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Worker pools»


Note that private workers are an Enterprise plan feature.

By default, Spacelift uses a managed worker pool hosted and operated by us. This is very convenient, but often you may have special requirements regarding infrastructure, security or compliance, which aren't served by the public worker pool. This is why Spacelift also supports private worker pools, which you can use to host the workers which execute Spacelift workflows on your end.

In order to enjoy the maximum level of flexibility and security with a private worker pool, temporary run state is encrypted end-to-end, so only the workers in your worker pool can look inside it. We use asymmetric encryption to achieve this and only you ever have access to the private key.


A worker is a logical entity that processes a single run at a time. As a result, your number of workers is equal to your maximum concurrency.

Typically, a virtual server (AWS EC2 or Azure/GCP VM) hosts a single worker to keep things simple and avoid coordination and resource management overhead.

Containerized workers can share the same virtual server because the management is handled by the orchestrator.

Setting up»

Generate Worker Private Key»

We use asymmetric encryption to ensure that any temporary run state can only be accessed by workers in a given worker pool. To support this, you need to generate a private key that can be used for this purpose, and use it to create a certificate signing request to give to Spacelift. We'll generate a certificate for you, so that workers can use it to authenticate with the Spacelift backend. The following command will generate the key and CSR:

openssl req -new -newkey rsa:4096 -nodes -keyout spacelift.key -out spacelift.csr


Don't forget to store the spacelift.key file (private key) in a secure location. You’ll need it later, when launching workers in your worker pool.

You can set up your worker pool from the Spacelift UI by navigating to Worker Pools section of your account, or you can also create it programmatically using the spacelift_worker_pool resource type within the Spacelift Terraform provider.

Add Worker Pool Entity»

Give your worker pool a name, and submit the spacelift.csr file in the worker pool creation form. After creation of the worker pool, you’ll receive a Spacelift token. This token contains configuration for your worker pool launchers, as well as the certificate we generated for you based on the certificate signing request.


After clicking create, you will receive a token for the worker pool. Don't forget to save your Spacelift token in a secure location as you'll need this later when launching the worker pool.

Upload the certificate you generated previously and create a worker pool.

Launch Worker Pool»

The launcher binaries are available here: x86_64 (amd64 CPU), aarch64 (arm64 CPU).

In order to work, the launcher expects to be able to write to the local Docker socket. Unless you're using a Docker-based container scheduler like Kubernetes or ECS, please make sure that Docker is installed and running.

Finally, you can run the launcher binary by setting two environment variables:

  • SPACELIFT_TOKEN - the token you’ve received from Spacelift on worker pool creation
  • SPACELIFT_POOL_PRIVATE_KEY - the contents of the private key file you generated, in base64.


You need to encode the entire private key using base-64, making it a single line of text. The simplest approach is to just run cat spacelift.key | base64 -w 0 in your command line. For Mac users, the command is cat spacelift.key | base64 -b 0.

Congrats! Your launcher should now connect to the Spacelift backend and start handling runs.


In general, arm64-based virtual machines are cheaper than amd64-based ones, so if your cloud provider supports them, we recommend using them. If you choose to do so, and you're using custom runner images, make sure they're compatible with ARM64. All Spacelift provided runner images are compatible with both CPU architectures.

Terraform Modules and Helm Chart»

For AWS, Azure and GCP users we've prepared an easy way to run Spacelift worker pools. This repository contains the code for Spacelift's base images, and the following repositories contain Terraform modules to customize and deploy worker pools to AWS, Azure or GCP:

In addition, the spacelift-helm-charts repository contains a Helm chart for deploying workers to Kubernetes.


Since the Launcher is getting downloaded during the instance startup, it is recommended to recycle the worker pool every once in a while to ensure that it is up to date. You don't want to miss out on the latest features and bug fixes! You can do this by draining all the workers one-by-one in the UI, then terminating the instances in your cloud provider.

It is also recommended to check the above repositories for updates from time to time.


AWS ECS is supported when using the EC2 launch type but Spacelift does not currently provide a Terraform module for this setup.

Configuration options»

A number of configuration variables is available to customize how your launcher behaves:

  • SPACELIFT_DOCKER_CONFIG_DIR - if set, the value of this variable will point to the directory containing Docker configuration, which includes credentials for private Docker registries. Private workers can populate this directory for example by executing docker login before the launcher process is started;
  • SPACELIFT_MASK_ENVS- comma-delimited list of whitelisted environment variables that are passed to the workers but should never appear in the logs;
  • SPACELIFT_WORKER_NETWORK - network ID/name to connect the launched worker containers, defaults to bridge;
  • SPACELIFT_WORKER_EXTRA_MOUNTS - additional files or directories to be mounted to the launched worker docker containers during either read or write runs, as a comma-separated list of mounts in the form of /host/path:/container/path;
  • SPACELIFT_WORKER_WO_EXTRA_MOUNTS - Additional directories to be mounted to the worker docker container during write only runs, as a comma separated list of mounts in the form of /host/path:/container/path;
  • SPACELIFT_WORKER_RO_EXTRA_MOUNTS - Additional directories to be mounted to the worker docker container during read only runs, as a comma separated list of mounts in the form of /host/path:/container/path;
  • SPACELIFT_WORKER_RUNTIME - runtime to use for worker container;
  • SPACELIFT_WHITELIST_ENVS - comma-delimited list of environment variables to pass from the launcher's own environment to the workers' environment. They can be prefixed with ro_ to only be included in read only runs or wo_ to only be included in write only runs;
  • SPACELIFT_LAUNCHER_LOGS_TIMEOUT - custom timeout (the default is 7 minutes) for killing jobs not producing any logs. This is a duration flag, expecting a duration-formatted value, eg 1000s ;
  • SPACELIFT_LAUNCHER_RUN_INITIALIZATION_POLICY - file that contains the run initialization policy that will be parsed/used; If the run initialized policy can not be validated at the startup the worker pool will exit with an appropriate error;
  • SPACELIFT_LAUNCHER_RUN_TIMEOUT - custom maximum run time - the default is 70 minutes. This is a duration flag, expecting a duration-formatted value, eg. 120m ;


Server-side initialization policies are being deprecated. SPACELIFT_LAUNCHER_RUN_INITIALIZATION_POLICY shouldn't be confused with that. This policy is a Worker-side initialization policy and it can be set by using the launcher run initialization policy flag.

For a limited time period we will be running both types of initialization policy checks but ultimately we're planning to move the pre-flight checks to the worker node, thus allowing customers to block suspicious looking jobs on their end.

Passing metadata tags»

When the launcher from a worker pool is registering with the mothership, you can send along some tags that will allow you to uniquely identify the process/machine for the purpose of draining or debugging. Any environment variables using SPACELIFT_METADATA_ prefix will be passed on. As an example, if you're running Spacelift workers in EC2, you can do the following just before you execute the launcher binary:

export SPACELIFT_METADATA_instance_id=$(ec2-metadata --instance-id | cut -d ' ' -f2)

Doing so will set your EC2 instance ID as instance_id tag in your worker.

VCS Agents»


VCS Agents are intended for version control systems (VCS) that cannot be accessed over the internet from the Spacelift backend.

If your VCS can be accessed over the internet, possibly after allowing the Spacelift backend IP addresses, then you do not need to use VCS Agents.

When using private workers with a privately accessible version control system, you will need to ensure that your private workers have direct network access to your Version Control System.

Additionally, you will need to inform the private workers of the target network address for each of your VCS Agent Pools by setting up the following variables:

  • SPACELIFT_PRIVATEVCS_MAPPING_BASE_ENDPOINT_<NUMBER>: IP address or hostname, with protocol, for the VCS system.

There can be multiple VCS systems so replace <NUMBER> with an integer. Start from 0 and increment it by one for each new VCS system.

Here is an example that configures access to two VCS systems:


Network Security»

Private workers need to be able to make outbound connections in order to communicate with Spacelift, as well as to access any resources required by your runs. If you have policies in place that require you to limit the outbound traffic allowed from your workers, you can use the following lists as a guide.

AWS Services»

Your worker needs access to the following AWS services in order to function correctly. You can refer to the AWS documentation for their IP address ranges.

  • Access to the public Elastic Container Registry if using our default runner image.
  • Access to, <your account name>, and which point at CloudFront.
  • Access to the AWS IoT Core endpoints in eu-west-1 for worker communication via MQTT.
  • Access to Amazon S3 in eu-west-1 for uploading run logs.


In addition, you will also need to allow access to the following:

  • Your VCS provider.
  • Access to any custom container registries you use if using custom runner images.
  • Access to any other infrastructure required as part of your runs.
  • Access to - required to download the PGP key used to sign Spacelift binaries.

Hardware recommendations»

The hardware requirments for the workers will vary depending on the stack size(How many resources managed, resource type, etc.), but we recommend at least 2GB of memory and 2 vCPUs of compute power.

These are the recommended server types for the three main cloud providers:

  • AWS: t3.small instance type
  • Azure: Standard_A2_V2 virtual machine
  • GCP: e2-medium instance type

Using worker pools»

Worker pools must be explicitly attached to stacks and/or modules in order to start processing their workloads. This can be done in the Behavior section of stack and module settings:

Example when editing the existing stack

Example when setting up a new module

Worker Pool Management Views»

You can view the activity and status of every aspect of your worker pool in the worker pool detail view. You can navigate to the worker pool of your choosing by clicking on the appropriate entry in the worker pools list view.

Private Worker Pool»

A private worker pool is a worker pool for which you are responsible for managing the workers.

private worker pool management view


The workers tab lists all workers for this worker pool and their status.


A worker can have three possible statuses:

  • DRAINED which indicates that the workers is not accepting new work.
  • BUSY which indicates that the worker is currently processing or about to process a run.
  • IDLE which indicates that the worker is available to start processing new runs.


Queued lists all the run that can be scheduled and are currently in progress. In progress runs will be the first entries in the list when using the view without any filtering.


Reasons a run might not be shown in this list: a tracked run is waiting on a tracked run, the run has is dependent on other runs.

Used by»

Stacks and/or Modules that are using the private worker pool.

Public Worker Pool»

The Public worker pool is a worker pool managed by Spacelift. Due to security and compliance requirements, we are not listing the workers of the public worker pool.

public worker pool management view


Queued lists all the run that can be scheduled and are currently in progress. In progress runs will be the first entries in the list when using the view without any filtering.


Reasons a run might not be shown in this list: a tracked run is waiting on a tracked run, the run has is dependent on other runs.

Used by»

Stacks and/or Modules that are using the public worker pool.