I'm new to monitoring the k8s cluster with prometheus, node exporter and so on.
I want to know that what the metrics exactly mean for though the name of metrics are self descriptive.
I already checked the github of node exporter, but I got not useful information.
Where can I get the descriptions of node exporter metrics?
Thanks
There is a short description along with each of the metrics. You can see them if you open node exporter in browser or just curl http://my-node-exporter:9100/metrics. You will see all the exported metrics and lines with # HELP are the description ones:
# HELP node_cpu_seconds_total Seconds the cpus spent in each mode.
# TYPE node_cpu_seconds_total counter
node_cpu_seconds_total{cpu="0",mode="idle"} 2.59840376e+07
Grafana can show this help message in the editor:
Prometheus (with recent experimental editor) can show it too:
And this works for all metrics, not just node exporter's. If you need more technical details about those values, I recommend searching for the information in Google and man pages (if you're on Linux). Node exporter takes most of the metrics from /proc almost as-is and it is not difficult to find the details. Take for example node_memory_KReclaimable_bytes. 'Bytes' suffix is obviously the unit, node_memory is just a namespace prefix, and KReclaimable is the actual metric name. Using man -K KReclaimable will bring you to the proc(5) man page, where you can find that:
KReclaimable %lu (since Linux 4.20)
Kernel allocations that the kernel will attempt to
reclaim under memory pressure. Includes
SReclaimable (below), and other direct allocations
with a shrinker.
Finally, if this intention to learn more about the metrics is inspired by the desire to configure alerts for your hardware, you can skip to the last part and grab some alerts shared by the community from here: https://awesome-prometheus-alerts.grep.to/rules#host-and-hardware
Related
I would like to create a time series and inject it into InfluxDb for a demo. I thought about using the top command (top -pid 1393 -stats cpu), and use the CPU value. And then use NodeJS to extract the data and inject it into an InfluxDB. However, there are a couple of but...:
1- The top command has a display section: can it be removed?
2- In Node, I would call (repeatedly) "top -pid 1393 -stats cpu -l 1" with the "-l 1" option to only get a singe sample. I feel it is a misuse of the fact that top generates data at given intervals (basically, I recreate in Node what top does automatically)
Is there a better way to do this - in the ideal world, I would launch top in node and "pipe" the output stream to a variable in an async way (to execute the insertion into InfluxDB).
Thanks for any hints you may have.
Christian
In actual fact, there is a node module for this: see npm usage.
Note that you may have an issue when installing the usage module, generated by node-gyp rebuild (usage requires this module, which requires XCode in Mac platform - see https://github.com/nodejs/node-gyp). To solve this, look here: xcode-select active developer directory error)
Thanks - C
To monitor the process' resource consuming metrics (correct me if I took your intentions wrong), you don't need your NodeJS stuff at all.
All you need is running Telegraf agent, with this plugin configured, on the machine(s) you're targeting.
Point the output plugin to your Influx - and that's it.
As mention in other comments, there are specific tools for that task. Anyway, if you still want to do it programmatically, I would suggest to either:
run top in non-interactive mode, as explained here: https://unix.stackexchange.com/questions/255100/get-top-output-for-non-interactive-shell
read directly the information that you need from /proc/<pid of your process>/<file of interest>
How can I benchmark a process in Linux? I need something like "top" and "time" put together for a particular process name (it is a multiprocess program so many PIDs will be given)?
Moreover I would like to have a plot over time of memory and cpu usage for these processes and not just final numbers.
Any ideas?
I typically throw together a simple script for this type of work.
Take a look at the kernel documentation for the proc filesystem (Google 'linux proc.txt').
The first line of /proc/stat (Section 1.8 in proc.txt) will give you cumulative cpu usage stats (i.e. user, nice, system, idle, ...). For each process, the file /proc/$PID/stat (Table 1-4 in proc.txt) will provide you with both process-specific cpu usage stats and memory usage stats (see rss).
If you google a bit you'll find plenty of detailed info on these files, and pointers to libraries / apps / code snippets that can help you obtain / derive the values you need. With that in mind, I'll focus on the high-level strategy.
For CPU stats, use your favorite scripting language to create an executable that takes a set of process ids for monitoring. At a fixed interval (ex: 1 second) poll / calculate the cumulative totals for each process and the system as a whole. During each poll interval, write all results on a single line to stdout.
For memory stats, write a similar script, but simply log the per-process memory usage. Memory is a bit easier as we directly obtain the instantaneous values.
Run these script for the duration of your test, passing the set of processes ids that you'd like to monitor and redirecting its output to a log file.
./logcpu $(pidof foo) $(pidof bar) > cpustats
./logmem $(pidof foo) $(pidof bar) > memstats
Import the contents of these files into a spreadsheet (for certain applications this is as easy as copy / paste). For CPU, you are after instantaneous values but have cumulative values, so you'll need to do some minor spreadsheet work to derive these values (it's just the delta 't(x + 1) - t(x)'). Of course you could have your cpu logger write the delta, but you'll be spending a bit more time up front on the script.
Finally, use your spreadsheet to generate a nice plot.
Following are the tools for monitoring a linux system
System commands like top, free -m, vmstat, iostat, iotop, sar, netstat, etc. Nothing comes near these linux utility when you are debugging a problem. These command give you a clear picture that is going inside your server
SeaLion: Agent executes all the commands mentioned in #1 (also user defined) and outputs of these commands can be accessed in a beautiful web interface. This tool comes handy when you are debugging across hundreds of servers as installation is clear simple. And its FREE
Nagios: It is the mother of all monitoring/alerting tools. It is very much customization but very much difficult to setup for beginners. There are sets of tools called nagios plugins that covers pretty much all important Linux metrics
Munin
Server Density: A cloudbased paid service that collects important Linux metrics and gives users ability to write own plugins.
New Relic: Another well know hosted monitoring service.
Zabbix
I need to write a script to check the disk every minute and report if it is failing by any reason. The error could be the absolute disk failure and a bad sector and so on .
First, I wonder if there is any script out there that does the same as it should be a standard procedure (because I really do not want to reinvent the wheel).
Second, I wonder if I want to look for errors in /var/log/messages, is there any list of standard error strings for disks that I can use?
I look for that on the net a lot, there are lots of info and at the same time no info about that.
Any help will be much appreciated.
Thanks,
You could simply parse the output of dmesg which usually reports fairly detailed information about drive errors, well that's how I've collected stats on failing drives before.
You might get better more well documented information by using Parse::Syslog or lower level kernel reporting directly though.
Logwatch does the /var/log/messages part of the ordeal (as well as any other logfiles that you choose to add). You can either choose to use that, or to use its code to roll your own sollution (it's all written in perl).
If your harddrives support SMART, i suggest you use smartctl output for diagnostics as it includes a lot of nice info that can be monitored over time to detect failure.
I am trying to profile my software (in Linux) with oprofile. My software consists of both userspace and kernel module. First my doubt is what does the --separate=kernel option do? What will be the difference when running without that option? I did try to see it but couldn't find any difference. Could you please post an example?
Can't i profile a kernel module without the --seperate=kernel option?
Thanks,
Bala
In oprofile when used with option --seperate=kernel, it seperates the kernel and kernel modules per application.
--seperate='library' seperates the samples for the dynamically linked object per application basis.
kernel, dynamically linked object are just not specific to the application we want to profile alone. But at the same time our application spends considerable amount of time in them.
So --seperate allows one to get the samples from the point of view of the application we are interested in profiling. It can also give samples based on individual threads also.
Kernel can be profiled by providing --vmlinux option to opcontrol.
Ex:- opcontrol --vmlinux=/boot/vmlinux-2.6.27.23-0.1-preempt
--seperate is additional option that allows us to see the samples at different resolutions.
I'm trying to find the best way to use 'top' as semi-permanent instrumentation in the development of a box running embedded Linux. (The instrumentation will be removed from the final-test and production releases.)
My first pass is to simply add this to init.d:
top -b -d 15 >/tmp/toploop.out &
This runs top in "batch" mode every 15 seconds. Let's assume that /tmp has plenty of space…
Questions:
Is 15 seconds a good value to choose for general-purpose monitoring?
Other than disk space, how seriously is this perturbing the state of the system?
What other (perhaps better) tools could be used like this?
Look at collectd. It's a very light weight system monitoring framework coded for performance.
We use sysstat to monitor things like this.
You might find that vmstat and iostat with a delay and no repeat counter is a better option.
I suspect 15 seconds would be more than adequate unless you actually want to watch what's happening in real time, but that doesn't appear to be the case here.
As far as load, on an idling PIII 900Mhz w/ 768MB of RAM running Ubuntu (not sure which version, but not more than a year old) I have top updating every 0.5 seconds and it's about 2% CPU utilization. At 15s updates, I'm seeing 0.1% CPU utilization.
depending upon what exactly you want, you could use the output of uptime, free, and ps to get most, if not all, of top's information.
If you are looking for overall load, uptime is probably sufficient. However, if you want specific information about processes, you are adventurous, and have the /proc filessystem enabled, you may want to write your own tools. The primary benefit in this environment is that you can focus on exactly what you want and minimize the load introduced to the system.
The proc file system gives your application read access to the kernel memory that keeps track of many of the interesting variables. Reading from /proc is one of the lightest ways to get this information. Additionally, you may be able to get more information than provided by top. I've done this in the past to get amount of time spent in user and system by this process. Additionally, you can use this to get information about the number of file descriptors open by the process. You might also use this to get detailed information about how the network system is working.
Much of this information is pre-processed by other applications which can be used if you get the information you need. However, it is rather straight-forward to read the raw information. Do a man proc for more information.
Pity you haven't said what you are monitoring for.
You should decide whether 15 seconds is ok or not. Feel free to drop it way lower if you wish (and have a fast HDD)
No worries unless you are running a soft real-time system
Have a look at tools suggested in other answers. I'll add another sugestion: "iotop", for answering a "who is thrashing the HDD" questions.
At work for system monitoring during stress tests we use a tool called nmon.
What I love about nmon is it has the ability to export to XLS and generate beautiful graphs for you.
It generates statistics for:
Memory Usage
CPU Usage
Network Usage
Disk I/O
Good luck :)