How wasteful is polling?

How wasteful is polling?

Timeliness and latency are among the most crucial challenges to increase engagement. If you rely on polling to aggregate content or get your content distributed, you have to increase the polling frequency to make sure the content is always fresh. But how wasteful is this?

At Superfeedr, we poll feeds so that nobody else has to do it and we have 3 mechanisms which trigger a feed fetching:

  • External pings: these are the pings we get from the publishers which support PuSH, or from other hubs, as well as RSSCloud endpoints. It also includes things like XML-RPC pings and a bunch of other less frequent mechanisms.
  • Scheduled fetches: For each feed, we keep track of the next time it needs to be fetched if nothing else happened until then.
  • Self pings: we maintain an internal feed graph which links feeds together so that when one updates, we are able to fetch other related feeds that might have been updated

For each of these mechanism, we are keeping track of a hit rate: the number of times we found at least one new entry divided by the number of times we tried to fetch the feed.

External pings get a hit rate of 58%. There are a lot of cases in which we get pings for feeds which have not actually been updated… This includes feeds which have uncontrolled caching mechanisms, or even feeds for which we had already identified the new content. All in all, this is a pretty efficient mechanism and we try to convince publishers to ping us when they can.

As expected, scheduled fetches have a low hit rate of barely 5%. This is obviously an area of concern for us when trying to save resources. This low number is the reason why we created our feed graph.

Self pings have a hit rate of 22%. In practice, we find roughly as many new entries through dumb polling than with our self pings, saving us a lot of resources: when scheduled fetches requires 20 requests to find a new update, it takes less than 5 requests from our feed graph.

The most important benefit of using Superfeedr as a subscriber means that you never have to poll a feed. We push the content so that 100% of your bandwidth is spent for fresh content, instead of 5% if you rely on dumb polling.

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On the same topic, check pubsubhubbub for drupal with multiping, ping me i'm famous and rsscloud and pubsubhubbub.

Previously, on the Superfeedr blog: Bridging AMP and RSS.