Server Hooks

on_starting

    1. def on_starting(server):
    2.     pass

Called just before the master process is initialized.

The callable needs to accept a single instance variable for the Arbiter.

on_reload

    1. def on_reload(server):
    2.     pass

Called to recycle workers during a reload via SIGHUP.

The callable needs to accept a single instance variable for the Arbiter.

when_ready

    1. def when_ready(server):
    2.     pass

Called just after the server is started.

The callable needs to accept a single instance variable for the Arbiter.

pre_fork

    1. def pre_fork(server, worker):
    2.     pass

Called just before a worker is forked.

The callable needs to accept two instance variables for the Arbiter and new Worker.

post_fork

    1. def post_fork(server, worker):
    2.     pass

Called just after a worker has been forked.

The callable needs to accept two instance variables for the Arbiter and new Worker.

post_worker_init

    1. def post_worker_init(worker):
    2.     pass

Called just after a worker has initialized the application.

The callable needs to accept one instance variable for the initialized Worker.

worker_int

    1. def worker_int(worker):
    2.     pass

Called just after a worker exited on SIGINT or SIGQUIT.

The callable needs to accept one instance variable for the initialized Worker.

worker_abort

    1. def worker_abort(worker):
    2.     pass

Called when a worker received the SIGABRT signal.

This call generally happens on timeout.

The callable needs to accept one instance variable for the initialized Worker.

pre_exec

    1. def pre_exec(server):
    2.     pass

Called just before a new master process is forked.

The callable needs to accept a single instance variable for the Arbiter.

pre_request

    1. def pre_request(worker, req):
    2.     worker.log.debug("%s %s" % (req.method, req.path))

Called just before a worker processes the request.

The callable needs to accept two instance variables for the Worker and the Request.

post_request

    1. def post_request(worker, req, environ, resp):
    2.     pass

Called after a worker processes the request.

The callable needs to accept two instance variables for the Worker and the Request.

child_exit

    1. def child_exit(server, worker):
    2.     pass

Called just after a worker has been exited, in the master process.

The callable needs to accept two instance variables for the Arbiter and the just-exited Worker.

New in version 19.7.

worker_exit

    1. def worker_exit(server, worker):
    2.     pass

Called just after a worker has been exited, in the worker process.

The callable needs to accept two instance variables for the Arbiter and the just-exited Worker.

nworkers_changed

    1. def nworkers_changed(server, new_value, old_value):
    2.     pass

Called just after num_workers has been changed.

The callable needs to accept an instance variable of the Arbiter and two integers of number of workers after and before change.

If the number of workers is set for the first time, old_value would be None.

on_exit

    1. def on_exit(server):
    2.     pass

Called just before exiting Gunicorn.

The callable needs to accept a single instance variable for the Arbiter.

Server Mechanics

preload_app

  • --preload
  • False

Load application code before the worker processes are forked.

By preloading an application you can save some RAM resources as well as speed up server boot times. Although, if you defer application loading to each worker process, you can reload your application code easily by restarting workers.

sendfile

  • --no-sendfile
  • None

Disables the use of sendfile().

If not set, the value of the SENDFILE environment variable is used to enable or disable its usage.

New in version 19.2.

Changed in version 19.4: Swapped --sendfile with --no-sendfile to actually allow disabling.

Changed in version 19.6: added support for the SENDFILE environment variable

reuse_port

  • --reuse-port
  • False

Set the SO_REUSEPORT flag on the listening socket.

New in version 19.8.

chdir

  • --chdir
  • /home/docs/checkouts/readthedocs.org/user_builds/gunicorn-docs/checkouts/19.10.0/docs/source

Chdir to specified directory before apps loading.

daemon

  • -D, --daemon
  • False

Daemonize the Gunicorn process.

Detaches the server from the controlling terminal and enters the background.

raw_env

  • -e ENV, --env ENV
  • []

Set environment variable (key=value).

Pass variables to the execution environment. Ex.:

  1. $ gunicorn -b 127.0.0.1:8000 --env FOO=1 test:app

and test for the foo variable environment in your application.

pidfile

  • -p FILE, --pid FILE
  • None

A filename to use for the PID file.

If not set, no PID file will be written.

worker_tmp_dir

  • --worker-tmp-dir DIR
  • None

A directory to use for the worker heartbeat temporary file.

If not set, the default temporary directory will be used.

Note

The current heartbeat system involves calling os.fchmod on temporary file handlers and may block a worker for arbitrary time if the directory is on a disk-backed filesystem.

See How do I avoid Gunicorn excessively blocking in os.fchmod? for more detailed information and a solution for avoiding this problem.

user

  • -u USER, --user USER
  • 1005

Switch worker processes to run as this user.

A valid user id (as an integer) or the name of a user that can be retrieved with a call to pwd.getpwnam(value) or None to not change the worker process user.

group

  • -g GROUP, --group GROUP
  • 205

Switch worker process to run as this group.

A valid group id (as an integer) or the name of a user that can be retrieved with a call to pwd.getgrnam(value) or None to not change the worker processes group.

umask

  • -m INT, --umask INT
  • 0

A bit mask for the file mode on files written by Gunicorn.

Note that this affects unix socket permissions.

A valid value for the os.umask(mode) call or a string compatible with int(value, 0) (0 means Python guesses the base, so values like 0, 0xFF, 0022 are valid for decimal, hex, and octal representations)

initgroups

  • --initgroups
  • False

If true, set the worker process’s group access list with all of the groups of which the specified username is a member, plus the specified group id.

New in version 19.7.

tmp_upload_dir

  • None

Directory to store temporary request data as they are read.

This may disappear in the near future.

This path should be writable by the process permissions set for Gunicorn workers. If not specified, Gunicorn will choose a system generated temporary directory.

secure_scheme_headers

  • {'X-FORWARDED-PROTOCOL': 'ssl', 'X-FORWARDED-PROTO': 'https', 'X-FORWARDED-SSL': 'on'}

A dictionary containing headers and values that the front-end proxy uses to indicate HTTPS requests. These tell Gunicorn to set wsgi.url_scheme to https, so your application can tell that the request is secure.

The dictionary should map upper-case header names to exact string values. The value comparisons are case-sensitive, unlike the header names, so make sure they’re exactly what your front-end proxy sends when handling HTTPS requests.

It is important that your front-end proxy configuration ensures that the headers defined here can not be passed directly from the client.

forwarded_allow_ips

  • --forwarded-allow-ips STRING
  • 127.0.0.1

Front-end’s IPs from which allowed to handle set secure headers. (comma separate).

Set to * to disable checking of Front-end IPs (useful for setups where you don’t know in advance the IP address of Front-end, but you still trust the environment).

By default, the value of the FORWARDED_ALLOW_IPS environment variable. If it is not defined, the default is "127.0.0.1".

pythonpath

  • --pythonpath STRING
  • None

A comma-separated list of directories to add to the Python path.

e.g. '/home/djangoprojects/myproject,/home/python/mylibrary'.

paste

  • --paste STRING, --paster STRING
  • None

Load a PasteDeploy config file. The argument may contain a # symbol followed by the name of an app section from the config file, e.g. production.ini#admin.

At this time, using alternate server blocks is not supported. Use the command line arguments to control server configuration instead.

proxy_protocol

  • --proxy-protocol
  • False

Enable detect PROXY protocol (PROXY mode).

Allow using HTTP and Proxy together. It may be useful for work with stunnel as HTTPS frontend and Gunicorn as HTTP server.

PROXY protocol: http://haproxy.1wt.eu/download/1.5/doc/proxy-protocol.txt

Example for stunnel config:

  1. [https]
  2. protocol = proxy
  3. accept  = 443
  4. connect = 80
  5. cert = /etc/ssl/certs/stunnel.pem
  6. key = /etc/ssl/certs/stunnel.key

proxy_allow_ips

  • --proxy-allow-from
  • 127.0.0.1

Front-end’s IPs from which allowed accept proxy requests (comma separate).

Set to * to disable checking of Front-end IPs (useful for setups where you don’t know in advance the IP address of Front-end, but you still trust the environment)

raw_paste_global_conf

  • --paste-global CONF
  • []

Set a PasteDeploy global config variable in key=value form.

The option can be specified multiple times.

The variables are passed to the the PasteDeploy entrypoint. Example:

  1. $ gunicorn -b 127.0.0.1:8000 --paste development.ini --paste-global FOO=1 --paste-global BAR=2

New in version 19.7.

strip_header_spaces

  • --strip-header-spaces
  • False

Strip spaces present between the header name and the the :.

This is known to induce vulnerabilities and is not compliant with the HTTP/1.1 standard. See https://portswigger.net/research/http-desync-attacks-request-smuggling-reborn.

Use with care and only if necessary.

Server Socket

bind

  • -b ADDRESS, --bind ADDRESS
  • ['127.0.0.1:8000']

The socket to bind.

A string of the form: HOST, HOST:PORT, unix:PATH. An IP is a valid HOST.

Multiple addresses can be bound. ex.:

  1. $ gunicorn -b 127.0.0.1:8000 -b [::1]:8000 test:app

will bind the test:app application on localhost both on ipv6 and ipv4 interfaces.

backlog

  • --backlog INT
  • 2048

The maximum number of pending connections.

This refers to the number of clients that can be waiting to be served. Exceeding this number results in the client getting an error when attempting to connect. It should only affect servers under significant load.

Must be a positive integer. Generally set in the 64-2048 range.

Worker Processes

workers

  • -w INT, --workers INT
  • 1

The number of worker processes for handling requests.

A positive integer generally in the 2-4 x $(NUM_CORES) range. You’ll want to vary this a bit to find the best for your particular application’s work load.

By default, the value of the WEB_CONCURRENCY environment variable. If it is not defined, the default is 1.

worker_class

  • -k STRING, --worker-class STRING
  • sync

The type of workers to use.

The default class (sync) should handle most “normal” types of workloads. You’ll want to read Design for information on when you might want to choose one of the other worker classes. Required libraries may be installed using setuptools’ extra_require feature.

A string referring to one of the following bundled classes:

  • sync
  • eventlet - Requires eventlet >= 0.24.1 (or install it via pip install gunicorn[eventlet])
  • gevent - Requires gevent >= 0.13 (or install it via pip install gunicorn[gevent])
  • tornado - Requires tornado >= 0.2 (or install it via pip install gunicorn[tornado])
  • gthread - Python 2 requires the futures package to be installed (or install it via pip install gunicorn[gthread])
  • gaiohttp - Deprecated.

Optionally, you can provide your own worker by giving Gunicorn a Python path to a subclass of gunicorn.workers.base.Worker. This alternative syntax will load the gevent class: gunicorn.workers.ggevent.GeventWorker.

Deprecated since version 19.8: The gaiohttp worker is deprecated. Please use aiohttp.worker.GunicornWebWorker instead. See AsyncIO Workers for more information on how to use it.

threads

  • --threads INT
  • 1

The number of worker threads for handling requests.

Run each worker with the specified number of threads.

A positive integer generally in the 2-4 x $(NUM_CORES) range. You’ll want to vary this a bit to find the best for your particular application’s work load.

If it is not defined, the default is 1.

This setting only affects the Gthread worker type.

Note

If you try to use the sync worker type and set the threads setting to more than 1, the gthread worker type will be used instead.

worker_connections

  • --worker-connections INT
  • 1000

The maximum number of simultaneous clients.

This setting only affects the Eventlet and Gevent worker types.

max_requests

  • --max-requests INT
  • 0

The maximum number of requests a worker will process before restarting.

Any value greater than zero will limit the number of requests a worker will process before automatically restarting. This is a simple method to help limit the damage of memory leaks.

If this is set to zero (the default) then the automatic worker restarts are disabled.

max_requests_jitter

  • --max-requests-jitter INT
  • 0

The maximum jitter to add to the max_requests setting.

The jitter causes the restart per worker to be randomized by randint(0, max_requests_jitter). This is intended to stagger worker restarts to avoid all workers restarting at the same time.

New in version 19.2.

timeout

  • -t INT, --timeout INT
  • 30

Workers silent for more than this many seconds are killed and restarted.

Generally set to thirty seconds. Only set this noticeably higher if you’re sure of the repercussions for sync workers. For the non sync workers it just means that the worker process is still communicating and is not tied to the length of time required to handle a single request.

graceful_timeout

  • --graceful-timeout INT
  • 30

Timeout for graceful workers restart.

After receiving a restart signal, workers have this much time to finish serving requests. Workers still alive after the timeout (starting from the receipt of the restart signal) are force killed.

keepalive

  • --keep-alive INT
  • 2

The number of seconds to wait for requests on a Keep-Alive connection.

Generally set in the 1-5 seconds range for servers with direct connection to the client (e.g. when you don’t have separate load balancer). When Gunicorn is deployed behind a load balancer, it often makes sense to set this to a higher value.

Note

sync worker does not support persistent connections and will ignore this option.