November 8, 2015

How To: Syncing local uploads between multiple NodeBB processes

Today’s article will be a short how-to guide regarding a common problem with horizontally scaled NodeBB installations:

In a deployment environment with more than one NodeBB server, locally uploaded files (post images, avatars, etc) are split between the application servers, and n-1/n images will always be missing, where n is the number of servers

The typical solution to this would be to install a third-party plugin to offload and/or centralise the hosting of the images. For example, the Imgur plugin allows uploaded images to be hosted on Imgur, thus neatly resolving this problem.

In some scenarios, however, using a third-party image hosting service may not be preferable or ideal. For example, a healthcare-related business may have strict regulations that disallow off-site hosting of images for security and confidentiality purposes.

In this case, setting up a simple network file system to expose a shared folder will allow uploaded data to stay within your server control.

Step 1: Prepare the shared folder

In the separate server, install the appropriate dependencies:

$ sudo apt-get install nfs-kernel-server

Once this is done, expose the shared folder (in our example, /usr/local/nodebb-uploads) via the configuration file /etc/exports. Open the file in your favourite editor and add this line:

/usr/local/nodebb-uploads *(rw,sync,no_root_squash)

Then start the NFS server:

$ sudo service nfs-kernel-server start

Step 2: Prepare the NodeBB servers

NodeBB expects uploaded files to be in public/uploads, relative to the installation directory, so to mount the shared folder into your NodeBB install, run this command:

$ sudo mount /path/to/nodebb/public/uploads

Where is the hostname of the other server (configured in step 1)

This temporarily mounts the shared folder into your local file system, but to make these changes persist upon reboot, you can also add a line into /etc/fstab: /path/to/nodebb/public/uploads nfs rsize=8192,wsize=8192,timeo=14,intr

Step 3: Testing/Permissions

$ cd /path/to/nodebb/public/uploads
$ ls

Ensure that the NodeBB server can write to the shared folder, and you should be good to go!

For more information, consult the NFS documentation here:

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