The downside to caching is it can occasionally delay feed updates, and cause scheduled mailings to behave unexpectedly.
Quick aside for the TL/DR crowd – don’t cache your feeds.
How Does Caching Affect Feeds Served by FeedBlitz?
Think of caching as a picture of a website. Rather than making calls for information on every part of a web page, the cache says “Hey, nothing new to see, refer to the picture.” That works out great for site visitors, they get a snappy response and it’s great for site owners because there are fewer calls on the server.
But what happens when FeedBlitz stops by to check a cached feed?
Let’s say Bob the blogger wrote a blog post at 1pm and has his daily mailing set to go out at 2pm. Well, the FeedBlitz agent will probably check his feed around 1:30pm. If the feed is cached, guess what? The snapshot says, “Sorry folks, nothing to see here, move along.”
No New Mail
With the appearance of having no new content, nothing is sent to the mailing list. The mail server will not be checking for new content until it’s time to package up the next scheduled delivery.
The next day, when FeedBlitz stops by for the next mailing, we’ll see the newer snapshot that contains the new post. But all is not well: While the ID of the post will look new, the timestamp will tell us it is too old to go out in this mailing. If the post had been published at 1pm, as the timestamp suggests, it would have been mailed in the previous collection.
But wait, there’s more, as always, there is more.
Content Delivery Networks
Some people may say, “But, I don’t use caching, I use a CDN to speed up my site’s load time.”
CDNs or Content Delivery Networks are in effect caching, they are simply distributed on third party networks rather than on the site’s server. The effect is the same. In addition to the timestamp, FeedBlitz user agents also check for something called etags. Please bear in mind that etags are not the same as meta tags used for site organization. A publisher will likely never come into contact with the automatically generated etags.
The good news for FeedBlitz publishers is the fix is simple.
When setting up your caching plugins or your CDN do not include your feed. FeedBlitz always needs to be able to get the most current version of a site’s feed, and with feed redirects properly in place FeedBlitz acts as the feed’s own CDN reducing calls on the server. Feed caching is generally the default, and publishers will likely need to change this in the settings.
Moral of the story: Fresh feeds keep FeedBlitz mailings on schedule.