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Pushl

A simple tool that parses content feeds and sends out appropriate push notifications (WebSub, webmention, etc.) when they change.

See http://publ.beesbuzz.biz/blog/113-Some-thoughts-on-WebMention for the motivation.

Features

  • Will send WebSub notifications for feeds which declare a WebSub hub
  • Will send WebMention notifications for entries discovered on those feeds or specified directly
  • Can perform autodiscovery of additional feeds on entry pages
  • Can do a full backfill on Atom feeds configured with RFC 5005
  • When configured to use a cache directory, can detect entry deletions and updates to implement the webmention update and delete protocols (as well as saving some time and bandwidth)

Site setup

First, you'll want to have your Atom (or RSS) feed implement the WebSub protocol. The short version is that you should have a <link rel="hub" href="http://path/to/hub" /> in your feed's top-level element.

There are a number of WebSub hubs available; I use Superfeedr.

For WebMentions, configure your site templates with the various microformats; by default, Pushl will use the following tags as the top-level entry container, in descending order of priority:

  • Anything with a class of h-entry
  • An <article> tag
  • Anything with a class of entry

For more information on how to configure your site templates, see the microformats h-entry specification.

Installation

You can install it using pip with e.g.:

pip3 install pushl

However, I recommend installing it in a virtual environment with e.g.:

virtualenv3 $HOME/pushl
$HOME/pushl/bin/pip3 install pushl

and then putting a symlink to $HOME/pushl/bin/pushl to a directory in your $PATH, e.g.

ln -s $HOME/pushl/bin/pushl $HOME/bin/pushl

Usage

Basic

pushl -c $HOME/var/pushl-cache http://example.com/feed.xml

While you can run it without the -c argument, its use is highly recommended so that subsequent runs are both less spammy and so that it can detect changes and deletions.

Sending pings from individual entries

If you just want to send webmentions from an entry page without processing an entire feed, the -e/--entry flag indicates that the following URLs are pages or entries, rather than feeds; e.g.

pushl -e http://example.com/some/page

will simply send the webmentions for that page.

Additional feed discovery

The -r/--recurse flag will discover any additional feeds that are declared on entries and process them as well. This is useful if you have per-category feeds that you would also like to send WebSub notifications on. For example, my site has per-category feeds which are discoverable from individual entries, so pushl -r http://beesbuzz.biz/feed will send WebSub notifications for all of the categories which have recent changes.

Note that -r and -e in conjunction will also cause the feed declared on the entry page to be processed further. While it is tempting to use this in a feed autodiscovery context e.g.

pushl -re http://example.com/blog/

this will also send webmentions from the blog page itself which is probably not what you want to do.

Backfilling old content

If your feed implements RFC 5005, the -a flag will scan past entries for WebMention as well. It is recommended to only use this flag when doing an initial backfill, as it can end up taking a long time on larger sites (and possibly make endpoint operators very grumpy at you). To send updates of much older entries it's better to just use -e to do it on a case-by-case basis.

Dual-protocol/multi-domain websites

If you have a website which has multiple URLs that can access it (for example, http+https, or multiple domain names), you generally only want WebMentions to be sent from the canonical URL. You can configure this in Pushl by having the secondary feeds be WebSub-only, using the -s/--websub-only flag:

pushl -r https://example.com/feed -s http://example.com/feed http://alt-domain.example.com/feed

Automated updates

pushl can be run from a cron job, although it's a good idea to use flock -n to prevent multiple instances from stomping on each other. An example cron job for updating a site might look like:

*/5 * * * * flock -n $HOME/.pushl-lock pushl -rc $HOME/.pushl-cache http://example.com/feed

My setup

In my setup, I have pushl installed in my website's pipenv:

cd $HOME/beesbuzz.biz
pipenv install pushl

and created this script as $HOME/beesbuzz.biz/pushl.sh:

#!/bin/sh

cd $(dirname "$0")
LOG=$(date +%Y%m%d.log)

if [ "$1" == "quiet" ] ; then
    exec >> $LOG 2>&1
else
    exec 2>&1 | tee -a $LOG
fi

date
flock -n run.lock $HOME/.local/bin/pipenv run pushl -rvvc $HOME/var/pushl \
    https://beesbuzz.biz/feed \
    http://publ.beesbuzz.biz/feed \
    https://tumblr.beesbuzz.biz/rss \
    -s http://beesbuzz.biz/feed

Then I have a cron job:

*/5 * * * * $HOME/beesbuzz.biz/pushl.sh quiet

which runs it every 5 minutes.

I also have a git deployment hook for my website, and its final step (after restarting gunicorn) is to run pushl.sh, in case a maximum latency of 5 minutes just isn't fast enough.

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