "statusDetails": [
          "message": string,
          "type": enum
      "recommendedSize": integer,
      "kind": string
  "nextPageToken": string,
  "selfLink": string,
  "warning": {
    "code": enum,
    "message": string,
    "data": [
        "key": string,
        "value": string
  "kind": string


[Output Only] Unique identifier for the resource; defined by the server.



A list of Autoscaler resources.


string (fixed64 format)

[Output Only] The unique identifier for the resource. This identifier is defined by the server.



[Output Only] Creation timestamp in RFC3339 text format.



Name of the resource. Provided by the client when the resource is created. The name must be 1-63 characters long, and comply with RFC1035. Specifically, the name must be 1-63 characters long and match the regular expression [a-z]([-a-z0-9]*[a-z0-9])? which means the first character must be a lowercase letter, and all following characters must be a dash, lowercase letter, or digit, except the last character, which cannot be a dash.



An optional description of this resource. Provide this property when you create the resource.



URL of the managed instance group that this autoscaler will scale. This field is required when creating an autoscaler.



The configuration parameters for the autoscaling algorithm. You can define one or more of the policies for an autoscaler: cpuUtilization, customMetricUtilizations, and loadBalancingUtilization.

If none of these are specified, the default will be to autoscale based on cpuUtilization to 0.6 or 60%.



The minimum number of replicas that the autoscaler can scale in to. This cannot be less than 0. If not provided, autoscaler chooses a default value depending on maximum number of instances allowed.



The maximum number of instances that the autoscaler can scale out to. This is required when creating or updating an autoscaler. The maximum number of replicas must not be lower than minimal number of replicas.





Maximum allowed number (or %) of VMs that can be deducted from the peak recommendation during the window autoscaler looks at when computing recommendations. Possibly all these VMs can be deleted at once so user service needs to be prepared to lose that many VMs in one step.



Specifies a fixed number of VM instances. This must be a positive integer.



Specifies a percentage of instances between 0 to 100%, inclusive. For example, specify 80 for 80%.



[Output Only] Absolute value of VM instances calculated based on the specific mode.

  • If the value is fixed, then the calculated value is equal to the fixed value.
  • If the value is a percent, then the calculated value is percent/100 * targetSize. For example, the calculated value of a 80% of a managed instance group with 150 instances would be (80/100 * 150) = 120 VM instances. If there is a remainder, the number is rounded up.


How far back autoscaling looks when computing recommendations to include directives regarding slower scale in, as described above.



The number of seconds that the autoscaler waits before it starts collecting information from a new instance. This prevents the autoscaler from collecting information when the instance is initializing, during which the collected usage would not be reliable. The default time autoscaler waits is 60 seconds.

Virtual machine initialization times might vary because of numerous factors. We recommend that you test how long an instance may take to initialize. To do this, create an instance and time the startup process.



Defines the CPU utilization policy that allows the autoscaler to scale based on the average CPU utilization of a managed instance group.



The target CPU utilization that the autoscaler maintains. Must be a float value in the range (0, 1]. If not specified, the default is 0.6.

If the CPU level is below the target utilization, the autoscaler scales in the number of instances until it reaches the minimum number of instances you specified or until the average CPU of your instances reaches the target utilization.

If the average CPU is above the target utilization, the autoscaler scales out until it reaches the maximum number of instances you specified or until the average utilization reaches the target utilization.



Configuration parameters of autoscaling based on a custom metric.



The identifier (type) of the Stackdriver Monitoring metric. The metric cannot have negative values.

The metric must have a value type of INT64 or DOUBLE.



A filter string, compatible with a Stackdriver Monitoring filter string for TimeSeries.list API call. This filter is used to select a specific TimeSeries for the purpose of autoscaling and to determine whether the metric is exporting per-instance or per-group data.

For the filter to be valid for autoscaling purposes, the following rules apply:

  • You can only use the AND operator for joining selectors.
  • You can only use direct equality comparison operator (=) without any functions for each selector.
  • You can specify the metric in both the filter string and in the metric field. However, if specified in both places, the metric must be identical.
  • The monitored resource type determines what kind of values are expected for the metric. If it is a gce_instance, the autoscaler expects the metric to include a separate TimeSeries for each instance in a group. In such a case, you cannot filter on resource labels.

    If the resource type is any other value, the autoscaler expects this metric to contain values that apply to the entire autoscaled instance group and resource label filtering can be performed to point autoscaler at the correct TimeSeries to scale upon. This is called a per-group metric for the purpose of autoscaling.

    If not specified, the type defaults to gce_instance.

Try to provide a filter that is selective enough to pick just one TimeSeries for the autoscaled group or for each of the instances (if you are using gce_instance resource type). If multiple TimeSeries are returned upon the query execution, the autoscaler will sum their respective values to obtain its scaling value.



The target value of the metric that autoscaler maintains. This must be a positive value. A utilization metric scales number of virtual machines handling requests to increase or decrease proportionally to the metric.

For example, a good metric to use as a utilizationTarget is The autoscaler works to keep this value constant for each of the instances.



If scaling is based on a per-group metric value that represents the total amount of work to be done or resource usage, set this value to an amount assigned for a single instance of the scaled group. Autoscaler keeps the number of instances proportional to the value of this metric. The metric itself does not change value due to group resizing.

A good metric to use with the target is for example or a custom metric exporting the total number of requests coming to your instances.

A bad example would be a metric exporting an average or median latency, since this value can't include a chunk assignable to a single instance, it could be better used with utilizationTarget instead.



Defines how target utilization value is expressed for a Stackdriver Monitoring metric. Either GAUGE, DELTA_PER_SECOND, or DELTA_PER_MINUTE.



Configuration parameters of autoscaling based on load balancer.



Fraction of backend capacity utilization (set in HTTP(S) load balancing configuration) that the autoscaler maintains. Must be a positive float value. If not defined, the default is 0.8.



Defines operating mode for this policy.



[Output Only] URL of the zone where the instance group resides (for autoscalers living in zonal scope).



[Output Only] URL of the region where the instance group resides (for autoscalers living in regional scope).



[Output Only] Server-defined URL for the resource.



[Output Only] The status of the autoscaler configuration. Current set of possible values:

  • PENDING: Autoscaler backend hasn't read new/updated configuration.
  • DELETING: Configuration is being deleted.
  • ACTIVE: Configuration is acknowledged to be effective. Some warnings might be present in the statusDetails field.
  • ERROR: Configuration has errors. Actionable for users. Details are present in the statusDetails field.
New values might be added in the future.



[Output Only] Human-readable details about the current state of the autoscaler. Read the documentation for Commonly returned status messages for examples of status messages you might encounter.



The status message.



The type of error, warning, or notice returned. Current set of possible values:

  • ALL_INSTANCES_UNHEALTHY (WARNING): All instances in the instance group are unhealthy (not in RUNNING state).
  • BACKEND_SERVICE_DOES_NOT_EXIST (ERROR): There is no backend service attached to the instance group.
  • CAPPED_AT_MAX_NUM_REPLICAS (WARNING): Autoscaler recommends a size greater than maxNumReplicas.
  • CUSTOM_METRIC_DATA_POINTS_TOO_SPARSE (WARNING): The custom metric samples are not exported often enough to be a credible base for autoscaling.
  • CUSTOM_METRIC_INVALID (ERROR): The custom metric that was specified does not exist or does not have the necessary labels.
  • MIN_EQUALS_MAX (WARNING): The minNumReplicas is equal to maxNumReplicas. This means the autoscaler cannot add or remove instances from the instance group.
  • MISSING_CUSTOM_METRIC_DATA_POINTS (WARNING): The autoscaler did not receive any data from the custom metric configured for autoscaling.
  • MISSING_LOAD_BALANCING_DATA_POINTS (WARNING): The autoscaler is configured to scale based on a load balancing signal but the instance group has not received any requests from the load balancer.
  • MODE_OFF (WARNING): Autoscaling is turned off. The number of instances in the group won't change automatically. The autoscaling configuration is preserved.
  • MODE_ONLY_UP (WARNING): Autoscaling is in the "Autoscale only out" mode. The autoscaler can add instances but not remove any.
  • MORE_THAN_ONE_BACKEND_SERVICE (ERROR): The instance group cannot be autoscaled because it has more than one backend service attached to it.
  • NOT_ENOUGH_QUOTA_AVAILABLE (ERROR): There is insufficient quota for the necessary resources, such as CPU or number of instances.
  • REGION_RESOURCE_STOCKOUT (ERROR): Shown only for regional autoscalers: there is a resource stockout in the chosen region.
  • SCALING_TARGET_DOES_NOT_EXIST (ERROR): The target to be scaled does not exist.
  • UNSUPPORTED_MAX_RATE_LOAD_BALANCING_CONFIGURATION (ERROR): Autoscaling does not work with an HTTP/S load balancer that has been configured for maxRate.
  • ZONE_RESOURCE_STOCKOUT (ERROR): For zonal autoscalers: there is a resource stockout in the chosen zone. For regional autoscalers: in at least one of the zones you're using there is a resource stockout.
New values might be added in the future. Some of the values might not be available in all API versions.



[Output Only] Target recommended MIG size (number of instances) computed by autoscaler. Autoscaler calculates the recommended MIG size even when the autoscaling policy mode is different from ON. This field is empty when autoscaler is not connected to an existing managed instance group or autoscaler did not generate its prediction.



[Output Only] Type of the resource. Always compute#autoscaler for autoscalers.



[Output Only] This token allows you to get the next page of results for list requests. If the number of results is larger than maxResults, use the nextPageToken as a value for the query parameter pageToken in the next list request. Subsequent list requests will have their own nextPageToken to continue paging through the results.



[Output Only] Informational warning message.



[Output Only] A warning code, if applicable. For example, Compute Engine returns NO_RESULTS_ON_PAGE if there are no results in the response.



[Output Only] A human-readable description of the warning code.[]


[Output Only] Metadata about this warning in key: value format. For example:

"data": [  {  "key": "scope",  "value": "zones/us-east1-d"  }[].key


[Output Only] A key that provides more detail on the warning being returned. For example, for warnings where there are no results in a list request for a particular zone, this key might be scope and the key value might be the zone name. Other examples might be a key indicating a deprecated resource and a suggested replacement, or a warning about invalid network settings (for example, if an instance attempts to perform IP forwarding but is not enabled for IP forwarding).[].value


[Output Only] A warning data value corresponding to the key.



Type of resource.

Authorization Scopes

Requires one of the following OAuth scopes:


For more information, see the Authentication Overview.

IAM Permissions

In addition to any permissions specified on the fields above, authorization requires one or more of the following IAM permissions:

  • compute.autoscalers.list

To find predefined roles that contain those permissions, see Compute Engine IAM Roles.