Welcome!

Java IoT Authors: Pat Romanski, Liz McMillan, Carmen Gonzalez, AppNeta Blog, Kevin Benedict

Related Topics: Java IoT, Industrial IoT, Microservices Expo, Open Source Cloud, @CloudExpo, Apache

Java IoT: Article

Tracing Black Boxes II: Monitoring Solr

Providing insight into Apache Solr instances by correlating individual traces with JMX metrics

Your site is indexed on Google, but that doesn't mean you're done with search. Content-rich websites provide native search functionality to keep users engaged, maintain visual consistency, and provide content-aware filtering. But it's very hard to implement an effective, scalable search system, which is why Apache Solr is just about the most popular ‘black box' in web application infrastructure. This Lucene-backed search appliance has seen wide adoption due to its performance, reliability, and ease of deployment. In fact, it's become so widely used that many Solr deployments are managed by people who have no other exposure to running Java applications. Documents go in, indexed RESTful search comes out - that is, until something breaks.

TraceView can provide insight into Apache Solr instances by correlating individual traces with JMX metrics, such as the rate of requests over the past 5 minutes. Even at a very low overall volume, an increased traffic rate is already increasing request latency.

TraceView can provide insight into Apache Solr instances by correlating individual traces with JMX metrics, such as the rate of requests over the past 5 minutes. Even at a very low overall volume, an increased traffic rate is already increasing request latency.

Unlike most web application front-ends, Solr is a complex, stateful application that contains persistent objects, runs background indexing processes, and maintains multiple tiers of caches. There are a lot of ways to deploy and configure Solr, and that means there are a lot of ways to make mistakes. But even when you have everything up and running, there's always the lingering question of whether you could be getting more out of your Solr instances (or reducing the number of them!).

One of the best ways to get insight into Solr's internal abstractions - such as cores, handlers, and components - is to monitor them directly via JMX. I've previously written about using JMX metrics to keep tabs on JVM memory internals, but JMX is a common API for collecting data from your Java applications and any application can make use of it. Because of this it's been widely adopted in the Java ecosystem to centralize the provision of application-specific performance data.

Solr provides JMX metrics on a variety of internals, such as queryResultCache.

 

Solr provides JMX metrics on a variety of internals, such as queryResultCache.

 

Solr exposes hundreds of JMX metrics across dozens of categories, and efficient use of them can help you delve into Solr performance in a variety of ways. Some metrics are better for providing a high-level view of Solr's overall workflow. The queryResultCachecategory, pictured above, provides a snapshot of how often your data was successfully cached, as well as how often cache entries had to be evicted due to insufficient space. Other metric categories are more granular and provide detail at the level of classes, or even objects. An update request will be routed to a different handler depending on whether the data was provided in XML, CSV, or JSON; each of these update handlers exposes metrics independently, like how long it has been running and the number of errors.

JMX metrics can even provide insight into advanced Solr use cases, like modifying result scoring to permit n-dimensional spatial searches or customizing results based on user data stored in Redis. Even without adding custom JMX metrics, Solr will report enough data to allow you to separately track the effectiveness of these custom searches relative to more traditional queries.

Let's look at a practical example. You just got paged because half of your distributed Solr cluster lost connectivity in a widespread EC2 outage. It looks like it might last a while, so you decide to add additional capacity in one of the functioning availability zones. Rather than spending time re-indexing your content, you decide to replicate your existing Solr data to the new servers. Using the high-level metrics provided byReplicationHandler, you determine that replication is proceeding smoothly. Halfway through your second replication, though, you realize that the first replicated server is taking five times as long as your original servers to respond to the same user queries, even though it's running on the same hardware. Checking out the cache metrics for a specific search handler, it looks like the hit ratios on its caches are abysmal - but wait, what's actually in those caches? After checking the metrics for that node's active Searcher instance, you realize you didn't set up Solr to warm the cache - it was starting off empty! Now you know to make a quick configuration change next time you spin up an instance so that the first users routed to it will have acceptable performance.

So, that sounds awesome - but how do you do it? The easiest approach is to view Solr's JMX statistics through its web interface (in Solr 3.x,
it's at /solr/admin/stats.jsp, while in Solr 4.x it's available at a collection-based URL like /solr/#/collection1/plugins/). However, web access won't be an option for most deployments. Alternately, you could use remote jconsole, but that requires either a complex remote configuration that's a tremendous hassle to set up or the glacially slow option of SSH X11 forwarding (e.g., ssh -X solr jconsole).

In practice, those approaches all suck. Solr is stunningly verbose: it exposes hundreds of JMX metrics out of the box, and that number expands quickly as you add additional handlers and components. Purpose-built JMX monitoring tools like jconsole are great for browsing the available metrics to see what's available, but they're horrible for pulling out the ones you want in a hurry. They also allow ‘write' operations like initiating garbage collection or clearing caches - definitely not something you want to give out to every developer!

TraceView automatically monitors the JMX metrics of every node involved in this distributed Solr Cloud trace.

 

TraceView automatically monitors the JMX metrics of every node involved in this distributed Solr Cloud trace.

On a day to day basis, it's more common to read JMX metrics via automated, ‘read-only' monitoring tools like NagiosGanglia, or AppNeta TraceView. These tools not only present a number of metrics at once, but they also generally let you filter down to a meaningful subset of the hundreds of lines exposed by Solr. On the other hand, "health check"-style metrics aren't necessarily the only way to look the problem. Each request has a number of metrics it can generate, and bringing together these data sources in one application has some real advantages. Looking at an individual request can tell you exactly what went wrong, it's often the context of JMX data that says why. Examining the concurrent host activity can disambiguate between whether a pause was due to a garbage collection event in the JVM or an overloaded document cache in Solr forcing additional disk access.

Next time, we'll talk about how TraceView captures these request-based metrics directly from the Solr internals. In the meantime, if you've got a Solr installation, sign up for your free account, put in on that server, and take a look inside that black box!

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.

@ThingsExpo Stories
Information technology is an industry that has always experienced change, and the dramatic change sweeping across the industry today could not be truthfully described as the first time we've seen such widespread change impacting customer investments. However, the rate of the change, and the potential outcomes from today's digital transformation has the distinct potential to separate the industry into two camps: Organizations that see the change coming, embrace it, and successful leverage it; and...
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.
Internet of @ThingsExpo, taking place June 6-8, 2017 at the Javits Center in New York City, New York, is co-located with the 20th International Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. @ThingsExpo New York Call for Papers is now open.
What happens when the different parts of a vehicle become smarter than the vehicle itself? As we move toward the era of smart everything, hundreds of entities in a vehicle that communicate with each other, the vehicle and external systems create a need for identity orchestration so that all entities work as a conglomerate. Much like an orchestra without a conductor, without the ability to secure, control, and connect the link between a vehicle’s head unit, devices, and systems and to manage the ...
We are always online. We access our data, our finances, work, and various services on the Internet. But we live in a congested world of information in which the roads were built two decades ago. The quest for better, faster Internet routing has been around for a decade, but nobody solved this problem. We’ve seen band-aid approaches like CDNs that attack a niche's slice of static content part of the Internet, but that’s it. It does not address the dynamic services-based Internet of today. It does...
20th Cloud Expo, taking place June 6-8, 2017, at the Javits Center in New York City, NY, will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud strategy.
Everyone knows that truly innovative companies learn as they go along, pushing boundaries in response to market changes and demands. What's more of a mystery is how to balance innovation on a fresh platform built from scratch with the legacy tech stack, product suite and customers that continue to serve as the business' foundation. In his General Session at 19th Cloud Expo, Michael Chambliss, Head of Engineering at ReadyTalk, discussed why and how ReadyTalk diverted from healthy revenue and mor...
The 20th International Cloud Expo has announced that its Call for Papers is open. Cloud Expo, to be held June 6-8, 2017, at the Javits Center in New York City, brings together Cloud Computing, Big Data, Internet of Things, DevOps, Containers, Microservices and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding business opportunity. Submit your speaking proposal ...
You have great SaaS business app ideas. You want to turn your idea quickly into a functional and engaging proof of concept. You need to be able to modify it to meet customers' needs, and you need to deliver a complete and secure SaaS application. How could you achieve all the above and yet avoid unforeseen IT requirements that add unnecessary cost and complexity? You also want your app to be responsive in any device at any time. In his session at 19th Cloud Expo, Mark Allen, General Manager of...
The Internet of Things (IoT) promises to simplify and streamline our lives by automating routine tasks that distract us from our goals. This promise is based on the ubiquitous deployment of smart, connected devices that link everything from industrial control systems to automobiles to refrigerators. Unfortunately, comparatively few of the devices currently deployed have been developed with an eye toward security, and as the DDoS attacks of late October 2016 have demonstrated, this oversight can ...
"ReadyTalk is an audio and web video conferencing provider. We've really come to embrace WebRTC as the platform for our future of technology," explained Dan Cunningham, CTO of ReadyTalk, in this SYS-CON.tv interview at WebRTC Summit at 19th Cloud Expo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
Bert Loomis was a visionary. This general session will highlight how Bert Loomis and people like him inspire us to build great things with small inventions. In their general session at 19th Cloud Expo, Harold Hannon, Architect at IBM Bluemix, and Michael O'Neill, Strategic Business Development at Nvidia, discussed the accelerating pace of AI development and how IBM Cloud and NVIDIA are partnering to bring AI capabilities to "every day," on-demand. They also reviewed two "free infrastructure" pr...
Major trends and emerging technologies – from virtual reality and IoT, to Big Data and algorithms – are helping organizations innovate in the digital era. However, to create real business value, IT must think beyond the ‘what’ of digital transformation to the ‘how’ to harness emerging trends, innovation and disruption. Architecture is the key that underpins and ties all these efforts together. In the digital age, it’s important to invest in architecture, extend the enterprise footprint to the cl...
"Dice has been around for the last 20 years. We have been helping tech professionals find new jobs and career opportunities," explained Manish Dixit, VP of Product and Engineering at Dice, in this SYS-CON.tv interview at 19th Cloud Expo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
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 smar...
Extracting business value from Internet of Things (IoT) data doesn’t happen overnight. There are several requirements that must be satisfied, including IoT device enablement, data analysis, real-time detection of complex events and automated orchestration of actions. Unfortunately, too many companies fall short in achieving their business goals by implementing incomplete solutions or not focusing on tangible use cases. In his general session at @ThingsExpo, Dave McCarthy, Director of Products...
Successful digital transformation requires new organizational competencies and capabilities. Research tells us that the biggest impediment to successful transformation is human; consequently, the biggest enabler is a properly skilled and empowered workforce. In the digital age, new individual and collective competencies are required. In his session at 19th Cloud Expo, Bob Newhouse, CEO and founder of Agilitiv, drew together recent research and lessons learned from emerging and established compa...
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, will discuss how AI can simplify cloud operations. He will cover the following topics: why clou...
The WebRTC Summit New York, to be held June 6-8, 2017, at the Javits Center in New York City, NY, announces that its Call for Papers is now open. Topics include all aspects of improving IT delivery by eliminating waste through automated business models leveraging cloud technologies. WebRTC Summit is co-located with 20th International Cloud Expo and @ThingsExpo. WebRTC is the future of browser-to-browser communications, and continues to make inroads into the traditional, difficult, plug-in web ...
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 sett...