Welcome!

@DevOpsSummit Authors: Elizabeth White, Flint Brenton, Sujoy Sen, Anders Wallgren, Liz McMillan

Blog Feed Post

10 Things We Forgot to Monitor

10 Things We Forgot to Monitor

After publishing Ben’s blog post about “Memory Monitoring with LXC” we realized there is a lot of interest in articles about Monitoring. I got in touch with Jehiah Czebotar, Head of Engineering at bitly, and asked him if we could republish his blog post about things bitly forgot to monitor.

Jehiah originally published his blog post on the bitly engeneering blog. You can find Jehiah on twitter and on his personal page. Definitely check out his “Personal Annual Reports“.


There is always a set of standard metrics that are universally monitored (Disk Usage, Memory Usage, Load, Pings, etc). Beyond that, there are a lot of lessons that we’ve learned from operating our production systems that have helped shape the breadth of monitoring that we perform at bitly.

One of my favorite all-time tweets is from @DevOps_Borat

What follows is a small list of things we monitor at bitly that have grown out of those (sometimes painful!) experiences, and where possible little snippets of the stories behind those instances.

1 – Fork Rate

We once had a problem where IPv6 was intentionally disabled on a box via options ipv6 disable=1 and alias ipv6 off in /etc/modprobe.conf. This caused a large issue for us: each time a new curl object was created, modprobe would spawn, checking net-pf-10 to evaluate IPv6 status. This fork bombed the box, and we eventually tracked it down by noticing that the process counter in /proc/stat was increasing by several hundred a second. Normally you would only expect a fork rate of 1-10/sec on a production box with steady traffic.

2 – flow control packets

TL;DR; If your network configuration honors flow control packets and isn’t configured to disable them, they can temporarily cause dropped traffic. (If this doesn’t sound like an outage, you need your head checked.)

$ /usr/sbin/ethtool -S eth0 | grep flow_control
rx_flow_control_xon: 0
rx_flow_control_xoff: 0
tx_flow_control_xon: 0
tx_flow_control_xoff: 0

Note: Read this to understand how these flow control frames can cascade to switch-wide loss of connectivity if you use certain Broadcom NIC’s. You should also trend these metrics on your switch gear. While at it, watch your dropped frames.

3 – Swap In/Out Rate

It’s common to check for swap usage above a threshold, but even if you have a small quantity of memory swapped, it’s actually the rate it’s swapped in/out that can impact performance, not the quantity. This is a much more direct check for that state.

4 – Server Boot Notification

Unexpected reboots are part of life. Do you know when they happen on your hosts? Most people don’t. We use a simple init script that triggers an ops email on system boot. This is valuable to communicate provisioning of new servers, and helps capture state change even if services handle the failure gracefully without alerting.

5 – NTP Clock Offset

If not monitored, yes, one of your servers is probably off. If you’ve never thought about clock skew you might not even be running ntpd on your servers. Generally there are 3 things to check for. 1) That ntpd is running, 2) Clock skew inside your datacenter, 3) Clock skew from your master time servers to an external source.

We use check_ntp_time for this check.

6 – DNS Resolutions

Internal DNS – It’s a hidden part of your infrastructure that you rely on more than you realize. The things to check for are 1) Local resolutions from each server, 2) If you have local DNS servers in your datacenter, you want to check resolution, and quantity of queries, 3) Check availability of each upstream DNS resolver you use.

External DNS – It’s good to verify your external domains resolve correctly against each of your published external nameservers. At bitly we also rely on several CC TLD’s and we monitor those authoritative servers directly as well (yes, it’s happened that all authoritative nameservers for a TLD have been offline).

7 – SSL Expiration

It’s the thing everyone forgets about because it happens so infrequently. The fix is easy, just check it and get alerted with enough timeframe to renew your SSL certificates.

define command{
    command_name    check_ssl_expire
    command_line    $USER1$/check_http --ssl -C 14 -H $ARG1$
}
define service{
    host_name               virtual
    service_description     bitly_com_ssl_expiration
    use                     generic-service
    check_command           check_ssl_expire!bitly.com
    contact_groups          email_only
    normal_check_interval   720
    retry_check_interval    10
    notification_interval   720
}

8 – DELL OpenManage Server Administrator (OMSA)

We run bitly split across two data centers, one is a managed environment with DELL hardware, and the second is Amazon EC2. For our DELL hardware it’s important for us to monitor the outputs from OMSA. This alerts us to RAID status, failed disks (predictive or hard failures), RAM Issues, Power Supply states and more.

9 – Connection Limits

You probably run things like memcached and mysql with connection limits, but do you monitor how close you are to those limits as you scale out application tiers?

Related to this is addressing the issue of processes running into file descriptor limits. We make a regular practice of running services with ulimit -n 65535 in our run scripts to minimize this. We also set Nginx worker_rlimit_nofile.

10 – Load Balancer Status.

We configure our Load Balancers with a health check which we can easily force to fail in order to have any given server removed from rotation.We’ve found it important to have visibility into the health check state, so we monitor and alert based on the same health check. (If you use EC2 Load Balancers you can monitor the ELB state from Amazon API’s).

Various Other things to watch

New entries written to Nginx Error Logs, service restarts (assuming you have something in place to auto-restart them on failure), numa stats, new process core dumps (great if you run any C code).


We want to thank Jehiah for making his original article available to our readers. Is there something missing on this list in your opportunity? Let us know in the comments!

Codeship – A hosted Continuous Deployment platform for web applications

Read the original blog entry...

More Stories By Manuel Weiss

I am the cofounder of Codeship – a hosted Continuous Integration and Deployment platform for web applications. On the Codeship blog we love to write about Software Testing, Continuos Integration and Deployment. Also check out our weekly screencast series 'Testing Tuesday'!

@DevOpsSummit Stories
SYS-CON Events announced today that EastBanc Technologies will exhibit at 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. EastBanc Technologies has been working at the frontier of technology since 1999. Today, the firm provides full-lifecycle software development delivering flexible technology solutions that seamlessly integrate with existing systems – whether on premise or cloud. EastBanc Technologies partners with public and private sector clients to solve their most difficult technology challenges. Headquartered ...
SYS-CON Events announced today that ContentMX, the marketing technology and services company with a singular mission to increase engagement and drive more conversations for enterprise, channel and SMB technology marketers, has been named “Sponsor & Exhibitor Lounge Sponsor” of SYS-CON's 18th Cloud Expo, which will take place on June 7-9, 2016, at the Javits Center in New York City, New York. “CloudExpo is a great opportunity to start a conversation with new prospects, but what happens after the show ends?” said Jeff Mesnik, ContentMX President. “We are here for the sponsors, resellers and clo...
SYS-CON Events announced today that AppNeta, the leader in performance insight for business-critical web applications, will exhibit and present at SYS-CON's @DevOpsSummit at Cloud Expo New York, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. AppNeta is the only application performance monitoring (APM) company to provide solutions for all applications – applications you develop internally, business-critical SaaS applications you use and the networks that deliver them.
SYS-CON Events announced today the Docker Meets Kubernetes – Intro into the Kubernetes World, being held June 9, 2016, in conjunction with 18th Cloud Expo | @ThingsExpo, at the Javits Center in New York, NY. Register for 'Docker Meets Kubernetes Workshop' Here! This workshop led by Sebastian Scheele, co-founder of Loodse, introduces participants to Kubernetes (container orchestration). Through a combination of instructor-led presentations, demonstrations, and hands-on labs, participants learn the key concepts and practices for setting up and maintaining container-based applications using Goo...
SYS-CON Events announced today that MangoApps will exhibit at 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. MangoApps provides modern company intranets and team collaboration software, allowing workers to stay connected and productive from anywhere in the world and from any device. For more information, please visit https://www.mangoapps.com/.
Join us at Cloud Expo | @ThingsExpo 2016 – June 7-9 at the Javits Center in New York City and November 1-3 at the Santa Clara Convention Center in Santa Clara, CA – and deliver your unique message in a way that is striking and unforgettable by taking advantage of SYS-CON's unmatched high-impact, result-driven event / media packages.
SYS-CON Events announced today that MobiDev will exhibit at 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. MobiDev is a software company that develops and delivers turn-key mobile apps, websites, web services, and complex software systems for startups and enterprises. Since 2009 it has grown from a small group of passionate engineers and business managers to a full-scale mobile software company with over 200 developers, designers, quality assurance engineers, project managers in house, specializing in the world-cla...
SoftLayer operates a global cloud infrastructure platform built for Internet scale. With a global footprint of data centers and network points of presence, SoftLayer provides infrastructure as a service to leading-edge customers ranging from Web startups to global enterprises. SoftLayer's modular architecture, full-featured API, and sophisticated automation provide unparalleled performance and control. Its flexible unified platform seamlessly spans physical and virtual devices linked via a worldwide network for secure, low-latency communications.
SYS-CON Events announced today TechTarget 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, and the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. TechTarget is the Web’s leading destination for serious technology buyers researching and making enterprise technology decisions. Its extensive global network of online and social media, powered by TechTarget’s Activity Intelligence™ platform, allows techno...
SYS-CON Events announced today that Commvault, a global leader in enterprise data protection and information management, has been named “Bronze 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, and the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Commvault is a leading provider of data protection and information management solutions, helping companies worldwide activate their data to drive more value and business insight...
Many banks and financial institutions are experimenting with containers in development environments, but when will they move into production? Containers are seen as the key to achieving the ultimate in information technology flexibility and agility. Containers work on both public and private clouds, and make it easy to build and deploy applications. The challenge for regulated industries is the cost and complexity of container security compliance. VM security compliance is already challenging, and containers increase the problem exponentially. Simplifying and automating security compliance wi...
A strange thing is happening along the way to the Internet of Things, namely far too many devices to work with and manage. It has become clear that we'll need much higher efficiency user experiences that can allow us to more easily and scalably work with the thousands of devices that will soon be in each of our lives. Enter the conversational interface revolution, combining bots we can literally talk with, gesture to, and even direct with our thoughts, with embedded artificial intelligence, which can process our conversational commands and orchestrate the outcomes we request across our perso...
SYS-CON Events announced today that Tintri Inc., a leading producer of VM-aware storage (VAS) for virtualization and cloud environments, will exhibit at the 18th International CloudExpo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, New York, and the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
Enterprise networks are complex. Moreover, they were designed and deployed to meet a specific set of business requirements at a specific point in time. But, the adoption of cloud services, new business applications and intensifying security policies, among other factors, require IT organizations to continuously deploy configuration changes. Therefore, enterprises are looking for better ways to automate the management of their networks while still leveraging existing capabilities, optimizing performance and reducing operational risk through standardization and best-practice architectures.
SYS-CON Events announced today that Alert Logic, Inc., the leading provider of Security-as-a-Service solutions for the cloud, will exhibit at 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. Alert Logic, Inc., provides Security-as-a-Service for on-premises, cloud, and hybrid infrastructures, delivering deep security insight and continuous protection for customers at a lower cost than traditional security solutions. Fully managed by a team of experts, the Alert Logic Security-as-a-Service solution provides network, sy...
SYS-CON Events announced today BZ Media LLC has been named “Media Sponsor” of SYS-CON's 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. BZ Media LLC is a high-tech media company that produces technical conferences and expositions, and publishes a magazine, newsletters and websites in the software development, SharePoint, mobile development and Commercial Drone markets.
IoT generates lots of temporal data. But how do you unlock its value? How do you coordinate the diverse moving parts that must come together when developing your IoT product? What are the key challenges addressed by Data as a Service? How does cloud computing underlie and connect the notions of Digital and DevOps What is the impact of the API economy? What is the business imperative for Cognitive Computing? Get all these questions and hundreds more like them answered at the 18th Cloud Expo | @ThingsExpo June 7-9, 2016, at the Javits Center, in New York City, NY. The Cloud Expo | @ThingsE...
The pace of innovation, vendor lock-in, production sustainability, cost-effectiveness, and managing risk… In his session at 18th Cloud Expo, Dan Choquette, Founder of RackN, will discuss how CIOs are challenged finding the balance of finding the right tools, technology and operational model that serves the business the best. He will discuss how clouds, open source software and infrastructure solutions have benefits but also drawbacks and how workload and operational portability between vendors and platforms give control back to the users and drives innovation.
SYS-CON Events announced today that Isomorphic Software will exhibit at SYS-CON's [email protected] at Cloud Expo New York, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. Isomorphic Software provides the SmartClient HTML5/AJAX platform, the most advanced technology for building rich, high-productivity enterprise web applications for any device. SmartClient couples the industry’s broadest, deepest UI component set with a java server framework to deliver an end-to-end solution for building web applications.
18th Cloud Expo, taking place June 7-9, 2016, 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. Meanwhile, 94% of enterprises are using some form of XaaS – software, platform, and infrastructure as a service.
SYS-CON Events announced today that Enzu, a leading provider of cloud hosting solutions, will exhibit at 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. Enzu’s mission is to be the leading provider of enterprise cloud solutions worldwide. Enzu enables online businesses to use its IT infrastructure to their competitive advantage. By offering a suite of proven hosting and management services, Enzu wants companies to focus on the core of their online business and let Enzu manage their IT hosting infrastructure.
As the rapid adoption of containers continues, companies are finding that they lack the operational tools to understand the behavior of applications deployed in these containers, and how to identify issues in their application infrastructure. For example, how are multiple containers within an application impacting each other’s performance? If an application’s service is degraded, which container is to blame? In the case of an application outage, what was the root cause of the outage?
SYS-CON Events announced today that 24Notion has been named “Bronze Sponsor” of SYS-CON's 18th Cloud Expo, which will take place on June 7-9, 2016, at the Javits Center in New York, New York. 24Notion is full-service global creative digital marketing, technology and lifestyle agency that combines strategic ideas with customized tactical execution. With a broad understand of the art of traditional marketing, new media, communications and social influence, 24Notion uniquely understands how to connect your brand strategy with the right consumer. 24Notion ranked #12 on Corporate Social Responsibi...
@DevOpsSummit taking place June 7-9, 2016 at Javits Center, New York City, and Nov 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with the 18th International @CloudExpo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world.
With major technology companies and startups seriously embracing IoT strategies, now is the perfect time to attend @ThingsExpo 2016 in New York and Silicon Valley. Learn what is going on, contribute to the discussions, and ensure that your enterprise is as "IoT-Ready" as it can be! Internet of @ThingsExpo, taking place Nov 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 17th 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 cha...