Setting up Nextcloud as a UnifiedPush provider on NixOS
2022-11-03

I recently set up Nextcloud as a UnifiedPush provider on NixOS. Since others might want to do the same, I’ve detailed the process in this blog post. First I will explain in a nutshell what UnifiedPush is and why anyone would want to use it, next I will go over the steps required for setting it up.

UnifiedPush

UnifiedPush is used to deliver push notifications to Android devices. It specifies how servers should talk with push providers, and how apps should talk with push distributors. The push distributor is the only app keeping open a connection to the push provider, making this a lot more efficient than every app that needs push notifications implementing its own polling mechanism. Since receiving push notifications is the only function of a push distributor, I also trust it more to do so efficiently. When the push distributor receives a notification, it distributes it to the corresponding app, which can now react to the actual notification.

Apps that want to receive push notifications need to register with the push distributor first. The push distributor will then give the app the information that the server backend needs to send the push notifications.

Note that nothing about this is Android-specific; one could implement a push distributor for any sufficiently open platform (in fact, a D-Bus distributor specification exists). However, since Android is the most widely-used mobile OS where something like this is possible, it is the platform where most of the development has happened.

UnifiedPush is a great alternative to Firebase Cloud Messaging (Google’s push notification service). Apps do not need to register with any central authority and do not need to pay to send push notifications. Users are free to choose which service their data flows through, and as this post shows, can even self-host this service. A number of apps already support this service; in my case I am using Tusky (a Mastodon client) and Element Android (a Matrix client).

Configuring Nextcloud

Prerequisites

I assume that you’ve already set up a Nextcloud instance (using the NixOS module). The module is not that complicated if not. Feel free to steal any part of my config.

NixOS configuration

First, you need to make sure that Nextcloud can load the redis PHP module, that you have a redis server running and that Nextcloud is configured to use it. Redis is used as a message broker in this case, so if this part is missing the communication from the notifying servers will not go through to the devices that are listening. In addition to redis, you also need to tweak nginx to allow the long-running requests that are typically used for push notifications.

The configuration for Nextcloud should look like this:

{
  services.nextcloud = {
    # Your other configuration here
    caching.redis = true;
    extraOptions.redis = {
      host = "127.0.0.1";
      port = 31638;
      dbindex = 0;
      timeout = 1.5;
    };
  };
}

Of course, you need to configure redis as well:

{
  services.redis.servers.nextcloud = {
    enable = true;
    port = 31638;
    bind = "127.0.0.1";
  };
}

And finally, you need to make sure you allow long-running requests in nginx:

{
  services.nginx.virtualHosts."your.nextcloud.hostname".extraConfig = ''
    fastcgi_connect_timeout 10m;
    fastcgi_read_timeout 10m;
    fastcgi_send_timeout 10m;
  '';
}

Make sure to switch to the new configuration after making your edits.

Nextcloud configuration

After setting up Nextcloud itself, you still need to install the “UnifiedPush Provider” app. This can be found under the Multimedia category in the Nextcloud apps admin interface. Note that you can also manage Nextcloud apps declaratively on NixOS, but I personally don’t do so, so I will not detail the process here.

Device configuration

To use UnifiedPush on your Android device you need to have both the Nextcloud and the NextPush app installed. Opening the NextPush app should guide you through setting it up. Once you’ve done that, you can start registering apps with NextPush. For example, to register Element Android go to the Notifications settings in Element Android and pick NextPush as your notification method. To set up Tusky, I haven’t found a better way than logging out and back in again.

Once you’ve followed these steps, you should have a working push notification setup.

Conclusion

As you can see, the process for setting up UnifiedPush using Nextcloud is not that involved. I was personally really impressed with how quickly I was able to get everything working. It is really nice to see that the open-source and free software community can implement the niceties that we’ve come to expect from modern life without needing a big tech giant to do so.

Comments or questions about this post? Feel free to contact me on Mastodon or send me an email.

Setting up Nextcloud as a UnifiedPush provider on NixOS2022-11-03