"Unable to determine path from Post Permalink"

A bit more digging and I found where it is in the code:

/* if there's a post id pushed, it needs to be invalidated in all cases */
                if ( !empty ( $post_id ) ) {

                        /* need permalink functions */
                        if ( !function_exists('get_permalink') )
                                include_once ( ABSPATH . 'wp-includes/link-template.php' );

                        /* get permalink */
                        $permalink = get_permalink( $post_id );

                        /* no path, don't do anything */
                        if ( empty( $permalink ) ) {
                                $this->log ( sprintf( __translate__( 'unable to determine path from Post Permalink, post ID: %s', $this->plugin_constant ),  $post_id ), LOG_WARNING );
                                return false;
                        }

How could $permalink be empty? Does it look like I am on the right track?

I’m also getting the same error:

[23-Oct-2014 20:32:08 UTC] PHP Warning: wp-ffpc unable to determine path from Post Permalink, post ID: 120 in /home/xxx/public_html/wp-content/plugins/wp-ffpc/wp-common/plugin_utils.php on line 126
[23-Oct-2014 20:32:08 UTC] PHP Warning: wp-ffpc unable to determine path from Post Permalink, post ID: 121 in /home/xxx/public_html/wp-content/plugins/wp-ffpc/wp-common/plugin_utils.php on line 126

I’m also getting the same error:
“PHP Warning: wp-ffpc unable to determine path from Post Permalink”

I’m afraid I will not be able to answer this; I’m using internal, WordPress provided functions to determine the permalink.

The only idea I have it to try to force-regenerate the permalink cache of WordPress by changing the permalink structure a bit ( and probably changing it back )

I have this same problem. My site still caches fine, but i get these errors flooding my error logs. In my case, I’ve tried forcing regeneration of the permalinks with no success. It appears the Post ID that it is trying to pull the permalink for doesn’t exist – the highest post id i have is 726 and all the errors reference post ids in the 10s of thousands.

PHP Warning: wp-ffpc unable to determine path from Post Permalink, post ID: 36502

I’m still working on finding the cause for this, thank you for the update.

May I please ask you to modify a line to see if it keeps happening?

Replace line #257 of wp-ffpc-backend.php from

if ( empty( $permalink ) ) {

to:

if ( empty( $permalink ) && $permalink != false ) {

That does indeed fix the noise.

This was included in the new release, thank you for the bug report.