Instance executor

History

The instance executor is an autoscale-enabled executor that creates instances on demand to accommodate the expected volume of jobs that the runner manager processes.

You can use the instance executor when jobs need full access to the host instance, operating system, and attached devices. The instance executor can also be configured to accommodate single-tenant and multi-tenant jobs with various levels of isolation and security.

Nested virtualization

The instance executor supports nested virtualization with the GitLab-developed nesting daemon. The nesting daemon enables creation and deletion of pre-configured virtual machines on host systems used for isolated and short-lived workloads, like jobs. Nesting is only supported on Apple Silicon instances.

Prepare the environment for autoscaling

To prepare the environment for autoscaling:

  1. Install a fleeting plugin for your target platform where the runner manager is installed and configured.
  2. Create a VM image for the platform you’re using. The image must include:
    • Git

    • GitLab Runner

      note
      You must install the GitLab Runner binary on the virtual machine, and keep the runner executable in the default path to process job artifacts and cache. You do not have to configure or start the GitLab Runner service itself on the virtual machine.
    • Dependencies required by the jobs you plan to run

Configure the executor to autoscale

Prerequisites:

  • You must be an administrator.

To configure the instance executor for autoscaling, update the following sections in the config.toml:

idle_count and preemptive mode

With fleeting and taskscaler:

  • If idle_count is greater than 0, preemptive mode is enabled. The runner manager does not request new CI/CD jobs until idle instances are available. In this mode, CI/CD jobs run almost immediately.
  • If idle_count is 0, preemptive mode is disabled. The runner manager requests new CI/CD jobs regardless of whether idle instances are available to run those jobs. The number of jobs is based on max_instances and capacity_per_instance. In this mode, start times for CI/CD jobs are slower. You might also not be able to provision new instances and so CI/CD jobs might not run.

AWS autoscaling group configuration examples

One job per instance

Prerequisites:

  • An AMI with at least git and GitLab Runner installed.
  • An AWS Autoscaling group. For the scaling policy use none. The runner handles the scaling.
  • An IAM Policy with the correct permissions.

This configuration supports:

  • A capacity of 1 for each instance.
  • A use count of 1.
  • An idle scale of 5.
  • An idle time of 20 minutes.
  • A maximum instance count of 10.

When the capacity and use count are set to 1, each job is given a secure ephemeral instance that cannot be affected by other jobs. When the job completes, the instance it was executed on is deleted immediately.

When the capacity for each instance is 1, and the idle scale is 5, the runner keeps 5 whole instances available for future demand. These instances remain for at least 20 minutes.

The runner concurrent field is set to 10 (maximum number of instances * capacity per instance). 

concurrent = 10

[[runners]]
  name = "instance autoscaler example"
  url = "https://gitlab.com"
  token = "<token>"
  shell = "sh"

  executor = "instance"

  # Autoscaler config
  [runners.autoscaler]
    plugin = "aws" # in GitLab 16.11 and later, ensure you run `gitlab-runner fleeting install` to automatically install the plugin

    # in GitLab 16.10 and earlier, manually install the plugin and use:
    # plugin = "fleeting-plugin-aws"

    capacity_per_instance = 1
    max_use_count = 1
    max_instances = 10

    [runners.autoscaler.plugin_config] # plugin specific configuration (see plugin documentation)
      name             = "my-linux-asg"                # AWS Autoscaling Group name
      profile          = "default"                     # optional, default is 'default'
      config_file      = "/home/user/.aws/config"      # optional, default is '~/.aws/config'
      credentials_file = "/home/user/.aws/credentials" # optional, default is '~/.aws/credentials'

    [runners.autoscaler.connector_config]
      username          = "ec2-user"
      use_external_addr = true

    [[runners.autoscaler.policy]]
      idle_count = 5
      idle_time = "20m0s"

Five jobs per instance with unlimited uses

Prerequisites:

  • An AMI with at least git and GitLab Runner installed.
  • An AWS Autoscaling group with the scaling policy set to none. The runner handles the scaling.
  • An IAM Policy with the correct permissions.

This configuration supports:

  • A capacity of 5 for each instance.
  • An unlimited use count.
  • An idle scale of 5.
  • An idle time of 20 minutes.
  • A maximum instance count of 10.

When the capacity per instance is set to 5 and the use count is unlimited, each instance concurrently executes 5 jobs for the lifetime of the instance.

When the idle scale is 5, 1 idle instance is created to accommodate an idle capacity of 5 (due to the capacity for each instance) whenever the in-use capacity is lower than 5. Idle instances remain for at least 20 minutes.

Jobs executed in these environments should be trusted as there is little isolation between them and each job can affect the performance of another.

The runner concurrent field is set to 50 (maximum number instances * capacity per instance). 

concurrent = 50

[[runners]]
  name = "instance autoscaler example"
  url = "https://gitlab.com"
  token = "<token>"
  shell = "sh"

  executor = "instance"

  # Autoscaler config
  [runners.autoscaler]
    plugin = "aws" # in GitLab 16.11 and later, ensure you run `gitlab-runner fleeting install` to automatically install the plugin

    # in GitLab 16.10 and earlier, manually install the plugin and use:
    # plugin = "fleeting-plugin-aws"

    capacity_per_instance = 5
    max_use_count = 0
    max_instances = 10

    [runners.autoscaler.plugin_config] # plugin specific configuration (see plugin documentation)
      name             = "my-windows-asg"              # AWS Autoscaling Group name
      profile          = "default"                     # optional, default is 'default'
      config_file      = "/home/user/.aws/config"      # optional, default is '~/.aws/config'
      credentials_file = "/home/user/.aws/credentials" # optional, default is '~/.aws/credentials'

    [runners.autoscaler.connector_config]
      username          = "Administrator"
      timeout           = "5m0s"
      use_external_addr = true

    [[runners.autoscaler.policy]]
      idle_count = 5
      idle_time = "20m0s"

Two jobs per instance, unlimited uses, nested virtualization on EC2 Mac instances

Prerequisites:

  • An Apple Silicon AMI with nesting and Tart installed.
  • The Tart VM images that the runner uses. The VM images are specified by the image keyword of the job. The VM images should have at least git and GitLab Runner installed.
  • An AWS Autoscaling group. For the scaling policy use none, because runner handles the scaling. For information about how to set up an ASG for MacOS, see Implementing autoscaling for EC2 Mac instances.
  • An IAM policy with the correct permissions.

This configuration supports:

  • A capacity of 2 for each instance.
  • An unlimited use count.
  • Nested virtualization to support isolated jobs. Nested virtualization is only available for Apple silicon instances with nesting installed.
  • An idle scale of 5.
  • An idle time of 20 minutes.
  • A maximum instance count of 10.

When the capacity for each instance is 2 and the use count is unlimited, each instance concurrently executes 2 jobs for the lifetime of the instance.

When the idle scale is 2, 1 idle instance is created to accommodate an idle capacity of 2 (due to the capacity per instance) whenever the in use capacity is lower than 2. Idle instances remain for at least 24 hours. This time frame is due to the 24 hour minimal allocation period of AWS MacOS instance hosts.

Jobs executed in this environment do not need to be trusted because nesting is used for nested virtualization of each job. This only works on Apple silicon instances.

The runner concurrent field is set to 8 (maximum number instances * capacity per instance). 

concurrent = 8

[[runners]]
  name = "macos applesilicon autoscaler example"
  url = "https://gitlab.com"
  token = "<token>"
  executor = "instance"

  [runners.instance]
    allowed_images = ["*"] # allow any nesting image

  [runners.autoscaler]
    capacity_per_instance = 2 # AppleSilicon can only support 2 VMs per host
    max_use_count = 0
    max_instances = 4

    plugin = "aws" # in GitLab 16.11 and later, ensure you run `gitlab-runner fleeting install` to automatically install the plugin

    # in GitLab 16.10 and earlier, manually install the plugin and use:
    # plugin = "fleeting-plugin-aws"

    [[runners.autoscaler.policy]]
      idle_count = 2
      idle_time  = "24h" # AWS's MacOS instances

    [runners.autoscaler.connector_config]
      username = "ec2-user"
      key_path = "macos-key.pem"
      timeout  = "1h" # connecting to a MacOS instance can take some time, as they can be slow to provision

    [runners.autoscaler.plugin_config]
      name = "mac2metal"
      region = "us-west-2"

    [runners.autoscaler.vm_isolation]
      enabled = true
      nesting_host = "unix:///Users/ec2-user/Library/Application Support/nesting.sock"

    [runners.autoscaler.vm_isolation.connector_config]
      username = "nested-vm-username"
      password = "nested-vm-password"
      timeout  = "20m"

Google Cloud instance group configuration examples

One job per instance using a Google Cloud instance group

Prerequisites:

  • A custom image with at least git and GitLab Runner installed.
  • A Google Cloud instance group where the autoscaling mode is set to do not autoscale. The runner handles the scaling.
  • An IAM policy with the correct permissions. If you’re deploying your runner in a GKE cluster, you can add an IAM binding between the Kubernetes service account and the GCP service account. You can add this binding with the iam.workloadIdentityUser role to authenticate to GCP instead of using a key file with credentials_file.

This configuration supports:

  • A capacity per instance of 1
  • A use count of 1
  • An idle scale of 5
  • An idle time of 20 minutes
  • A maximum instance count of 10

When the capacity and use count are both set to 1, each job is given a secure ephemeral instance that cannot be affected by other jobs. When the job completes, the instance it was executed on is immediately deleted.

When the idle scale is set to 5, the runner keeps 5 instances available for future demand (because the capacity per instance is 1). These instances stay for at least 20 minutes.

The runner concurrent field is set to 10 (maximum number instances * capacity per instance). 

concurrent = 10

[[runners]]
  name = "instance autoscaler example"
  url = "https://gitlab.com"
  token = "<token>"
  shell = "sh"

  executor = "instance"

  # Autoscaler config
  [runners.autoscaler]
    plugin = "googlecloud" # for >= 16.11, ensure you run `gitlab-runner fleeting install` to automatically install the plugin

    # for versions < 17.0, manually install the plugin and use:
    # plugin = "fleeting-plugin-googlecompute"

    capacity_per_instance = 1
    max_use_count = 1
    max_instances = 10

    [runners.autoscaler.plugin_config] # plugin specific configuration (see plugin documentation)
      name             = "my-linux-instance-group" # Google Cloud Instance Group name
      project          = "my-gcp-project"
      zone             = "europe-west1-c"
      credentials_file = "/home/user/.config/gcloud/application_default_credentials.json" # optional, default is '~/.config/gcloud/application_default_credentials.json'

    [runners.autoscaler.connector_config]
      username          = "runner"
      use_external_addr = true

    [[runners.autoscaler.policy]]
      idle_count = 5
      idle_time = "20m0s"

Five jobs per instance, unlimited uses, using Google Cloud Instance group

Prerequisites:

  • A custom image with at least git and GitLab Runner installed.
  • An Instance group. For the “Autoscaling mode” select “do not autoscale”, as Runner handles the scaling.
  • An IAM Policy with the correct permissions.

This configuration supports:

  • A capacity per instance of 5
  • An unlimited use count
  • An idle scale of 5
  • An idle time of 20 minutes
  • A maximum instance count of 10

When the capacity is set 5 and the use count is unlimited, each instance concurrently executes 5 jobs for the lifetime of the instance.

Jobs executed in these environments should be trusted as there is little isolation between them and each job can affect the performance of another.

When the idle scale is set to 5, 1 idle instance is created to accommodate an idle capacity of 5 (due to the capacity per instance) whenever the in-use capacity is lower than 5. Idle instances stay for at least 20 minutes.

The runner concurrent field is set to 50 (maximum number instances * capacity per instance). 

concurrent = 50

[[runners]]
  name = "instance autoscaler example"
  url = "https://gitlab.com"
  token = "<token>"
  shell = "sh"

  executor = "instance"

  # Autoscaler config
  [runners.autoscaler]
    plugin = "googlecloud" # for >= 16.11, ensure you run `gitlab-runner fleeting install` to automatically install the plugin

    # for versions < 17.0, manually install the plugin and use:
    # plugin = "fleeting-plugin-googlecompute"

    capacity_per_instance = 5
    max_use_count = 0
    max_instances = 10

    [runners.autoscaler.plugin_config] # plugin specific configuration (see plugin documentation)
      name             = "my-windows-instance-group" # Google Cloud Instance Group name
      project          = "my-gcp-project"
      zone             = "europe-west1-c"
      credentials_file = "/home/user/.config/gcloud/application_default_credentials.json" # optional, default is '~/.config/gcloud/application_default_credentials.json'

    [runners.autoscaler.connector_config]
      username          = "Administrator"
      timeout           = "5m0s"
      use_external_addr = true

    [[runners.autoscaler.policy]]
      idle_count = 5
      idle_time = "20m0s"

Azure scale set configuration examples

One job per instance using a Azure scale set

Prerequisites:

  • A custom image with at least git and GitLab Runner installed.
  • An Azure scale set where the autoscaling mode is set to manual. The runner handles the scaling.

This configuration supports:

  • A capacity per instance of 1
  • A use count of 1
  • An idle scale of 5
  • An idle time of 20 minutes
  • A maximum instance count of 10

When the capacity and use count are both set to 1, each job is given a secure ephemeral instance that cannot be affected by other jobs. When the job completes, the instance it was executed on is immediately deleted.

When the idle scale is set to 5, the runner keeps 5 instances available for future demand (because the capacity per instance is 1). These instances stay for at least 20 minutes.

The runner concurrent field is set to 10 (maximum number instances * capacity per instance). 

concurrent = 10

[[runners]]
  name = "instance autoscaler example"
  url = "https://gitlab.com"
  token = "<token>"
  shell = "sh"

  executor = "instance"

  # Autoscaler config
  [runners.autoscaler]
    plugin = "azure" # for >= 16.11, ensure you run `gitlab-runner fleeting install` to automatically install the plugin

    # for versions < 17.0, manually install the plugin and use:
    # plugin = "fleeting-plugin-azure"

    capacity_per_instance = 1
    max_use_count = 1
    max_instances = 10

    [runners.autoscaler.plugin_config] # plugin specific configuration (see plugin documentation)
      name                = "my-linux-scale-set" # Azure scale set name
      subscription_id     = "9b3c4602-cde2-4089-bed8-889e5a3e7102"
      resource_group_name = "my-resource-group"

    [runners.autoscaler.connector_config]
      username               = "runner"
      password               = "my-scale-set-static-password"
      use_static_credentials = true
      timeout                = "10m"
      use_external_addr      = true

    [[runners.autoscaler.policy]]
      idle_count = 5
      idle_time  = "20m0s"

Five jobs per instance, unlimited uses, using Google Cloud Instance group

Prerequisites:

  • A custom image with at least git and GitLab Runner installed.
  • An Azure scale set where the autoscaling mode is set to manual. The runner handles the scaling.

This configuration supports:

  • A capacity per instance of 5
  • An unlimited use count
  • An idle scale of 5
  • An idle time of 20 minutes
  • A maximum instance count of 10

When the capacity is set 5 and the use count is unlimited, each instance concurrently executes 5 jobs for the lifetime of the instance.

Jobs executed in these environments should be trusted as there is little isolation between them and each job can affect the performance of another.

When the idle scale is set to 5, 1 idle instance is created to accommodate an idle capacity of 5 (due to the capacity per instance) whenever the in-use capacity is lower than 5. Idle instances stay for at least 20 minutes.

The runner concurrent field is set to 50 (maximum number instances * capacity per instance). 

concurrent = 50

[[runners]]
  name = "instance autoscaler example"
  url = "https://gitlab.com"
  token = "<token>"
  shell = "sh"

  executor = "instance"

  # Autoscaler config
  [runners.autoscaler]
    plugin = "azure" # for >= 16.11, ensure you run `gitlab-runner fleeting install` to automatically install the plugin

    # for versions < 17.0, manually install the plugin and use:
    # plugin = "fleeting-plugin-azure"

    capacity_per_instance = 5
    max_use_count = 0
    max_instances = 10

    [runners.autoscaler.plugin_config] # plugin specific configuration (see plugin documentation)
      name                = "my-windows-scale-set" # Azure scale set name
      subscription_id     = "9b3c4602-cde2-4089-bed8-889e5a3e7102"
      resource_group_name = "my-resource-group"

    [runners.autoscaler.connector_config]
      username               = "Administrator"
      password               = "my-scale-set-static-password"
      use_static_credentials = true
      timeout                = "10m"
      use_external_addr      = true

    [[runners.autoscaler.policy]]
      idle_count = 5
      idle_time = "20m0s"

Troubleshooting

When working with the Instance executor, you might encounter the following issues:

sh: 1: eval: Running on ip-x.x.x.x via runner-host...n: not found

This error typically occurs when the eval command in the preparation step fails. To resolve this error, switch to bash shell and enable the feature flag FF_USE_NEW_BASH_EVAL_STRATEGY.