By default, Cloud Run for Anthos on Google Cloud scales in to the number of instances based on the number of incoming requests. However, if your service requires reduced latency and you want to limit the number of cold starts, you can change this default behavior by specifying a minimum number of container instances to be kept warm and ready to serve requests.
Instances kept running in this way do incur billing costs.
This page describes how to enable idle instances for your service using the minimum instances setting.
Revisions and minimum instances
Minimum instances are started only if the revision is addressable. A revision is addressable if either of the following is true:
- It receives a percentage of the traffic
- it was assigned a revision tag
Setting and updating minimum instances
Any configuration change leads to the creation of a new revision. Subsequent revisions will also automatically get this configuration setting unless you make explicit updates to change it.
By default, container instances have min-instances
turned off, with a setting
of 0
. You can change this default using the Cloud Console, the gcloud
command line, or a YAML file when you create a new service or
deploy a new revision:
Console
Click Create Service if you are configuring a new service you are deploying to. If you are configuring an existing service, click on the service, then click Edit and Deploy New Revision.
Under Advanced Settings, click Container.
In the field labelled Minimum number of instances, specify the desired number of container instances to be kept warm, ready to receive requests.
Click Create or Deploy.
Command line
You can update min-instance
of a given service by using the following command:
gcloud beta run services update SERVICE --min-instances MIN-VALUE
Replace
- SERVICE with the name of your service and
- MIN-VALUE with the desired number of container
instances to be kept warm, ready to receive requests. Specify
default
to clear any minimum instance setting.
You can also set min-instance
during
deployment using the command:
gcloud beta run deploy --image IMAGE_URL --min-instances MIN-VALUE
Replace
IMAGE_URL
with a reference to the container image, for example,gcr.io/myproject/my-image:latest
- MIN-VALUE with the desired number of container
instances to be kept warm, ready to receive requests. Specify
default
to clear any minimum instance setting.
YAML
You can download and view existing service configuration using the
gcloud run services describe --format export
command, which yields
cleaned results in YAML format. You can then modify the fields described below and
upload the modified YAML using the gcloud beta run services replace
command.
Make sure you only modify fields as documented.
To view and download the configuration:
gcloud run services describe SERVICE --format export > service.yaml
Update the
autoscaling.knative.dev/minScale:
attribute:spec: template: metadata: annotations: autoscaling.knative.dev/minScale: 'MIN-INSTANCE'
Replace
- MIN-INSTANCE with the desired number of instances to be kept warm, ready to receive requests.
Replace the service with its new configuration using the following command:
gcloud beta run services replace service.yaml