buildah never invalidates the cache of a RUN --mount=type=bind layer

[wegel]

Description

buildah never invalidates the cache of a RUN --mount=type=bind or RUN --mount=type=cache when the contents of the source changes.

Steps to reproduce the issue:

mkdir files
for M in bind cache; do
for I in 1 2; do
echo "$M: Iteration $I"
echo "$M: $I" > files/$M$I
buildah build --layers -f -<<EOF
FROM ubuntu:22.04
RUN --mount=type=$M,source=files,target=/files ls -l /files
EOF
done
done

Describe the results you received:

bind: Iteration 1
STEP 1/2: FROM ubuntu:22.04
STEP 2/2: RUN --mount=type=bind,source=files,target=/files ls -l /files
total 4
-rw-r--r-- 1 root root 8 Mar 13 01:52 bind1
COMMIT
--> b325129d4a91
b325129d4a91df893b6d698c1db8f89c218173d89516d627977bf53b0158828c

bind: Iteration 2
STEP 1/2: FROM ubuntu:22.04
STEP 2/2: RUN --mount=type=bind,source=files,target=/files ls -l /files
--> Using cache b325129d4a91df893b6d698c1db8f89c218173d89516d627977bf53b0158828c
--> b325129d4a91
b325129d4a91df893b6d698c1db8f89c218173d89516d627977bf53b0158828c

cache: Iteration 1
STEP 1/2: FROM ubuntu:22.04
STEP 2/2: RUN --mount=type=cache,source=files,target=/files ls -l /files
total 0
COMMIT
--> e074a87a9cc3
e074a87a9cc3ef55550cd83fc0cef080478797c382deec45c7b63bd8825a2367
cache: Iteration 2

STEP 1/2: FROM ubuntu:22.04
STEP 2/2: RUN --mount=type=cache,source=files,target=/files ls -l /files
--> Using cache e074a87a9cc3ef55550cd83fc0cef080478797c382deec45c7b63bd8825a2367
--> e074a87a9cc3
e074a87a9cc3ef55550cd83fc0cef080478797c382deec45c7b63bd8825a2367

Describe the results you expected:

I expected the image to be rebuilt during the second iteration, since the contents of files had changed.

Output of rpm -q buildah or apt list buildah:

$ pacman -Q | grep buildah
buildah 1.34.1-1

Output of buildah version:

Version:         1.34.1
Go Version:      go1.22.0
Image Spec:      1.1.0-rc.6
Runtime Spec:    1.1.0
CNI Spec:        1.0.0
libcni Version:  v1.1.2
image Version:   5.29.1-dev
Git Commit:      a2bab63fdbf32b6b5e45b0750f122327e09842a6
Built:           Thu Feb 29 15:53:12 2024
OS/Arch:         linux/amd64
BuildPlatform:   linux/amd64

Output of podman version if reporting a podman build issue:

podman build has the same issue:

Client:       Podman Engine
Version:      4.8.3
API Version:  4.8.3
Go Version:   go1.21.5
Git Commit:   85dc30df56566a654700722a4dd190e1b9680ee7-dirty
Built:        Thu Jan  4 11:14:11 2024
OS/Arch:      linux/amd64

Output of cat /etc/*release:

NAME="Arch Linux"
VERSION_ID=20240101.0.204074

Output of uname -a:

Linux archlinux 6.6.9-arch1-1 #1 SMP PREEMPT_DYNAMIC Tue, 02 Jan 2024 02:28:28 +0000 x86_64 GNU/Linux

Output of cat /etc/containers/storage.conf:

# This file is the configuration file for all tools
# that use the containers/storage library. The storage.conf file
# overrides all other storage.conf files. Container engines using the
# container/storage library do not inherit fields from other storage.conf
# files.
#
#  Note: The storage.conf file overrides other storage.conf files based on this precedence:
#      /usr/containers/storage.conf
#      /etc/containers/storage.conf
#      $HOME/.config/containers/storage.conf
#      $XDG_CONFIG_HOME/containers/storage.conf (If XDG_CONFIG_HOME is set)
# See man 5 containers-storage.conf for more information
# The "container storage" table contains all of the server options.
[storage]

# Default Storage Driver, Must be set for proper operation.
driver = "overlay"

# Temporary storage location
runroot = "/run/containers/storage"

# Primary Read/Write location of container storage
# When changing the graphroot location on an SELINUX system, you must
# ensure  the labeling matches the default locations labels with the
# following commands:
# semanage fcontext -a -e /var/lib/containers/storage /NEWSTORAGEPATH
# restorecon -R -v /NEWSTORAGEPATH
graphroot = "/var/lib/containers/storage"

# Optional alternate location of image store if a location separate from the
# container store is required. If set, it must be different than graphroot.
# imagestore = ""


# Storage path for rootless users
#
# rootless_storage_path = "$HOME/.local/share/containers/storage"

# Transient store mode makes all container metadata be saved in temporary storage
# (i.e. runroot above). This is faster, but doesn't persist across reboots.
# Additional garbage collection must also be performed at boot-time, so this
# option should remain disabled in most configurations.
# transient_store = true

[storage.options]
# Storage options to be passed to underlying storage drivers

# AdditionalImageStores is used to pass paths to additional Read/Only image stores
# Must be comma separated list.
additionalimagestores = [
]

# Allows specification of how storage is populated when pulling images. This
# option can speed the pulling process of images compressed with format
# zstd:chunked. Containers/storage looks for files within images that are being
# pulled from a container registry that were previously pulled to the host.  It
# can copy or create a hard link to the existing file when it finds them,
# eliminating the need to pull them from the container registry. These options
# can deduplicate pulling of content, disk storage of content and can allow the
# kernel to use less memory when running containers.

# containers/storage supports three keys
#   * enable_partial_images="true" | "false"
#     Tells containers/storage to look for files previously pulled in storage
#     rather then always pulling them from the container registry.
#   * use_hard_links = "false" | "true"
#     Tells containers/storage to use hard links rather then create new files in
#     the image, if an identical file already existed in storage.
#   * ostree_repos = ""
#     Tells containers/storage where an ostree repository exists that might have
#     previously pulled content which can be used when attempting to avoid
#     pulling content from the container registry
pull_options = {enable_partial_images = "false", use_hard_links = "false", ostree_repos=""}

# Remap-UIDs/GIDs is the mapping from UIDs/GIDs as they should appear inside of
# a container, to the UIDs/GIDs as they should appear outside of the container,
# and the length of the range of UIDs/GIDs.  Additional mapped sets can be
# listed and will be heeded by libraries, but there are limits to the number of
# mappings which the kernel will allow when you later attempt to run a
# container.
#
# remap-uids = "0:1668442479:65536"
# remap-gids = "0:1668442479:65536"

# Remap-User/Group is a user name which can be used to look up one or more UID/GID
# ranges in the /etc/subuid or /etc/subgid file.  Mappings are set up starting
# with an in-container ID of 0 and then a host-level ID taken from the lowest
# range that matches the specified name, and using the length of that range.
# Additional ranges are then assigned, using the ranges which specify the
# lowest host-level IDs first, to the lowest not-yet-mapped in-container ID,
# until all of the entries have been used for maps. This setting overrides the
# Remap-UIDs/GIDs setting.
#
# remap-user = "containers"
# remap-group = "containers"

# Root-auto-userns-user is a user name which can be used to look up one or more UID/GID
# ranges in the /etc/subuid and /etc/subgid file.  These ranges will be partitioned
# to containers configured to create automatically a user namespace.  Containers
# configured to automatically create a user namespace can still overlap with containers
# having an explicit mapping set.
# This setting is ignored when running as rootless.
# root-auto-userns-user = "storage"
#
# Auto-userns-min-size is the minimum size for a user namespace created automatically.
# auto-userns-min-size=1024
#
# Auto-userns-max-size is the maximum size for a user namespace created automatically.
# auto-userns-max-size=65536

[storage.options.overlay]
# ignore_chown_errors can be set to allow a non privileged user running with
# a single UID within a user namespace to run containers. The user can pull
# and use any image even those with multiple uids.  Note multiple UIDs will be
# squashed down to the default uid in the container.  These images will have no
# separation between the users in the container. Only supported for the overlay
# and vfs drivers.
#ignore_chown_errors = "false"

# Inodes is used to set a maximum inodes of the container image.
# inodes = ""

# Path to an helper program to use for mounting the file system instead of mounting it
# directly.
#mount_program = "/usr/bin/fuse-overlayfs"

# mountopt specifies comma separated list of extra mount options
mountopt = "nodev"

# Set to skip a PRIVATE bind mount on the storage home directory.
# skip_mount_home = "false"

# Size is used to set a maximum size of the container image.
# size = ""

# ForceMask specifies the permissions mask that is used for new files and
# directories.
#
# The values "shared" and "private" are accepted.
# Octal permission masks are also accepted.
#
#  "": No value specified.
#     All files/directories, get set with the permissions identified within the
#     image.
#  "private": it is equivalent to 0700.
#     All files/directories get set with 0700 permissions.  The owner has rwx
#     access to the files. No other users on the system can access the files.
#     This setting could be used with networked based homedirs.
#  "shared": it is equivalent to 0755.
#     The owner has rwx access to the files and everyone else can read, access
#     and execute them. This setting is useful for sharing containers storage
#     with other users.  For instance have a storage owned by root but shared
#     to rootless users as an additional store.
#     NOTE:  All files within the image are made readable and executable by any
#     user on the system. Even /etc/shadow within your image is now readable by
#     any user.
#
#   OCTAL: Users can experiment with other OCTAL Permissions.
#
#  Note: The force_mask Flag is an experimental feature, it could change in the
#  future.  When "force_mask" is set the original permission mask is stored in
#  the "user.containers.override_stat" xattr and the "mount_program" option must
#  be specified. Mount programs like "/usr/bin/fuse-overlayfs" present the
#  extended attribute permissions to processes within containers rather than the
#  "force_mask"  permissions.
#
# force_mask = ""

[storage.options.thinpool]
# Storage Options for thinpool

# autoextend_percent determines the amount by which pool needs to be
# grown. This is specified in terms of % of pool size. So a value of 20 means
# that when threshold is hit, pool will be grown by 20% of existing
# pool size.
# autoextend_percent = "20"

# autoextend_threshold determines the pool extension threshold in terms
# of percentage of pool size. For example, if threshold is 60, that means when
# pool is 60% full, threshold has been hit.
# autoextend_threshold = "80"

# basesize specifies the size to use when creating the base device, which
# limits the size of images and containers.
# basesize = "10G"

# blocksize specifies a custom blocksize to use for the thin pool.
# blocksize="64k"

# directlvm_device specifies a custom block storage device to use for the
# thin pool. Required if you setup devicemapper.
# directlvm_device = ""

# directlvm_device_force wipes device even if device already has a filesystem.
# directlvm_device_force = "True"

# fs specifies the filesystem type to use for the base device.
# fs="xfs"

# log_level sets the log level of devicemapper.
# 0: LogLevelSuppress 0 (Default)
# 2: LogLevelFatal
# 3: LogLevelErr
# 4: LogLevelWarn
# 5: LogLevelNotice
# 6: LogLevelInfo
# 7: LogLevelDebug
# log_level = "7"

# min_free_space specifies the min free space percent in a thin pool require for
# new device creation to succeed. Valid values are from 0% - 99%.
# Value 0% disables
# min_free_space = "10%"

# mkfsarg specifies extra mkfs arguments to be used when creating the base
# device.
# mkfsarg = ""

# metadata_size is used to set the `pvcreate --metadatasize` options when
# creating thin devices. Default is 128k
# metadata_size = ""

# Size is used to set a maximum size of the container image.
# size = ""

# use_deferred_removal marks devicemapper block device for deferred removal.
# If the thinpool is in use when the driver attempts to remove it, the driver
# tells the kernel to remove it as soon as possible. Note this does not free
# up the disk space, use deferred deletion to fully remove the thinpool.
# use_deferred_removal = "True"

# use_deferred_deletion marks thinpool device for deferred deletion.
# If the device is busy when the driver attempts to delete it, the driver
# will attempt to delete device every 30 seconds until successful.
# If the program using the driver exits, the driver will continue attempting
# to cleanup the next time the driver is used. Deferred deletion permanently
# deletes the device and all data stored in device will be lost.
# use_deferred_deletion = "True"

# xfs_nospace_max_retries specifies the maximum number of retries XFS should
# attempt to complete IO when ENOSPC (no space) error is returned by
# underlying storage device.
# xfs_nospace_max_retries = "0"

[wegel]

Is this normal/accepted behaviour?

[flouthoc]

This looks like a bug to me, since buildkit clears the cache when source content is changed. I'll take a look at this issue. Thanks for creating this.

[flouthoc]

Buildah's cache works on history statements, I think in order to make this work we need to store some additional information in history statements, (maybe like checksum of source) in history stmts and invalidate cache when there is a diff in checksum. If this looks good I can create a PR for this.

@containers/buildah-maintainers @nalind WDYT ?

[github-actions]

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