Welcome!

Open Source Cloud Authors: Zakia Bouachraoui, Yeshim Deniz, Liz McMillan, Pat Romanski, Elizabeth White

Related Topics: Agile Computing, Linux Containers, Open Source Cloud, Eclipse, Machine Learning , Apache

Agile Computing: Article

TraceView’s Oboe Symfony No. 1

The adoption of Symfony has already let it pull in some beautiful pieces of architecture

Dvořák’s Symphony No. 9 requires two oboes. Instrumenting Symfony only required one liboboe!

Here at AppNeta we’re still recovering from an immensely productive DrupalCon Portland 2013. Our partnership with Acquia and our continuing support for the contrib TraceView Drupal module made sponsoring the event a natural decision. We’re glad we made the long flight out West, as there was a lot of interest in TraceView. In fact, on the plane ride back to Boston I brought back not only three Voodoo Dozens but a stack of business cards two inches high. (I’ll leave it to you to guess which one ran out first!)

But for as much fun as I had exploring Portland’s unique culture, my favorite part of the con took place well before it. I spent a lot of time coding up improvements for TraceView’s Drupal support based on customer feedback. My personal goal was to submit enough patches to the TraceView Drupal module to warrant a version bump before DrupalCon, and thanks to the hard work of module maintainer Peter Drake, we were able to get there with room to spare. If you’re running Drupal 7, check out the changelog, and then go install it on your site!

The TraceView Drupal module now supports full-stack application tracing using drupal_http_request, including via the Apache Solr module.

I was able to code up more than just improvements in the months leading up to DrupalCon, though. If you stopped by our booth, you’ll have heard all about this, but we have a second important release to announce: we have a beta Symfony bundle and a (very!) preliminary port of our module to Drupal 8! While I had initially planned to just work on Drupal 6 and 7 improvements for TraceView, the announcement that Drupal 8′s SCOTCH and WSCII initiatives had resulted in the incorporation of Symfony components into Drupal 8 prompted me to take another look at what I’d lumped into ‘yet another PHP MVC framework’. It quickly became clear that I’d horribly misjudged Symfony. Drupal 8 hasn’t quite hit code freeze yet, but the adoption of Symfony has already let it pull in some beautiful pieces of architecture.

My favorite architectural decision in Symfony is its robust sub-request framework because of the degree of support that it lends to one of my favorite technologies, Edge Side Includes (ESI). Many large-scale sites leverage CDNs to deliver cached pages and static assets, but they don’t cope with logged-in users well because the content served to them is so heavily customized. ESI allows you to offload mostly cacheable pages to a CDN and only request the uncacheable portions of the page from the origin server, but it’s currently underutilized because most web frameworks can’t render just a portion of a page. In Symfony, though, any component of a page (such as a block or a sidebar) can be built as a sub-request for little additional developer effort. A year from now, large-scale Drupal 8 sites may entirely bypass common performance pain points by taking an ‘ESI Everywhere’ approach and leaving the CDN servers to do the work of assembling a dynamic page from a static cache entry.

Symfony had caught my interest, and my first instinct towards interesting software is to hack on it. That meant I had to create a Symfony site, so naturally, I chose Drupal 8 as a starting point. The codebase is still in flux, but it’s stable enough to install and it already makes use of several core Symfony components. All that I had to do to get an environment running was spin up an Amazon EC2 server, set up a LAMP stack and install TraceView (by far the fastest part of the process). The Drupal 8 installation required installing the trunk version of Drush, but after that I was only a `drush qd` away from a functioning Drupal 8 site.

I hit a wall fairly quickly, since like most Drupal developers I’d never tried writing Symfony code or using Composer to manage packages. Instead of getting frustrated, I took a step back and began to read articles about both Symfony in its own right and how it’s being leveraged to rewrite Drupal. I made heavy use of the Drupal core issue queue and the Symfony API documentation, but I also turned to blogs written by Drupal and Symfony developers. Of particular note, chx wrote an introduction to Symfony in two articles as well as an article that helped me fix my first Drupal 8 performance issue:

Every request to the Drupal 8 server triggered well over a hundred `file_get_contents` calls.

Before writing any integration code, I pulled up some Symfony traces because I was curious what they would look like. Even without code modification, TraceView picked up on Drupal 8 making a huge number of `file_get_contents` calls on each request. While individually fast, the calls often added up to more than 100ms; worse yet, that many disk reads has severe negative implications for scalability. At my last job, a sudden increase in traffic took down our entire distributed filesystem just by repeatedly fetching a single JavaScript file!

When I examined the `file_get_contents` calls in TraceView and realized they were all fetching module-related files, I immediately made the connection to Symfony’s dependency injection container (DIC) (one of its major design paradigms) thanks to another post by chx about how the DIC is stored on the filesystem. The filesystem calls were due to Drupal not finding the DIC on the filesystem and instead recompiling it using a dependency-checking mechanism similar to a package manager but made more complicated by the ability of classes to define additional compiler passes and other overrides. Like most problems I run into on Linux, I was able to trace it back to incorrect permissions:  because I had run Drush as a normal user, I had changed the permissions on the relevant directory and prevented the webserver from writing the compiled DIC so that it could be loaded on future requests. One `chown` later and my testbed site was running more than five times faster.

I kept an open mind to Symfony as I continued to read, but coming from the perspective of a Drupal developer, I was quite surprised to hear that the familiar hook-based event system has already been partially replaced with Symfony’s event listeners (bringing it more in line with some other PHP frameworks that we support). It’s new territory for me, but I can understand the rationale as there are some serious advantages to the switch. Unlike hooks, events don’t need to check every module on the site for an implementation; they can also have their propagation stopped if no further work is necessary. This means that developers will have much finer control over how modules respond to events, rather than having to use unusual hooks simply because they get called at the ‘right’ point in page loading (I’m looking at you, `hook_footer`!). Interestingly, a total switchover has been postponed until Drupal 9, which means that these overlapping systems will both remain in place for the foreseeable future.

The differences between Drupal hooks and Symfony event listeners were quite relevant to building out TraceView support, so I spent a lot of time reading about them. It’s there that I stumbled across another excellent addition to Drupal 8: the `terminate` kernel event! This import from Symfony is the replacement for the recently removed `hook_exit`, with the key difference being that it can be run after a response is returned to a browser. This lets expensive cache setting operations be performed in a way that won’t harm end user performance, emails be fired off only when the request is complete, or disk writes take place after an upload confirmation screen has been shown to the user.

It took about a month to get up to speed on Drupal 8 and Symfony to a degree where I felt ready to stop reading and start writing. That left me with about a month to go before DrupalCon, and in that time I was able to turn out not only the Drupal 7 module improvements but a really awesome DrupalCon booth demo!

The top tier of Drupalception included both our beta TraceView Drupal 8 module and our TraceView Symfony bundle.

I couldn’t think of any better way to show that we’re serious about our Drupal support than to demonstrate every version of Drupal we support at once, and so I built Drupalception: a Drupal 8 + Symfony AWS instance using cURL (via Guzzle) to call into our Drupal 7 demo site, which in turn uses drupal_http_request to call into our Drupal 6 demo site. TraceView catches the entire stack as a single trace even when blocking calls are nested fifteen layers deep!

But wait, aren’t I skipping a step – how did I get from reading a bunch of blog articles about Drupal 8 in Symfony to a functioning Drupal 8 module and Symfony bundle? Well, that’s a story in its own right – and for now, one that you’ll have to wait for another blog post for! Until next time, sign up for our 14 day trial and try out firsthand our support for Drupal 6, 7, or even 8 (or any other stack we support, for that matter).

Related Articles

Drupal Performance Profiling With Tracelytics

Headnet Improves Drupal Performance and Reliability With TraceView

Case Study: Penton Media Improves its Drupal Application Performance

More Stories By James Meickle

James started as a hobbyist web developer, even though his academic background is in social psychology and political science. Lately his interests as a professional Drupal developer have migrated towards performance, security, and automation. His favorite languages is Python, his favorite editor is Sublime, and his favorite game is Dwarf Fortress.

Comments (0)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


IoT & Smart Cities Stories
SYS-CON Events announced today that DatacenterDynamics has been named “Media Sponsor” of SYS-CON's 18th International Cloud Expo, which will take place on June 7–9, 2016, at the Javits Center in New York City, NY. DatacenterDynamics is a brand of DCD Group, a global B2B media and publishing company that develops products to help senior professionals in the world's most ICT dependent organizations make risk-based infrastructure and capacity decisions.
A valuable conference experience generates new contacts, sales leads, potential strategic partners and potential investors; helps gather competitive intelligence and even provides inspiration for new products and services. Conference Guru works with conference organizers to pass great deals to great conferences, helping you discover new conferences and increase your return on investment.
DXWorldEXPO LLC announced today that ICOHOLDER named "Media Sponsor" of Miami Blockchain Event by FinTechEXPO. ICOHOLDER gives detailed information and help the community to invest in the trusty projects. Miami Blockchain Event by FinTechEXPO has opened its Call for Papers. The two-day event will present 20 top Blockchain experts. All speaking inquiries which covers the following information can be submitted by email to [email protected] Miami Blockchain Event by FinTechEXPOalso offers sp...
Headquartered in Plainsboro, NJ, Synametrics Technologies has provided IT professionals and computer systems developers since 1997. Based on the success of their initial product offerings (WinSQL and DeltaCopy), the company continues to create and hone innovative products that help its customers get more from their computer applications, databases and infrastructure. To date, over one million users around the world have chosen Synametrics solutions to help power their accelerated business or per...
Poor data quality and analytics drive down business value. In fact, Gartner estimated that the average financial impact of poor data quality on organizations is $9.7 million per year. But bad data is much more than a cost center. By eroding trust in information, analytics and the business decisions based on these, it is a serious impediment to digital transformation.
@DevOpsSummit at Cloud Expo, taking place November 12-13 in New York City, NY, is co-located with 22nd international CloudEXPO | first international DXWorldEXPO and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The widespread success of cloud computing is driving the DevOps revolution in enterprise IT. Now as never before, development teams must communicate and collaborate in a dynamic, 24/7/365 environment. There is no time t...
When talking IoT we often focus on the devices, the sensors, the hardware itself. The new smart appliances, the new smart or self-driving cars (which are amalgamations of many ‘things'). When we are looking at the world of IoT, we should take a step back, look at the big picture. What value are these devices providing. IoT is not about the devices, its about the data consumed and generated. The devices are tools, mechanisms, conduits. This paper discusses the considerations when dealing with the...
SYS-CON Events announced today that IoT Global Network has been named “Media Sponsor” of SYS-CON's @ThingsExpo, which will take place on June 6–8, 2017, at the Javits Center in New York City, NY. The IoT Global Network is a platform where you can connect with industry experts and network across the IoT community to build the successful IoT business of the future.
IoT is rapidly becoming mainstream as more and more investments are made into the platforms and technology. As this movement continues to expand and gain momentum it creates a massive wall of noise that can be difficult to sift through. Unfortunately, this inevitably makes IoT less approachable for people to get started with and can hamper efforts to integrate this key technology into your own portfolio. There are so many connected products already in place today with many hundreds more on the h...
CloudEXPO New York 2018, colocated with DXWorldEXPO New York 2018 will be held November 11-13, 2018, in New York City and will bring together Cloud Computing, FinTech and Blockchain, Digital Transformation, Big Data, Internet of Things, DevOps, AI, Machine Learning and WebRTC to one location.