This document describes the current stable version of Celery (4.2). For development docs, go here.

Daemonization

Generic init-scripts

See the extra/generic-init.d/ directory Celery distribution.

This directory contains generic bash init-scripts for the celery worker program, these should run on Linux, FreeBSD, OpenBSD, and other Unix-like platforms.

Init-script: celeryd

Usage:/etc/init.d/celeryd {start|stop|restart|status}
Configuration file:
 /etc/default/celeryd

To configure this script to run the worker properly you probably need to at least tell it where to change directory to when it starts (to find the module containing your app, or your configuration module).

The daemonization script is configured by the file /etc/default/celeryd. This is a shell (sh) script where you can add environment variables like the configuration options below. To add real environment variables affecting the worker you must also export them (e.g., export DISPLAY=":0")

Superuser privileges required

The init-scripts can only be used by root, and the shell configuration file must also be owned by root.

Unprivileged users don’t need to use the init-script, instead they can use the celery multi utility (or celery worker --detach):

$ celery multi start worker1 \
    -A proj \
    --pidfile="$HOME/run/celery/%n.pid" \
    --logfile="$HOME/log/celery/%n%I.log"

$ celery multi restart worker1 \
    -A proj \
    --logfile="$HOME/log/celery/%n%I.log" \
    --pidfile="$HOME/run/celery/%n.pid

$ celery multi stopwait worker1 --pidfile="$HOME/run/celery/%n.pid"

Example configuration

This is an example configuration for a Python project.

/etc/default/celeryd:

# Names of nodes to start
#   most people will only start one node:
CELERYD_NODES="worker1"
#   but you can also start multiple and configure settings
#   for each in CELERYD_OPTS
#CELERYD_NODES="worker1 worker2 worker3"
#   alternatively, you can specify the number of nodes to start:
#CELERYD_NODES=10

# Absolute or relative path to the 'celery' command:
CELERY_BIN="/usr/local/bin/celery"
#CELERY_BIN="/virtualenvs/def/bin/celery"

# App instance to use
# comment out this line if you don't use an app
CELERY_APP="proj"
# or fully qualified:
#CELERY_APP="proj.tasks:app"

# Where to chdir at start.
CELERYD_CHDIR="/opt/Myproject/"

# Extra command-line arguments to the worker
CELERYD_OPTS="--time-limit=300 --concurrency=8"
# Configure node-specific settings by appending node name to arguments:
#CELERYD_OPTS="--time-limit=300 -c 8 -c:worker2 4 -c:worker3 2 -Ofair:worker1"

# Set logging level to DEBUG
#CELERYD_LOG_LEVEL="DEBUG"

# %n will be replaced with the first part of the nodename.
CELERYD_LOG_FILE="/var/log/celery/%n%I.log"
CELERYD_PID_FILE="/var/run/celery/%n.pid"

# Workers should run as an unprivileged user.
#   You need to create this user manually (or you can choose
#   a user/group combination that already exists (e.g., nobody).
CELERYD_USER="celery"
CELERYD_GROUP="celery"

# If enabled pid and log directories will be created if missing,
# and owned by the userid/group configured.
CELERY_CREATE_DIRS=1

Using a login shell

You can inherit the environment of the CELERYD_USER by using a login shell:

CELERYD_SU_ARGS="-l"

Note that this isn’t recommended, and that you should only use this option when absolutely necessary.

Example Django configuration

Django users now uses the exact same template as above, but make sure that the module that defines your Celery app instance also sets a default value for DJANGO_SETTINGS_MODULE as shown in the example Django project in First steps with Django.

Available options

  • CELERY_APP

    App instance to use (value for --app argument).

  • CELERY_BIN

    Absolute or relative path to the celery program. Examples:

    • celery
    • /usr/local/bin/celery
    • /virtualenvs/proj/bin/celery
    • /virtualenvs/proj/bin/python -m celery
  • CELERYD_NODES

    List of node names to start (separated by space).

  • CELERYD_OPTS

    Additional command-line arguments for the worker, see celery worker –help for a list. This also supports the extended syntax used by multi to configure settings for individual nodes. See celery multi –help for some multi-node configuration examples.

  • CELERYD_CHDIR

    Path to change directory to at start. Default is to stay in the current directory.

  • CELERYD_PID_FILE

    Full path to the PID file. Default is /var/run/celery/%n.pid

  • CELERYD_LOG_FILE

    Full path to the worker log file. Default is /var/log/celery/%n%I.log Note: Using %I is important when using the prefork pool as having multiple processes share the same log file will lead to race conditions.

  • CELERYD_LOG_LEVEL

    Worker log level. Default is INFO.

  • CELERYD_USER

    User to run the worker as. Default is current user.

  • CELERYD_GROUP

    Group to run worker as. Default is current user.

  • CELERY_CREATE_DIRS

    Always create directories (log directory and pid file directory). Default is to only create directories when no custom logfile/pidfile set.

  • CELERY_CREATE_RUNDIR

    Always create pidfile directory. By default only enabled when no custom pidfile location set.

  • CELERY_CREATE_LOGDIR

    Always create logfile directory. By default only enable when no custom logfile location set.

Init-script: celerybeat

Usage:/etc/init.d/celerybeat {start|stop|restart}
Configuration file:
 /etc/default/celerybeat or /etc/default/celeryd.

Example configuration

This is an example configuration for a Python project:

/etc/default/celerybeat:

# Absolute or relative path to the 'celery' command:
CELERY_BIN="/usr/local/bin/celery"
#CELERY_BIN="/virtualenvs/def/bin/celery"

# App instance to use
# comment out this line if you don't use an app
CELERY_APP="proj"
# or fully qualified:
#CELERY_APP="proj.tasks:app"

# Where to chdir at start.
CELERYBEAT_CHDIR="/opt/Myproject/"

# Extra arguments to celerybeat
CELERYBEAT_OPTS="--schedule=/var/run/celery/celerybeat-schedule"

Example Django configuration

You should use the same template as above, but make sure the DJANGO_SETTINGS_MODULE variable is set (and exported), and that CELERYD_CHDIR is set to the projects directory:

export DJANGO_SETTINGS_MODULE="settings"

CELERYD_CHDIR="/opt/MyProject"

Available options

  • CELERY_APP

    App instance to use (value for --app argument).

  • CELERYBEAT_OPTS

    Additional arguments to celery beat, see celery beat --help for a list of available options.

  • CELERYBEAT_PID_FILE

    Full path to the PID file. Default is /var/run/celeryd.pid.

  • CELERYBEAT_LOG_FILE

    Full path to the log file. Default is /var/log/celeryd.log.

  • CELERYBEAT_LOG_LEVEL

    Log level to use. Default is INFO.

  • CELERYBEAT_USER

    User to run beat as. Default is the current user.

  • CELERYBEAT_GROUP

    Group to run beat as. Default is the current user.

  • CELERY_CREATE_DIRS

    Always create directories (log directory and pid file directory). Default is to only create directories when no custom logfile/pidfile set.

  • CELERY_CREATE_RUNDIR

    Always create pidfile directory. By default only enabled when no custom pidfile location set.

  • CELERY_CREATE_LOGDIR

    Always create logfile directory. By default only enable when no custom logfile location set.

Troubleshooting

If you can’t get the init-scripts to work, you should try running them in verbose mode:

# sh -x /etc/init.d/celeryd start

This can reveal hints as to why the service won’t start.

If the worker starts with “OK” but exits almost immediately afterwards and there’s no evidence in the log file, then there’s probably an error but as the daemons standard outputs are already closed you’ll not be able to see them anywhere. For this situation you can use the C_FAKEFORK environment variable to skip the daemonization step:

# C_FAKEFORK=1 sh -x /etc/init.d/celeryd start

and now you should be able to see the errors.

Commonly such errors are caused by insufficient permissions to read from, or write to a file, and also by syntax errors in configuration modules, user modules, third-party libraries, or even from Celery itself (if you’ve found a bug you should report it).

Usage systemd

Usage:systemctl {start|stop|restart|status} celery.service
Configuration file:
 /etc/conf.d/celery

Service file: celery.service

This is an example systemd file:

/etc/systemd/system/celery.service:

[Unit]
Description=Celery Service
After=network.target

[Service]
Type=forking
User=celery
Group=celery
EnvironmentFile=/etc/conf.d/celery
WorkingDirectory=/opt/celery
ExecStart=/bin/sh -c '${CELERY_BIN} multi start ${CELERYD_NODES} \
  -A ${CELERY_APP} --pidfile=${CELERYD_PID_FILE} \
  --logfile=${CELERYD_LOG_FILE} --loglevel=${CELERYD_LOG_LEVEL} ${CELERYD_OPTS}'
ExecStop=/bin/sh -c '${CELERY_BIN} multi stopwait ${CELERYD_NODES} \
  --pidfile=${CELERYD_PID_FILE}'
ExecReload=/bin/sh -c '${CELERY_BIN} multi restart ${CELERYD_NODES} \
  -A ${CELERY_APP} --pidfile=${CELERYD_PID_FILE} \
  --logfile=${CELERYD_LOG_FILE} --loglevel=${CELERYD_LOG_LEVEL} ${CELERYD_OPTS}'

[Install]
WantedBy=multi-user.target

Once you’ve put that file in /etc/systemd/system, you should run systemctl daemon-reload in order that Systemd acknowledges that file. You should also run that command each time you modify it.

To configure user, group, chdir change settings: User, Group, and WorkingDirectory defined in /etc/systemd/system/celery.service.

You can also use systemd-tmpfiles in order to create working directories (for logs and pid).

file:/etc/tmpfiles.d/celery.conf
d /var/run/celery 0755 celery celery -
d /var/log/celery 0755 celery celery -

Example configuration

This is an example configuration for a Python project:

/etc/conf.d/celery:

# Name of nodes to start
# here we have a single node
CELERYD_NODES="w1"
# or we could have three nodes:
#CELERYD_NODES="w1 w2 w3"

# Absolute or relative path to the 'celery' command:
CELERY_BIN="/usr/local/bin/celery"
#CELERY_BIN="/virtualenvs/def/bin/celery"

# App instance to use
# comment out this line if you don't use an app
CELERY_APP="proj"
# or fully qualified:
#CELERY_APP="proj.tasks:app"

# How to call manage.py
CELERYD_MULTI="multi"

# Extra command-line arguments to the worker
CELERYD_OPTS="--time-limit=300 --concurrency=8"

# - %n will be replaced with the first part of the nodename.
# - %I will be replaced with the current child process index
#   and is important when using the prefork pool to avoid race conditions.
CELERYD_PID_FILE="/var/run/celery/%n.pid"
CELERYD_LOG_FILE="/var/log/celery/%n%I.log"
CELERYD_LOG_LEVEL="INFO"

# you may wish to add these options for Celery Beat
CELERYBEAT_PID_FILE="/var/run/celery/beat.pid"
CELERYBEAT_LOG_FILE="/var/log/celery/beat.log"

Service file: celerybeat.service

This is an example systemd file for Celery Beat:

/etc/systemd/system/celerybeat.service:

[Unit]
Description=Celery Beat Service
After=network.target

[Service]
Type=simple
User=celery
Group=celery
EnvironmentFile=/etc/conf.d/celery
WorkingDirectory=/opt/celery
ExecStart=/bin/sh -c '${CELERY_BIN} beat  \
  -A ${CELERY_APP} --pidfile=${CELERYBEAT_PID_FILE} \
  --logfile=${CELERYBEAT_LOG_FILE} --loglevel=${CELERYD_LOG_LEVEL}'

[Install]
WantedBy=multi-user.target

Running the worker with superuser privileges (root)

Running the worker with superuser privileges is a very dangerous practice. There should always be a workaround to avoid running as root. Celery may run arbitrary code in messages serialized with pickle - this is dangerous, especially when run as root.

By default Celery won’t run workers as root. The associated error message may not be visible in the logs but may be seen if C_FAKEFORK is used.

To force Celery to run workers as root use C_FORCE_ROOT.

When running as root without C_FORCE_ROOT the worker will appear to start with “OK” but exit immediately after with no apparent errors. This problem may appear when running the project in a new development or production environment (inadvertently) as root.