Akismet

Akismet uses round-robin DNS and load balancers to distribute the work of checking comments for spam across multiple servers. A DNS lookup of rest.akismet.com (the domain used for Akismet API calls) returns not one but several IP addresses, corresponding to the multiple servers. When your blog uses Akismet to check a comment, it will (more or less)... randomly choose an Akismet server IP to use. Each time it checks a new comment, it might use a different Akismet server IP. If a web host blocks all connections to all Akismet server IPs, the Akismet plugin can easily detect the problem and report an error. The plugin has always included a connectivity check as part of its configuration process, that will warn the user if Akismet servers are unreachable. If a web host allows connections to some Akismet server IPs, but blocks connections to the others, the connectivity check might succeed (if it happens to connect to one of the allowed IPs), while some subsequent connections will fail (when they try to connect to one of the blocked IPs). Result: the plugin appears to be working fine, but in fact only some API calls are working. Users often won't notice anything wrong, because some spam is caught. The new revision expands the connectivity check to include all known Akismet servers. It displays a status message or warning to the user if some servers are unreachable. It also stores a list of server IPs and their status, with a 24 hour expiry. That list of IPs is used when checking and reporting spam, to ensure that only servers that are known to be reachable are used. The list will be refreshed after 24 hours so as to adapt to any changes in availability - such as when a web host changes their firewall and blocks or unblocks an Akismet server. (Which is something that a few hosts have been known to do without warning, unfortunately). NB: feedback about this new revision is welcome here, but please don't post general Akismet support requests in comments. Post them here instead.Read More