Welcome!

Machine Learning Authors: Liz McMillan, Elizabeth White, Yeshim Deniz, Flint Brenton, Pat Romanski

Related Topics: Java IoT, Open Source Cloud, Machine Learning , Agile Computing, @CloudExpo, @DXWorldExpo

Java IoT: Article

How to Identify a MongoDB Performance Anti Pattern in Five Minutes

Analyzing the application

The other day I was looking at a web application that was using MongoDB as its central database. We were analyzing the application for potential performance problems and inside five minutes I detected what I must consider to be a MongoDB anti pattern and had a 40% impact on response time. The funny thing: It was a Java best practice that triggered it.

Analyzing the Application
The first thing I always do is look at the topology of an application to get a feel for it.

Overall Transaction Flow of the Application

As we see it's a modestly complex web application and it's using MongoDB as its datastore. Overall MongoDB contributes about 7% to the response time of the application. I noticed that about half of all transactions are actually calling MongoDB so I took a closer look.

Flow of Transactions that access MongoDB, showing 10% response time contribution of MongoDB

Those transactions that actually do call MongoDB spend about 10% of their response time in that popular document database. As a next step I wanted to know what was being executed against MongoDB.

Overview of all MongoDB commands. This shows that the JourneyCollection find and getCount contribute the most to response time

One immediately notices the first two lines, which contribute much more to the response time per transaction than all the others. What was interesting was that thegetCount on the JourneyCollection had the highest contribution time, but the developer responsible was not aware that he was even using it anywhere.

Things get interesting - the mysterious getCount call
Taking things one level deeper, we looked at all transactions that were executing the ominous getCount on the JourneyCollection.

Transactions that call JourneyCollection.getCount spend nearly half their time in MongoDB

What jumps out is that those particular transactions spend indeed over 40% of their time in MongoDB, so there was a big potential for improvement here. Another click and we looked at all MongoDB calls that were executed within the context of the same transaction as the getCount call we found so mysterious.

All MongoDB Statements that run within the same transaction context as the JourneyCollection.getCount

What struck us as interesting was that the number of executions per transaction of thefind and getCount on the JourneyCollection seemed closely connected. At this point we decided to look at the transactions themselves - we needed to understand why that particular MongoDB call was executed.

Single Transactions that execute the ominous getCount call

It's immediately clear that several different transaction types are executing that particulargetCount. What that meant for us is that the problem was likely in the core framework of that particular application rather than being specific to any one user action. Here is the interesting snippet:

The Transaction Trace shows where the getCount is executed exactly

We see that the WebService findJourneys spends all its time in the two MongoDB calls. The first is the actual find call to the Journey Collection. The MongoDB client is good at lazy loading, so the find does not actually do much yet. It only calls the server once we access the result set. We can see the round trip to MongoDB visualized in the call node at the end.

We also see the offending getCount. We see that it is executed by a method called sizewhich turns out to be com.mongodb.DBCursor.size method. This was news to our developer. Looking at several other transactions we found that this was a common pattern. Every time we search for something in the JourneyCollection the getCountwould be executed by com.mongodb.DBCursor.size. This always happens before we would really execute the send the find command to the server(which happens in the callmethod). So we used CompuwareAPM DTM's (a.k.a dynaTrace) developer integration and took a look at the offending code. Here is what we found:

BasicDBObject fields = new BasicDBObject();
fields.put(journeyStr + "." + MongoConstants.ID, 1);
fields.put(MongoConstants.ID, 0);

Collection locations = find(patternQuery, fields);

ArrayList results = new ArrayList(locations.size());
for (DBObject dbObject : locations) {
String loc = dbObject.getString(journeyStr);
results.add(loc);
}
return results;


The code looks harmless enough; we execute a find, create an array for the result and fill it. The offender is the location.size(). MongoDBs DBCursor is similar to the ResultSet in JDBC, it does not return the whole data set at once, but only a subset. As a consequence it doesn't really know how many elements the find will end up with. The only way for MongoDB to determine the final size seems to be to execute a getCountwith the same criteria as the original find. In our case that additional unnecessary roundtrip made up 40% of the web services response time!

An Anti-Patter triggered by a Best Practice
So it turns out that calling size on the DBCursor must be considered an anti-pattern! The real funny thing is that the developer thought he was writing performant code. He was following the best practice to pre-size arrays. This avoids any unnecessary re-sizing. In this particular case however, that minor theoretical performance improvement led to a 40% performance degradation!

Conclusion
The take away here is not that MongoDB is bad or doesn't perform. In fact the customer is rather happy with it. But mistakes happen and similar to other database applications we need to have the visibility into a running application to see how much it contributes to the overall response time. We also need to have that visibility to understand which statements are called where and why.

In addition this also demonstrates nicely why premature micro optimization, without leveraging an APM solution, in production will not lead to better performance. In some cases - like this one - it can actually lead to worse performance.

More Stories By Michael Kopp

Michael Kopp has over 12 years of experience as an architect and developer in the Enterprise Java space. Before coming to CompuwareAPM dynaTrace he was the Chief Architect at GoldenSource, a major player in the EDM space. In 2009 he joined dynaTrace as a technology strategist in the center of excellence. He specializes application performance management in large scale production environments with special focus on virtualized and cloud environments. His current focus is how to effectively leverage BigData Solutions and how these technologies impact and change the application landscape.

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.


@CloudExpo Stories
When shopping for a new data processing platform for IoT solutions, many development teams want to be able to test-drive options before making a choice. Yet when evaluating an IoT solution, it’s simply not feasible to do so at scale with physical devices. Building a sensor simulator is the next best choice; however, generating a realistic simulation at very high TPS with ease of configurability is a formidable challenge. When dealing with multiple application or transport protocols, you would be...
As organizations shift towards IT-as-a-service models, the need for managing and protecting data residing across physical, virtual, and now cloud environments grows with it. Commvault can ensure protection, access and E-Discovery of your data – whether in a private cloud, a Service Provider delivered public cloud, or a hybrid cloud environment – across the heterogeneous enterprise. In his general session at 18th Cloud Expo, Randy De Meno, Chief Technologist - Windows Products and Microsoft Part...
Data is the fuel that drives the machine learning algorithmic engines and ultimately provides the business value. In his session at Cloud Expo, Ed Featherston, a director and senior enterprise architect at Collaborative Consulting, discussed the key considerations around quality, volume, timeliness, and pedigree that must be dealt with in order to properly fuel that engine.
Dion Hinchcliffe is an internationally recognized digital expert, bestselling book author, frequent keynote speaker, analyst, futurist, and transformation expert based in Washington, DC. He is currently Chief Strategy Officer at the industry-leading digital strategy and online community solutions firm, 7Summits.
In his session at 20th Cloud Expo, Scott Davis, CTO of Embotics, discussed how automation can provide the dynamic management required to cost-effectively deliver microservices and container solutions at scale. He also discussed how flexible automation is the key to effectively bridging and seamlessly coordinating both IT and developer needs for component orchestration across disparate clouds – an increasingly important requirement at today’s multi-cloud enterprise.
In his session at 20th Cloud Expo, Brad Winett, Senior Technologist for DDN Storage, will present several current, end-user environments that are using object storage at scale for cloud deployments including private cloud and cloud providers. Details on the top considerations of features and functions for selecting object storage will be included. Brad will also touch on recent developments in tiering technologies that deliver single solution and an end-user view of data across files and objects...
"I will be talking about ChatOps and ChatOps as a way to solve some problems in the DevOps space," explained Himanshu Chhetri, CTO of Addteq, in this SYS-CON.tv interview at @DevOpsSummit at 20th Cloud Expo, held June 6-8, 2017, at the Javits Center in New York City, NY.
Businesses and business units of all sizes can benefit from cloud computing, but many don't want the cost, performance and security concerns of public cloud nor the complexity of building their own private clouds. Today, some cloud vendors are using artificial intelligence (AI) to simplify cloud deployment and management. In his session at 20th Cloud Expo, Ajay Gulati, Co-founder and CEO of ZeroStack, discussed how AI can simplify cloud operations. He covered the following topics: why cloud mana...
In his session at 21st Cloud Expo, Michael Burley, a Senior Business Development Executive in IT Services at NetApp, described how NetApp designed a three-year program of work to migrate 25PB of a major telco's enterprise data to a new STaaS platform, and then secured a long-term contract to manage and operate the platform. This significant program blended the best of NetApp’s solutions and services capabilities to enable this telco’s successful adoption of private cloud storage and launching o...
In his keynote at 18th Cloud Expo, Andrew Keys, Co-Founder of ConsenSys Enterprise, provided an overview of the evolution of the Internet and the Database and the future of their combination – the Blockchain. Andrew Keys is Co-Founder of ConsenSys Enterprise. He comes to ConsenSys Enterprise with capital markets, technology and entrepreneurial experience. Previously, he worked for UBS investment bank in equities analysis. Later, he was responsible for the creation and distribution of life settl...
You know you need the cloud, but you’re hesitant to simply dump everything at Amazon since you know that not all workloads are suitable for cloud. You know that you want the kind of ease of use and scalability that you get with public cloud, but your applications are architected in a way that makes the public cloud a non-starter. You’re looking at private cloud solutions based on hyperconverged infrastructure, but you’re concerned with the limits inherent in those technologies.
For organizations that have amassed large sums of software complexity, taking a microservices approach is the first step toward DevOps and continuous improvement / development. Integrating system-level analysis with microservices makes it easier to change and add functionality to applications at any time without the increase of risk. Before you start big transformation projects or a cloud migration, make sure these changes won’t take down your entire organization.
It is ironic, but perhaps not unexpected, that many organizations who want the benefits of using an Agile approach to deliver software use a waterfall approach to adopting Agile practices: they form plans, they set milestones, and they measure progress by how many teams they have engaged. Old habits die hard, but like most waterfall software projects, most waterfall-style Agile adoption efforts fail to produce the results desired. The problem is that to get the results they want, they have to ch...
With tough new regulations coming to Europe on data privacy in May 2018, Calligo will explain why in reality the effect is global and transforms how you consider critical data. EU GDPR fundamentally rewrites the rules for cloud, Big Data and IoT. In his session at 21st Cloud Expo, Adam Ryan, Vice President and General Manager EMEA at Calligo, examined the regulations and provided insight on how it affects technology, challenges the established rules and will usher in new levels of diligence arou...
Organizations planning enterprise data center consolidation and modernization projects are faced with a challenging, costly reality. Requirements to deploy modern, cloud-native applications simultaneously with traditional client/server applications are almost impossible to achieve with hardware-centric enterprise infrastructure. Compute and network infrastructure are fast moving down a software-defined path, but storage has been a laggard. Until now.
In his session at 20th Cloud Expo, Mike Johnston, an infrastructure engineer at Supergiant.io, discussed how to use Kubernetes to set up a SaaS infrastructure for your business. Mike Johnston is an infrastructure engineer at Supergiant.io with over 12 years of experience designing, deploying, and maintaining server and workstation infrastructure at all scales. He has experience with brick and mortar data centers as well as cloud providers like Digital Ocean, Amazon Web Services, and Rackspace. H...
DXWorldEXPO LLC announced today that All in Mobile, a mobile app development company from Poland, will exhibit at the 22nd International CloudEXPO | DXWorldEXPO. All In Mobile is a mobile app development company from Poland. Since 2014, they maintain passion for developing mobile applications for enterprises and startups worldwide.
Digital Transformation is much more than a buzzword. The radical shift to digital mechanisms for almost every process is evident across all industries and verticals. This is often especially true in financial services, where the legacy environment is many times unable to keep up with the rapidly shifting demands of the consumer. The constant pressure to provide complete, omnichannel delivery of customer-facing solutions to meet both regulatory and customer demands is putting enormous pressure on...
The best way to leverage your CloudEXPO | DXWorldEXPO presence as a sponsor and exhibitor is to plan your news announcements around our events. The press covering CloudEXPO | DXWorldEXPO will have access to these releases and will amplify your news announcements. More than two dozen Cloud companies either set deals at our shows or have announced their mergers and acquisitions at CloudEXPO. Product announcements during our show provide your company with the most reach through our targeted audienc...
With 10 simultaneous tracks, keynotes, general sessions and targeted breakout classes, @CloudEXPO and DXWorldEXPO are two of the most important technology events of the year. Since its launch over eight years ago, @CloudEXPO and DXWorldEXPO have presented a rock star faculty as well as showcased hundreds of sponsors and exhibitors!
More and more brands have jumped on the IoT bandwagon. We have an excess of wearables – activity trackers, smartwatches, smart glasses and sneakers, and more that track seemingly endless datapoints. However, most consumers have no idea what “IoT” means. Creating more wearables that track data shouldn't be the aim of brands; delivering meaningful, tangible relevance to their users should be. We're in a period in which the IoT pendulum is still swinging. Initially, it swung toward "smart for smart...