I suddenly got a spike in CPU usage on shared hosting and my website has been taken offline for the past 48 hours. I have already tried the following, and it did not help (or only a bit):
Updated Drupal 7 and all modules to the latest version
activated CloudFlare
disabled any unused modules
Caching was already on (min cache lifetime: none; expiration cached pages: 1 hour; bandwidth optimization: all options checked). I had no problems before, and visitor numbers have remained fairly constant at 1500-2000 a day. Could it be hacked? Spam? The logs only show lots of Google bot "access denied" activity, but somehow doubt that can take the site down.
Thanks in advance for any advice!
Use boost module, this will help you improve the performance by creating HTML files.
Boost provides static page caching for Drupal enabling a very
significant performance and scalability boost for sites that receive
mostly anonymous traffic. For shared hosting this is your best option
in terms of improving performance. On dedicated servers, you may want
to consider Varnish instead.
Apache is fully supported, with Nginx, Lighttpd and IIS 7
semi-supported. Boost will cache & gzip compress html, xml, ajax, css,
& javascript. Boosts cache expiration logic is very advanced; it's
fairly simple to have different cache lifetimes for different parts of
your site. The built in crawler makes sure expired content is quickly
regenerated for fast page loading.
Related
I'am trying to cache static files on my server using varnish cache. I configured varnish to cache files with image extensions (.jpg, .png etc.). After that I open my website and debug it with browser developer tools and check load time of all images on my site and there is no difference in load time when I use varnish or not. There is a "HIT" in X-Cache entry in response header so images are available in my cache right? Any idea what can I doing wrong?
Ps. I'm using nginx as a backend server
Varnish shoudln't have a real impact on static files, especially when they're located on a SSD. Very heavy frequented sites may be an exception, particulary when the data is stored on a (slow) HDD. Here you have a huge amout of I/O which can be highly reduced by caching the images in the ram with Varnish. But these might be some special cases where caching of static files make sense. For nginx is also noticeable that this is a very fast webserver which is very good at delivering static files.
The main purpose for Varnish is HTML generated by some server-side backend like PHP, ASP.NET, and other languages which are designed for this task. Compared with serving static files it's very time-sensitive to generate dynamic content: The backend hat to work for example on database-querys which are very common in web-applications today or parsing templates. Wordpress is a widespread CMS and also a good example for this: Several 10k of php-code are executed on a single request and depending on the amout of plugins 100 database-querys and more are no exception.
So there are a lot of things to do for the server - for every request. For you as a site-owner this has the following effects:
The loadtime of the page increases which will result in to problems when its too high:
Visitors are not very patient and they're going to leave your page when they're thinking it's not fast enough. A online-shop which is making $100k per day can be loss up to $2.5 million per year by a delay of 1 second (see https://blog.kissmetrics.com/loading-time/ for more information)
As a result of this its not unexpected that Google is using the loadtime as an indicator for your ranking (see http://www.shoutmeloud.com/google-started-ranking-websites-based-on-load-time-and-speed.html)
Depending on the amount of visitors it can cost you money for more or more powerfull servers
Varnish can store the HTML generated by a backend in the RAM or on a hard drive. Especially with a SSD the latter make sense. Depending of the structure and use of your site, Varnish will at least improve the speed of your page and maybe also save money because less (powerfull) servers will do the job.
When Varnish is used as fronted for dynamic-generated content, you'll notice a noticeable difference. Depending of the application even a big difference. I configured varnish for a vBulletin based forum and could improve the page load time about 5 times.
Summarizing you should focus on caching dynamic pages instead of static stuff like images or clientscript because in most cases the webserver is already good enough to deliver those things. When static content is really slow, this can probably improved by using a CDN. Or maybe your webserver is not well configured for optimal speed. Perhaps there is no lifetime defined for images as example. This can have a negative impact on performance, especially on larger ones. But without further about your application and configuration its not possible to investigate the performance-issue and give concret tipps how this can be enhanced.
We're currently doing optimizations to our web project when our lead told us to push the use of CDNs for external libraries as opposed to including them into a compile+compress process and shipping them off a cache-enabled nginx setup.
His assumption is that if the user has visits example.com which uses a CDN'ed version of jQuery, the jQuery is cached that time. If the user happens to visit example2.com and happen to use the same CDN'ed jQuery, the jQuery will be loaded from cache instead of over the network.
So my question is: Do domains actually share their cache?
I argued that even if it is possible the browser does share cache, the problem is that we are running on the assumption that the previous sites use the same exact CDN'ed file from the same exact CDN. What are the chances of running into a user browsing through a site using the same CDN'ed file? He said to use the largest CDN to increase chances.
So the follow-up question would be: If the browser does share cache, is it worth the hassle to optimize based on his assumption?
I have looked up topics about CDNs and I have found nothing about this "shared domain cache" or CDNs being used this way.
Well your lead is right this is basic HTTP.
All you are doing is indicating to the client where it can find the file.
The client then handles sending a request to the CDN in compliance with their caching rules.
But you shouldn't over-use CDNs for libraries either, keep in mind that if you need a specific version of the library, especially older ones, you won't be likely to get much cache hits because of version fragmentation.
For widely used and heavy libraries like jQuery you want the latest version of it is recommended.
If you can take them all from the same CDN all the better (ie: Google's) especially as http2 is coming.
Additionally they save you bandwidth, which can amount to a lot when you have high loads of traffic, and can reduce the load time for users far from your server (Google's is great for this).
In the past, when I checked the site speed in google page speed or many similar tools, the site got very high scores (good css & js optimize). I installed the Advanced CSS/JS Aggregation module and boost module to get high score.
Then, suddenly, I started to get message on the google page speed (and other tools), saying my server response time is slow - around 3 seconds.
My site built with Drupal 7 and hosted on Bluehost Shared hosting.
Bluehost technical support says that the problem is not in their side
What do you think causing the server to be slow?
How can I fix it?
Or at least, what should I check (images, caching, something else)?
The first thing to figure out is what's a desirable response time. For example, if you have lots of modules and pretty heavy site/homepage then maybe 3 seconds is ok unless something is done to change the processing time(caching, using less modules etc).
Back to your case of where should i check:
Check, your homepage and what views and other things are loading for your homepage to be rendered. Then make a list and go one by one to ask:
Is it optimal/can it be improved? maybe something is throwing the caching out(dynamic parameters be injected by each request for the item etc).
If you're using views, enable the sql view to see what sql statements its using and you can use tools to analyze/improve it(this could be a question by itself)
Look at the modules that load/being used to make sure you need them.
Check on the drupal caching(/admin/config/development/performance) and make sure the correct checkboxes are checked.
This could as well be blue host's problem because if they're hosting so many sites on the server, the server will start kicking some sites out of memory and load them back as they're requested by the visitors hence the slow load(server requests the site, drupal loads it from database etc).
You can ask specific questions after you check those.
I am trying to reduce the latency on site goldealers.co.uk
The site appears to have a latency of anywhere between 950ms and 1500ms.
I have checked:
Processes
RAM usage
HTTP connections
Ping
Removing ALL plugins
Removing plugins doesn't make the slightest bit of difference.
The server is a VPS Cloud Server with dedicated 1.5ghz processor and 1GB RAM.
My question:
Is latency a server / programming problem?
Do wordpress sites generally have a high latency?
I have checked the latency on Forbes.com (a wordpress site) - This only has a latency of 151ms!!!
I will soon be working on caching, adding expires headers, possibly using a CDN for images etc... but to be honest, there is no point if it takes over 1 second to even start to return any data.
Any advice that you can provide is much appreciated.
Your analysis and priority are correct - starting with the base page load time first, then later optimizing the remaining front-end components.
In general WordPress sites by default can be a bit slow to deliver the HTML pages. Times in the range you mentioned 1-1.5 seconds are not uncommon. (For comparison, an unoptimized WordPress site I run is in the 1-3 second range.)
I would look into two areas:
Basic speed on that host
Database query speed
It could be that your webhost does not have a very fast connection. You can test this (and eliminate the WordPress part of the equation) by fetching a static file. On your site, for example, I can pull the robots.txt file down in about 0.3 seconds. The speed to serve a static file is about your minimum baseline.
Next I would look at the MySQL database query speed. Is MySQL being served on the same host or a different one? The Debug Queries plugin can show you the exact queries being made and performance for each. If the DB queries appear to be the problem, the DB Cache Reloaded plugin can sometimes be helpful. It adds an additional layer of caching for frequent DB calls.
There are also some good suggestions in the answers to this SO question: How can I figure out why my site pages load so slowly?
Your latency is almost certainly a server-related issue. You said you have a VPS and most VPS installations come with all Apache modules enabled - all of which you DO NOT NEED for Wordpress.
Eliminating all of the modules you don't need reduces how much memory each PHP instance will consume.
I've answered this question here on stack overflow: How can I figure out why my Wordpress pages load so slowly?
When I took a look at your site I saw that a lot of time is being killed on Facebook widgets. Testing from different locations around the world, looks like you are losing 2-3 seconds just for the facebook widgets. Drop those and you will have a much faster site.
I was studying about browser performance when loading static files and this doubt has come.
Some people say that use CDN static files (i.e. Google Code, jQuery
latest, AJAX CDN,...) is better for performance, because it requests
from another domain than the whole web page.
Other manner to improve the performance is to set the Expires header
equal to some months later, forcing the browser to cache the static
files and cutting down the requests.
I'm wondering which manner is the best, thinking about performance and
if I may combine both.
Ultimately it is better to employ both techniques if you are doing web performance optimization (WPO) of a site, also known as front-end optimization (FEO). They can work amazingly hand in hand. Although if I had to pick one over the other I'd definitely pick caching any day. In fact I'd say it's imperative that you setup proper resource caching for all web projects even if you are going to use a CDN.
Caching
Setting Expires headers and caching of resources is a must and should be done 100% of the time for your resources. There really is no excuse for not doing caching. On Apache this is super easy to config after enabling mod_expires.c and mod_headers.c. The HTML5 Boilerplate project has good implementation example in the .htaccess file and if your server is something else like nginx, lighttpd or IIS check out these other server configs.
Here's a good read if anyone is interested in learning about caching: Mark Nottingham's Caching Tutorial
Content Delivery Network
You mentioned Google Code, jQuery latest, AJAX CDN and I want to just touch on CDN in general including those you pay for and host your own resources on but the same applies if you are simply using the jquery hosted files cdn or loading something from http://cdnjs.com/ for example.
I would say a CDN is less important than setting server side header caching but a CDN can provide significant performance gains but your content delivery network performance will vary depending on the provider.
This is especially true if your traffic is a worldwide audience and the CDN provider has many worldwide edge/peer locations. It will also reduce your webhosting bandwidth significantly and cpu usage (a bit) since you're offloading some of the work to the CDN to deliver resources.
A CDN can, in some rarer cases, cause a negative impact on performance if the latency of the CDN ends up being slower then your server. Also if you over optimize and employ too much parallelization of resources (using multi subdomains like cdn1, cdn2, cdn3, etc) it is possible to end up slowing down the user experience and cause overhead with extra DNS lookups. A good balance is needed here.
One other negative impact that can happen is if the CDN is down. It has happened, and will happen again. This is more true with free CDN. If the CDN goes down for whatever reason, so does your site. It is yet another potential single point of failure (SPOF). For javascript resources you can get clever and load the resource from the CDN and should it fail, for whatever the case, then detect and load a local copy. Here's an example of loading jQuery from ajax.googleapis.com with a fallback (taken from the HTML5 Boilerplate):
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js"></script>
<script>window.jQuery || document.write('<script src="js/vendor/jquery-1.8.2.min.js"><\/script>')</script>
Besides obvious free API resources out there (jquery, google api, etc) if you're using a CDN you may have to pay a fee for usage so it is going to add to hosting costs. Of course for some CDN you have to even pay extra to get access to certain locations, for example Asian nodes might be additional cost then North America.
For public applications, go for CDN.
Caching helps for repeated requests, but not for the first request.
To ensure fast load on first page visit use a CDN, chances are pretty good that the file is already cached by another site already.
As other have mentioned already CDN results are of course heavily cached too.
However if you have an intranet website you might want to host the files yourself as they typically load faster from an internal source than from a CDN.
You then also have the option to combine several files into one to reduce the number of requests.
A CDN has the benefit of providing multiple servers and automatically routing your traffic to the closest location to your client. This can result in faster delivery, optimized by location.
Also, static content doesn't require special application servers (like dynamic content) so for you to be able to offload it to a CDN means you completely reduce that traffic. A streaming video clip may be too big to cache or should not be cached. But you don't neccessarily want to support that bandwidth. A CDN will take on that traffic for you.
It is not always about the cache. A small application web server may just want to provide the dynamic content but needs a solution for the heavy hitting media that rarely changes. CDNs handle the scaling issue for you.
Agree with #Anthony_Hatzopoulos (+1)
CDN complements Caching; also in some cases, it will help optimize Caching directives.
For example, a company I work for has integrated behavior-learning algorithms into its CDN, to identify and dynamically cache generated objects.
Ordinarily, these objects would be un-Cachable (i.e. [Cache-Control: max-age=0] Http header). But in this case, the system is able to identify Caching possibilities and override original HTTP Header directions. (For example: a dynamically generated popular product that should be Cached, or popular Search result page that, while being generated dynamically, is still presented time over time in the same form to thousands of users).
And yes, before you ask, the system can also identify personalized data and very freshness, to prevent false positives... :)
Implementing such an algorithm was only possible due to a reverse-proxy CDN technology. This is an example of how CDN and Caching can complement each other, to create better and smarter acceleration solutions.
Above those experts quotes, the explanation are perfect to understand CDN tech and also cache
I would just provide my personal experience, I had worked on the joomla virtuemart site and unfortunately it will not allow update new joomla and virtuemart version cause it was too much customised fields in product pages, so once the visitor up to 900/DAY and lots user could not put their items in their basket because each time to called lots js and ajax called for order items takes too much time
After optimise the site, we decide to use CDN, then the performance is really getting good, along by record from gtmetrix, the first YSlow Score was 50% then after optimise + CDN it goes to 74%
https://gtmetrix.com/reports/www.florihana.com/jWlY35im
and from dashboard of CDN you could see which datacenter cost most and data charged most to get your improvement of marketing:
But yes to configure CDN it has to be careful of purge time and be balancing numbers of resource CDN cause if it down some problem you need to figure out which resource CDN cause
Hope this does help