Client Push

Update notifications for nextcloud clients

About

This app attempts to solve the issue where Nextcloud clients have to periodically check the server if any files have been changed. In order to keep sync snappy, clients wants to check for updates often, which increases the load on the server.

With many clients all checking for updates a large portion of the server load can consist of just these update checks.

By providing a way for the server to send update notifications to the clients, the need for the clients to make these checks can be greatly reduced.

Update notifications are provided on a "best effort" basis, updates might happen without a notification being send and a notification can be send even if no update has actually happened. Clients are advised to still perform periodic checks for updates on their own, although these can be run on a much lower frequency.

Requirements

This app requires a redis server to be setup and for nextcloud to be configured to use the redis server.

Quick setup

The app comes with a setup wizard that should guide you through the setup process for most setups.

• Install the "Client Push" (notify_push) app from the appstore
• Run occ notify_push:setup and follow the provided instructions, If the setup wizard fails you can find manual instructions below.

Manual setup

The setup required consists of three steps

• Install the notify_push app from the appstore
• Setting up the push server
• Configuring the reverse proxy
• Configuring the nextcloud app

Push server

Setting up the service

The push server should be setup to run as a background daemon, the recommended way is by setting up a systemd service to run the server.

You can create a systemd service by creating a file named /etc/systemd/system/notify_push.service with the following content.

[Unit]
Description = Push daemon for Nextcloud clients

[Service]
Environment = PORT=7867 # Change if you already have something running on this port
ExecStart = /path/to/push/binary/notify_push /path/to/nextcloud/config/config.php
User=www-data

[Install]
WantedBy = multi-user.target

Adjusting the paths and ports as needed.

Configuration

The push server can be configured either by loading the config from the nextcloud config.php or by setting all options through environment variables.

Re-using the configuration from nextcloud is the recommended way, as it ensures that the configuration remains in sync.

If using the config.php isn't possible, you can configure the push server by setting the following environment variables:

• DATABASE_URL connection url for the Nextcloud database, e.g. postgres://user:[email protected]_host/db_name
• DATABASE_PREFIX database prefix configured in Nextcloud, e.g. oc_
• REDIS_URL connection url for redis, e.g. redis://redis_host
• NEXTCLOUD_URL url for the nextcloud instance, e.g. https://cloud.example.com

Or you can specify the options as command line arguments, see notify_push --help for information about the command line arguments.

If a config option is set in multiple sources, the values from the command line argument overwrite values from the environment which in turns overwrites the values from the config.php.

The port the server listens to can only be configured through the environment variable PORT, or --port argument and defaults to 7867. Alternatively you can configure the server to listen on a unix socket by setting the SOCKET_PATH environment variable or --socket-path argument.

Starting the service

Once the systemd service file is setup with the correct configuration you can start it using

sudo systemctl start notify_push

and enable it to automatically start on boot using

sudo systemctl enable notify_push

Every time this app receives an update you should restart the systemd service using

sudo systemctl restart notify_push

Reverse proxy

It is strongly recommended to setup the push service behind a reverse proxy, this both removes the need to open a new port to the internet and handles the TLS encryption of the connection to prevent sending credentials in plain text.

You can probably use the same webserver that you're already using for your nextcloud

Nginx

If you're using nginx, add the following location block to the existing server block of the nextcloud server.

location /push/ {
    proxy_pass http://127.0.0.1:7867/;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "Upgrade";
    proxy_set_header Host $host;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}

Note that both trailing slashes are required.

Once the nginx configuration is edit you can reload nginx using.

sudo nginx -s reload

Apache

To use apache as a reverse proxy you first need to enable the proxy modules using

sudo a2enmod proxy
sudo a2enmod proxy_http
sudo a2enmod proxy_wstunnel

Then add the following lines to the <VirtualHost> block used for the Nextcloud server.

ProxyPass /push/ws ws://127.0.0.1:7867/ws
ProxyPass /push/ http://127.0.0.1:7867/
ProxyPassReverse /push/ http://127.0.0.1:7867/

Afterwards you can restart apache using

sudo systemctl restart apache2

Nextcloud app

Once the push server is configured and the reverse proxy setup, you can enable the notify_push app and tell it where the push server is listening.

• enable the app occ app:enable notify_push
• set the url of the push server occ notify_push:setup https://cloud.example.com/push

The app will automatically run some tests to verify that the push server is configured correctly.

Logging

By default, the push server only logs warnings, you can temporarily change the log level with an occ command

occ notify_push:log <level>

Where level is error, warn, info, debugortrace`, or restore the log level to the previous value using

occ notify_push:log --restore

Alternatively you can set the log level of the push server in the LOG environment variable.

Metrics

The push server can expose some basic metrics about the number of connected clients and the traffic flowing through the server by setting the METRICS_PORT environment variable.

Once set the metrics are available in a prometheus compatible format at /metrics on the configured port.

Self-signed certificates

If your nextcloud is using a self-signed certificate then you either need to set the NEXTCLOUD_URL to a non-https, local url, or disable certificate verification by setting ALLOW_SELF_SIGNED=true.

Developing

As developer of a Nextcloud app or client you can use the notify_push app to receive real time notifications from the Nextcloud server.

Nextcloud web interface

If you want to listen to incoming events from the web interface of your Nextcloud app, you can use the @nextcloud/notify_push javascript library. Which will handle all the details for authenticating and connecting to the push server.

Clients

Desktop and other clients that don't run in the Nextcloud web interface can use the following steps to receive notifications.

• Get the push server url from the notify_push capability by sending an authenticated request to https://cloud.example.com/ocs/v2.php/cloud/capabilities
• Open a websocket connection to the provided websocket url
• Send the username over the websocket connection
• Send the password over the websocket connection
• If the credentials are correct, the server will return with "authenticated"
• The server will send the following notifications
  • "notify_file" when a file for the user has been changed
  • "notify_activity" when a new activity item for a user is created (note, due to workings of the activity app, file related activity doesn't trigger this notification)
  • "notify_notification" when a notification is created, processed or dismissed for a user

Example

An example javascript implementation would be

function discover_endpoint(nextcloud_url, user, password) {
    let headers = new Headers();
    headers.set('Accept', 'application/json');
    headers.set('OCS-APIREQUEST', 'true');
    headers.set('Authorization', 'Basic ' + btoa(user + ":" + password));

    return fetch(`${nextcloud_url}/ocs/v2.php/cloud/capabilities`, {
        method: 'GET',
        headers: headers,
    })
        .then(response => response.json())
        .then(json => json.ocs.data.capabilities.notify_push.endpoints.websocket);
}

function listen(url, user, password) {
    let ws = new WebSocket(url);
    ws.onmessage = (msg) => {
        console.log(msg);
    }
    ws.onopen = () => {
        ws.send(user);
        ws.send(password);
    }
}

let username = "...";
let password = "...";
let nextcloud_url = "https://cloud.example.com";
discover_endpoint(nextcloud_url, username, password).then((endpoint) => {
    console.log(`push server is at ${endpoint}`)
    listen(endpoint, "admin", "admin");
});

Test client

For development purposes a test client is provided which can be downloaded from the github actions page.
(Click on a run from the list, e.g. this one, scroll to the bottom and click on test_client to download the binary.)
Please note: the Test client only works on x86_64 Linux currently.

test_client https://cloud.example.com username password

Note that this does not support two-factor authentication of non-default login flows, you can use an app-password in those cases.

Building

The server binary is built using rust and cargo, 0.1.3 requires a minimum of rust 1.46 while later versions can be build with 1.45.

• Install rust through your package manager or rustup
• Run cargo build

Any build intended for production use or distribution should be compiled in release mode for optimal performance and targeting musl libc for improved portability.

cargo build --release --target=x86_64-unknown-linux-musl

Cross compiling for other platform is done easiest using cross, for example:

cross build --release --target=aarch64-unknown-linux-musl