PuSHPress: A PubSubHubbub Plugin For WordPress

03 Mar 2010

PubSubHubbub, or PuSH, is now supported on all WordPress.com blogs. For those running sites using the WordPress.org software the PuSHPress plugin is available to do the same thing. The big difference in this plugin compared to the other PuSH WordPress plugins is that it includes a PuSH hub built in.

A little bit of PubSubHubbub background

Like rssCloud, PuSH adds a line to your feed to let clients know where they can send PuSH subscription requests. In the RSS2 feed this looks like:

<atom:link rel="hub" href="http://josephscott.org/?pushpress=hub">

and in Atom looks like:

<link rel="hub" href="http://josephscott.org/?pushpress=hub">

The href attribute contains the URL that subscribers can send requests to. Details on what that request looks like are in the PubSubHubbub Spec. The short version, it’s a simple HTTP POST call with some specific field names.

Here’s an example PHP subscription request asking that updates to http://example.com/feed/ be sent to http://example.com/push/ via the hub at http://example.com/?pushpress=hub

$curl = curl_init( );

curl_setopt( $curl, CURLOPT_URL, 'http://example.com/?pushpress=hub' );
curl_setopt( $curl, CURLOPT_POSTFIELDS, 'hub.callback=http://example.com/push/&hub.mode=subscribe&hub.secret=not-telling-you&hub.verify=sync&hub.topic=http://example.com/feed/&hub.verify_token=133t-$7r1n9' );
curl_setopt( $curl, CURLOPT_VERBOSE, 1 );
curl_setopt( $curl, CURLOPT_POST, 1 );

curl_exec( $curl );
print_r( curl_getinfo( $curl ) );
curl_close( $curl );

The hub at example.com will then send new content (in feed format) right after it’s published to URL provided in hub.callback.

Why the PuSHPress plugin?

I love that there are large, open PuSH hubs available for anyone to use. There’s a list at http://code.google.com/p/pubsubhubbub/wiki/Hubs. In PuSH since most of the hard work (figuring out what’s new in a feed and sending that out to subscribers) is done via the hub this is very handy and really great for testing.

I also think there’s a role for a readily available simple hub that anyone can put up and use, in this case built on top of WordPress. And by leveraging WordPress the hub part can be greatly simplified. The real bonus for users is choice, they can relay the updates through 3rd party hubs, or use the built in hub in PuSHPress.

It’s worth noting that PuSHPress has a WordPress filter on the array of hubs; pushpress_hubs. This allows other plugins to easily add to or replace the hubs mentioned in the feeds by PuSHPress.

To help keep things simple and limit potential abuse the PuSHPress plugin will only allow subscriptions for the RSS2 and Atom feeds of the WordPress blog that it is installed on.

My thanks to Brett Slatkin for helping test PuSHPress. His tests revealed a few bugs that were quickly addressed.

How fast?

When talking about these realtime-ish update features this question often comes up. Fair enough, I’d want to know too :-)

The PuSHPress plugin schedules pings to go out right away via the wp_schedule_single_event function in WordPress. I suspect for most people this will be quite fast. If your server is under tremendous load and really slow, then this will be really slow too, just like the rest of the server ;-)

On WordPress.com the details are a bit different. Instead of scheduling pings to be sent out with wp_schedule_single_event it adds them to our asynchronous jobs system ( more info available at http://code.trac.wordpress.org/ ). The jobs system is setup to do exactly these kinds of tasks really, really fast. Don’t be surprised if the ping shows up before you get a chance to finish the first Mississippi.

The future

So where is all this going? Who knows, but it is fun to watch! :-)

Julien 3 Mar 2010

Well done Joseph, this is a very exciting news!

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- Joseph Scott 3 Mar 2010
  
  Thanks.
  
  Reply
Matt Terenzio 3 Mar 2010

Looks great. The wheels keep turning.

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mark k. 3 Mar 2010

Is anyone working on making the rss widget to be a client of rsscloud and PuSH whenever they are supported at the originating server of the rss feed?

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- Joseph Scott 3 Mar 2010
  
  Excellent question. I haven’t heard anyone mention that, but would be neat to see. Really any plugin that consumes RSS/Atom feeds could potentially benefit from having rssCloud and PuSH support.
  
  Reply
Ipstenu 3 Mar 2010

Interesting… how will this work with FeedBurner feeds? The rssCloud plugin manages to plugin into those. Will this too?

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- Joseph Scott 3 Mar 2010
  
  I haven’t tried it with FeedBurner. I’d be interested to hear what happens in the feed from people using FeedBurner.
  
  I suspect that they pass the hub element through untouched, though I haven’t confirmed that yet.
  
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  - Ipstenu 3 Mar 2010
    
    I’ll give her a whirl then :) On WP 3.0 multisite no less.
    
    Reply
  - John 3 Mar 2010
    
    My feedburner entry returns
    this XML, just for reference.
    
    Reply
    - Joseph Scott 3 Mar 2010
      
      I looked at http://feeds.feedburner.com/jleveron and the only hub it lists is http://pubsubhubbub.appspot.com/. Do you still have the PuSHPress plugin enabled on your site?
      
      Reply
      - John 3 Mar 2010
        
        Aye, Version 0.1.4 shows active. Perhaps there’s a config spot I missed ? Thanks for the plugin . . .
      - Joseph Scott 4 Mar 2010
        
        I’ll need to look closer at what FeedBurner is actually doing then.
      - John 4 Mar 2010
        
        I’m not sure why my feed isn’t passing through to feedburner then, gahhh :) Since it seems to be working for others.
        
        There were blog entries made after the plugin was added (plain WP 2.9.2, etc.)
  - Ipstenu 4 Mar 2010
    
    Seems to be working for me, so yay :)
    
    Reply
  - Big City Informer 4 Mar 2010
    
    After we enabled the plugin on our WPMU site (sitewide activated) it seems like the hub element is just passed through for all feeds as you expected. Check it out here if you like:
    
    http://feeds.feedburner.com/BigCityInformer
    
    Now we need to see how feed applications use it and if it really speeds things up as compared to the usual old ping – options :-)
    
    Thanks
    Big City News
    
    Reply
    - Joseph Scott 4 Mar 2010
      
      Yep, I see the PuSHPress hub listed in your FeedBurner feed. Looks like FeedBurner is just passing it through, which is what I’d expected/hoped.
      
      Reply
      - Big City Informer 5 Mar 2010
        
        Hey, it is lightning fast I would say. Feedburner used to take up to 30 minutes for a new item to be updated in the feeds properly. Now as soon as we press publish, it gets updated from the guys at Feedburner. So maximum 5 minutes and all other Feedburner – attached services are also updated.That’s so cool, thanks again for the plugin Joseph :-)
        Is there a good list available somewhere with all the services using PuSHPress for fetching?
        
        Can the same process be used for Google sitemaps somehow? Are they using PuSHPress in any way? That would be perfect, once published directly in the index :-)
      - Joseph Scott 5 Mar 2010
        
        I’m not aware of a list like that, though PuSHPress is just PubSubHubbub, so any service that supports that will work fine with PuSHPress.
        
        I don’t know exactly what Google’s plans are, you’ll have to ask them :-)
Moja Izba 3 Mar 2010

Great news, I am trying this PubSubHubbub plugin too.

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Lopo Lencastre de Almeida 3 Mar 2010

How is yours different from http://www.onlineaspect.com/2010/01/23/updated-pubsubhubbub-plugin-for-wordpress-mu/

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- Joseph Scott 3 Mar 2010
  
  I mentioned in a few different places that what makes PuSHPress different from the other PuSH plugins available is that it has a built in hub. The plugin you linked to uses a 3rd party hub to relay updates out to subscribers. Either one will enable PuSH for your WordPress site, how exactly do that is the difference.
  
  Reply
Tschai 4 Mar 2010

Works fan-tas-tic, even with feedburner: http://feeds.feedburner.com/fan-tas-tic

The feeds is published (almost) real-time!

Thanks a lot!

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- Joseph Scott 4 Mar 2010
  
  Interesting, I do see the PuSHPress hub in your FeedBurner feed.
  
  Reply
Jonathan Stegall 4 Mar 2010

I’m curious: does this negate the need for the Update Services in WordPress (http://codex.wordpress.org/Update_Services if others are curious)? If so, would you recommend that folks clear out that field and install this plugin instead? Can you give a quick comparison, maybe?

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- Joseph Scott 4 Mar 2010
  
  I don’t see this as directly replacing the update services.
  
  Reply
UbuntuLinuxHelp 4 Mar 2010

I think I’m missing something.

Please can someone help?

I installed and activated the PuSH Press plugin. NOTHING has changed with my feeds. Even when I manually use:

http://ubuntulinuxhelp.com/?pushpress=hub

It returns an error that says:

“hub.callback is empty”

If I click the RSS icon in the address bar of the browser and select either RSS2 or Atom, it functions the way it’s always done. That is the RSS2 and Atom links do NOT look like the ones displayed in your “A little bit of PubSubHubbub background” section above.

What, if anything, have I done wrong. The installation information for the PuSH Press plugin said there was nothing to configure, just install and go.

Any help would be appreciated. Thanks!

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- Joseph Scott 4 Mar 2010
  
  I tried to look at your feed by requesting http://ubuntulinuxhelp.com/feed/ but it returned a 403 Forbidden error.
  
  Reply
  - UbuntuLinuxHelp 4 Mar 2010
    
    That’s strange! I just clicked the link you provided me and it redirected to here: http://feeds2.feedburner.com/ubuntulinuxhelp/ERrG
    
    Which link was giving you the 403 error?
    
    The browser address bar RSS or the left side bar RSS?
    
    Reply
    - UbuntuLinuxHelp 4 Mar 2010
      
      Oops… that should have been “Right” side bar.
      
      The “Click to edit” here (Ajax editor), just opens as a blank white page, so could not edit it.
      
      Reply
    - Joseph Scott 4 Mar 2010
      
      The ‘Post feed’ in your sidebar links to http://ubuntulinuxhelp.com/feed/ and the same for the feed URL in your HTML header. When I request URL it returns 403 Forbidden.
      
      Since you mentioned http://feeds2.feedburner.com/ubuntulinuxhelp/ERrG I looked at that feed and it does have the PuSHPress hub listed.
      
      Reply
      - UbuntuLinuxHelp 6 Mar 2010
        
        @Joseph Scott
        
        THANK YOU!
        
        I do have two questions (can you answer them?)
        
        1) Where do I see that PuSHPress hub is listed (I cannot see it so am obviously not looking where you are)?
        
        2) What application are you using to access the RSS feed, or how? (After your 403 error, I got worried and had several people test it; and they could all access it).
        
        Thanks muchly again.
      - Joseph Scott 8 Mar 2010
        
        1) In your feeds search for the line that contains pushpress=hub, that’s the element that describes where your hub is at.
        
        2) curl
Eric Williams 4 Mar 2010

It probably depends on if “PingShot” is enabled in FeedBurner, enabling it also enables FeedBurner’s built-in PubSubHubbub support. If you’re using FeedBurner’s features, you probably don’t want WordPress handling PubSubHubbub, it’ll prevent FeedBurner’s modifications (such as feedflairs) and tracking (subscriber count, clicks) from working properly. (WordPress will notify directly, FeedBurner won’t get a chance to process it)

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- Joseph Scott 4 Mar 2010
  
  Figuring out what feed proxies should when a feed already has a hub is something that is being talked about on the PuSH email list.
  
  Reply
radekg 8 Mar 2010

Great work! Thank you :)
I write about this plugin on my blog: http://izbieractwo.pl/2010/03/09/wordpress-i-pubsubhubbub-push/ (in polish)

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windhamdavid 9 Mar 2010

very nicely done! thank u

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Tzafrir 16 Mar 2010

I tried to look through the code but could not find the answer – Does this function as a generic hub, or is it married to WordPress?

What I’d like to do is to add the wordpress hub to the rss feeds on a phpbb forum, and have the hub ping the forums often to get feed updates. PuSH defines that the hub should ping the source every interval, so this isn’t against standard use, and will be much easier than hacking a pinging mechanism into phpbb.

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- Joseph Scott 16 Mar 2010
  
  The PuSHPress plugin will only accept subscription requests for the WordPress RSS2 and Atom feeds.
  
  Reply
- Eric Williams 17 Mar 2010
  
  If you define a hub in your feed, you should probably ping it, that’s kind-of the point. Without the pings it’s not live… the point of PuSH is to send messages via a push system, not a polling system. The polling you’re talking about is to make sure the feed still exists, and, in the case of some hubs, allow a PuSH-only subscriber to subscribe to non-PuSH feeds.
  
  In terms of which hub to use, you might consider just using an open hub, such as http://pubsubhubbub.appspot.com/, if you don’t want to implement/run your own.
  
  Reply
phrozen77 22 Mar 2010

Hi Joseph,

great plugin – thanks for that!

I just wonder, will there be some way to see the subscriber count via PuSH sometime?

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- Joseph Scott 22 Mar 2010
  
  That certainly something that could be added. I don’t have any immediate plans for adding them, but it’s something I’ll keep in mind.
  
  Reply