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211 lines
7.1 KiB
ReStructuredText
211 lines
7.1 KiB
ReStructuredText
.. _faq:
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===
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FAQ
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===
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WSGI Bits
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=========
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How do I set SCRIPT_NAME?
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-------------------------
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By default ``SCRIPT_NAME`` is an empty string. The value could be set by
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setting ``SCRIPT_NAME`` in the environment or as an HTTP header.
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Server Stuff
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============
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How do I reload my application in Gunicorn?
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-------------------------------------------
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You can gracefully reload by sending HUP signal to gunicorn::
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$ kill -HUP masterpid
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How might I test a proxy configuration?
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---------------------------------------
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The Hey_ program is a great way to test that your proxy is correctly
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buffering responses for the synchronous workers::
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$ hey -n 10000 -c 100 http://127.0.0.1:5000/
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This runs a benchmark of 10000 requests with 100 running concurrently.
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How can I name processes?
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-------------------------
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If you install the Python package setproctitle_ Gunicorn will set the process
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names to something a bit more meaningful. This will affect the output you see
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in tools like ``ps`` and ``top``. This helps for distinguishing the master
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process as well as between masters when running more than one app on a single
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machine. See the proc_name_ setting for more information.
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Why is there no HTTP Keep-Alive?
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--------------------------------
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The default Sync workers are designed to run behind Nginx which only uses
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HTTP/1.0 with its upstream servers. If you want to deploy Gunicorn to
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handle unbuffered requests (ie, serving requests directly from the internet)
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you should use one of the async workers.
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.. _Hey: https://github.com/rakyll/hey
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.. _setproctitle: https://pypi.python.org/pypi/setproctitle
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.. _proc_name: settings.html#proc-name
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Worker Processes
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================
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How do I know which type of worker to use?
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------------------------------------------
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Read the :ref:`design` page for help on the various worker types.
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What types of workers are there?
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--------------------------------
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Check out the configuration docs for worker_class_.
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How can I figure out the best number of worker processes?
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---------------------------------------------------------
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Here is our recommendation for tuning the `number of workers`_.
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How can I change the number of workers dynamically?
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---------------------------------------------------
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TTIN and TTOU signals can be sent to the master to increase or decrease
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the number of workers.
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To increase the worker count by one::
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$ kill -TTIN $masterpid
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To decrease the worker count by one::
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$ kill -TTOU $masterpid
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Does Gunicorn suffer from the thundering herd problem?
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------------------------------------------------------
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The thundering herd problem occurs when many sleeping request handlers, which
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may be either threads or processes, wake up at the same time to handle a new
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request. Since only one handler will receive the request, the others will have
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been awakened for no reason, wasting CPU cycles. At this time, Gunicorn does
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not implement any IPC solution for coordinating between worker processes. You
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may experience high load due to this problem when using many workers or
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threads. However `a work has been started
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<https://github.com/benoitc/gunicorn/issues/792>`_ to remove this issue.
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.. _worker_class: settings.html#worker-class
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.. _`number of workers`: design.html#how-many-workers
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Why I don't see any logs in the console?
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----------------------------------------
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In version R19, Gunicorn doesn't log by default in the console.
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To watch the logs in the console you need to use the option ``--log-file=-``.
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In version R20, Gunicorn logs to the console by default again.
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Kernel Parameters
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=================
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When dealing with large numbers of concurrent connections there are a handful
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of kernel parameters that you might need to adjust. Generally these should only
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affect sites with a very large concurrent load. These parameters are not
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specific to Gunicorn, they would apply to any sort of network server you may be
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running.
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These commands are for Linux. Your particular OS may have slightly different
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parameters.
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How can I increase the maximum number of file descriptors?
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----------------------------------------------------------
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One of the first settings that usually needs to be bumped is the maximum number
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of open file descriptors for a given process. For the confused out there,
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remember that Unices treat sockets as files.
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.. warning::
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Considering non-privileged users are not able to relax the limit, you should
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firstly switch to root user, increase the limit, then run gunicorn. Using ``sudo
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ulimit`` would not take effect.
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Try systemd's service unit file, or an initscript which runs as root.
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How can I increase the maximum socket backlog?
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----------------------------------------------
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Listening sockets have an associated queue of incoming connections that are
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waiting to be accepted. If you happen to have a stampede of clients that fill
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up this queue new connections will eventually start getting dropped.
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::
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$ sudo sysctl -w net.core.somaxconn="2048"
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How can I disable the use of ``sendfile()``
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-------------------------------------------
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Disabling the use ``sendfile()`` can be done by using the ``--no-sendfile``
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setting or by setting the environment variable ``SENDFILE`` to 0.
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Troubleshooting
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===============
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How do I fix Django reporting an ``ImproperlyConfigured`` error?
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----------------------------------------------------------------
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With asynchronous workers, creating URLs with the ``reverse`` function of
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``django.core.urlresolvers`` may fail. Use ``reverse_lazy`` instead.
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.. _blocking-os-fchmod:
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How do I avoid Gunicorn excessively blocking in ``os.fchmod``?
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--------------------------------------------------------------
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The current heartbeat system involves calling ``os.fchmod`` on temporary file
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handlers and may block a worker for arbitrary time if the directory is on a
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disk-backed filesystem. For example, by default ``/tmp`` is not mounted as
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``tmpfs`` in Ubuntu; in AWS an EBS root instance volume may sometimes hang for
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half a minute and during this time Gunicorn workers may completely block in
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``os.fchmod``. ``os.fchmod`` may introduce extra delays if the disk gets full.
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Also Gunicorn may refuse to start if it can't create the files when the disk is
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full.
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Currently to avoid these problems you can use a ``tmpfs`` mount (for a new
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directory or for ``/tmp``) and pass its path to ``--worker-tmp-dir``. First,
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check whether your ``/tmp`` is disk-backed or RAM-backed::
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$ df /tmp
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Filesystem 1K-blocks Used Available Use% Mounted on
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/dev/xvda1 ... ... ... ... /
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No luck. If you are using Fedora or Ubuntu, you should already have a ``tmpfs``
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mount at ``/dev/shm``::
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$ df /dev/shm
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Filesystem 1K-blocks Used Available Use% Mounted on
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tmpfs ... ... ... ... /dev/shm
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In this case you can set ``--worker-tmp-dir /dev/shm``, otherwise you can
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create a new ``tmpfs`` mount::
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sudo cp /etc/fstab /etc/fstab.orig
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sudo mkdir /mem
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echo 'tmpfs /mem tmpfs defaults,size=64m,mode=1777,noatime,comment=for-gunicorn 0 0' | sudo tee -a /etc/fstab
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sudo mount /mem
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Check the result::
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$ df /mem
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Filesystem 1K-blocks Used Available Use% Mounted on
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tmpfs 65536 0 65536 0% /mem
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Now you can set ``--worker-tmp-dir /mem``.
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