- Typical First-Noticed Symptoms
- Nagios Engine Program-Wide Performance Information (Check Latency)
- Linux System Utilities
- The Linux Utility, top
- The Linux Utility, uptime
- The Linux Utility, vmstat
- Linux utility: sar
- RRD Performance Data Collection
- GroundWork Subsystems
- GroundWork Diagnostics Tool
This document is intended to help you assess your GroundWork Monitoring Server's performance. As the server's workload increases towards its upper range, certain functions will begin to manifest problematic behavior.
- One typical symptom of a over-loaded server is gaps in RRD Performance Graphs. As check latencies increase, data points may start falling outside the allowed tolerances and be dropped from the graphs.
- Changes made in the Monarch 'Configuration' Tab take noticeably longer to propagate from a Monarch 'commit' to the GroundWork Status Viewer pages.
The first place to look for indications that your system is over-loaded is the Nagios Performance CGI. From the GroundWork Portal, click on 'Monitoring Server' option. This will bring you to a Nagios display of the Monitoring Server and its services. In the secondary menu, you then pick 'Performance Information'.
The most likely metric to show you any performance load on the server is the Active Service Check Latency metrics (Min,Max,Avg) in the top right table shown. These metrics are in seconds. 180 seconds is three minutes, which isn't bad. But 1800 seconds is thirty minutes, which is bad.
Check Latency is the time difference between when a service check was scheduled to run and when it actually ran.
Nagiosstats is a command-line version of the CGI shown above. It is simpler and has less dependencies. It also carries slightly different information, such as 'Total Services' and 'Total Hosts'
The Linux Utility, top
Another assessment of performance is CPU Load. This metric is expressed in how many processes are in a runnable state averaged over 1 minute, 5 minute and 10 minute intervals. If this number is, say 4, that means that there were 4 runnable processes on average over the minute intervals. The following top output shows load averages of 0.58, 0.63, 0.64. These numbers state that about half of the time there were no processes in a runnable state.
Top's main strength is in showing you which processes are in what states. Which processes are taking the most resources? Top can show you. A typical scenario is where the Java listener that accepts feeds of data and posts them to the Collage DB, and the MySQL daemon, are the most active processes.
Top also gives you Memory and Swap metrics. These can also help pinpoint why a system is slowing. So, load numbers above 3, which means that, on average, there were over three runnable processes, with only one running and the others waiting to run, would indicate a slowing system.
The Linux Utility, uptime
The Linux Utility, vmstat
Many useful metrics are here: free memory, free swap and pages paged/swapped in/out. These metrics tell you whether you have enough memory.
Linux utility: sar
Sar is the system activity reporter. By interpreting the reports that sar produces, you can locate system bottlenecks and suggest some possible solutions to those annoying performance problems. The Linux kernel maintains internal counters that keep track of requests, completion times, I/O block counts, etc. From this and other information, sar calculates rates and ratios that give insight into where the bottlenecks are.
The key to understanding sar is that it reports on system activity over a period of time. You must take care to collect sar data at an appropriate time (not at lunch time or on weekends, for example).
A good sar tutorial can be found at http://perso.orange.fr/sebastien.godard/tutorial.html.
Other sar Utilities
Installing & Configuring sar (Sysstat)
GroundWork can collect performance data using an eventhandler. It runs after each check finishes, reading a DB Table and trying to log performance data. Performance data collection can contribute to a slow system.
The simplest way to gauge this is to count the RRD files in /usr/local/groundwork/rrd that have been modified that day.
There are various log files and other audit aids in GroundWork Monitor that can give you hints about how well the server is performing.
For the purposes of this discussion, we will want to focus on the eventhandler logfile, /usr/local/groundwork/nagios/var/log/process_service_perfdata_file.log.
Output to this logfile is controlled by a debug_level variable, at the beginning of the perfdata properties file
First, this debug_level variable only needs to be set to a value above 1 when you are actively debugging something in the Performance data collection subsystem. Otherwise, it should be set to 0 or 1.
The contents of the log can be illuminating. This is a special-purpose eventhandler, one that runs after each service check that has performance data handling enabled - that's the default. Many checks, though, don't have a metric - such as any check that returns true or false. To tune the system, you should disable performance data collection for those services whose results aren't suited for such.
Also, just because you could plot the data on a graph doesn't mean that you should. Conservation of effort here will pay off. If no one is asking for the data, and you aren't particularly interested either, then turn it off.
To turn off performance data handling on a particular host or service, go into the Service record in the Monarch 'Configuration' Tab and, in the 'Service Detail' Tab, uncheck the 'Process Perf Data' property. In the 'Host Detail' Tab it is called the 'Process performance data' property.
Executing the Process-Perf-Data eventhandler only for services that actually are set up for performance data collection and not others, and turning off the logging function when not actively tuning the system, will save computing resources.
GroundWork Customer Support has created a tool that methodically collects the above information and more. You could run the GroundWork Diagnostics Tool and send the information to Support or use it in your own analysis. See the kb article for more information: Running the gwdiags diagnostic tool
Having assessed your system and tuned it as well as possible, you might find that you still have a performance issue. Contact Support, or your GroundWork Account Representative to explore other options.