Remote Cache

You can use remote cache to accelerate the build process. envd build cache^[1] can be uploaded to the image registry, local directories or other places. There are five types supported:

• registry: push the image and the cache separately to a image registry.
• inline: embed the cache into the image, and push them to the registry together
• local: export/import cache from a local directory
• gha (experimental 🧪): export/import cache from GitHub Actions cache
• s3 (experimental 🧪): export/import cache from s3

registry is recommended in most cases.

How to use?

The arguments --export-cache and --import-cache are used to export and import the cache.

The build cache will be exported to the given location if --export-cache is specified. And the build cache will be imported from the given location if --import-cache is specified.

envd build ... \
  --output type=image,name=docker.io/username/image,push=true \
  --export-cache type=registry,ref=docker.io/username/cache-name \
  --import-cache type=registry,ref=docker.io/username/cache-name

You can use the mechanism to accelerate the build process dramatically.

Reference

This feature is supported by BuildKit.

Registry (push image and cache separately)

envd build ... \
  --output type=image,name=docker.io/username/image,push=true \
  --export-cache type=registry,ref=docker.io/username/image \
  --import-cache type=registry,ref=docker.io/username/image

--export-cache options:

• type=registry
• mode=<min|max>: specify cache layers to export (default: min)
  • min: only export layers for the resulting image
  • max: export all the layers of all intermediate steps
• ref=<ref>: specify repository reference to store cache, e.g. docker.io/user/image:tag
• oci-mediatypes=<true|false>: whether to use OCI mediatypes in exported manifests (default: true, since BuildKit v0.8)
• compression=<uncompressed|gzip|estargz|zstd>: choose compression type for layers newly created and cached, gzip is default value. estargz and zstd should be used with oci-mediatypes=true
• compression-level=<value>: choose compression level for gzip, estargz (0-9) and zstd (0-22)
• force-compression=true: forcibly apply compression option to all layers

--import-cache options:

• type=registry
• ref=<ref>: specify repository reference to retrieve cache from, e.g. docker.io/user/image:tag

Inline (push image and cache together)

envd build ... \
  --output type=image,name=docker.io/username/image,push=true \
  --export-cache type=inline \
  --import-cache type=registry,ref=docker.io/username/image

Note that the inline cache is not imported unless --import-cache type=registry,ref=... is provided.

Inline cache embeds cache metadata into the image config. The layers in the image will be left untouched compared to the image with no cache information.

Local directory

envd build ... --export-cache type=local,dest=path/to/output-dir
envd build ... --import-cache type=local,src=path/to/input-dir

The directory layout conforms to OCI Image Spec v1.0.

--export-cache options:

• type=local
• mode=<min|max>: specify cache layers to export (default: min)
  • min: only export layers for the resulting image
  • max: export all the layers of all intermediate steps
• dest=<path>: destination directory for cache exporter
• oci-mediatypes=<true|false>: whether to use OCI mediatypes in exported manifests (default true, since BuildKit v0.8)
• compression=<uncompressed|gzip|estargz|zstd>: choose compression type for layers newly created and cached, gzip is default value. estargz and zstd should be used with oci-mediatypes=true.
• compression-level=<value>: compression level for gzip, estargz (0-9) and zstd (0-22)
• force-compression=true: forcibly apply compression option to all layers

--import-cache options:

• type=local
• src=<path>: source directory for cache importer
• digest=sha256:<sha256digest>: specify explicit digest of the manifest list to import
• tag=<tag>: determine custom tag of image. Defaults "latest" tag digest in index.json is for digest, not for tag

GitHub Actions cache (experimental)

envd build ... \
  --output type=image,name=docker.io/username/image,push=true \
  --export-cache type=gha \
  --import-cache type=gha

GitHub Actions cache saves both cache metadata and layers to GitHub's Cache service. This cache currently has a size limit of 10GB that is shared across different caches in the repo. If you exceed this limit, GitHub will save your cache but will begin evicting caches until the total size is less than 10 GB. Recycling caches too often can result in slower runtimes overall.

Similarly to using actions/cache, caches are scoped by branch, with the default and target branches being available to every branch.

Following attributes are required to authenticate against the GitHub Actions Cache service API:

• url: Cache server URL (default $ACTIONS_CACHE_URL)
• token: Access token (default $ACTIONS_RUNTIME_TOKEN)

--export-cache options:

• type=gha
• mode=<min|max>: specify cache layers to export (default: min)
  • min: only export layers for the resulting image
  • max: export all the layers of all intermediate steps
• scope=<scope>: which scope cache object belongs to (default buildkit)

--import-cache options:

• type=gha
• scope=<scope>: which scope cache object belongs to (default buildkit)

S3 cache (experimental)

envd 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 manifest 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. 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|max>: specify cache layers to export (default: min)
  • min: only export layers for the resulting image
  • max: export all the layers of all intermediate steps
• prefix=<prefix>: set global prefix to store / read files on s3 (default: empty)
• name=<manifest>: specify 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=<prefix>: set global prefix to store / read files on s3 (default: empty)
• blobs_prefix=<prefix>: set global prefix to store / read blobs on s3 (default: blobs/)
• manifests_prefix=<prefix>: set global prefix to store / read manifests on s3 (default: manifests/)
• name=<manifest>: name of the manifest to use (default buildkit)

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1. remote cache feature is built on top of buildkit ↩︎