Automated System Monitoring Josh Malone Systems Administrator [email protected] National Radio Astronomy Observatory Charlottesville, VA https://blogs.nrao.edu/jmalone 2 One night, about 8 or 9 years ago, the chiller in our DC failed. Co-worker arrive in the morning to find room was 90F ambient. Quickly set up fans to vent the room. Checked servers - found that main web server had lost both disks in its OS RAID mirror. (15k disks, ran hot) Main page was being served from memory, but the OS was freaking out. We had minimal monitoring scripts. No environment monitoring. No disk health checks. Failure caught us completely by surprise. We decided that we weren’t going to let this happen ever again. Over the next year or so we implemented 2 independent monitoring systems - one for servers/ services and one for environmentals. Set up each system to also monitor the other. WHAT IS AUTOMATED MONITORING? 7 Some sort of dedicated, automatic instrumentation to check services and/or servers Detect and report service problems, server hardware issues Usually provides a central “dashboard” to track problems Can be distributed; but still under control of a central daemon * Diferentiates it from “a bunch of scripts” used to check on things; that doesn’t have the ability to determine cause or eliminate false alarms. Automated Monitoring Workflow 8 Most packages implement this type of workflow Not all packages provide event handlers ack’ing page is important - let’s other admins know that someone is working on the problem so they don’t step on each other’s toes Monitoring Packages: Open Source • • Pandora FMS • Opsview Core • Naemon • • • • • • Captialware ServerStatus • Core • Sensu All Trademarks and Logos are property of their respective trademark or copyright holders and are used by permission or fair use for education. Neither the presenter nor the conference organizers are affiliated in any way with any companies mentioned here. 9 Service monitoring is a very crowded space Monitoring Packages: Commercial • Nagios XI • Sensaphone (IMS 4000) • Groundwork • Statseeker • PRTG network monitor • CopperEgg • WhatsUp Gold • PRTG network monitor • op5 (Naemon) All Trademarks and Logos are property of their respective trademark or copyright holders and are used by permission or fair use for education. Neither the presenter nor the conference organizers are affiliated in any way with any companies mentioned here. 10 Your ideal monitoring solution may consist of multiple monitoring platforms. I mentioned in beginning that we set up 2 parallel monitors: NRAO uses a combination of * network monitoring - StatSeeker * server / service monitoring - Nagios * environment monitoring - IMS4000 & Nagios What can monitoring do for you? • Spot small problems before they become big ones • Checklist when restoring from a power outage • Learn about outages before your users do • Gives you better problem reports than users • Problems you might never spot otherwise • Failed HDDs in RAIDs • Full /var partitions • Logs not rotating • System temperature rising 11 Monitoring gives you warnings: things are still *working* but they’re gonna break soon unless u fix it Without Monitoring With Monitoring • dhcp out of leases “The Internet’s down - • dhcp server down fix it!!!” • dns server not responding • ethernet switch down • ISP link down / saturated 12 Takes a typical problem report like “the internet’s down!”… Proper monitoring knows the diference between these possible causes. Can easily narrow the scope of the problem Without Monitoring With Monitoring •connectivity issues “ZOMG! Our web site •web server down is down! O Noes!!!” •apache not running •web server disk full •server load too high 13 With some thing like the infamous “Oh No - our website is down!” Again, a monitor can often pinpoint the root cause of the problem. What can monitoring do for you? • Capacity planning • Performance data can generate graphs of utilization • RAM, Disk, etc. • Availability reports - CAUTION • Easy to generate -- even easier to generate wrong • Make sure your configurations actually catch problems • Will also include problems with Nagios itself :( • If you’re going to quote your availability numbers (SLAs, etc.) make sure you understand what you’re actually monitoring. 14 Beyond just spotting problems, monitoring can be good for capacity planning. In Nagios, graphing requires add-on (PNP4Nagios); many other packages include it in the base install Nagios builds a wealth of historical data about your services. PNP graphs that data so you can visualize it. availability: make sure Nagios is being honest; audit your plugins ENVIRONMENT MONITORING 15 Before we get to host and service monitoring, take a quick look at options for environment monitoring. Environment Monitoring • Temperature • Smoke • Water • Humidity • Motion • Door / closure • Mains power 16 What do we mean by environment monitoring? Any of these, plus perhaps many more. Basically - anything about your servers or server room other than the services. Environment Monitoring • Sensaphone IMS-4000 • Connect sensors to measure desired metrics • IP-based “Nodes” can connect remote sensors • Wireless sensors available • Notification via POTS line and voice dialer as well as email • SNMP support Use my plugin w/ Nagios! 17 IMS-4000 is a standalone env monitoring solution. In order to centralize monitoring and track long-term temp data I developed a plugin for Nagios; Nagios can pull status and perfdata from IMS. https://github.com/48kRAM/nagios-plugins/tree/master/IMS4000 Environment Monitoring • ServersCheck • Temp, Humidity • Wireless (2.4GHz) • NetBotz • Temp, humidity, smoke, water, vibration, doors, cameras 18 NetBotz 200 ~$450; plus cost of sensors (Temp ~$100) Plenty of plugins for Nagios NetBotz integration NAGIOS 19 Nagios • Open source host / service monitoring package • “Nagios Ain't Gonna Insist On Sainthood” • Originally released in 1999 as “NetSaint” • Available in 2 versions: Core and XI • Nagios Core: Open-source, freely available • Nagios XI: Commercial • Free license for up to 7 hosts • Available as source installer or VMware appliance 20 XI available with support contracts if your company likes having those :) Easy to install — no excuses not to be running good monitoring software Nagios Architecture 21 Nagios gets its super powers from it’s plugins. 3rd-party Add-ons: NConf is a GUI configurator for Nagios What’s a plugin? • Plugins actually run the service or host checks. • Each plugin monitors a different type of service • Data from plugin is communicated to Nagios using a (very) simple API • Plugins can also report “Performance Data” (perfdata) to be graphed or tracked • Requires a perfdata add-on (or Nagios XI) • Plugins can be written in any language • Perl plugins can run using Nagios’s embedded perl interpreter for increased performance 22 Where to Monitor a Service? Host ping Is server host alive? TCP port 443 Is Apache listening? SSL handshake Is SSL functional? HTTP return code Is the page found? Page load time Does page load quickly? Page content Is it the right page? 23 when you’re setting up a service monitor, consider how you really want to monitor it. If I’m monitoring a web server; here’s 6 diferent places I could potentially monitor. * Is server listening on a TCP port? - bind probs, web server configured for wrong IP * Is SSL working? - expired SSL certificate High load time? - server overloaded, DoS attack.. HTTP 200: OK just means it found the page you wanted. But is that the “Welcome to Apache” default page? (pkg update might overwrite your config file) One “service” might require multiple checks to monitor everything you care about. You might also use a local agent to check the web server process itself (number of children, memory usage, etc.) Each point tells you diferent things about that service… can answer a diferent question. Consider what you want to know about a service. Custom Plugins • Nagios can monitor anything you can write a script to check • Simple API: just write text to stdout and exit with a value • You can write plugins in ANY language you choose! • bash, python, tcl, expect • perl (Nagios has embedded perl interpreter for speed) • C, C++ • Huge collection of plugins available at: http://exchange.nagios.org https://www.monitoringexchange.org • Be wary of some community plug-ins! • Test first!!! 24 Plugins are the lifeblood of a Nagios system. Nagios is literally useless without them. That script you have to check X… turn it into a Nagios plugin. Some plugins even contributed by companies like Dell Don’t be afraid to inspect the code (you might be afraid of what you find, though) Performance Data • Metrics about the state of the service • Can be used to generate graphs showing trends, etc. • Performance data processing requires some external add-on like PNP4Nagios 25 Example of a perfdata graph in PNP4Nagios My Plugins Framework • https://github.com/48kRAM/nagios-plugins • Perl • Net::SNMP • Plugin for APC Smart-UPS, 26 Constantly evolving. Check regularly Agent-less vs Agent-full Checks Agent-less Agent-full • No agent installed on the • Must install agent on monitored host server to be monitored • All check plugins run on the • Check logic runs on monitoring server monitored host • Service to be monitored • Can access services non- must be network-accessible network services • Default mode of Nagios • SNMP can be a powerful agent for checks • Server-specific agents 27 These plugins implement 2 basic types of checks… Agents: NRPE (remote plugin executor), NSClient++ (Windows system monitor agent) Many, if not most, devices and operating systems provide an SNMP agent. * printers Dell OMSA - agent for Dell server health info USING NAGIOS 28 About Nagios Replacements When Nagios went commercial, the “open-source community” decided that it needed not one, not two, but three replacements for Nagios: Icinga and Naemon (forks of Nagios) and Shinken (a drop-in replacement). Most linux distros are now shipping one or more of these compatible replacements rather than the official Nagios Core.