podman build --jobs is not parallelized

[AkihiroSuda]

Is this a BUG REPORT or FEATURE REQUEST? (leave only one on its own line)

/kind bug

Description

podman build --jobs is not parallelized

Steps to reproduce the issue:

Run podman build --no-cache --jobs 0 with the following Dockefile

FROM busybox
RUN sleep 3
RUN date
RUN touch /foo

FROM busybox
RUN sleep 3
RUN date
RUN touch /foo

FROM scratch
COPY --from=0 /foo /foo-0
COPY --from=1 /foo /foo-1

Describe the results you received:

The second date was delayed 6 seconds compared to the first one.

$ podman build -t foo --no-cache --jobs 0 .
STEP 1: FROM busybox
STEP 2: RUN sleep 3
--> fd4acb7d8da
STEP 3: RUN date
Fri Feb  5 09:45:54 UTC 2021
--> 67c9465fad5
STEP 4: RUN touch /foo
--> 981e9437014
STEP 5: FROM busybox
STEP 6: RUN sleep 3
--> 6a163b44b4e
STEP 7: RUN date
Fri Feb  5 09:46:00 UTC 2021
--> 14190eb3948
STEP 8: RUN touch /foo
--> 36af2beb782
STEP 9: FROM scratch
STEP 10: COPY --from=0 /foo /foo-0
--> b9a93476274
STEP 11: COPY --from=1 /foo /foo-1
STEP 12: COMMIT foo
--> 88b5aef3e67
88b5aef3e6727df594710dfaa14d28eda7ef929dccb9a84bb373906bf3906341

Describe the results you expected:

The second date and the first one should be executed almost simultaneously.
Buildah (containers/buildah@1040f105) works as expected:

$ buildah bud -t foo --no-cache --jobs 0 .
STEP 1: FROM scratch
STEP 2: FROM busybox
STEP 3: FROM busybox
STEP 4: COPY --from=0 /foo /foo-0
STEP 5: RUN sleep 3
STEP 6: RUN sleep 3
STEP 7: RUN date
STEP 8: RUN date
Fri Feb  5 09:48:31 UTC 2021
STEP 9: RUN touch /foo
Fri Feb  5 09:48:31 UTC 2021
STEP 10: RUN touch /foo
STEP 11: COPY --from=1 /foo /foo-1
STEP 12: COMMIT foo
--> 306a36bbaab
306a36bbaab0730d8d8233158370aeb61b002598766f1ed0c021acd98f6e0348

Additional information you deem important (e.g. issue happens only occasionally):

Buildah works as expected, Podman does not.

Output of podman version:

Version:      3.0.0-dev
API Version:  3.0.0
Go Version:   go1.16rc1
Git Commit:   42d4652fed759904bb51a5d3420724dc25009494
Built:        Fri Feb  5 18:44:45 2021
OS/Arch:      linux/amd64

Output of podman info --debug:

host:
  arch: amd64
  buildahVersion: 1.19.3
  cgroupManager: systemd
  cgroupVersion: v2
  conmon:
    package: Unknown
    path: /usr/local/bin/conmon
    version: 'conmon version 2.0.25, commit: 05ce716ac6d1cfeeb27b9280832abd2e9d1a085f'
  cpus: 4
  distribution:
    distribution: ubuntu
    version: "20.10"
  eventLogger: journald
  hostname: suda-ws01
  idMappings:
    gidmap:
    - container_id: 0
      host_id: 1001
      size: 1
    - container_id: 1
      host_id: 100000
      size: 65536
    uidmap:
    - container_id: 0
      host_id: 1001
      size: 1
    - container_id: 1
      host_id: 100000
      size: 65536
  kernel: 5.8.0-41-generic
  linkmode: dynamic
  memFree: 11428253696
  memTotal: 16757456896
  ociRuntime:
    name: crun
    package: Unknown
    path: /usr/local/bin/crun
    version: |-
      crun version 0.17
      commit: 0e9229ae34caaebcb86f1fde18de3acaf18c6d9a
      spec: 1.0.0
      +SYSTEMD +SELINUX +APPARMOR +CAP +SECCOMP +EBPF +CRIU +YAJL
  os: linux
  remoteSocket:
    path: /run/user/1001/podman/podman.sock
  security:
    apparmorEnabled: false
    capabilities: CAP_AUDIT_WRITE,CAP_CHOWN,CAP_DAC_OVERRIDE,CAP_FOWNER,CAP_FSETID,CAP_KILL,CAP_MKNOD,CAP_NET_BIND_SERVICE,CAP_NET_RAW,CAP_SETFCAP,CAP_SETGID,CAP_SETPCAP,CAP_SETUID,CAP_SYS_CHROOT
    rootless: true
    seccompEnabled: true
    selinuxEnabled: false
  slirp4netns:
    executable: /usr/local/bin/slirp4netns
    package: Unknown
    version: |-
      slirp4netns version 1.1.8
      commit: d361001f495417b880f20329121e3aa431a8f90f
      libslirp: 4.4.0
      SLIRP_CONFIG_VERSION_MAX: 3
      libseccomp: 2.4.3
  swapFree: 2147479552
  swapTotal: 2147479552
  uptime: 2h 48m 12.48s (Approximately 0.08 days)
registries:
  search:
  - docker.io
store:
  configFile: /home/suda/.config/containers/storage.conf
  containerStore:
    number: 0
    paused: 0
    running: 0
    stopped: 0
  graphDriverName: overlay
  graphOptions:
    overlay.mount_program:
      Executable: /usr/local/bin/fuse-overlayfs
      Package: Unknown
      Version: |-
        fusermount3 version: 3.9.3
        fuse-overlayfs: version 1.3
        FUSE library version 3.4.1
        using FUSE kernel interface version 7.27
  graphRoot: /home/suda/.local/share/containers/storage
  graphStatus:
    Backing Filesystem: extfs
    Native Overlay Diff: "false"
    Supports d_type: "true"
    Using metacopy: "false"
  imageStore:
    number: 63
  runRoot: /tmp/1001
  volumePath: /home/suda/.local/share/containers/storage/volumes
version:
  APIVersion: 3.0.0
  Built: 1612518285
  BuiltTime: Fri Feb  5 18:44:45 2021
  GitCommit: 42d4652fed759904bb51a5d3420724dc25009494
  GoVersion: go1.16rc1
  OsArch: linux/amd64
  Version: 3.0.0-dev

Package info (e.g. output of rpm -q podman or apt list podman):

Installed from source.

Have you tested with the latest version of Podman and have you checked the Podman Troubleshooting Guide?

Yes

[rhatdan]

If you specify --jobs=3 does it work correctly?

[AkihiroSuda]

No

[github-actions]

A friendly reminder that this issue had no activity for 30 days.

[rhatdan]

I believe this is fixed in the main branch.