Buildbarn

Free plan APILinuxSelf-hosted

What Buildbarn is

Buildbarn is open-source software for creating a build farm that queues and runs build actions remotely. Its remote execution tools include bb_scheduler for queuing actions, bb_worker for coordinating execution and file transfers, and bb_runner for running commands. These components work with Buildbarn’s storage daemon, and the project names Bazel, BuildStream, and recc as clients that can call a Buildbarn build farm. The supported build systems also include Buck2, Pants, and Goma.

The worker and runner communicate through a gRPC-based protocol, which allows teams to use custom runners, including one based on QEMU user-mode emulation. Keeping those processes separate supports privilege separation intended to help prevent build actions from overwriting cached input files. The project supplies container images and example deployments for Docker Compose and Kubernetes. Setups can range from single-node remote caching to large-scale remote execution. The storage daemon supports configurable authorizers, Prometheus metrics, and pprof diagnostics. Its bare runner image includes neither a userland nor a Linux installation, so some build actions may need a separate userland environment. Remote builds can also encounter glibc version mismatches between the local and remote environments. Buildbarn is free under the Apache-2.0 license and is available for API, Linux, and self-hosted use.

Who it suits

Buildbarn suits teams using Bazel, Buck2, BuildStream, recc, Pants, or Goma that want remote execution or caching. It is also suited to operators who can deploy and run the components themselves, from a single node to a larger build farm.

What it does well

Free and open source under Apache-2.0.
Supports multiple build systems, including Bazel, Buck2, and Pants.
Offers Docker Compose and Kubernetes deployment examples.
Custom runners can communicate with the worker over gRPC.
Storage daemon supports Prometheus metrics and pprof diagnostics.

What to know first

Remote execution requires Buildbarn’s storage daemon as well.
The bare runner image has no userland or Linux installation.
Remote builds can encounter glibc version mismatches.

Getting started

Open the Buildbarn remote execution repository.
Choose a deployment example, such as Docker Compose or Kubernetes.
Deploy the required components, including the storage daemon.
Connect a supported build system to the Buildbarn build farm.
Provide a userland environment if your build actions require one.

Verdict

Choose Buildbarn if you need an open-source remote execution system with separate scheduler, worker, and runner components, and can operate the deployment. Consider the runner’s userland requirement and possible glibc mismatches when planning build environments.

Questions

Is Buildbarn free?

Yes. Its pricing model is free, and the repository identifies the license as Apache-2.0.

Which build systems does it support?

The supported list includes Bazel, Buck2, BuildStream, recc, Pants, and Goma.

Can Buildbarn be self-hosted?

Yes. It is available for self-hosted use and provides container images and deployment examples, including Docker Compose and Kubernetes.

What components handle remote execution?

bb_scheduler queues build actions, bb_worker coordinates their execution and file transfers, and bb_runner executes commands. They work with Buildbarn’s storage daemon.

Does Buildbarn support custom runners?

Yes. The worker communicates with the runner over gRPC, allowing custom implementations such as one using QEMU user-mode emulation.

What support or hosting is available?

Users are directed to a Slack channel. Commercial support and hosting can be procured through partners.

Facts from Buildbarn's own pages

Build clients: The project names Bazel, Buck2, BuildStream, and recc as tools that use the Remote Execution protocol. · github.com, 5 Oct 2026
Build services: The repository provides bb_scheduler to queue build actions, bb_worker to coordinate their execution and file transfers, and bb_runner to execute commands. · github.com, 4 Oct 2026
Commercial hosting: Listed commercial hosting options include self-hosted managed Buildbarn and cloud-hosted Buildbarn services. · github.com, 5 Oct 2026
Deployment: The project provides container images for its components and links to example deployments. · github.com, 4 Oct 2026
Deployment caveat: The Buildbarn deployment guide notes that remote builds can encounter glibc version mismatches between the build environment and the remote environment. · github.com, 5 Oct 2026
Deployment options: The project provides container images for its components, and its deployment examples include Docker Compose and Kubernetes configurations. · github.com, 5 Oct 2026
Deployment scale: Buildbarn deployments can range from single-node remote caching setups to large-scale remote execution setups. · github.com, 4 Oct 2026
Execution architecture: The worker communicates with the runner over a gRPC-based protocol, allowing a custom runner such as one using QEMU user-mode emulation. · github.com, 5 Oct 2026
Extensibility: bb_worker communicates with bb_runner over a gRPC-based protocol, allowing custom runner implementations such as one using QEMU user-mode emulation. · github.com, 4 Oct 2026
License: The remote execution repository is published under the Apache-2.0 license. · github.com, 5 Oct 2026
Monitoring: The storage daemon configuration supports Prometheus metrics and pprof diagnostics. · github.com, 5 Oct 2026
Operational requirement: The bb_runner_bare image contains no userland or Linux installation, and build actions may require a userland environment. · github.com, 4 Oct 2026
Privilege separation: Separating worker and runner processes supports privilege separation to help prevent build actions from overwriting cached input files. · github.com, 5 Oct 2026
Purpose: Buildbarn implements the Remote Execution protocol to cache and optionally execute build actions remotely. · github.com, 5 Oct 2026
Remote execution tools: The remote execution repository provides a scheduler, worker, and runner for queuing and executing build actions. · github.com, 5 Oct 2026
Scale: Buildbarn deployment examples describe use cases ranging from single-node remote caching to large-scale remote execution. · github.com, 5 Oct 2026
Security configuration: The storage daemon supports configurable authorizers for cache and execution operations; its README example uses allow-all authorizers. · github.com, 5 Oct 2026
Security design: Separating bb_worker and bb_runner enables privilege separation intended to prevent build actions from overwriting input files. · github.com, 4 Oct 2026
Storage dependency: Remote execution tools work in combination with Buildbarn’s storage daemon. · github.com, 5 Oct 2026
Support: Buildbarn points users to a community Slack channel and lists community members and companies offering commercial support or hosting. · github.com, 5 Oct 2026

Where Buildbarn stands on Freedom251

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