ERROR: Executor "docker-autoscaler" is not known

Summary

Hello, I recently saw the Docker Autoscaler executor (Alpha) feature and was about to try it out, but I got Executor "docker-autoscaler" is not known error when running gitlab-runner run.

This feature is of great significance to our team. I would like to ask if I missed any settings or this feature has not been released yet? (But official document says "The Docker Autoscaler feature (alpha) was introduced in GitLab Runner 15.10.0"?) Thanks!

Steps to reproduce

I followed the official tutorial to setup runner.

I've create an AWS Auto Scaling Groups and associated IAM, and have the AWS fleeting plugin placed in /usr/bin inside the GitLab Runner Container. My AWS fleeting plugin installation flow is as follows:

docker exec -it "${runner_name}" wget -O /usr/bin/fleeting-plugin-aws https://gitlab.com/gitlab-org/fleeting/fleeting-plugin-aws/-/releases/v0.2.0/downloads/fleeting-plugin-aws-linux-amd64
docker exec -it "${runner_name}" chmod 755 /usr/bin/fleeting-plugin-aws
docker exec -it "${runner_name}" fleeting-plugin-aws --version

# Output:
Name:         fleeting-plugin-aws
Version:      v0.2.0
Git revision: 4cf7851c
Git ref:      refs/pipelines/808977267
GO version:   go1.19.6
Built:        2023-03-16T17:21:20+0000
OS/Arch:      linux/amd64

And got error after running:

docker exec -d "${runner_name}" gitlab-runner --debug run

Actual behavior

ERROR: Executor "docker-autoscaler" is not known.

Expected behavior

Run the executor normally.

Relevant logs and/or screenshots

Starting worker                                     builds=0 worker=0
Feeding runner to channel                           builds=0 runner=pt91xCsH
Processing runner                                   builds=0 runner=pt91xCsH
ERROR: Executor "docker-autoscaler" is not known; marking Runner as unhealthy  builds=0 runner=pt91xCsH

Environment description

Self host GitLab

GitLab Server version: 15.10.2-ce.0

GitLab Runner Docker image: gitlab/gitlab-runner:v15.10.1

config.toml contents

concurrent = 10
check_interval = 0
shutdown_timeout = 0

[session_server]
    session_timeout = 1800

[[runners]]
    name = "gitlab-share-runner"
    url = "${My GitLab self host URL}"
    id = 1178
    token = ""
    token_obtained_at = 2023-04-14T06:36:20Z
    token_expires_at = 0001-01-01T00:00:00Z
    executor = "docker-autoscaler"

    [runners.custom_build_dir]
        enabled = true

    [runners.docker]
        image = "tiangolo/docker-with-compose"

    [runners.autoscaler]
        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             = "gitlab-autoscaling-group" # AWS Autoscaling Group name

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

        [[runners.autoscaler.policy]]
        idle_count = 5
        idle_time = "1m0s"

Used GitLab Runner version

Version:      15.10.1
Git revision: dcfb4b66
Git branch:   15-10-stable
GO version:   go1.19.6
Built:        2023-03-29T13:01:22+0000
OS/Arch:      linux/amd64