Wordpress REST API Caching Issue - WP Engine - php

Question

I have created a custom plugin that actually just registeres a few API endpoints.
Right now the issue I'm having is that all of the endpoints are working fine locally, but when I push this code to WpEngine where I've hosted my WordPress site the API responses are getting cached.
If I clear the cache through WPEngine and make the request again the API is working fine until a 200 success response is received for the first time, once success is received then from the point the endpoint is always returning the same response no matter what header, parameter value I give to that endpoint.
In the wp-config.php file I've disabled the cache - define( 'WP_CACHE', false );
also tried adding
wp_cache_flush();
nocache_headers();
in the request action call back functions too, still no success, always the response are cached.
Few Code snippets for your reference -
// This is the route I've registered
public function register_routes()
{
register_rest_route($namespace, '/config' ,[
'methods' => 'GET',
'callback' => array($this, 'Action_GetConfig'),
'permission_callback' => 'authCheck'
]);
}
add_action( 'rest_api_init', array( $this, 'register_routes' ) );
function Action_GetConfig(WP_REST_Request $request)
{
try {
// wp_cache_flush();
// nocache_headers();
$headers = $request->get_headers();
// Basic Validation
if (IsNullOrEmptyString($headers['platform'][0]) or IsNullOrEmptyString($headers['version'][0])) {
$resp = new WP_HTTP_Response();
// $resp->set_headers( array('Cache-Control' => 'no-cache, must-revalidate, max-age=0'));
$resp->set_status(400);
return $resp;
}
// Service Invocation
$results = $this->getConfig($headers['platform'][0], $headers['version'][0]);
$resp = new WP_HTTP_Response($results);
$resp->set_status(200);
return $resp;
} catch (Throwable $e) {
//$log->error($e);
$resp = new WP_HTTP_Response($e);
$resp->set_status(500);
return $resp;
}
}
Can someone help in solving this API response caching issue? Thanks!

Answer 1

I believe WP ENGINE USES, WP Engine MU PLUGIN. If so with this plugin you will have access to a few functions called
wpecommon::purge_varnish_cache()
, if you pass the ID of a particular post that you were targeted for, this function will clear the post cache. But if you use the function without passing the ID then it will clear all the cache of the entire domain( I would certainly not recommend this way, as it will cause a performance issue on a large site).
function your_call_of_action(WP_REST_Request $request){
$id = $request->get_param( 'id' );
if ( FALSE === get_post_status( $id ) ) {
$resp = new WP_HTTP_Response([]);
$resp->set_status(500);
return $resp;
}
wpecommon::purge_varnish_cache( $id )
// rest of your code goes here
}
Also, you can call the following API to clear the cache :
/installs/{install_id}/purge_cache
Read the following documents:
Read this document: https://wpengine.com/support/cache/
API Document: https://wpengineapi.com/reference

Answer 2

I solved this issue by adding a Cache Exclusion Policy in WPEngine. Because by default in WPEngine all the Endpoints responses are cached. So if we want NOT to cache a specific route, then we have to add that route to the Exclusion list.
path: ^/wp-json/nx/services/?
I added this above Route RegEx in WPEngine.