Welcome!

Agile Computing Authors: Carmen Gonzalez, Yeshim Deniz, AppNeta Blog, Liz McMillan, Harry Trott

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'!

@ThingsExpo Stories
The Internet of Things can drive efficiency for airlines and airports. In their session at @ThingsExpo, Shyam Varan Nath, Principal Architect with GE, and Sudip Majumder, senior director of development at Oracle, discussed the technical details of the connected airline baggage and related social media solutions. These IoT applications will enhance travelers' journey experience and drive efficiency for the airlines and the airports.
In his keynote at @ThingsExpo, Chris Matthieu, Director of IoT Engineering at Citrix and co-founder and CTO of Octoblu, focused on building an IoT platform and company. He provided a behind-the-scenes look at Octoblu’s platform, business, and pivots along the way (including the Citrix acquisition of Octoblu).
SYS-CON Events announced today that Technologic Systems Inc., an embedded systems solutions company, will exhibit at SYS-CON's @ThingsExpo, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Technologic Systems is an embedded systems company with headquarters in Fountain Hills, Arizona. They have been in business for 32 years, helping more than 8,000 OEM customers and building over a hundred COTS products that have never been discontinued. Technologic Systems’ pr...
In his keynote at @ThingsExpo, Chris Matthieu, Director of IoT Engineering at Citrix and co-founder and CTO of Octoblu, focused on building an IoT platform and company. He provided a behind-the-scenes look at Octoblu’s platform, business, and pivots along the way (including the Citrix acquisition of Octoblu).
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, whic...
SYS-CON Events announced today that CA Technologies has been named “Platinum Sponsor” of SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY, and the 21st International Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. CA Technologies helps customers succeed in a future where every business – from apparel to energy – is being rewritten by software. From ...
With 10 simultaneous tracks, keynotes, general sessions and targeted breakout classes, Cloud Expo and @ThingsExpo are two of the most important technology events of the year. Since its launch over eight years ago, Cloud Expo and @ThingsExpo have presented a rock star faculty as well as showcased hundreds of sponsors and exhibitors! In this blog post, I provide 7 tips on how, as part of our world-class faculty, you can deliver one of the most popular sessions at our events. But before reading the...
The best way to leverage your Cloud Expo presence as a sponsor and exhibitor is to plan your news announcements around our events. The press covering Cloud Expo and @ThingsExpo 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 Cloud Expo. Product announcements during our show provide your company with the most reach through our targeted audiences.
In his session at @ThingsExpo, Steve Wilkes, CTO and founder of Striim, will delve into four enterprise-scale, business-critical case studies where streaming analytics serves as the key to enabling real-time data integration and right-time insights in hybrid cloud, IoT, and fog computing environments. As part of this discussion, he will also present a demo based on its partnership with Fujitsu, highlighting their technologies in a healthcare IoT use-case. The demo showcases the tracking of patie...
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.
Have you ever noticed how some IT people seem to lead successful, rewarding, and satisfying lives and careers, while others struggle? IT author and speaker Don Crawley uncovered the five principles that successful IT people use to build satisfying lives and careers and he shares them in this fast-paced, thought-provoking webinar. You'll learn the importance of striking a balance with technical skills and people skills, challenge your pre-existing ideas about IT customer service, and gain new in...
With major technology companies and startups seriously embracing Cloud strategies, now is the perfect time to attend @CloudExpo | @ThingsExpo, June 6-8, 2017, at the Javits Center in New York City, NY and October 31 - November 2, 2017, Santa Clara Convention Center, CA. Learn what is going on, contribute to the discussions, and ensure that your enterprise is on the right path to Digital Transformation.
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...
Buzzword alert: Microservices and IoT at a DevOps conference? What could possibly go wrong? In this Power Panel at DevOps Summit, moderated by Jason Bloomberg, the leading expert on architecting agility for the enterprise and president of Intellyx, panelists peeled away the buzz and discuss the important architectural principles behind implementing IoT solutions for the enterprise. As remote IoT devices and sensors become increasingly intelligent, they become part of our distributed cloud enviro...
Almost two-thirds of companies either have or soon will have IoT as the backbone of their business. Though, IoT is far more complex than most firms expected with a majority of IoT projects having failed. How can you not get trapped in the pitfalls? In his session at @ThingsExpo, Tony Shan, Chief IoTologist at Wipro, will introduce a holistic method of IoTification, which is the process of IoTifying the existing technology portfolios and business models to adopt and leverage IoT. He will delve in...
SYS-CON Events announced today that Outlyer, a monitoring service for DevOps and operations teams, has been named “Bronze Sponsor” of SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Outlyer is a monitoring service for DevOps and Operations teams running Cloud, SaaS, Microservices and IoT deployments. Designed for today's dynamic environments that need beyond cloud-scale monitoring, we make monitoring effortless so you...
It is one thing to build single industrial IoT applications, but what will it take to build the Smart Cities and truly society changing applications of the future? The technology won’t be the problem, it will be the number of parties that need to work together and be aligned in their motivation to succeed. In his Day 2 Keynote at @ThingsExpo, Henrik Kenani Dahlgren, Portfolio Marketing Manager at Ericsson, discussed how to plan to cooperate, partner, and form lasting all-star teams to change the...
SYS-CON Events announced today that LeaseWeb USA, a cloud Infrastructure-as-a-Service (IaaS) provider, will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. LeaseWeb is one of the world's largest hosting brands. The company helps customers define, develop and deploy IT infrastructure tailored to their exact business needs, by combining various kinds cloud solutions.
The buzz continues for cloud, data analytics and the Internet of Things (IoT) and their collective impact across all industries. But a new conversation is emerging - how do companies use industry disruption and technology enablers to lead in markets undergoing change, uncertainty and ambiguity? Organizations of all sizes need to evolve and transform, often under massive pressure, as industry lines blur and merge and traditional business models are assaulted and turned upside down. In this new da...
There are 66 million network cameras capturing terabytes of data. How did factories in Japan improve physical security at the facilities and improve employee productivity? Edge Computing reduces possible kilobytes of data collected per second to only a few kilobytes of data transmitted to the public cloud every day. Data is aggregated and analyzed close to sensors so only intelligent results need to be transmitted to the cloud. Non-essential data is recycled to optimize storage.