Sticky Disks

Overview

useblacksmith/stickydisk is a GitHub Action that helps persist state written to disk across jobs. This action can serve as a superior alternative to the Actions cache, especially when the cache artifacts are extremely large. Each sticky disk is hot-loaded into the runner and mounted at the specified path. The sticky disk is formatted as an ext4 filesystem.

The useblacksmith/stickydisk action is currently in beta. There may be bugs and behavior may change. Please report issues on the GitHub repository.

Basics

Cache Performance Comparison

Caching Solution	Cache Size	Average Download Speed	Time to Access
GitHub Actions Cache	6GB	90 MB/s	~1m6s
Blacksmith Cache	6GB	400 MB/s	~15s
Sticky Disks	6GB	N/A	3 seconds

Note that Sticky Disks can use much more than 6 GB of space - these numbers are simply a performance comparison.

Use Cases

NPM Package Caching

Node.js projects can have extensive dependency trees, leading to large node_modules directories. Sticky disks provide persistent, high-performance storage for your NPM packages.

Diff Example

jobs:
  build:
    runs-on: blacksmith
    steps:
      - uses: actions/checkout@v6
      
      - name: Setup Node.js
        uses: useblacksmith/setup-node@v5
        with:
          node-version: '18.x'
      
      - name: Mount NPM Cache
        uses: useblacksmith/stickydisk@v1
        with:
          key: ${{ github.repository }}-npm-cache
          path: ~/.npm
      
      - name: Mount node_modules
        uses: useblacksmith/stickydisk@v1
        with:
          key: ${{ github.repository }}-node-modules
          path: ./node_modules
      
      - name: Install Dependencies
        run: npm ci

      - name: Build
        run: npm run build

Bazel Build Caching

Bazel’s remote cache can significantly improve build times, but uploading and downloading cached artifacts can still be a bottleneck. Using sticky disks with Blacksmith runners provides near-instant access to your Bazel caches as they are bind mounted into your runners on demand. Our useblacksmith/setup-bazel@v2 action is a zero-config way to use sticky disks to store the disk, repository, and external cache.

Diff Example

jobs:
  build:
    runs-on: blacksmith
    steps:
      - uses: actions/checkout@v6
      
      - name: Setup Bazel
        uses: useblacksmith/setup-bazel@v2
        with:
          version: '6.x'
      
      - name: Build
        run: |
          bazel build //...

How it works

Blacksmith stores sticky disk artifacts in a secure, highly performant Ceph cluster, running on local NVMe drives. Our runners proxy their requests through our Storage Agents to interact with the Ceph cluster. Each sticky disk is uniquely identified by a key. When a GitHub Action job requests a sticky disk, the last committed snapshot will be cloned and mounted into the runner at the specified path. Once the job completes, the sticky disk will be unmounted and committed for future invocations. At the moment, customers can use up to 5 sticky disks in a single GitHub Action job.

Using Sticky Disks inside a container

If your GitHub Actions job runs inside a container, you will need to ensure that the container is hydrated with certain Blacksmith specific environment variables and is running in privileged mode. These environment variables allow the runner to coordinate with our control plane to hotload and commit the sticky disks used in the workflow. The privileged mode is required for mounting and unmounting block devices inside a container. The following changes can be made to your service container config in the workflow file:

Diff Example

   container:
      image: mcr.microsoft.com/playwright:v1.41.1
      options: --privileged
      env:
        VM_ID: ${{ env.VM_ID }}
        GITHUB_REPO_NAME: ${{ env.GITHUB_REPO_NAME }}
        BLACKSMITH_STICKYDISK_TOKEN: ${{ env.BLACKSMITH_STICKYDISK_TOKEN }}
        BLACKSMITH_INSTALLATION_MODEL_ID: ${{ env.BLACKSMITH_INSTALLATION_MODEL_ID }}
        BLACKSMITH_REGION: ${{ env.BLACKSMITH_REGION }}

If the container image does not have sudo installed, you will need to install it as a step inside the container. sudo is required for mounting and formatting the sticky disk with proper permissions.

   steps:
      - name: Install sudo
        run: |
          apk add --no-cache sudo

Without these steps, you will see a 401 error, an Unauthenticated error, or permission-related errors when attempting to mount or use the sticky disk.

useblacksmith/stickydisk-delete

useblacksmith/stickydisk-delete allows you to delete sticky disks programmatically. It supports two deletion methods:

Delete by Key

Delete a specific sticky disk using its key:

- name: Delete sticky disk
  uses: useblacksmith/stickydisk-delete@v1
  with:
    delete-key: my-cache-disk

Delete Docker Cache

Delete Docker build cache for your repository. This should be used in conjunction with useblacksmith/setup-docker-builder@v1, which sets up the sticky disk for Docker build caching:

- name: Delete Docker cache
  uses: useblacksmith/stickydisk-delete@v1
  with:
    delete-docker-cache: true

Example: Cleanup After Build

name: Build with Cleanup
on: push

jobs:
  build:
    runs-on: blacksmith-4vcpu-ubuntu-2204
    steps:
      - name: Create sticky disk for dependencies
        uses: useblacksmith/stickydisk@v1
        with:
          key: deps-cache
          path: ~/.npm

      - uses: actions/checkout@v6

      - name: Install and build
        run: |
          npm ci
          npm run build

  cleanup:
    runs-on: blacksmith-4vcpu-ubuntu-2204
    needs: build
    if: always()
    steps:
      - name: Delete sticky disk
        uses: useblacksmith/stickydisk-delete@v1
        with:
          delete-key: deps-cache

Pricing

Sticky disks are charged at $0.50/GB/mo. For pricing details, please visit our pricing page.

FAQ

What is the eviction policy?

Sticky disks are automatically evicted after 7 days of inactivity. The “last used” timestamp is updated each time a job mounts the sticky disk. As long as a sticky disk is used at least once within a 7-day window, it will remain available. If no jobs use a sticky disk for 7 consecutive days, it will be automatically purged.

Getting Started

Performance

Testboxes

Observability

Administration

FAQ

Overview

Basics

Cache Performance Comparison

Use Cases

NPM Package Caching

Bazel Build Caching

How it works

Using Sticky Disks inside a container

useblacksmith/stickydisk-delete

Delete by Key

Delete Docker Cache

Example: Cleanup After Build

Pricing

FAQ

​Overview

​Basics

​Cache Performance Comparison

​Use Cases

​NPM Package Caching

​Bazel Build Caching

​How it works

​Using Sticky Disks inside a container

​useblacksmith/stickydisk-delete

​Delete by Key

​Delete Docker Cache

​Example: Cleanup After Build

​Pricing

​FAQ

Overview

Basics

Cache Performance Comparison

Use Cases

NPM Package Caching

Bazel Build Caching

How it works

Using Sticky Disks inside a container

useblacksmith/stickydisk-delete

Delete by Key

Delete Docker Cache

Example: Cleanup After Build

Pricing

FAQ