MODULE FAILURE: No start of json char found on macOS and aarch64 Linux

[basictheprogram]

SUMMARY

Migrating from ansible-core-2.12 to ansible-core-2.18.7 on macOS. Basic molecule tests using ansible_connection: docker and apt fail.

The problem seams to be macOS specific or ARM specific. The same tests succeed on AMD64 Linux.

ISSUE TYPE

• Bug Report

COMPONENT NAME

I suspect community.docker.plugins.connection.docker.py

ANSIBLE VERSION

$ ansible --version
ansible [core 2.18.7]
  config file = /workspace/collections/ansible_collections/realtime/logging/roles/alloy/ansible.cfg
  configured module search path = ['/home/vscode/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /home/vscode/.venv/lib/python3.13/site-packages/ansible
  ansible collection location = /home/vscode/.ansible/collections:/usr/share/ansible/collections:/workspace/collections
  executable location = /home/vscode/.venv/bin/ansible
  python version = 3.13.6 (main, Aug  8 2025, 17:10:04) [Clang 20.1.4 ] (/home/vscode/.venv/bin/python)
  jinja version = 3.1.6
  libyaml = True

macOS

$ sw_vers 
ProductName:		macOS
ProductVersion:		15.6
BuildVersion:		24G84

python

$ python -V
Python 3.13.6

Docker

$ docker --version
Docker version 28.3.3-1, build 980b85681696fbd95927fd8ded8f6d91bdca95b0

docker desktop
4.44.0 (201307)

COLLECTION VERSION

$ ansible-galaxy collection list community.docker

# /home/vscode/.ansible/collections/ansible_collections
Collection       Version
---------------- -------
community.docker 4.7.0  

# /home/vscode/.venv/lib/python3.13/site-packages/ansible_collections
Collection       Version
---------------- -------
community.docker 4.6.1  

# /workspace/collections/ansible_collections
Collection       Version
---------------- -------
community.docker 4.7.0  

CONFIGURATION

$ ansible-config dump --only-changed
ANSIBLE_PIPELINING(/workspace/collections/ansible_collections/realtime/logging/roles/alloy/ansible.cfg) = False
COLLECTIONS_PATHS(/workspace/collections/ansible_collections/realtime/logging/roles/alloy/ansible.cfg) = ['/home/vscode/.ansible/collections', '/usr/sh>
CONFIG_FILE() = /workspace/collections/ansible_collections/realtime/logging/roles/alloy/ansible.cfg
DEFAULT_DEBUG(/workspace/collections/ansible_collections/realtime/logging/roles/alloy/ansible.cfg) = False
DEFAULT_REMOTE_USER(/workspace/collections/ansible_collections/realtime/logging/roles/alloy/ansible.cfg) = ansible
DEFAULT_ROLES_PATH(/workspace/collections/ansible_collections/realtime/logging/roles/alloy/ansible.cfg) = ['/home/vscode/.ansible/roles', '/usr/share/a>
DEPRECATION_WARNINGS(/workspace/collections/ansible_collections/realtime/logging/roles/alloy/ansible.cfg) = True
RETRY_FILES_ENABLED(/workspace/collections/ansible_collections/realtime/logging/roles/alloy/ansible.cfg) = False

OS / ENVIRONMENT

Ubuntu 22.04.5 LTS

$ uname -a
Linux jammy 6.10.14-linuxkit #1 SMP Sat May 17 08:28:57 UTC 2025 aarch64 aarch64 aarch64 GNU/Linux

STEPS TO REPRODUCE

hosts.yml

    docker_containers:
      hosts:
        jammy:
          ansible_connection: docker

test-docker-connection.yml

---
- name: Testing
  hosts: all
  gather_facts: false
  become: true

  tasks:
    - name: Package update (apt)
      ansible.builtin.apt:
        update_cache: true

EXPECTED RESULTS

ansible-playbook [core 2.18.7]
  config file = /workspace/sites/real-time.com/ansible.cfg
  configured module search path = ['/home/vscode/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /home/vscode/.venv/lib/python3.13/site-packages/ansible
  ansible collection location = /home/vscode/.ansible/collections:/usr/share/ansible/collections:/workspace/collections
  executable location = /home/vscode/.venv/bin/ansible-playbook
  python version = 3.13.6 (main, Aug  8 2025, 17:08:22) [Clang 20.1.4 ] (/home/vscode/.venv/bin/python)
  jinja version = 3.1.6
  libyaml = True
Using /workspace/sites/real-time.com/ansible.cfg as config file
setting up inventory plugins
Loading collection ansible.builtin from 
host_list declined parsing /workspace/sites/real-time.com/testing/hosts.yml as it did not pass its verify_file() method
script declined parsing /workspace/sites/real-time.com/testing/hosts.yml as it did not pass its verify_file() method
Parsed /workspace/sites/real-time.com/testing/hosts.yml inventory source with yaml plugin
Loading callback plugin default of type stdout, v2.0 from /home/vscode/.venv/lib/python3.13/site-packages/ansible/plugins/callback/default.py
Skipping callback 'default', as we already have a stdout callback.
Skipping callback 'minimal', as we already have a stdout callback.
Skipping callback 'oneline', as we already have a stdout callback.

PLAYBOOK: test-docker-connection.yml *****************************************************************************************************************************************************************
Positional arguments: playbooks/test-docker-connection.yml
verbosity: 4
remote_user: root
connection: ssh
become_method: sudo
tags: ('all',)
inventory: ('/workspace/sites/real-time.com/testing/hosts.yml',)
subset: jammy
forks: 5
1 plays in playbooks/test-docker-connection.yml

PLAY [Testing] ***************************************************************************************************************************************************************************************

TASK [Gathering Facts] *******************************************************************************************************************************************************************************
task path: /workspace/sites/real-time.com/playbooks/test-docker-connection.yml:2
redirecting (type: connection) ansible.builtin.docker to community.docker.docker
Loading collection community.docker from /workspace/collections/ansible_collections/community/docker
<jammy> ESTABLISH DOCKER CONNECTION FOR USER: root
<jammy> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'jammy', '/bin/sh', '-c', "/bin/sh -c 'echo ~root && sleep 0'"]
<jammy> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'jammy', '/bin/sh', '-c', '/bin/sh -c \'( umask 77 && mkdir -p "` echo /root/.ansible/tmp `"&& mkdir "` echo /root/.ansible/tmp/ansible-tmp-1755032528.1298847-10631-1985867414768 `" && echo ansible-tmp-1755032528.1298847-10631-1985867414768="` echo /root/.ansible/tmp/ansible-tmp-1755032528.1298847-10631-1985867414768 `" ) && sleep 0\'']
Using module file /home/vscode/.venv/lib/python3.13/site-packages/ansible/modules/setup.py
<jammy> PUT /home/vscode/.ansible/tmp/ansible-local-10625uvmvq25c/tmpjbbnq5_x TO /root/.ansible/tmp/ansible-tmp-1755032528.1298847-10631-1985867414768/AnsiballZ_setup.py
<jammy> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'jammy', '/bin/sh', '-c', "/bin/sh -c 'chmod u+rwx /root/.ansible/tmp/ansible-tmp-1755032528.1298847-10631-1985867414768/ /root/.ansible/tmp/ansible-tmp-1755032528.1298847-10631-1985867414768/AnsiballZ_setup.py && sleep 0'"]
<jammy> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'jammy', '/bin/sh', '-c', "/bin/sh -c '/usr/bin/python3 /root/.ansible/tmp/ansible-tmp-1755032528.1298847-10631-1985867414768/AnsiballZ_setup.py && sleep 0'"]
<jammy> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'jammy', '/bin/sh', '-c', "/bin/sh -c 'rm -f -r /root/.ansible/tmp/ansible-tmp-1755032528.1298847-10631-1985867414768/ > /dev/null 2>&1 && sleep 0'"]
ok: [jammy]

TASK [Package update (apt)] **************************************************************************************************************************************************************************
task path: /workspace/sites/real-time.com/playbooks/test-docker-connection.yml:13
redirecting (type: connection) ansible.builtin.docker to community.docker.docker
Loading collection community.docker from /workspace/collections/ansible_collections/community/docker
<jammy> ESTABLISH DOCKER CONNECTION FOR USER: root
<jammy> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'jammy', '/bin/sh', '-c', "/bin/sh -c 'echo ~root && sleep 0'"]
<jammy> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'jammy', '/bin/sh', '-c', '/bin/sh -c \'( umask 77 && mkdir -p "` echo /root/.ansible/tmp `"&& mkdir "` echo /root/.ansible/tmp/ansible-tmp-1755032529.8738043-10730-39478951980603 `" && echo ansible-tmp-1755032529.8738043-10730-39478951980603="` echo /root/.ansible/tmp/ansible-tmp-1755032529.8738043-10730-39478951980603 `" ) && sleep 0\'']
Using module file /home/vscode/.venv/lib/python3.13/site-packages/ansible/modules/apt.py
<jammy> PUT /home/vscode/.ansible/tmp/ansible-local-10625uvmvq25c/tmp8nlh1mhi TO /root/.ansible/tmp/ansible-tmp-1755032529.8738043-10730-39478951980603/AnsiballZ_apt.py
<jammy> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'jammy', '/bin/sh', '-c', "/bin/sh -c 'chmod u+rwx /root/.ansible/tmp/ansible-tmp-1755032529.8738043-10730-39478951980603/ /root/.ansible/tmp/ansible-tmp-1755032529.8738043-10730-39478951980603/AnsiballZ_apt.py && sleep 0'"]
<jammy> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'jammy', '/bin/sh', '-c', "/bin/sh -c '/usr/bin/python3 /root/.ansible/tmp/ansible-tmp-1755032529.8738043-10730-39478951980603/AnsiballZ_apt.py && sleep 0'"]
<jammy> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'jammy', '/bin/sh', '-c', "/bin/sh -c 'rm -f -r /root/.ansible/tmp/ansible-tmp-1755032529.8738043-10730-39478951980603/ > /dev/null 2>&1 && sleep 0'"]
ok: [jammy] => {
    "cache_update_time": 1755030556,
    "cache_updated": false,
    "changed": false,
    "invocation": {
        "module_args": {
            "allow_change_held_packages": false,
            "allow_downgrade": false,
            "allow_unauthenticated": false,
            "autoclean": false,
            "autoremove": false,
            "cache_valid_time": 0,
            "clean": false,
            "deb": null,
            "default_release": null,
            "dpkg_options": "force-confdef,force-confold",
            "fail_on_autoremove": false,
            "force": false,
            "force_apt_get": false,
            "install_recommends": null,
            "lock_timeout": 60,
            "only_upgrade": false,
            "package": null,
            "policy_rc_d": null,
            "purge": false,
            "state": "present",
            "update_cache": true,
            "update_cache_retries": 5,
            "update_cache_retry_max_delay": 12,
            "upgrade": null
        }
    }
}

PLAY RECAP *******************************************************************************************************************************************************************************************
jammy                      : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   

ACTUAL RESULTS

$ ansible-playbook -i hosts.yml  -u root test-docker-connection.yml -vvvv
ansible-playbook [core 2.18.7]
  config file = /workspace/sites/real-time.com/ansible.cfg
  configured module search path = ['/home/vscode/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /home/vscode/.venv/lib/python3.13/site-packages/ansible
  ansible collection location = /home/vscode/.ansible/collections:/usr/share/ansible/collections:/workspace/collections
  executable location = /home/vscode/.venv/bin/ansible-playbook
  python version = 3.13.6 (main, Aug  8 2025, 17:10:04) [Clang 20.1.4 ] (/home/vscode/.venv/bin/python)
  jinja version = 3.1.6
  libyaml = True
Using /workspace/sites/real-time.com/ansible.cfg as config file
setting up inventory plugins
Loading collection ansible.builtin from 
host_list declined parsing /workspace/sites/real-time.com/testing/hosts.yml as it did not pass its verify_file() method
Parsed /workspace/sites/real-time.com/testing/hosts.yml inventory source with yaml plugin
Loading callback plugin default of type stdout, v2.0 from /home/vscode/.venv/lib/python3.13/site-packages/ansible/plugins/callback/default.py
Skipping callback 'default', as we already have a stdout callback.
Skipping callback 'minimal', as we already have a stdout callback.
Skipping callback 'oneline', as we already have a stdout callback.

PLAYBOOK: test-docker-connection.yml *******************************************************************************************************************
Positional arguments: playbooks/test-docker-connection.yml
verbosity: 4
remote_user: root
connection: ssh
become_method: sudo
tags: ('all',)
inventory: ('/workspace/sites/real-time.com/testing/hosts.yml',)
subset: jammy
forks: 5
1 plays in playbooks/test-docker-connection.yml

PLAY [Testing] *****************************************************************************************************************************************

TASK [Package update (apt)] ****************************************************************************************************************************
task path: /workspace/sites/real-time.com/playbooks/test-docker-connection.yml:13
redirecting (type: connection) ansible.builtin.docker to community.docker.docker
Loading collection community.docker from /workspace/collections/ansible_collections/community/docker
<jammy> ESTABLISH DOCKER CONNECTION FOR USER: root
<jammy> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'jammy', '/bin/sh', '-c', "/bin/sh -c 'echo ~root && sleep 0'"]
<jammy> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'jammy', '/bin/sh', '-c', '/bin/sh -c \'( umask 77 && mkdir -p "` echo /root/.ansible/tmp `"&& mkdir "` echo /root/.ansible/tmp/ansible-tmp-1755032388.6888099-5035-90015542539782 `" && echo ansible-tmp-1755032388.6888099-5035-90015542539782="` echo /root/.ansible/tmp/ansible-tmp-1755032388.6888099-5035-90015542539782 `" ) && sleep 0\'']
Using module file /home/vscode/.venv/lib/python3.13/site-packages/ansible/modules/apt.py
<jammy> PUT /home/vscode/.ansible/tmp/ansible-local-502988q4_v__/tmpu7hkqbi6 TO /root/.ansible/tmp/ansible-tmp-1755032388.6888099-5035-90015542539782/AnsiballZ_apt.py
<jammy> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'jammy', '/bin/sh', '-c', "/bin/sh -c 'chmod u+rwx /root/.ansible/tmp/ansible-tmp-1755032388.6888099-5035-90015542539782/ /root/.ansible/tmp/ansible-tmp-1755032388.6888099-5035-90015542539782/AnsiballZ_apt.py && sleep 0'"]
<jammy> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'jammy', '/bin/sh', '-c', "/bin/sh -c '/usr/bin/python3 /root/.ansible/tmp/ansible-tmp-1755032388.6888099-5035-90015542539782/AnsiballZ_apt.py && sleep 0'"]
<jammy> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'jammy', '/bin/sh', '-c', "/bin/sh -c 'rm -f -r /root/.ansible/tmp/ansible-tmp-1755032388.6888099-5035-90015542539782/ > /dev/null 2>&1 && sleep 0'"]
fatal: [jammy]: FAILED! => {
    "changed": false,
    "module_stderr": "",
    "module_stdout": "",
    "msg": "MODULE FAILURE: No start of json char found\nSee stdout/stderr for the exact error",
    "rc": 0
}

PLAY RECAP *********************************************************************************************************************************************
jammy                      : ok=0    changed=0    unreachable=0    failed=1    skipped=0    rescued=0    ignored=0   

[basictheprogram]

Same test results with macOS 26

$  sw_vers 
ProductName:		macOS
ProductVersion:		26.0
BuildVersion:		25A5338b

I was not sure if this was an issue or a "personal problem", I started asking for help on the Ansible Forum. There is documentation of my troubleshooting journey.

[felixfontein]

Have you tried using the community.docker.docker_api connection plugin?

[basictheprogram]

Slightly updated playbook

---
- name: Testing
  hosts: all
  gather_facts: true
  become: true

  tasks:
    - name: Update
      ansible.builtin.apt:
        update_cache: true

    - name: Install
      ansible.builtin.apt:
        name:
          - curl
          - gpg
        state: present

Host inventory files

    docker_containers:
      hosts:
        jammy:
          ansible_connection: community.docker.docker_api

Success for ansible-playbook!

PLAY [Testing] *****************************************************************************************************************************************

TASK [Gathering Facts] *********************************************************************************************************************************
ok: [jammy]

TASK [Update] ******************************************************************************************************************************************
changed: [jammy]

TASK [Install] *****************************************************************************************************************************************
ok: [jammy]

PLAY RECAP *********************************************************************************************************************************************
jammy                      : ok=3    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   

Still problems with molecule. Updating molecule.yml, ansible_connection: community.docker.docker_api

---
# driver:
#   name: docker

platforms:
  - name: jammy
    hostnme: jammy
    container_name: jammy
    image: geerlingguy/docker-ubuntu2204-ansible
    command: /lib/systemd/systemd
    pre_build_image: true
    cgroupns_mode: host
    privileged: true
    ansible_connection: community.docker.docker_api
    volumes:
      - /sys/fs/cgroup:/sys/fs/cgroup:rw
    tmpfs:
      - /tmp
      - /run

converge.yml snippet

---
- name: Converge
  hosts: all
  gather_facts: true
  become: true

  pre_tasks:
    - name: Package update apt cache
      ansible.builtin.apt:
        update_cache: true
      changed_when: false

• Problem with community.docker v4.6.1 vs v4.7.0? Thought precedence was project scope before venv scope?
• Problem that molecule cannot use community.docker.docker_api?

$ molecule converge
<snip>
WARNING  Another version of 'community.docker' 4.7.0 was found installed in /workspace/collections/ansible_collections, only the first one will be used, 4.6.1 (/home/vscode/.venv/lib/python3.13/site-packages/ansible_collections).
<snip>
  config file = /workspace/roles/realtime.alloy/ansible.cfg
  configured module search path = ['/home/vscode/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /home/vscode/.venv/lib/python3.13/site-packages/ansible
  ansible collection location = /workspace/collections
  executable location = /home/vscode/.venv/bin/ansible-playbook
  python version = 3.13.6 (main, Aug  8 2025, 17:10:04)  (/home/vscode/.venv/bin/python)
  jinja version = 3.1.6
  libyaml = True
PLAY [Converge] ****************************************************************

TASK [Gathering Facts] *********************************************************
fatal: [jammy]: UNREACHABLE! => {"changed": false, "msg": "Failed to connect to the host via ssh: ssh: Could not resolve hostname jammy: Name or service not known", "unreachable": true}

Some provisioner hackery?

provisioner:
  name: ansible
  inventory:
    host_vars:
      jammy:
        ansible_connection: community.docker.docker_api
  config_options:
    defaults:
      remote_tmp: /tmp/.ansible/tmp

I think molecule only works with docker driver?

$ molecule converge
<snip>
WARNING  Another version of 'community.docker' 4.7.0 was found installed in /workspace/collections/ansible_collections, only the first one will be used, 4.6.1 (/home/vscode/.venv/lib/python3.13/site-packages/ansible_collections).
<snip>
  config file = /workspace/roles/realtime.alloy/ansible.cfg
  configured module search path = ['/home/vscode/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /home/vscode/.venv/lib/python3.13/site-packages/ansible
  ansible collection location = /workspace/collections
  executable location = /home/vscode/.venv/bin/ansible-playbook
  python version = 3.13.6 (main, Aug  8 2025, 17:10:04)  (/home/vscode/.venv/bin/python)
  jinja version = 3.1.6
  libyaml = True
<snip>
PLAY [Converge] ****************************************************************

TASK [Gathering Facts] *********************************************************
fatal: [jammy]: UNREACHABLE! => {"changed": false, "msg": "Could not find container \"jammy\" (404 Client Error for http+docker://localhost/v1.51/containers/jammy/exec: Not Found (\"No such container: jammy\"))", "unreachable": true}

PLAY RECAP *********************************************************************
jammy                      : ok=0    changed=0    unreachable=1    failed=0    skipped=0    rescued=0    ignored=0

The container is called jammy and it is running

$ docker ps | grep jammy
486ec671d402   geerlingguy/docker-ubuntu2204-ansible   "/lib/systemd/systemd"   39 seconds ago      Up 38 seconds                 jammy

[basictheprogram]

Same problem on debian13, output with display.debug() enabled

Shouldn't the _low_level_execute_command() done: rc=0, stdout=, stderr= have the command output?

30732 1755293426.50905: opening command with Popen()
<trixie> EXEC ['/usr/bin/docker', b'exec', b'-i', 'trixie', '/bin/sh', '-c', "/bin/sh -c '/usr/bin/python3.13 /tmp/.ansible/tmp/ansible-tmp-1755293425.4453852-30908-106639179953030/AnsiballZ_apt.py && sleep 0'"]
 30732 1755293426.51024: done running command with Popen()
 30732 1755293426.51037: getting output with communicate()
 30732 1755293427.05066: done communicating
 30732 1755293427.05078: done with docker.exec_command()
 30732 1755293427.05094: _low_level_execute_command() done: rc=0, stdout=, stderr=
 30732 1755293428.95340: done with _execute_module (ansible.builtin.apt, {'update_cache': True, 'force_apt_get': True, '_ansible_check_mode': False, '_ansible_no_log': False, '_ansible_debug': True, '_ansible_diff': False, '_ansible_verbosity': 4, '_ansible_version': '2.18.7', '_ansible_module_name': 'ansible.builtin.apt', '_ansible_syslog_facility': 'LOG_USER', '_ansible_selinux_special_fs': ['fuse', 'nfs', 'vboxsf', 'ramfs', '9p', 'vfat'], '_ansible_string_conversion_action': 'warn', '_ansible_socket': None, '_ansible_shell_executable': '/bin/sh', '_ansible_keep_remote_files': True, '_ansible_tmpdir': '/tmp/.ansible/tmp/ansible-tmp-1755293425.4453852-30908-106639179953030/', '_ansible_remote_tmp': '/tmp/.ansible/tmp', '_ansible_ignore_unknown_opts': False, '_ansible_target_log_info': None})
 30732 1755293428.95365: handler run complete
 30732 1755293428.95393: attempt loop complete, returning result
 30732 1755293428.95406: _execute() done
 30732 1755293428.95415: dumping result to json
 30732 1755293428.95424: done dumping result, returning
 30732 1755293428.95457: done running TaskExecutor() for trixie/TASK: Package update apt cache [96f2c85b-14db-f3c3-afe0-000000000004]
 30732 1755293428.95478: sending task result for task 96f2c85b-14db-f3c3-afe0-000000000004
 30732 1755293428.95614: done sending task result for task 96f2c85b-14db-f3c3-afe0-000000000004
 30732 1755293428.95627: WORKER PROCESS EXITING
 30732 1755293428.95714: marking trixie as failed
 30732 1755293428.95740: marking host trixie failed, current state: HOST STATE: block=1, task=1, rescue=0, always=0, handlers=0, run_state=1, fail_state=0, pre_flushing_run_state=None, update_handlers=True, pending_setup=False, tasks child state? (None), rescue child state? (None), always child state? (None), did rescue? False, did start at task? False
 30732 1755293428.95770: ^ failed state is now: HOST STATE: block=1, task=1, rescue=0, always=0, handlers=0, run_state=5, fail_state=2, pre_flushing_run_state=None, update_handlers=True, pending_setup=False, tasks child state? (None), rescue child state? (None), always child state? (None), did rescue? False, did start at task? False
 30732 1755293428.95798: getting the next task for host trixie
 30732 1755293428.95805: host trixie is done iterating, returning
fatal: [trixie]: FAILED! => {
    "changed": false,
    "module_stderr": "",
    "module_stdout": "",
    "msg": "MODULE FAILURE: No start of json char found\nSee stdout/stderr for the exact error",
    "rc": 0
}
 30732 1755293428.95964: no more pending results, returning what we have
 30732 1755293428.95977: results queue empty
 30732 1755293428.95980: checking for any_errors_fatal
 30732 1755293428.95983: done checking for any_errors_fatal
 30732 1755293428.95985: checking for max_fail_percentage
 30732 1755293428.95991: done checking for max_fail_percentage
 30732 1755293428.95994: checking to see if all hosts have failed and the running result is not ok
 30732 1755293428.95997: done checking to see if all hosts have failed
 30732 1755293428.95999: getting the remaining hosts for this loop
 30732 1755293428.96004: done getting the remaining hosts for this loop
 30732 1755293428.96008: getting the next task for host trixie
 30732 1755293428.96012: host trixie is done iterating, returning
 30732 1755293428.96015: done queuing things up, now waiting for results queue to drain
 30732 1755293428.96032: results queue empty
 30732 1755293428.96039: checking for any_errors_fatal
 30732 1755293428.96041: done checking for any_errors_fatal
 30732 1755293428.96044: checking for max_fail_percentage
 30732 1755293428.96049: done checking for max_fail_percentage
 30732 1755293428.96053: checking to see if all hosts have failed and the running result is not ok
 30732 1755293428.96057: done checking to see if all hosts have failed
 30732 1755293428.96077: getting the next task for host trixie
 30732 1755293428.96084: host trixie is done iterating, returning

PLAY RECAP *********************************************************************
trixie                     : ok=1    changed=0    unreachable=0    failed=1    skipped=0    rescued=0    ignored=0

[basictheprogram]

Adding more display.debug(), looks like stdout data is being returned from self._connection.exec_command()

       rc, stdout, stderr = self._connection.exec_command(
            cmd, in_data=in_data, sudoable=sudoable
        )
        display.debug(
            "_connection.exec_command() done: rc=%d, stdout=%s, stderr=%s"
            % (rc, stdout, stderr)
        )

Logs

<trixie> EXEC ['/usr/bin/docker', b'exec', b'-i', 'trixie', '/bin/sh', '-c', "/bin/sh -c '/usr/bin/python3.13 /tmp/.ansible/tmp/ansible-tmp-1755297500.0905535-8038-138170215532443/AnsiballZ_apt.py && sleep 0'"]
  7833 1755297500.85136: done communicating
  7833 1755297500.85148: done with docker.exec_command()
  7833 1755297500.85154: _connection.exec_command() done: rc=0, stdout=b'', stderr=b'' <-- HERE
  7833 1755297500.85157: _low_level_execute_command() done: rc=0, stdout=, stderr=

The self._connection has the ansible_name=community.docker.docker digging around in community.docker.docker lead me to docker.py:_get_docker_remote_user() and this code

out, err = p.communicate()

Making the assumption the subprocess.py:communicate() (or python-3.13.6) is not the problem but out,err are always zero bytes.

[basictheprogram]

Fedora42, same problem.
converge.yml

    - name: Update dnf cache (Fedora workaround)
      raw: |
        dnf makecache --quiet
      become: true

    - name: Package update dnf cache
      ansible.builtin.dnf:
        update_cache: yes

molecule.yml

  - name: fedora42
    hostnme: fedora42
    container_name: fedora42
    image: geerlingguy/docker-fedora42-ansible
    command: /usr/sbin/init
    pre_build_image: true
    cgroupns_mode: host
    privileged: true
    volumes:
      - /sys/fs/cgroup:/sys/fs/cgroup:rw
    tmpfs:
      - /tmp
      - /run

molecule converge -- -vvvv

TASK [Package update dnf cache] ************************************************
task path: /workspace/roles/realtime.alloy/molecule/default/converge.yml:29
Loading collection community.docker from /home/vscode/.venv/lib/python3.13/site-packages/ansible_collections/community/docker
Running ansible.legacy.dnf5 as the backend for the dnf action plugin
<fedora42> ESTABLISH DOCKER CONNECTION FOR USER: root
<fedora42> EXEC ['/usr/bin/docker', b'exec', b'-i', 'fedora42', '/bin/sh', '-c', '/bin/sh -c \'( umask 77 && mkdir -p "` echo /tmp/.ansible/tmp `"&& mkdir "` echo /tmp/.ansible/tmp/ansible-tmp-1755302865.873486-9088-69378029456348 `" && echo ansible-tmp-1755302865.873486-9088-69378029456348="` echo /tmp/.ansible/tmp/ansible-tmp-1755302865.873486-9088-69378029456348 `" ) && sleep 0\'']
Using module file /home/vscode/.venv/lib/python3.13/site-packages/ansible/modules/dnf5.py
<fedora42> PUT /home/vscode/.ansible/tmp/ansible-local-8972vmewqbrm/tmpul8u14k1 TO /tmp/.ansible/tmp/ansible-tmp-1755302865.873486-9088-69378029456348/AnsiballZ_dnf5.py
<fedora42> EXEC ['/usr/bin/docker', b'exec', b'-i', 'fedora42', '/bin/sh', '-c', "/bin/sh -c 'chmod u+rwx /tmp/.ansible/tmp/ansible-tmp-1755302865.873486-9088-69378029456348/ /tmp/.ansible/tmp/ansible-tmp-1755302865.873486-9088-69378029456348/AnsiballZ_dnf5.py && sleep 0'"]
<fedora42> EXEC ['/usr/bin/docker', b'exec', b'-i', 'fedora42', '/bin/sh', '-c', "/bin/sh -c '/usr/sbin/python3.13 /tmp/.ansible/tmp/ansible-tmp-1755302865.873486-9088-69378029456348/AnsiballZ_dnf5.py && sleep 0'"]
fatal: [fedora42]: FAILED! => {
    "changed": false,
    "module_stderr": "",
    "module_stdout": "",
    "msg": "MODULE FAILURE: No start of json char found\nSee stdout/stderr for the exact error",
    "rc": 0
}

PLAY RECAP *********************************************************************
fedora42                   : ok=2    changed=1    unreachable=0    failed=1    skipped=0    rescued=0    ignored=0

[basictheprogram]

In docker.py:exec_command()

local_cmd = [to_bytes(i, errors='surrogate_or_strict') for i in local_cmd]

value is

[b'/usr/bin/docker', b'exec', b'-i', b'trixie', b'/bin/sh', b'-c', b"/bin/sh -c '/usr/bin/python3.13 /tmp/.ansible/tmp/ansible-tmp-1755380588.2208173-36054-200456832902368/AnsiballZ_apt.py && sleep 0'"]

I underststand this code runs the AnsiballZ_apt.py on the remote system, setups on non-blocking IO, reads any data when it is available, and this next code snippet is where stdout does not get set a proper JSON value from p.communicate. Both stdout and stderr are empty. Logging on the remote system shows AnsiballZ_apt.py does call exit_json() properly (next post).

       p = subprocess.Popen(
            local_cmd,
            stdin=subprocess.PIPE,
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE,
        )
        display.debug("done running command with Popen()")

        if self.become and self.become.expect_prompt() and sudoable:
            fcntl.fcntl(p.stdout, fcntl.F_SETFL, fcntl.fcntl(p.stdout, fcntl.F_GETFL) | os.O_NONBLOCK)
            fcntl.fcntl(p.stderr, fcntl.F_SETFL, fcntl.fcntl(p.stderr, fcntl.F_GETFL) | os.O_NONBLOCK)
            selector = selectors.DefaultSelector()
            selector.register(p.stdout, selectors.EVENT_READ)
            selector.register(p.stderr, selectors.EVENT_READ)

            become_output = b''
            try:
                while not self.become.check_success(become_output) and not self.become.check_password_prompt(become_output):
                    events = selector.select(self.timeout)
                    if not events:
                        stdout, stderr = p.communicate()
                        raise AnsibleError('timeout waiting for privilege escalation password prompt:\n' + to_native(become_output))

                    for key, event in events:
                        if key.fileobj == p.stdout:
                            chunk = p.stdout.read()
                        elif key.fileobj == p.stderr:
                            chunk = p.stderr.read()

                    if not chunk:
                        stdout, stderr = p.communicate()
                        raise AnsibleError('privilege output closed while waiting for password prompt:\n' + to_native(become_output))
                    become_output += chunk
            finally:
                selector.close()

            if not self.become.check_success(become_output):
                become_pass = self.become.get_option('become_pass', playcontext=self._play_context)
                p.stdin.write(to_bytes(become_pass, errors='surrogate_or_strict') + b'\n')
            fcntl.fcntl(p.stdout, fcntl.F_SETFL, fcntl.fcntl(p.stdout, fcntl.F_GETFL) & ~os.O_NONBLOCK)
            fcntl.fcntl(p.stderr, fcntl.F_SETFL, fcntl.fcntl(p.stderr, fcntl.F_GETFL) & ~os.O_NONBLOCK)

        display.debug("getting output with communicate()")
        stdout, stderr = p.communicate(in_data)    # <-- HERE mangled? 
        display.debug("done communicating")

stdout=b''
stderr=b''

AnsiballZ_apt.py may not be sending a response or writing JSON to stdout? Details in the next comment.

[basictheprogram]

I am confident the AnsiballZ_apt.py is sending back valid JSON.

Edit basic.py added _debug to exit_json()

    def exit_json(self, **kwargs):
        ''' return from the module, without error '''

        self.do_cleanup_files()
        self._return_formatted(kwargs)
        _debug("kwargs ", kwargs)
        sys.exit(0)

The _debug is to keep from polluting stdout

def _debug(msg, data=None):
    try:
        with open("/tmp/ansible_apt_debug.log", "a") as f:
            f.write(msg)
            if data is not None:
                f.write(": " + json.dumps(data, indent=2))
            f.write("\n")
    except Exception:
        # Avoid crashing the module if logging fails
        pass

Keep the remote files and run the test

ANSIBLE_KEEP_REMOTE_FILES=1
$ molecule converge -- -vvv 
<snip>
fatal: [trixie]: FAILED! => {
    "changed": false,
    "module_stderr": "",
    "module_stdout": "",
    "msg": "MODULE FAILURE: No start of json char found\nSee stdout/stderr for the exact error",
    "rc": 0
}

On the trixie (remote system), valid JSON, _debug uses json.dumps() and that is right before the exit()

# cat /tmp/ansible_apt_debug.log 
kwargs kwargs : {
  "changed": false,
  "cache_updated": false,
  "cache_update_time": 1755382140,
  "invocation": {
    "module_args": {
      "update_cache": true,
      "force_apt_get": true,
      "state": "present",
      "update_cache_retries": 5,
      "update_cache_retry_max_delay": 12,
      "cache_valid_time": 0,
      "purge": false,
      "force": false,
      "upgrade": null,
      "dpkg_options": "force-confdef,force-confold",
      "autoremove": false,
      "autoclean": false,
      "fail_on_autoremove": false,
      "only_upgrade": false,
      "clean": false,
      "allow_unauthenticated": false,
      "allow_downgrade": false,
      "allow_change_held_packages": false,
      "lock_timeout": 60,
      "package": null,
      "deb": null,
      "default_release": null,
      "install_recommends": null,
      "policy_rc_d": null
    }
  }
}

[felixfontein]

Would you mind providing a full reproducer? So far I only see bits spread out through the various posts here. I never used molecule and don't know how to combine these bits to a working reproducer (and from how I understand it the issue only seems to happen with molecule).

[basictheprogram]

Been discussing this issue over at the Ansible Forums and getting wires crossed. The problem is not just molecule. I think the problem is docker on ARM64 macOS.

Here is full reproducer in-line. I can create a git repository with the files, if that is easier.

host inventory files, testing/inventory.yml

---
all:
  children:
    docker_containers:
      hosts:
        trixie:
          ansible_connection: community.docker.docker

playbook, playbooks/test-docker-connection.yml

---
- name: Testing
  hosts: all
  gather_facts: true
  become: true

  tasks:
    - name: Update
      ansible.builtin.apt:
        update_cache: true

    - name: Install
      ansible.builtin.apt:
        name:
          - curl
          - gpg
        state: present

Spin up debian13, trixie, docker container

docker run -d \
  --name trixie \
  --hostname trixie \
  --privileged \
  --cgroupns=host \
  --tmpfs /tmp \
  --tmpfs /run \
  -v /sys/fs/cgroup:/sys/fs/cgroup:rw \
  geerlingguy/docker-debian13-ansible \
  /lib/systemd/systemd

Execution without ANSIBLE_KEEP_REMOTE_FILES=1

ansible-playbook -i testing/inventory.yml --limit="trixie" playbooks/test-docker-connection.yml  -u root -vvvv
[DEPRECATION WARNING]: [defaults]collections_paths option. Reason: does not fit var naming standard, use the singular form collections_path instead 
Alternatives: none. This feature will be removed in version 2.19. Deprecation warnings can be disabled by setting deprecation_warnings=False in 
ansible.cfg.
ansible-playbook [core 2.18.8]
  config file = /workspace/sites/real-time.com/ansible.cfg
  configured module search path = ['/home/vscode/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /home/vscode/.venv/lib/python3.13/site-packages/ansible
  ansible collection location = /workspace/collections
  executable location = /home/vscode/.venv/bin/ansible-playbook
  python version = 3.13.6 (main, Aug 14 2025, 16:24:06) [Clang 20.1.4 ] (/home/vscode/.venv/bin/python)
  jinja version = 3.1.6
  libyaml = True
Using /workspace/sites/real-time.com/ansible.cfg as config file
setting up inventory plugins
Loading collection ansible.builtin from 
host_list declined parsing /workspace/sites/real-time.com/testing/inventory.yml as it did not pass its verify_file() method
Parsed /workspace/sites/real-time.com/testing/inventory.yml inventory source with yaml plugin
Loading callback plugin default of type stdout, v2.0 from /home/vscode/.venv/lib/python3.13/site-packages/ansible/plugins/callback/default.py
Skipping callback 'default', as we already have a stdout callback.
Skipping callback 'minimal', as we already have a stdout callback.
Skipping callback 'oneline', as we already have a stdout callback.

PLAYBOOK: test-docker-connection.yml *********************************************************************************************************************
Positional arguments: playbooks/test-docker-connection.yml
verbosity: 4
remote_user: root
connection: ssh
become_method: sudo
tags: ('all',)
inventory: ('/workspace/sites/real-time.com/testing/inventory.yml',)
subset: trixie
forks: 5
1 plays in playbooks/test-docker-connection.yml

PLAY [Testing] *******************************************************************************************************************************************

TASK [Gathering Facts] ***********************************************************************************************************************************
task path: /workspace/sites/real-time.com/playbooks/test-docker-connection.yml:2
Loading collection community.docker from /workspace/collections/ansible_collections/community/docker
<trixie> ESTABLISH DOCKER CONNECTION FOR USER: root
<trixie> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'trixie', '/bin/sh', '-c', "/bin/sh -c 'echo ~root && sleep 0'"]
<trixie> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'trixie', '/bin/sh', '-c', '/bin/sh -c \'( umask 77 && mkdir -p "` echo /root/.ansible/tmp `"&& mkdir "` echo /root/.ansible/tmp/ansible-tmp-1755438566.091109-182443-278766449845440 `" && echo ansible-tmp-1755438566.091109-182443-278766449845440="` echo /root/.ansible/tmp/ansible-tmp-1755438566.091109-182443-278766449845440 `" ) && sleep 0\'']
<trixie> Attempting python interpreter discovery
<trixie> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'trixie', '/bin/sh', '-c', '/bin/sh -c \'echo PLATFORM; uname; echo FOUND; command -v \'"\'"\'python3.13\'"\'"\'; command -v \'"\'"\'python3.12\'"\'"\'; command -v \'"\'"\'python3.11\'"\'"\'; command -v \'"\'"\'python3.10\'"\'"\'; command -v \'"\'"\'python3.9\'"\'"\'; command -v \'"\'"\'python3.8\'"\'"\'; command -v \'"\'"\'/usr/bin/python3\'"\'"\'; command -v \'"\'"\'python3\'"\'"\'; echo ENDFOUND && sleep 0\'']
<trixie> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'trixie', '/bin/sh', '-c', "/bin/sh -c '/usr/bin/python3.13 && sleep 0'"]
<trixie> Python interpreter discovery fallback (unsupported Linux distribution: debian)
Using module file /home/vscode/.venv/lib/python3.13/site-packages/ansible/modules/setup.py
<trixie> PUT /home/vscode/.ansible/tmp/ansible-local-1824374u_46mis/tmp_2202wok TO /root/.ansible/tmp/ansible-tmp-1755438566.091109-182443-278766449845440/AnsiballZ_setup.py
<trixie> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'trixie', '/bin/sh', '-c', "/bin/sh -c 'chmod u+rwx /root/.ansible/tmp/ansible-tmp-1755438566.091109-182443-278766449845440/ /root/.ansible/tmp/ansible-tmp-1755438566.091109-182443-278766449845440/AnsiballZ_setup.py && sleep 0'"]
<trixie> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'trixie', '/bin/sh', '-c', "/bin/sh -c '/usr/bin/python3.13 /root/.ansible/tmp/ansible-tmp-1755438566.091109-182443-278766449845440/AnsiballZ_setup.py && sleep 0'"]
<trixie> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'trixie', '/bin/sh', '-c', "/bin/sh -c 'rm -f -r /root/.ansible/tmp/ansible-tmp-1755438566.091109-182443-278766449845440/ > /dev/null 2>&1 && sleep 0'"]
[WARNING]: Platform linux on host trixie is using the discovered Python interpreter at /usr/bin/python3.13, but future installation of another Python
interpreter could change the meaning of that path. See https://docs.ansible.com/ansible-core/2.18/reference_appendices/interpreter_discovery.html for
more information.
ok: [trixie]

TASK [Update] ********************************************************************************************************************************************
task path: /workspace/sites/real-time.com/playbooks/test-docker-connection.yml:8
Loading collection community.docker from /workspace/collections/ansible_collections/community/docker
<trixie> ESTABLISH DOCKER CONNECTION FOR USER: root
<trixie> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'trixie', '/bin/sh', '-c', "/bin/sh -c 'echo ~root && sleep 0'"]
<trixie> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'trixie', '/bin/sh', '-c', '/bin/sh -c \'( umask 77 && mkdir -p "` echo /root/.ansible/tmp `"&& mkdir "` echo /root/.ansible/tmp/ansible-tmp-1755438567.1280227-182571-68492570804986 `" && echo ansible-tmp-1755438567.1280227-182571-68492570804986="` echo /root/.ansible/tmp/ansible-tmp-1755438567.1280227-182571-68492570804986 `" ) && sleep 0\'']
Using module file /home/vscode/.venv/lib/python3.13/site-packages/ansible/modules/apt.py
<trixie> PUT /home/vscode/.ansible/tmp/ansible-local-1824374u_46mis/tmp64wobiek TO /root/.ansible/tmp/ansible-tmp-1755438567.1280227-182571-68492570804986/AnsiballZ_apt.py
<trixie> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'trixie', '/bin/sh', '-c', "/bin/sh -c 'chmod u+rwx /root/.ansible/tmp/ansible-tmp-1755438567.1280227-182571-68492570804986/ /root/.ansible/tmp/ansible-tmp-1755438567.1280227-182571-68492570804986/AnsiballZ_apt.py && sleep 0'"]
<trixie> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'trixie', '/bin/sh', '-c', "/bin/sh -c '/usr/bin/python3.13 /root/.ansible/tmp/ansible-tmp-1755438567.1280227-182571-68492570804986/AnsiballZ_apt.py && sleep 0'"]
<trixie> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'trixie', '/bin/sh', '-c', "/bin/sh -c 'rm -f -r /root/.ansible/tmp/ansible-tmp-1755438567.1280227-182571-68492570804986/ > /dev/null 2>&1 && sleep 0'"]
fatal: [trixie]: FAILED! => {
    "changed": false,
    "module_stderr": "",
    "module_stdout": "",
    "msg": "MODULE FAILURE: No start of json char found\nSee stdout/stderr for the exact error",
    "rc": 0
}

PLAY RECAP ***********************************************************************************************************************************************
trixie                     : ok=1    changed=0    unreachable=0    failed=1    skipped=0    rescued=0    ignored=0   

Execution with ANSIBLE_KEEP_REMOTE_FILES=1

ANSIBLE_KEEP_REMOTE_FILES=1  ansible-playbook -i testing/inventory.yml 
--limit="trixie" playbooks/test-docker-connection.yml  -u root -vvvv
[DEPRECATION WARNING]: [defaults]collections_paths option. Reason: does not fit var naming standard, use the singular form collections_path instead 
Alternatives: none. This feature will be removed in version 2.19. Deprecation warnings can be disabled by setting deprecation_warnings=False in 
ansible.cfg.
ansible-playbook [core 2.18.8]
  config file = /workspace/sites/real-time.com/ansible.cfg
  configured module search path = ['/home/vscode/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /home/vscode/.venv/lib/python3.13/site-packages/ansible
  ansible collection location = /workspace/collections
  executable location = /home/vscode/.venv/bin/ansible-playbook
  python version = 3.13.6 (main, Aug 14 2025, 16:24:06) [Clang 20.1.4 ] (/home/vscode/.venv/bin/python)
  jinja version = 3.1.6
  libyaml = True
Using /workspace/sites/real-time.com/ansible.cfg as config file
setting up inventory plugins
Loading collection ansible.builtin from 
host_list declined parsing /workspace/sites/real-time.com/testing/inventory.yml as it did not pass its verify_file() method
Parsed /workspace/sites/real-time.com/testing/inventory.yml inventory source with yaml plugin
Loading callback plugin default of type stdout, v2.0 from /home/vscode/.venv/lib/python3.13/site-packages/ansible/plugins/callback/default.py
Skipping callback 'default', as we already have a stdout callback.
Skipping callback 'minimal', as we already have a stdout callback.
Skipping callback 'oneline', as we already have a stdout callback.

PLAYBOOK: test-docker-connection.yml *********************************************************************************************************************
Positional arguments: playbooks/test-docker-connection.yml
verbosity: 4
remote_user: root
connection: ssh
become_method: sudo
tags: ('all',)
inventory: ('/workspace/sites/real-time.com/testing/inventory.yml',)
subset: trixie
forks: 5
1 plays in playbooks/test-docker-connection.yml

PLAY [Testing] *******************************************************************************************************************************************

TASK [Gathering Facts] ***********************************************************************************************************************************
task path: /workspace/sites/real-time.com/playbooks/test-docker-connection.yml:2
Loading collection community.docker from /workspace/collections/ansible_collections/community/docker
<trixie> ESTABLISH DOCKER CONNECTION FOR USER: root
<trixie> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'trixie', '/bin/sh', '-c', "/bin/sh -c 'echo ~root && sleep 0'"]
<trixie> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'trixie', '/bin/sh', '-c', '/bin/sh -c \'( umask 77 && mkdir -p "` echo /root/.ansible/tmp `"&& mkdir "` echo /root/.ansible/tmp/ansible-tmp-1755439374.780623-185378-204077928211643 `" && echo ansible-tmp-1755439374.780623-185378-204077928211643="` echo /root/.ansible/tmp/ansible-tmp-1755439374.780623-185378-204077928211643 `" ) && sleep 0\'']
<trixie> Attempting python interpreter discovery
<trixie> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'trixie', '/bin/sh', '-c', '/bin/sh -c \'echo PLATFORM; uname; echo FOUND; command -v \'"\'"\'python3.13\'"\'"\'; command -v \'"\'"\'python3.12\'"\'"\'; command -v \'"\'"\'python3.11\'"\'"\'; command -v \'"\'"\'python3.10\'"\'"\'; command -v \'"\'"\'python3.9\'"\'"\'; command -v \'"\'"\'python3.8\'"\'"\'; command -v \'"\'"\'/usr/bin/python3\'"\'"\'; command -v \'"\'"\'python3\'"\'"\'; echo ENDFOUND && sleep 0\'']
<trixie> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'trixie', '/bin/sh', '-c', "/bin/sh -c '/usr/bin/python3.13 && sleep 0'"]
<trixie> Python interpreter discovery fallback (unsupported Linux distribution: debian)
Using module file /home/vscode/.venv/lib/python3.13/site-packages/ansible/modules/setup.py
<trixie> PUT /home/vscode/.ansible/tmp/ansible-local-185369q2u278ub/tmpab68d5ow TO /root/.ansible/tmp/ansible-tmp-1755439374.780623-185378-204077928211643/AnsiballZ_setup.py
<trixie> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'trixie', '/bin/sh', '-c', "/bin/sh -c 'chmod u+rwx /root/.ansible/tmp/ansible-tmp-1755439374.780623-185378-204077928211643/ /root/.ansible/tmp/ansible-tmp-1755439374.780623-185378-204077928211643/AnsiballZ_setup.py && sleep 0'"]
<trixie> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'trixie', '/bin/sh', '-c', "/bin/sh -c '/usr/bin/python3.13 /root/.ansible/tmp/ansible-tmp-1755439374.780623-185378-204077928211643/AnsiballZ_setup.py && sleep 0'"]
[WARNING]: Platform linux on host trixie is using the discovered Python interpreter at /usr/bin/python3.13, but future installation of another Python
interpreter could change the meaning of that path. See https://docs.ansible.com/ansible-core/2.18/reference_appendices/interpreter_discovery.html for
more information.
ok: [trixie]

TASK [Update] ********************************************************************************************************************************************
task path: /workspace/sites/real-time.com/playbooks/test-docker-connection.yml:8
Loading collection community.docker from /workspace/collections/ansible_collections/community/docker
<trixie> ESTABLISH DOCKER CONNECTION FOR USER: root
<trixie> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'trixie', '/bin/sh', '-c', "/bin/sh -c 'echo ~root && sleep 0'"]
<trixie> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'trixie', '/bin/sh', '-c', '/bin/sh -c \'( umask 77 && mkdir -p "` echo /root/.ansible/tmp `"&& mkdir "` echo /root/.ansible/tmp/ansible-tmp-1755439375.7545745-185494-141774834492454 `" && echo ansible-tmp-1755439375.7545745-185494-141774834492454="` echo /root/.ansible/tmp/ansible-tmp-1755439375.7545745-185494-141774834492454 `" ) && sleep 0\'']
Using module file /home/vscode/.venv/lib/python3.13/site-packages/ansible/modules/apt.py
<trixie> PUT /home/vscode/.ansible/tmp/ansible-local-185369q2u278ub/tmpfsh3v5qs TO /root/.ansible/tmp/ansible-tmp-1755439375.7545745-185494-141774834492454/AnsiballZ_apt.py
<trixie> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'trixie', '/bin/sh', '-c', "/bin/sh -c 'chmod u+rwx /root/.ansible/tmp/ansible-tmp-1755439375.7545745-185494-141774834492454/ /root/.ansible/tmp/ansible-tmp-1755439375.7545745-185494-141774834492454/AnsiballZ_apt.py && sleep 0'"]
<trixie> EXEC ['/usr/bin/docker', b'exec', b'-u', 'root', b'-i', 'trixie', '/bin/sh', '-c', "/bin/sh -c '/usr/bin/python3.13 /root/.ansible/tmp/ansible-tmp-1755439375.7545745-185494-141774834492454/AnsiballZ_apt.py && sleep 0'"]
fatal: [trixie]: FAILED! => {
    "changed": false,
    "module_stderr": "",
    "module_stdout": "",
    "msg": "MODULE FAILURE: No start of json char found\nSee stdout/stderr for the exact error",
    "rc": 0
}

PLAY RECAP ***********************************************************************************************************************************************
trixie                     : ok=1    changed=0    unreachable=0    failed=1    skipped=0    rescued=0    ignored=0   

[felixfontein]

Ok, I wasn't able to reproduce it, but then I don't use macOS or an ARM machine. Docker on macOS being the culprit is quite possible, especially when another CPU architecture comes into play. I've labelled this third-party-bug unless there's evidence that the collection can do something about it.

[hax0rbana-adam]

I'm getting this same "No start of json char found" issue from an ARMv6 system. Specifically a BCM2835 CPU (Raspberry Pi Zero W). It's running Debian 10 (buster). I'm curious to see if anyone can reproduce this.

Running the same playbook on Debian 11 (bullseye) does not have this error. What's strange is that this is a CI job that used to work just fine. The only things that could have changed would be the versions of software/libraries (on both the target and the orchestrator)

Update to add: There's no docker involved in my setup

[felixfontein]

@hax0rbana-adam if there's no Docker involved, how is this related to the community.docker collection?

[hax0rbana-adam]

Oops. 🤦 I took a wrong on the internet while looking for a solution to my "No start of json char found" issue. But hey, on a lighter note at least now you know there's evidence that this might be an issue with Ansible Core/Python on ARM and not something Docker-specific.