I have a website with Wordpress and PHPBB integrated - and it's been fine for months.. then all of a sudden, it's unbelievably slow to load.

There are no errors in the apache logs, but looking at the page in firebug shows a 20 second pause, before the page is delivered.

more confusing, on the same server, same apache installation, PHPBB loads in 30ms, no delay.

I tried the hogdetector wordpress plugin, which indicates that the delay is before the header is sent - which seems to agree with firebug.

Any ideas how to troubleshoot this one further?

5 Answers 5


Probably a DNS lookup problem ! Check DNS configuration.

  • +1 I would also start by checking if you can do reverse DNS resolutions propperly on the server. Waiting for reverse DNS to time out often causes these kind of delays in odd places.
    – pehrs
    Apr 1, 2010 at 12:30
  • 1
    what do you know... the IP address of the upstream DNS server in the datacentre had been changed.
    – TheoJones
    Apr 2, 2010 at 11:45

If you have it running on a Linux (or Linux-like environment), try running a packet sniffer on it when doing a request and see what it's asking for and pausing. Something like tcpdump or wireshark. Run that, request some pages, see what the results are. If it's a DNS problem it should show up there. If networking is fine, then you would need to next start checking for local problems with the installation.


One of your WP plugins is likely at fault. Try disabling them one by one and seeing which one is causing the issue.


I observed (tcpdump) that when WordPress is attempting to load external content from the server side, it may retry 3 times when failing, waiting ~5 seconds between each attempt. That's a 15 seconds systematic delay if external data is permanently unavailable; with further WordPress page processing, you get to your 20 seconds response time in Firefox as I did.

I experienced this issue with a youtube plugin, which attempted to load content from youtube.com directly from server. DNS resolutions were OK on my setup, however a firewall was sending TCP RESET to WordPress connexion attempts.

I solved this by disabling server side loading of external content (may or may not be the correct approach for you), with the following directive in wp-config.php: define('WP_HTTP_BLOCK_EXTERNAL', true);

There is a complementary directive for fine grained control: define('WP_ACCESSIBLE_HOSTS', 'example1.com, example2.com');


Really odd that the blog is slow but the BBS is fine. If possible use a browser on the server (text based?) or something like wget. If performance is correct locally the only thing I can think of is a proxy problem. Of course if the local performance is poor then at least you know it's on the sever.

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