Welcome!

PHP Authors: Liz McMillan, Carmen Gonzalez, Hovhannes Avoyan, Lori MacVittie, Trevor Parsons

Related Topics: Ruby-On-Rails, Java IoT, Industrial IoT, Microservices Expo, Open Source Cloud, Machine Learning , PHP

Ruby-On-Rails: Article

Monitoring Background Jobs in Ruby’s Resque

How to get visibility into an important component of any complex system: the messaging queue

Here at AppNeta, we get to see a lot about how people build their web applications. From simple PHP scripts to heavily service-oriented Java clouds to monolithic Django apps, everybody’s product is architected a little differently. We’re still out to trace everything, and today I want to talk how to get visibility into an important component of any complex system: the messaging queue. Specifically, let’s look at how to trace a job from Rails using Resque.

Messaging Queues
If you haven’t used a messaging queue in your app, the idea is simple. Instead of forcing all the work to happen during the request, while the user is waiting, you can delay some of the more time-consuming tasks. You can do anything in these tasks, ranging from a simple insert to kicking off a series of user analytics that touch all parts of your infrastructure. The advantage is that you can return a speedy response to the user, or, if they are actually waiting on the task results, give them a better loading interface than a white screen and browser loading bar.

A Quick Resque Tutorial
In Ruby, Resque is a task runner, which by default stores the task descriptions in Redis (though other options are available). Resque jobs are just Ruby classes, with a single mandatory method perform. Resque will call perform with the arguments given in the task description. Let’s look at a minimal task, that takes a single argument and prints it. (Useless, I know.)

LogInfo

The @queue variable defines a name that a worker can bind to, in case you want to spread different types of jobs across different machines. To create a task that this worker could run, we just call it from our request:

HoorayTrace

And that’s our job! Maybe not the most interesting job, and probably not prone to performance issues, but we don’t know that yet. So let’s measure it!

Tracing a Resque Task
Now that we’ve added this to our system, we should have monitoring around it. The easiest way to do this would be to just measure the time each task takes, and log that information:

MeasureLog

Unfortunately, the data presentation here leaves a bit to be desired, so I’m going to use TraceView to log this information instead. This also has the benefit of logging any SQL queries, cache accesses, or service calls that we might do in a more complex task, as well as reporting errors. To start a trace fresh, we can wrap this call in the start_trace block:

That’s a start! We’ve now got some visibility into our Resque jobs, and we can rest easy knowing that this is running smoothly in production.

Tracing a Resque Job (with multiple tasks!)
For cron-style jobs, the approach of tracing each task individually works fine. For reference, let’s look at the events we’re generating with that code:

Tracing Resque

Pretty straightforward. Now let’s consider a more complicated set of tasks: a document-processing pipeline. That code might look like this:

ProcessPipeline

In this case, our first task takes a document, and the second one archives it. If we have multiple tasks, each one gets logged separately, and we can figure out same statistics for each — average, std. dev., percentiles, and the like. But what if you have a job that spans multiple tasks? We can further aggregate the stats, but we might be starting to miss things, like large inputs that cause the entire pipeline to slow down.

What we’d really like is to correlate the related tasks, so instead of timing the each task, we’re timing the entire job. Under the hood, TraceView generates a token for each request. If we pass this ID (generally stored in xtrace, after the X-Trace header it’s passed around in) to each task, we can correlate those timings before storing them, and retrieve them all together. To do this, we can modify each task to take this token, and trace using that ID. ProcessDoc then becomes:

ProcessDoc

Now we need to start the trace somewhere, but we’re not doing it in the job. We could start it in the first task, or we could link this one step further up the chain and tie it back to the web request that started it in the first place. In a default rails stack, that request generates the following events:

Tracing Resque

To add in the task queue call to the logged request, we can call the following function:

TaskQueue-LoggedRequest

We have to force a fork in the execution path to indicate that we’re running an asynchronous task, possibly in parallel, with the rest of the web request, which is done with the call to fromString. Aside from that, this is the same underlying call as is done by start_trace above — log that we’re entering a named block of code, and start timing it.

When we put it all together, we get a secondary execution path attached to the web request, and the logged events look like this:

Tracing Resque

Now we’ve got everything: the original request, all tasks, individual timing information, and a global view of how the process performed. Not that we now have an additional timing measurement here: the delay before starting the task at all. In this case, we waited a full 500ms between queuing the job actually executing it! Once we were in the pipeline, the tasks happened much faster (only 25ms between processing and archiving).

Caveats
Lest you think that everything was easy, there’s a couple things to keep in mind when you use this in your own application.

  • Because we’re starting the timing in the web request and ending it in a task queue, we’re relying on those two processes to have an identical clock. If they’re on the same machine, it won’t be a problem, but on different machines, any clock skew will effect the timing.
  • I’ve quietly assumed everything in this system is reliable, which is almost certainly wrong. Whatever your error handling is, make sure you always log the exit event for ‘job’, or you may never know that you have errors!

As long as I haven’t totally dissuaded you from trying this out, all the code is available in one place in this gist, and you can try in out in your application today with our free version of TraceView!

Related Articles

Ruby 2.0 Released: Let The Tracing Begin!

AppNeta Rubygems Verified

Relieve Event Binding Aches in Backbone.js

More Stories By TR Jordan

A veteran of MIT’s Lincoln Labs, TR is a reformed physicist and full-stack hacker – for some limited definition of full stack. After a few years as Software Development Lead with Thermopylae Science and Techology, he left to join Tracelytics as its first engineer. Following Tracelytics merger with AppNeta, TR was tapped to run all of its developer and market evangelism efforts. TR still harbors a not-so-secret love for Matlab-esque graphs and half-baked statistics, as well as elegant and highly-performant code. Read more of his articles at www.appneta.com/blog or visit www.appneta.com.

@ThingsExpo Stories
SYS-CON Events announced today that mruby Forum will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. mruby is the lightweight implementation of the Ruby language. We introduce mruby and the mruby IoT framework that enhances development productivity. For more information, visit http://forum.mruby.org/.
Elon Musk is among the notable industry figures who worries about the power of AI to destroy rather than help society. Mark Zuckerberg, on the other hand, embraces all that is going on. AI is most powerful when deployed across the vast networks being built for Internets of Things in the manufacturing, transportation and logistics, retail, healthcare, government and other sectors. Is AI transforming IoT for the good or the bad? Do we need to worry about its potential destructive power? Or will we...
SYS-CON Events announced today that B2Cloud will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. B2Cloud specializes in IoT devices for preventive and predictive maintenance in any kind of equipment retrieving data like Energy consumption, working time, temperature, humidity, pressure, etc.
In his session at @ThingsExpo, Greg Gorman is the Director, IoT Developer Ecosystem, Watson IoT, will provide a short tutorial on Node-RED, a Node.js-based programming tool for wiring together hardware devices, APIs and online services in new and interesting ways. It provides a browser-based editor that makes it easy to wire together flows using a wide range of nodes in the palette that can be deployed to its runtime in a single-click. There is a large library of contributed nodes that help so...
What is the best strategy for selecting the right offshore company for your business? In his session at 21st Cloud Expo, Alan Winters, U.S. Head of Business Development at MobiDev, will discuss the things to look for - positive and negative - in evaluating your options. He will also discuss how to maximize productivity with your offshore developers. Before you start your search, clearly understand your business needs and how that impacts software choices.
SYS-CON Events announced today that SIGMA Corporation will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. uLaser flow inspection device from the Japanese top share to Global Standard! Then, make the best use of data to flip to next page. For more information, visit http://www.sigma-k.co.jp/en/.
SYS-CON Events announced today that NetApp has been named “Bronze Sponsor” of SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. NetApp is the data authority for hybrid cloud. NetApp provides a full range of hybrid cloud data services that simplify management of applications and data across cloud and on-premises environments to accelerate digital transformation. Together with their partners, NetApp em...
Agile has finally jumped the technology shark, expanding outside the software world. Enterprises are now increasingly adopting Agile practices across their organizations in order to successfully navigate the disruptive waters that threaten to drown them. In our quest for establishing change as a core competency in our organizations, this business-centric notion of Agile is an essential component of Agile Digital Transformation. In the years since the publication of the Agile Manifesto, the conn...
SYS-CON Events announced today that MIRAI Inc. will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. MIRAI Inc. are IT consultants from the public sector whose mission is to solve social issues by technology and innovation and to create a meaningful future for people.
There is huge complexity in implementing a successful digital business that requires efficient on-premise and cloud back-end infrastructure, IT and Internet of Things (IoT) data, analytics, Machine Learning, Artificial Intelligence (AI) and Digital Applications. In the data center alone, there are physical and virtual infrastructures, multiple operating systems, multiple applications and new and emerging business and technological paradigms such as cloud computing and XaaS. And then there are pe...
Real IoT production deployments running at scale are collecting sensor data from hundreds / thousands / millions of devices. The goal is to take business-critical actions on the real-time data and find insights from stored datasets. In his session at @ThingsExpo, John Walicki, Watson IoT Developer Advocate at IBM Cloud, will provide a fast-paced developer journey that follows the IoT sensor data from generation, to edge gateway, to edge analytics, to encryption, to the IBM Bluemix cloud, to Wa...
SYS-CON Events announced today that Keisoku Research Consultant Co. will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Keisoku Research Consultant, Co. offers research and consulting in a wide range of civil engineering-related fields from information construction to preservation of cultural properties. For more information, vi...
While some developers care passionately about how data centers and clouds are architected, for most, it is only the end result that matters. To the majority of companies, technology exists to solve a business problem, and only delivers value when it is solving that problem. 2017 brings the mainstream adoption of containers for production workloads. In his session at 21st Cloud Expo, Ben McCormack, VP of Operations at Evernote, will discuss how data centers of the future will be managed, how th...
SYS-CON Events announced today that Fusic will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Fusic Co. provides mocks as virtual IoT devices. You can customize mocks, and get any amount of data at any time in your test. For more information, visit https://fusic.co.jp/english/.
SYS-CON Events announced today that Mobile Create USA will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Mobile Create USA Inc. is an MVNO-based business model that uses portable communication devices and cellular-based infrastructure in the development, sales, operation and mobile communications systems incorporating GPS capabi...
SYS-CON Events announced today that Enroute Lab will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Enroute Lab is an industrial design, research and development company of unmanned robotic vehicle system. For more information, please visit http://elab.co.jp/.
SYS-CON Events announced today that Interface Corporation will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Interface Corporation is a company developing, manufacturing and marketing high quality and wide variety of industrial computers and interface modules such as PCIs and PCI express. For more information, visit http://www.i...
SYS-CON Events announced today that Ryobi Systems will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Ryobi Systems Co., Ltd., as an information service company, specialized in business support for local governments and medical industry. We are challenging to achive the precision farming with AI. For more information, visit http:...
SYS-CON Events announced today that N3N will exhibit at SYS-CON's @ThingsExpo, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. N3N’s solutions increase the effectiveness of operations and control centers, increase the value of IoT investments, and facilitate real-time operational decision making. N3N enables operations teams with a four dimensional digital “big board” that consolidates real-time live video feeds alongside IoT sensor data a...
Internet of @ThingsExpo, taking place October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 21st Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devic...