Add s3 remote cache

.github/workflows/build.yml

@@ -126,6 +126,29 @@ jobs:
           name: coverage
           path: ./coverage
 
+  test-s3:
+    runs-on: ubuntu-latest
+    needs:
+      - base
+    steps:
+      -
+        name: Checkout
+        uses: actions/checkout@v2
+      -
+        name: Expose GitHub Runtime
+        uses: crazy-max/ghaction-github-runtime@v1
+      -
+        name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+        with:
+          version: ${{ env.BUILDX_VERSION }}
+          driver-opts: image=${{ env.REPO_SLUG_ORIGIN }}
+          buildkitd-flags: --debug
+      -
+        name: Test
+        run: |
+          hack/s3_test/run_test.sh
+
   test-os:
     runs-on: ${{ matrix.os }}
     strategy:

README.md

@@ -58,6 +58,7 @@ You don't need to read this document unless you want to use the full-featured st
     - [Registry (push image and cache separately)](#registry-push-image-and-cache-separately)
     - [Local directory](#local-directory-1)
     - [GitHub Actions cache (experimental)](#github-actions-cache-experimental)
+    - [S3 cache (experimental)](#s3-cache-experimental)
   - [Consistent hashing](#consistent-hashing)
 - [Metadata](#metadata)
 - [Systemd socket activation](#systemd-socket-activation)
@@ -426,6 +427,52 @@ in your workflow to expose the runtime.
 * `type=gha`
 * `scope=buildkit`: which scope cache object belongs to (default `buildkit`)
 
+#### S3 cache (experimental)
+
+```bash
+buildctl build ... \
+  --output type=image,name=docker.io/username/image,push=true \
+  --export-cache type=s3,region=eu-west-1,bucket=my_bucket,name=my_image \
+  --import-cache type=s3,region=eu-west-1,bucket=my_bucket,name=my_image
+```
+
+The following attributes are required:
+* `bucket`: AWS S3 bucket (default: `$AWS_BUCKET`)
+* `region`: AWS region (default: `$AWS_REGION`)
+
+Storage locations:
+* blobs: `s3://<bucket>/<prefix><blobs_prefix>/<sha256>`, default: `s3://<bucket>/blobs/<sha256>`
+* manifests: `s3://<bucket>/<prefix><manifests_prefix>/<name>`, default: `s3://<bucket>/manifests/<name>`
+
+S3 configuration:
+* `blobs_prefix`: global prefix to store / read blobs on s3. (default: `blobs/`)
+* `manifests_prefix`: global prefix to store / read blobs on s3. (default: `manifests/`)
+* `endpoint_url`: specify a specific S3 endpoint. (default: empty)
+* `use_path_style`: if set to `true`, put the bucket name in the URL instead of in the hostname. (default: `false`)
+
+AWS Authentication:
+
+The simplest way is to use an IAM Instance profile.
+Others options are:
+
+* Any system using environment variables / config files supported by the [AWS Go SDK](https://docs.aws.amazon.com/sdk-for-go/v1/developer-guide/configuring-sdk.html). The configuration must be available for the buildkit daemon, not for the client.
+* Access key ID and Secret Access Key, using the `access_key_id` and `secret_access_key` attributes.
+
+
+`--export-cache` options:
+* `type=s3`
+* `mode=min` (default): only export layers for the resulting image
+* `mode=max`: export all the layers of all intermediate steps.
+* `prefix`: global prefix to store / read files on s3. Default: empty
+* `name=buildkit`: name of the manifest to use (default `buildkit`). Multiple manifest names can be specified at the same time, separated by `;`. The standard use case is to use the git sha1 as name, and the branch name as duplicate, and load both with 2 `import-cache` commands.
+
+`--import-cache` options:
+* `type=s3`
+* `prefix=`: global prefix to store / read files on s3. Default: empty
+* `blobs_prefix=`: global prefix to store / read blobs on s3. (default: `blobs/`)
+* `manifests_prefix=`: global prefix to store / read blobs on s3. (default: `manifests/`)
+* `name=buildkit`: name of the manifest to use (default `buildkit`)
+
 ### Consistent hashing
 
 If you have multiple BuildKit daemon instances but you don't want to use registry for sharing cache across the cluster,

cache/remotecache/s3/readerat.go

@@ -0,0 +1,75 @@
+package s3
+
+import (
+	"io"
+)
+
+type ReaderAtCloser interface {
+	io.ReaderAt
+	io.Closer
+}
+
+type readerAtCloser struct {
+	offset int64
+	rc     io.ReadCloser
+	ra     io.ReaderAt
+	open   func(offset int64) (io.ReadCloser, error)
+	closed bool
+}
+
+func toReaderAtCloser(open func(offset int64) (io.ReadCloser, error)) ReaderAtCloser {
+	return &readerAtCloser{
+		open: open,
+	}
+}
+
+func (hrs *readerAtCloser) ReadAt(p []byte, off int64) (n int, err error) {
+	if hrs.closed {
+		return 0, io.EOF
+	}
+
+	if hrs.ra != nil {
+		return hrs.ra.ReadAt(p, off)
+	}
+
+	if hrs.rc == nil || off != hrs.offset {
+		if hrs.rc != nil {
+			hrs.rc.Close()
+			hrs.rc = nil
+		}
+		rc, err := hrs.open(off)
+		if err != nil {
+			return 0, err
+		}
+		hrs.rc = rc
+	}
+	if ra, ok := hrs.rc.(io.ReaderAt); ok {
+		hrs.ra = ra
+		n, err = ra.ReadAt(p, off)
+	} else {
+		for {
+			var nn int
+			nn, err = hrs.rc.Read(p)
+			n += nn
+			p = p[nn:]
+			if nn == len(p) || err != nil {
+				break
+			}
+		}
+	}
+
+	hrs.offset += int64(n)
+	return
+}
+
+func (hrs *readerAtCloser) Close() error {
+	if hrs.closed {
+		return nil
+	}
+	hrs.closed = true
+	if hrs.rc != nil {
+		return hrs.rc.Close()
+	}
+
+	return nil
+}