Troubleshooting

How do I fix Django reporting an ImproperlyConfigured error?

With asynchronous workers, creating URLs with the reverse function of django.core.urlresolvers may fail. Use reverse_lazy instead.

How do I avoid Gunicorn excessively blocking in os.fchmod?

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. For example, by default /tmp is not mounted as tmpfs in Ubuntu; in AWS an EBS root instance volume may sometimes hang for half a minute and during this time Gunicorn workers may completely block in os.fchmod. os.fchmod may introduce extra delays if the disk gets full. Also Gunicorn may refuse to start if it can’t create the files when the disk is full.

Currently to avoid these problems you can use a tmpfs mount (for a new directory or for /tmp) and pass its path to --worker-tmp-dir. First, check whether your /tmp is disk-backed or RAM-backed:

$ df /tmp
Filesystem     1K-blocks    Used Available Use% Mounted on
/dev/xvda1           ...     ...       ...  ... /

No luck. If you are using Fedora or Ubuntu, you should already have a tmpfs mount at /dev/shm:

$ df /dev/shm
Filesystem     1K-blocks     Used Available Use% Mounted on
tmpfs                 ...     ...       ...  ... /dev/shm

In this case you can set --worker-tmp-dir /dev/shm, otherwise you can create a new tmpfs mount:

sudo cp /etc/fstab /etc/fstab.orig
sudo mkdir /mem
echo 'tmpfs       /mem tmpfs defaults,size=64m,mode=1777,noatime,comment=for-gunicorn 0 0' | sudo tee -a /etc/fstab
sudo mount /mem

Check the result:

$ df /mem
Filesystem     1K-blocks  Used Available Use% Mounted on
tmpfs              65536     0     65536   0% /mem

Now you can set --worker-tmp-dir /mem.