How to Enable Two-Factor Auth (2FA) for WordPress

When running a WordPress site, security should be first and foremost at the front of your mind. One of the best ways to prevent malicious users from accessing your /wp-admin area is enabling two-factor auth (2FA) for WordPress.

The easiest way to enable two factor auth for WordPress is the use the Wordfence Security plugin freely available on the WordPress plugin directory.

Installing Wordfence

The first step to getting two-factor auth enabled for your WordPress site is to install Wordfence. To do that:

  1. Log in WordPress and go to Plugins.
  2. Click “Add New”.
  3. Search for “Wordfence”
  4. Install and activate Wordfence
Showing Wordfence installed in the WordPress admin.
Wordfence installed

Configuring Wordfence

Now that Wordfence is installed you’ll need to enable and configure two-factor auth. To do that click the “Wordfence” menu that appeared after activation and then go to the “Login Security” sub-menu.

Wordfence 2FA activation screen.
Login Security (local site, not this one)

Now you’ll need to choose two factor authentication. I personally use FreeOTP (iOS, Android). Once your authenticator application is installed, scan the code and create the authenticator entry on your phone. Be sure to download your recovery codes too, just in case your phone is bricked, lost, or otherwise unavailable.

Testing Two-Factor Auth Out

Now that two-factor authentication is enabled for your WordPress site, you need to try it out! Log out of your admin, and now when you log back in you’ll be presented with this screen:

Wordfence 2FA code entry
Two Factor Auth enabled

Go to your authenticate app, press the entry for your site, enter the code, and log in!

Conclusions

Wordfence makes is really easy to set up 2FA on WordPress. With it being this easy, it’s hard to justify not having it. After all, even if someone manages to get your password they still won’t be able to log in unless the can compromise your phone too. If you’re worried about performance, this feature of Wordfence doesn’t effect your site’s performance in a meaningful way (which can not be said about Wordfence’s other features). All in all, the Wordfence team has done a great job making this level of security accessible to the wider WordPress community.

Need automatic updates for your premium plugins & themes? Check out Kernl.

UpCloud WordPress Hosting Review

If you spend time in the WordPress hosting space and few names constantly come up, and one of them is UpCloud. UpCloud is a European cloud provider with data centers all over the world that claims to have the world’s “fastest cloud servers”. In this review we’re going to take a look at how WordPress performs while hosted on UpCloud and also see how the reliability of the service is.

Want to run your own WordPress load tests? Sign up for Kernl.

Hardware Tested

For our test of WordPress running on UpCloud, we tested 3 different hardware configurations.

  • 1vCPU + 1GB RAM – This is the cheapest possible option for hosting WordPress on UpCloud at $5 / month.
  • 2vCPU + 4GB RAM – At $20 / month, this option is a nice balance of processing power and memory. If I were to host a few sites on UpCloud with moderate amounts of traffic I would probably start here.
  • 4vCPU + 8GB RAM – This machine was as expensive as I was willing to go for this review, coming in at $40 / month.

Software Used

The software used in this test was the latest available from the included repositories with Ubuntu 20.04.

  • Ubuntu 20.04 LTS
  • MariaDB
  • Nginx
  • PHP-FPM 7.4
  • Memcached

What was tested?

For each test we ran on UpCloud we used Kernl’s WordPress Load Testing service to generate load against each virtual machine. The content for the load tests was a copy of this blog. The load generators for each test lived in DigitalOcean’s SFO2 data center and ran against UpCloud’s Chicago data center.

UpCloud WordPress Load Tests

We ran a total of 6 WordPress load tests on UpCloud’s servers. For each machine we tested we ran a test where nothing was cached and a test where everything was cached (using W3 Total Cache backed by Memcached). Each test was for 1000 concurrent users for 45 minutes.

1vCPU + 1GB RAM (No Cache)

For this configuration the requests per second peaked at around 41/s before failure rates started to increase. Once failures started in earnest, successful requests leveled off at around 11/s.

UpCloud 1vCPU 1GB RAM - Requests/Failures
Not bad for no caching!

On the response time front, things weren’t great. As the request (and error) rate increased, the response times started to get pretty unwieldy.

UpCloud 1vCPU 1GB RAM - Response Time
Less than a 1000ms, then 2500-3000

A graph of median and average response times doesn’t always tell the whole story, so lets take a look at the response time distribution.

UpCloud 1vCPU 1GB RAM - Response Time Distribution
No great.

The response time distribution tells us that 50% of requests finished in under 5000ms, but that 99% finished in under 6000ms. Usually you want to see a large difference between 50th and 99th percentile. But here they’re awfully close, meaning that most request response times were pretty terrible.

1vCPU + 1GB RAM (Cached)

Now that we’ve looked at uncached performance, lets take a look at how this UpCloud server handled WordPress with caching enabled.

UpCloud 1vCPU 1GB RAM Cached – Requests/Failures Per Second

As you can see, performance is much better. We end up leveling off at around 436 request per second. The only issue here is that we still have quite a few failures. Certainly more failures than would be acceptable in a production situation.

UpCloud 1vCPU 1GB RAM Cached – Average / Median Response Time

Looking at response times you can see performance is a lot better, and much more in line with what you’d expect from a WordPress site that’s under heavy load. Average response time was a hair less than 1000ms, with the median response time (doesn’t include outliers) closer to 475ms. This is a bit less than an order of magnitude improve in performance just be turning on caching with W3 Total Cache.

UpCloud 1vCPU 1GB RAM Cached – Response Time Distribution

So far everything looked great (with the exception of the request failures) for this UpCloud configuration with caching enabled. However if we take a look at the response time distribution you can see that all is not what it seems. 80% of requests returned in less than 600ms, but the upper 20% too anywhere between 3000ms and 12000ms. 20% of your customers waiting more than 3 seconds for the page to load isn’t awesome.

2vCPU + 4GB RAM (No Cache)

The next machine we tested was far better provisioned than the first machine with twice the CPUs and 4x the RAM.

UpCloud 2vCPU 4GB RAM - Request / Failures per Second

As you can see request throughput peaked at around 50 per second, and then leveled off at 22 per second when the error rate elevated. I honestly expected the throughput to be better for this scenario given how much more hardware there was to work with.

UpCloud 2vCPU 4GB RAM - Average / Median Response Times

Response times slowly increased as load increased on the server, with average response times ending up near 5000ms and the median response times closer to 5500ms. At that point, 500ms probably doesn’t matter that much.

UpCloud 2vCPU 4GB RAM - Response Time Distribution

The response time distribution for this test was predictably bad. The difference between the lower 50% and upper 50% is only 1000ms, which doesn’t give me warm fuzzy feelings. If anything, this is a great example of how much you need caching in a WordPress installation. Throwing twice as much hardware at it barely even makes a difference uncached.

2vCPU + 4GB RAM (Cached)

Now lets take a look at the same machine, but this time with caching enabled via W3 Total Cache and Memcached.

UpCloud 2vCPU 4GB RAM Cached – Requests / Failures per Second

No we’re getting somewhere! Requests per second leveled out at around 600, which is actually quite high. We also didn’t start to see failures increase until around 300 per second, which is pretty amazing for a $20/month machine.

UpCloud 2vCPU 4GB RAM Cached – Average / Median Response Time

The response times for the cached version were pretty great until the failure started accumulating. Up until the failures started we were seeing response times right around the 60ms mark, which is excellent under heavy load. After that they leveled out at around 450ms, which still isn’t bad when you are serving ~600 requests/s.

UpCloud 2vCPU 4GB RAM Cached – Response Time Distribution

The response time distribution wasn’t terrible here either considering all the failures we were seeing. 95% of requests finished in under 1000ms and 50% finished in under 500ms.

4vCPU + 8GB RAM (No Cache)

Our final test was with a fairly robust machine (by my standards anyway).

4vCPU 8GB RAM – Requests / Failures Per Second

As you can see the results in an uncached situation were pretty solid until failures started in a major way. This machine was able to handle about 175 req/s uncached, and then leveled out at 215 req/s once the errors started. Obviously this number of errors isn’t great, but at the 175 req/s mark thats enough to serve 15 million requests a day.

UpCloud 4vCPU 8GB RAM – Average / Median Response Times

As expected in an uncached situation the response times weren’t great, but they weren’t terrible either given the amount of load the system was under. Prior to elevated error rates we were seeing response times around 100ms. Once errors picked up they leveled off at 2500ms.

4vCPU 8GB RAM – Response Time Distribution

The response time distribution is what we would expect from an uncached WordPress installation under heavy load. 50% of requests finished in 2500ms and 99% of requests finished in 3250ms. That’s not all bad considering there wasn’t any caching.

4vCPU + 8GB RAM (Cached)

Our final load test was a cached version of the previous test. Given drastic improvements we saw in the other tests, the same sort of results were expected here.

4vCPU 8GB RAM Cached – Requests / Failures Per Second

Now that we have a more robust machine + caching enabled, you can see that the server was able to process quite a few requests concurrently before errors started. Even once errors started they stayed relatively low. Initial errors didn’t show up until around 500 req/s and eventually we leveled off at 850 req/s. Not bad for $40/month.

4vCPU 8GB RAM Cached – Average / Median Response Times

The response times were also excellent in the cached scenario. Before errors and failures we were seeing 65ms and after we were stilling coming in at around 100ms. Not too shabby for the intense load the server was under.

UpCloud 4vCPU 8GB RAM Cached – Response Time Distribution

My favorite chart this time around is the response time distribution. 99% of all requests finished in under 300ms. With 1000 concurrent users.

UpCloud WordPress Reliability

An often overlooked metric when comparing VPS providers like UpCloud is reliability. To get some objective numbers on that, I ran a reliability test with Kernl for 30 consecutive hours. The test is low volume (25 concurrent users), but enough to make sure the server stays active and that we’ll notice is sometimes goes awry.

Reliability test

Over the course of 30 hours we saw one error spike that was quickly resolved. After that, no errors at all. Over the entire test we saw 400 requests fail, which is roughly 16 seconds of failures. I’ve done quite a few of these reliability tests with different hosts and this is pretty average.

Conclusions

UpCloud is solid choice for VPS hosting though their claim to be the “fastest” may not be completely substantiated (with WordPress at least). If I wanted to use a VPS host based in Europe they would definitely be near the top of my list. The only odd thing about them is their billing model where you add “credits” to your account versus just having a credit card of file. This is likely to prevent fraud, but doesn’t really make for a great user experience.

Vultr One-Click WordPress Review

If you want to host your own copy of WordPress but don’t want to go through all the trouble of setting it up, it might be worth your time to explore using “one-click” installs from some of the major cloud providers. In this article, we’re going to explore the Vultr One-Click WordPress install and see what it’s all about.

Ease of Installation

Before anything else you need to get a WordPress box spun up on Vultr. Overall, the experience was pretty easy:

  1. Log in / sign up for Vultr
  2. Click “Deploy new server”
  3. Select your server type (we used “Cloud Compute”) and server location (Atlanta for us).
  4. Click the “Application” tab and then select WordPress.
  5. Select your server size (25GB SSD $5/month for this test)
  6. Add your SSH key
  7. Fill out your host name
  8. Click “Deploy Now”

So obviously this isn’t a single click to install, but it is a lot easier than setting up and configuring a WordPress installation from scratch.

Whats included?

Aside from the obvious stuff (WordPress, MySQL, etc) which we’ll cover in the next section, what else is included with your One-Click Vultr WordPress installation?

  • XHProf – XHProf is a tool for profiling PHP applications. This could be very helpful if you find your site getting real slow after installing a plugin or theme. It could help you determine the source of the slowness.
  • PHPMyAdmin – The classic MySQL database administration tool for the web. If you haven’t used it before, its a great way to browse your database and make changes.
  • Maldet – Maldet is a Linux malware detection tool that runs periodically on your system to see if it has been infected. This is disabled by default, but can easily be enabled with the directions included with your new server.
  • Cockpit – Cockpit is a web based interface for your server. You can easily see how your server is configured, what resource usage looks like, and update packages all without even SSHing into your server.

What’s WordPress Running On?

The Vultr One-Click WordPress system that we decided to use had the following hardware and software:

  • Hardware
    • 1 vCPU
    • 1GB RAM
    • 25GB SSD
    • 1TB Bandwidth
  • Software
    • Ubuntu 18.04 LTS
    • Nginx
    • PHP 7.2
    • MySQL 5.7

Overall the software is a pretty standard LEMP setup and the hardware is as performant as you would expect for $5 per month. It’s also worth noting that the installation script for this one click install might need some updating because it installs the previous version of WordPress.

Performance Out of the Box

So you’ve spun up your new Vultr One-Click WordPress server, but what sort of performance can you get out of it? Using Kernl’s WordPress Load Testing we can easily see the performance that this $5 per month server gives you.

For both this test and the cached test (next section) we attempted to have 200 concurrent users browse the WordPress site for 30 minutes. The traffic was generated from Digital Ocean’s NYC3 datacenter.

Vultr One-Click WordPress Requests / Failures per second
Requests / Failures per second

As you can see we get up to about 20 requests per second before the server starts returning failures. For a $5 machine this isn’t bad at all. 20 req/s over the course of 24 hours is ~1.7 million requests.

Vultr One-Click WordPress Response Times
Response Times

Initially response times are pretty good, but as resource contention on the server increases the average and median response times start to go up. Even when under full load, the pages returned in under 5 seconds. Not terrible, but you definitely aren’t winning friends with that sort of performance.

Vultr One-Click WordPress Response Time Distribution
Response Time Distribution

The response time distribution is mostly what you would expect after seeing the error rate and the average response time. 99% of requests return in under 5.5 seconds. In general you want to see your 99th and 100th percentiles be low, but given the duress the server was under this isn’t surprising at all.

Overall the system performed well and was configured well enough to handle a small-ish load test.

Performance with Caching

The test above is almost silly in that most people will definitely be using some form of caching on their WordPress site. For a more realistic test, I enabled W3 Total Cache on the WordPress installation. There wasn’t any Memcached or Redis installation available, so all cache settings were tuned to “Disk (enhanced)”.

Requests / Failures per second

As you can see the difference in performance with caching enabled is quite good. We didn’t see any errors at all for the duration of the test and the maximum concurrent requests per second peaked at 160. Over a 24 hour period, that would be 13.8 million requests.

Average / Median Response Time

The response time over the course of the test was also quite good. Initially it hovered around 35ms on average, but as resource contention on the server increased it leveled out at around 140ms. Not too bad for $5 and nearly zero configuration.

Response Time Distribution

Finally we come to the response time distribution. You can see here that 50% of requests finished in under 100ms, 99% finished in under 700ms, and all requests finished by 1800ms. These are good numbers.

Final Thoughts

If you need to host a WordPress site and don’t want to much around with configuration, the Vultr One-Click WordPress service is pretty good. In the long-term you’ll still need to know a little about system administration to apply updates, but it is definitely a great place to start and gets you a lot of the way to a fully functioning WordPress site.

What’s New With Kernl – March 2020

With all the uncertainty in the world right now due to COVID-19, we are intentionally keeping things boring at Kernl. Bug fixes, new docs, and increased capacity are all we did this month.

Stay safe out there everyone!

Features, Bugs, Updates

  • NEW DOCUMENTATION! – After 5 years we finally moved to a real documentation generator! In the process of moving docs to the new system, all of the docs were updated and checked for accuracy. Check it out at https://docs.kernl.us.
  • Site Health – You can now change you wp-json root. Some people change this for security reasons. Site Health needs it for some of the more advanced functionality.
  • Site Health Timezone Bugs – Timezones are hard and our Site Health service wasn’t using them correctly.
  • Analytics VM Changes – The Kernl Analytics service was starting to get bogged down with increased traffic. It now has 2 vCPUs and 2GB of RAM (up from 1 vCPU and 1GB).
  • Analytics Bug – We were logging analytics data for customers that aren’t paying for it. This is no longer the case.
  • Plugin/Theme Git Status – The plugin and theme list pages were displaying inconsistent results for the Git status of plugins/themes. There was an error in our Mongo query that populated this data which has been resolved.
  • Load Testing Remain Resources – The remaining resources page can take a while to load sometimes because we have to call out to external services. An indeterminate loading spinner was added to let customers know that it’s still working.
  • System Updates – All operating system level packages have been upgraded to their latest available version.
new documentation by docsify
New documentation by Docsify

What’s New With Kernl – February 2020

I hope everyone had a great February! We didn’t too much feature development this month, but there was a lot of bug fixing and performance improvements, so let’s dive in!

Feature, Bugs, and Performance

  • Node.js – Kernl is now on Node.js 12.16.1. This release was all about security fixes.
  • Load Testing Machine Provisioning – We weren’t calculating the correct number of machines to provision on DigitalOcean. This lead to some serious over-provisioning when running load tests. This has been resolved, which means more customers can run more load tests at the same time.
  • Load Testing Secondary Node Behavior – Kernl uses Locust under the covers to run our WordPress Load Testing service. The Locust primary node has an argument called “–expect-slaves”. It tells Locust “Don’t start the load test until at this this many secondary nodes have connected.”. We weren’t calculating this number correctly which led to some weird behavior. This is now resolved so load tests should start in every situation now.
  • Easy Digital Downloads Domains – Kernl wasn’t passing the domain along to EDD. We now do this, which allows you to restrict updates to specific domains while using EDD.
  • Load Testing Snapshots – Kernl used to build up each load testing machine from the ground up every time a load test was started. We now start from a snapshot that gets us 50% of the way there. This has improved load test start times (especially on large tests) by an average of 30%.
  • GitHub Authorization Changes – The GitHub API is changing how it handles authorization headers. We’ve update Kernl to handle this change, so we’ll be good going forward when GitHub deprecates the old method.
  • High Traffic Endpoint Audit – We did an audit of our high-traffic API endpoints and cleaned some things up. Slight performance improvements were had (1%-2%), but mostly the improvements have been in code readability and comprehension.
  • GitLab Deployment Issues – In a recent release of GitLab they changed the required fields when asking for an access token via a refresh token. This broke all GitLab deployments for Kernl for a few days while we tracked down the issue. This has since been resolved.
  • Load Testing Unit & Integration Tests – When our load testing service was launched we weren’t sure if it was going to be successful. We’ve proven that it is a worthwhile feature, so now we’re focusing on reliability. We’re in the process of adding a suite of unit and integration tests around this functionality.

That’s it for this month! See you in March.

Should I use Memcached or Redis for WordPress caching?

Choosing between Memcached or Redis for your WordPress cache is a tough decision. Not because they have vastly different performance profiles (they don’t), but because either choice is a good one depending on your needs. In this post we’re going to explore the differences between Redis and Memcached, how they perform for WordPress, and a lot of different non-performance things you should consider when making your choice.

What is Memcached?

memcached logo

Memcached is an open-source, high performance, distributed memory object caching system. What does that mean? It means you can store a bunch of strings in memory and access them really fast. From a WordPress perspective, it means that using a caching plugin like W3 Total Cache we can store the results of the complicated SQL queries that WordPress does in memory and have them available instantly.

What is Redis?

Redis Logo

Redis is an open source in-memory store that can be used as a cache or a message broker. It’s a bit different then Memcached because you get a lot more out of the box with it. For example, Redis has built in replication, transactions, disk persistence, and provides high availability and partitioning. All those features means that managing WordPress can be a little harder to do, but not much harder. Especially if you just need to use it as a cache.

Performance

Both Redis and Memcached have excellent performance. They’re both used by some of the largest websites in the world and are fully ingrained in the Fortune 500. Given that all things are not created equal, let’s see how they perform with a read-heavy WordPress site (this blog).

The Setup

The load tests are performed against the DigitalOcean WordPress Marketplace image with either Redis or Memcached installed alongside of it. The machines have 2 vCPUs, 2 GB RAM and live in DigitalOcean’s SFO2 (San Francisco) data center.

The load test configuration:

  • 500 concurrent users
  • 2 users / second ramp up
  • 45 minute test ( ran twice )
  • Traffic comes from Digital Ocean’s NYC3 data center.

The content of the load test is a copy of this blog.

Baseline Performance (No Cache)

The baseline performance for WordPress with no cache isn’t great.

baseline requests/failures
50 requests / second with LOTS of failures

The response time also isn’t great. A little over 2 seconds on average.

baseline response times
~2 seconds response time on average.

Redis Performance

Once we install Redis and configure W3 Total Cache to use it, the number of requests that we can handle increases substantially.

redis requests/failures
300 requests per second

The requests remain steady at around 300 per second and no failures are recorded. The response time also improves quite a bit.

redis response times
Average ~475ms response time

475ms isn’t bad at all. That’s 4 times faster response times then without any caching at all.

Memcached Performance

With Memcached installed and W3 Total Cache configured to use it, we see some excellent performance.

memcached requests/failures
425 requests per second

In this situation, Memcached performs even better then Redis with 425 req/s versus Redis’ 300 req/s. Response time improvements are similar.

memcached response times
115ms response time

The Memcached response time is almost 3 times faster than the Redis response time. In general, the results where Memcached is faster than Redis are surprising. In most benchmarks Redis is equal or faster than Memcached, so it’s likely a configuration problem.

Other Considerations

When deciding what cache to use with your WordPress setup, there are a few other considerations your should be looking at:

  • Ease of setup – As you can see from the performance results above, Memcached has better performance out of the box. Knowing what I know about Redis this is likely a configuration issue, but the fact that I could get that level of performance with no configuration from Memcached is a good data point.
  • 3rd Party Hosting – Do you really want to manage your own Redis or Memcached server? If you don’t, you’ll want to look at the landscape of 3rd party providers. Redis has a robust provider ecosystem. Memcached’s is a little less robust.
  • Persistence – Do you need your cache to survive a reboot? This is important if the cost of re-populating your cache is too high for your system. If you do need persistence, Redis is your best option.
  • High Availability If you need high availability of your caching cluster, Redis is the clear winner here. Memcached can be made to operate this way, but Redis has it baked in to the core of the application.

If you’d like to see the full results of the load testing runs on Kernl, see the links below.

The Crucible – Extreme WordPress Performance Challenge

Load testing is fun. Breaking things is fun. Breaking WordPress with load testing is even more fun. But in the era of highly scaleable WordPress hosting solutions, can we even break WordPress anymore? Oh yes, yes we can. The Crucible Challenge can.

Crucible Challenge

The Crucible WordPress Performance challenge is a deceptively simple test inspired by the poor ops teams that have to handle traffic from Super Bowl advertisements. Given a WordPress site with consistent content and URL mappings:

  • Handle 50,000 (@ 500 per second ramp up) concurrent authenticated users for 2 hours with load test generators in New York, London, Amsterdam, Singapore, Bangalore, San Francisco, Toronto and Frankfurt.
  • Have an error rate below 0.1%.
  • Average response time should be below 800ms.
  • Median response time should be below 700ms.
  • 99th percentile response time should be below 800ms.
  • Half way through the test, you must flush your cache.

Simple, yes. Easy, no. Why is this hard?

  • 50,000 is a LOT of people.
  • 500 per second ramp up does not give any time for warming your cache. It’s like your site getting hit in the face with a sledgehammer.
  • Low error rate doesn’t give you a lot of room for problems.
  • Keeping your response times below 1000ms with traffic coming from all over the world presents interesting problems.
  • Flushing your cache after the load test is already in progress shows us you have a good cache invalidation strategy and can handle dog-piling.

Example Results

To give everyone an idea of what results might look like, I took at $160 / month CPU Optimized Digital Ocean droplet, put Open LiteSpeed + WordPress on it and ran The Crucible against it.

Shows the crucible request per second graph at 18,000 requests per second.
18,000 requests per second

I only ran the test for 2 minutes, but as you can see it started to max out near the 18,000 req/s mark, with failures in 1,800 failures/s area.

Can your service beat this? Want to find out? Drop an email to jack@kernl.us and we can get a test run scheduled.

What’s New With Kernl – January 2020

January was a pretty great month for Kernl. We got a lot of bug fixes, some performance improvements, and even a new beta feature out the door. Let’s dive in!

WordPress Site Health Beta

This month we released a beta of our WordPress Site Health service. The goal of this service is to help you determine where performance problems are and why they are happening. The dashboard below gives you a high level view of how performance looks on each of your sites.

Kernl WordPress Site Health

Once you click in to any site you see data for the last 7 days.

Kernl WordPress Site Health Detail Page

The data here helps you diagnose performance issues. Using the plugin changes panel you can tie performance issues back to adding/removing/updating of plugins. Google Lighthouse scores show trends on you site’s performance, usability, SEO and more over time.

If you’d like the join the beta, send an email to jack@kernl.us.

Bugs & Performance

  • Improved performance of plugin/theme list pages – The API calls to /api/v1/plugins and /api/v1/themes were incredibly inefficient. They hadn’t really been touched since Kernl’s inception and needed some love. After doing some query optimization and stripping out unnecessary data, the payload and response time were reduced by a factor of 10. The worst case example was response size going from ~750KB to ~75KB and response time from ~4000ms to ~250ms.
  • Server resource increases – Kernl’s main Node.js application servers have been running with 1 vCPU and 1GB of RAM for about the last 2 years. Lately we’ve seen some resource exhaustion and decided it was time to upgrade. The new app servers now run with 2 vCPUs and 2GB of RAM.
  • Server disk space / inode exhaustion – The process of building plugins and themes can use up a lot of space and file system resources. We weren’t doing a great job of cleaning those resources up periodically which could cause some performance issue. We now clean up all temporary files once a day which should prevent this from happening anymore.
  • Easy Digital Download License Validation Error – There was a bug in EDD license validation where the source system wouldn’t send back valid JSON. This would break license validation instead of handling the error gracefully.
  • Profile page autocomplete – If you had form auto-completion on it would sometimes cause the profile page to reset your password. We’ve disabled autocomplete on this form to resolve the issue.
  • Theme tiles not showing correct build status – During the course of our performance improvement work we noticed that theme tiles were not showing the correct build status. This has now been resolved.

Yoast SEO: WordPress Plugin Performance Implications

Yoast SEO is a popular SEO enablement plugin for WordPress. It helps you avoid common mistakes when it comes to SEO on your blog and also handles things like social media “og:meta” tags. If your blog has a public audience, then it stands a good chance that you are using Yoast.

As with the previous article in this series, we’ll focus on what performance implications are of using Yoast and how you can make it faster.

What was tested?

For this test we used the lowest-tier (1vCPU, 1GB RAM, $5) DigitalOcean droplet out of their SFO2 datacenter. Our server setup was as follows:

  • Ubuntu 19.04 with all updates installed.
  • Nginx 1.16.1
  • PHP-FPM 7.3
  • MariaDB 10.3

The theme that was used was TwentyTwenty with no modifications and the content tested was 3 “What’s new with Kernl?” posts from earlier this year. We selected a small number due to the effort of filling out all of the SEO data in Yoast.

The WordPress setup was bare-bones. There were no plugins installed except for when we were running the Yoast test.

As with our previous post in this series, the load for this test was generated out of DigitalOcean’s NYC3 datacenter.

Test Methodology

For testing Yoast we only ran two tests:

The tests were with 200 concurrent users over the course of 1 hour.

Max Requests per Second

One method for determining website performance is what is the maximum number of requests that in can field in a given second. For our purposes this is a pretty good indicator of the performance hit you take for installing plugins.

Yoast SEO - Max Requests / Second
Higher is better.

As you can see from the image above you lose about 25% of your maximum capacity from installing Yoast SEO. With no plugins installed we were able to hit 43 req/s, while with Yoast installed that number went down to 30 req/s.

It’s worth noting here that 30 req/s is 2.5 million requests a day.

First Error Occurrence

The next chart shows when we first started to see errors in our two tests.

Yoast SEO - First Error Occurrence
Higher is better.

Without the plugin installed WordPress was able to hit 38 req/s before seeing errors. Once we enabled Yoast that number went down to 28 req/s. Once again, this is consistent with the performance penalty we saw with the maximum requests per second of about 25%.

Average Response Time

The average response time with and without Yoast SEO tells a similar story to the requests per second measures we have done.

Yoast SEO - Average Response Time
Less is better.

The chart above shows us that without any plugins installed, the average response time under load is around 3000ms. With the Yoast plugin installed the response time goes up to about 4300ms. We’re looking at a roughly 25% change in response time.

99th Percentile Response Time

The 99th percentile chart can be read as “99% of all requests finished in under this time”.

Yoast SEO - 99th Percentile Response Time
Smaller is better.

The chart above tells us that without any plugins installed 99% of our requests finished in under ~3600ms. With Yoast SEO installed 99% of our requests finished in ~4900ms. Once again, a roughly 25% penalty for having Yoast installed.

Yoast SEO Performance Conclusions

Yoast is a really good SEO plugin. If SEO matters to you it’s definitely a plugin you should have installed. However you should use caching if you do use it. This goes for WordPress in general, but every plugin you add to WordPress has a performance cost associated with it. If you run a site where caching is difficult you’ll have to carefully weigh the performance cost versus benefit of installing Yoast SEO.

WordPress Plugin Performance Implications: Wordfence

In the world of WordPress there are a lot of different plugins you can install to extend its functionality. One of the most popular plugins is Wordfence, a security plugin developed by the fine folks over at Defiant.

Test the performance implications of your own WordPress plugins with Kernl WordPress Load Testing.

Most WordPress developers understand that the more plugins you add to your site the slower it goes, but exactly how much slower isn’t something that is often measured. More importantly, nobody has bothered to figure out the performance implications of installing many of the most popular plugins available to WordPress users today.

This all changes now with this series of blog posts exploring the performance implications of different WordPress plugins. In this series of posts we’ll test each plugin in isolation and then with caching enabled using Kernl’s WordPress load testing service. First up, is Wordfence.

Machine Setup

The test machine for these tests was a $5 Digital Ocean droplet in their SFO2 (San Francisco) data center. The machine has 1GB of RAM, 1 vCPU, and a 25GB hard disk.

The software installed on the machine is as follows:

  • Ubuntu 19.04 with all updates installed.
  • Nginx 1.16.1
  • PHP-FPM 7.3
  • MariaDB 10.3

For tests that required caching we used our favorite caching plugin, W3 Total Cache, with memcached as the data store.

The theme that was used was TwentyTwenty with no modifications and the content was an export of this blog.

All traffic was generated out of Digital Ocean’s NYC3 (New York City) data center.

Test Methodology

A series of 4 tests were run to test the performance implications of installing Wordfence. They were:

Each test was with 200 concurrent users for 1 hour.

Maximum Requests per Second

The first metric that we looked at was the maximum requests per second that the site was able to handle under each situation outlined above.

Wordfence - Maximum Requests per Second
Wordfence – Maximum Requests per Second

As you can see the difference between having Wordfence enabled and having Wordfence disabled is huge. The non-cached site with no plugins enabled handled a maximum of 26 requests per second. With Wordfence enabled it could only handle 12.

More interesting though was that with caching enabled (W3 Total Cache) the site could handle 165 requests per second, but only 67 requests per second with Wordfence enabled.

These results were so surprising that we ran the tests twice. The results were the same (within 1%-2%) each time.

First Error Occurrence

The next metric we looked at was when did the first error occur during our load tests.

Wordfence - First Error req/s
Wordfence – First Error req/s

Once again we see that adding Wordfence took a pretty serious toll on our performance. For the baseline test (no plugins, no cache) we see our first error at around 26 requests / second. In the Wordfence test with no cache we saw it at 12 requests / second.

With our caching enabled test, we never saw any errors when Wordfence wasn’t enabled. However with Wordfence enabled we saw our first error at 56 requests / second.

Average Response Time

Now that we’ve looked at server capacity metrics (max requests, first error), let’s take a look at how your end user experience changes with Wordfence enabled.

Wordfence - Avg. Response Time (milliseconds)
Wordfence – Avg. Response Time (milliseconds)

These results were fairly interesting and not at all what was expected. The average response time for the baseline test was around 4.6 seconds, while the average response with Wordfence enabled was about 2.5 seconds. So why might that be? Looking through the data it appears that the baseline test had far more successful requests and that with Wordfence enabled the requests seemed to fail faster. In short, baseline test had higher throughput but slower response time. The Wordfence test had lower throughput and faster response time.

Turning our attention to the caching scenarios, we can see that enabling Wordfence is extremely problematic at scale. With caching enabled, our baseline test had an average response time of 146ms. With caching + Wordfence that time ballooned over 10x to 1874ms.

99th Percentile Response Time

Our final metric was looking at the 99th percentile response times for our different scenarios. What does that mean? It answers the question “How long does it take for 99% of requests to finish?”. This intentionally leaves out the last 1% because those are often outliers.

Wordfence - 99th Percentile Response Time
Wordfence – 99th Percentile Response Time

As you can see above, the un-cached 99th percentile hovers right around 5s when Wordfence is enabled or disabled. Since this is the 99th percentile such a high response time isn’t too surprising in both scenarios.

The more interesting scenario is when caching is enabled. For WordPress with only a caching plugin running, the 99th percentile is 370ms. That means 99% of all requests finished in 370ms. With Wordfence also enabled (Wordfence + caching), that number jumped to 2400ms. That’s a ~7X increase.

Conclusions

From these tests we came to a few conclusions:

  1. Caching does not solve all of your performance problems. If your cache strategy relies on requests making it all the way through to WordPress, then you are very likely to still take a performance hit from other plugins. Things like Cloudflare, Varnish, Litespeed, or Nginx can help alleviate this problem.
  2. Running Wordfence is expensive from a performance standpoint. The data suggests that by simply enabling Wordfence you lose about 50% of your maximum capacity and can increase your response time between 2x-7x.
  3. Wordfence is still worth it for a lot of people. If you’ve operated a WordPress site for any length of time you know how often they get attacked. Wordfence does a great job of reducing attack surface area and making it hard for people to attack you.

Test the performance implications of your own WordPress plugins with Kernl WordPress Load Testing.