Self Hosted Agent Pools

Note

Agents are only available on the pro tier. See Scalr pricing here.

Note

Agent pools can be created and managed as code through the Scalr Terraform Provider.

By default, when executing a Terraform run in scalr.io, it will execute on a shared pool of resources that is maintained by Scalr. This method suffices for the majority of use cases, but sometimes there are use cases due to security, compliance, or network requirements that require the runs to be executed on a self-hosted pool of agents. The Scalr self-hosted agent pools are deployed on your infrastructure, fully encrypted, and will only need network access back to Scalr.io to report the run results. Scalr.io will never need network access back to the agent.

Configuring Agent Pools

Prerequisites:

  • Agents can be deployed on RHEL/CentOS 7.x/8.x. Ubuntu 18.04, or Docker (version 18+) containers. If RHEL/CentOS 7.x is used, the scalr-agent package has a dependency on the container-SELinux package from the “extras” repository. If you do not have that repository enabled, please do so by following the Enable Extras Repo page.

  • The agents must have HTTPS connections to *scalr.io and *docker.io.

  • Agent sizing depends on your workloads. For the majority of workloads, 512MB of RAM and 1 CPU allocated for each run / container will be sufficient. For larger workloads, you may need to increase the memory size to ensure sufficient memory. If you need more than one concurrent run, the sizing to consider is calculated with RAM x Concurrency, where RAM is the amount of RAM allocated for a container and concurrency is how many parallel runs are required. For example, if two concurrent runs are needed, then the sizing should be 1024MB RAM. Free RAM is the main factor with agents, always ensure there is enough allocated for the OS to continue to run as well.

Agent pools can be created at the account or environment scope. If a pool is created at the account scope, all environments and workspaces within those environments will have access to use the pool. If a pool is created at the environment scope, then only the workspaces in that environment can use that pool.

To create a pool, click on the Scalr icon on the top left of your screen and select “Agent Pools”:

Account scope:

_images/account_pool.png

Environment scope:

_images/env_pool.png

Click “New Agent Pool”, which will ask you to name that pool. At this point, you can choose to assign workspaces to the agent pool or do so later within the workspace settings:

_images/link_workspaces.png

Once you click create, Scalr will provide instructions to setup the agent:

_images/agent_setup.png

As mentioned, if you choose to skip linking the agent during the initial setup, you can do so within the workspace settings:

_images/enable_agent_workspace.png

Managing Agent Pools

Once a pool is created, you can check the status of the agent by going back to the “Agent Pool” page and selecting your pool:

_images/agent_pool_maintenance.png

The logs for the agents can be seen by running journalctl -xe -u scalr-agent on the instance that the agent is running on.

Each pool can be managed individually and only deleted if the pool is not linked to a workspace.

_images/agent_pool_maintenance2.png

Run the Agent as Root

Agents can be updated to run as root giving you the privilege to configure (i.e. add apt repositories, install software via apt-get, add rootCA certificates, etc…) the container through local-exec. To configure the agent as root, run the following commands:

sudo scalr-agent configure --user=root
sudo systemctl daemon-reload scalr-agent
sudo systemctl restart scalr-agent # if agent is already running
sudo systemctl start scalr-agent # if agent is not running

In future release, you will be able to fully customize the Docker images that are running on the agent.

Adding a Proxy

If the agent requires a proxy to get back to scalr.io, please insert the following lines into /etc/systemd/system/scalr-agent.service:

Environment="HTTP_PROXY=http://<proxy_IP:port>"
Environment="HTTPS_PROXY=http://<proxy_IP:port>"

Once the above is added, exectue the following commands:

systemctl daemon-reload
systemctl restart scalr-agent

Coming Soon

In a future release, Scalr will be able to restrict and enforce which environments use which pools from the account scope.