Web Server occasionally taking a very long time to serve pages - performance

I am on a virtual dedicated webserver and my site has very little traffic at the moment. Everything was fine up until a couple of weeks ago, my pages would always load very quickly but now a problem has developed.
About one in every 3 page loads it takes 10 seconds or more to load the pages that usually take about a second. Using Google chrome the grey icon where that precedes the favicon spends a long time rotating anticlockwise but is normal once it begins rotating clockwise leading me to believe that there is a problem connecting to the server. This problem occurs wherever I or anyone else connects from so it is not a problem with my own interenet connection or anything like that.
Strangely everything is always fine loading index.php, the problems only occur with the other pages on the site.
I've been suspecting it has something to do with DNS but I don't know much about it.
I have been trying hard to work out what the problem is for myself, but I am not much of an expert on servers etc and most of the stuff I come find with google is about slow internet connections. If anyone has had this problem themselves and managed to solve it or can help in anyway I would be very grateful.

Related

Random slow content download, while TTFB remains low

I'm developing a Magento2 website, everything is running well for now, except a random issue I can't figure out how to solve.
The website is using Varnish, and all pages have a varnish cache HIT, with a very low TTFB about 30ms and low content download too (about 40ms)
But randomly, the download timing increases to more than 2 seconds, and on the next page visit it will go down to normal 40ms.
Same issue on all browsers, so not a browser issue.
Would someone have an idea ?
Many thanks
There are so many factors at play. The most important thing is whether or not you can simulate the issue and predict when the issue will appear again.
Once you're able to simulate, you need to determine what type of resource is slow:
Is it the graphical rendering of the page in the browser?
Is there a 3rd party JS resource that is slow?
Is it the actual TTFB of the main page that is slow for that resource?
Please use your browser's development tools and check the breakdown in the networking tab. With enough attempts, you'll be able to spot the issue. When you do, please add a screenshot of the breakdown in this question.
In parallel, you can keep the following command running to identify requests that took more than 2 seconds to process:
varnishlog -g request -q "Timestamp:Resp[2] > 2.0"
You can also add the output to your question.

Time spent in network exploding randomly - (website speed)

We are a PHP web app hosted with Amazon in Dublin. Lately we have had a very strange problem.
The problem:
All of a sudden our site gets incredibly slow, sometimes to a point were it is no longer available. This typically lasts for a couple of minutes and then everything is fine again. It seems to happen randomly. Sometimes it happens several times in one day and then we won't have this problem for a period of days.
We track our website speed with New Relic. In the monitoring I found that the "time spent in network" seems to explode all of a sudden (definition here: https://newrelic.com/docs/features/how-does-real-user-monitoring-work#what-does-the-network-time-include). It is normally around 0.5 seconds per request. This value explodes to anywhere between 9-15 seconds. After about 10-15 minutes it goes back to 0.5 seconds.
Things that I can exclude as causes:
There are no traffic spikes causing this (it also happens during normal load) + we have sufficient CPU and DB power so that small spikes shouldn't be creating issues.
There aren't any expensive internal scripts running that are causing the problem.
It doesn't seem to be related to external software being unresponsive (even individual pages that have no 3rd party components implemented are incredibly slow (they don't even have google analytics).
What I think it could be:
To be entirely honest I am kind of lost.
The only thing I can imagine is that the time spent between the application and the database is super high for an unknown reason, e.g. because they are in different Amazon availability zones for a period of time or something like this, but this kind of problem should then be affecting everyone once in a while and I don't really know how to solve or detect this.
I have reached out to Amazon, but am still waiting for an answer.
Have you had a similar problem or any idea what could be the cause for this issue?
Many thanks for any tips.

Monitoring Hosting Performance

I've been building a site, running Wordpress 3.2.1 and noticed
the performance is sluggish in the front and back end.
I believe the problem is hosting specific.
The problem seems to be the connection loading the actual HTML
which is taking about 5.5 seconds. It appears to finish after
about 500ms, but does not stop loading for 3-4 more seconds.
Here is the development URL:
http://d1001488.u57.ukisp.com/dev/
Hosting:
Windows NT
PHP Version 5.2.10
There are a couple of jQuery select boxes that get
replaced and styled onload (in the footer), these take a
long time to get replaced after the page fully loads.
The hosts are claiming all is running properly. Is there
any thing I can try and tweak or monitor to see what
is going on? Or any suggestions?
Thanks.
For largely extrinsic causes, try YSlow. This will identify a number of things you can work on. It won't tell you anything about the internal behavior of your server, but it may help you narrow down what's going on.
The problem may be a specific plugin. Here's what I would recommend:
Try going through each plugin, deactivating it, and see if that makes your site load faster. Do this for each plugin, and if a deactivated plugin doesn't improve performance then just reactivate it and move to the next one.
Try temporarily activating the default Twenty Eleven theme. See if the default theme loads faster. If it does, then we can look at your custom theme.
These two things may help narrow down at least where the problem is coming from. Let me know how it goes!
Do you have CPanel access with your hosting account? If you do, look in the left side toolbar at the bottom you should see where it says server status (click to view) you will see various details about your server performance.

How do I know how much traffic my wordpress/buddypress based social media website could hold? What to do when traffic goes up?

Right now I'm paying 5 dollars a month for hosting to godaddy.com. Although there are no users registered yet (it's closed for maintenance mode as I'm testing and buiding it), it's slower than e.g. facebook. Does anyone have experience on using buddypress? What happens if my site blows up and draws a lot of users very fast. I guess I can get more expensive and better quality hosting, but is there a limit for buddypress based sites, especially when I'm using quite a few plugins.
BuddyPress scales quite high, so the code itself won't be a problem, even with tens of thousands of users. Your problems will probably be imposed by your host--limiting database transactions or sizes of tables--or specific themes taking a long time to render.
Firebug can be a great tool to use if you want to identify what component is causing a site to be slow. Instructions on using Firebug

Firefox cache bug

This is a bug/issue which has cost my time for at least 3 years now.
I have complex, dynamic pages in ASP.NET which use a lot of javascript (which is more or less static).
Now I have a behaviour which happens only in Firefox and then only every few 10.000 requests.
Users are playing games on my site so they are hitting the same page again and again, every day. And then the game locks up with javascript errors on the page. I have never been able to find out what exactly happens. A file is corrupt perhaps?
Shift-F5 or simple reloading does not help. If the user clears his cache, the problem is gone.
This has been reported hundreds of times now. Every time the user has been a Firefox user, every time, clearing the cache fixed the issue.
I can't nail down the bug since I can't reproduce it.
There are lots of reports that Firefox is caching files which it shouldn't cache. But that doesn't seem to be the issue in my case. Something else is going on.
Anyone got an idea what's going on?

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