Illumos Telegraf Plugins
11 September 2021

Some time ago I made some Solaris collectors for Diamond, and I also wrote about making them. Those collectors work great: I’ve had them running for about four years with no issue, in conjunction with a Wavefront output that ain’t never getting merged.

I used Diamond because at that time Telegraf wouldn’t build on anything Solarish. But some smart people soon fixed that, even though none of the OS-related plugins could make any sense of a SunOS kernel.

So I cobbled together some really sketchy Telegraf inputs. They worked well enough, but they weren’t well written, had no tests, and they didn’t have anything like the coverage of the Diamond ones. Because I was using the lamented Joyent Public Cloud at the time, I targeted them specifically for non-global SmartOS zones, so they weren’t much good for monitoring servers.

Recently I decided to rework the Telegraf plugins, hoping to replace my creaky old Diamond setup.

Philosophy and Excuses

Most of the plugins generate metrics from kstats. Kstats have a snaptime value, which allows extremely accurate calculation of rates of change. Any smart person would use snaptime to calculate diffs between values and send them as rates. But not me.

I chose to send the raw kstat value, stamped with the time at which it was collected. This was partly down to the “just get it done” first iteration, but I’ve found it works perfectly well.

Most of my charts, as you’ll see later, simply convert the raw values with a rate() function, which is no effort at all, and I’ve even found that raw values can even be better than rates, in some circumstances. Often I wish to alert off changes over time, rather than thresholds, and it’s far easier to reliably turn a counter into a rate than the other way round.

I also chose to drop Solaris support. I don’t run Solaris any more, and there’s significant divergence now between it and Illumos.

CPU

The first thing people tend to want to measure, probably because it’s easy, is CPU usage.1

My telegraf.conf stanza for the CPU plugin looks like this:

[[inputs.illumos_cpu]]
  sys_fields = ["cpu_nsec_dtrace", "cpu_nsec_intr", "cpu_nsec_kernel", "cpu_nsec_user"]
  cpu_info_stats = true
  zone_cpu_stats = true

sys_fields is a list of cpu::sys kstats you want to collect. I use the nsec ones, which are counters of the nanoseconds spent by the CPU in one of a number of states.

$ kstat cpu:0:sys | grep nsec
        cpu_nsec_dtrace                 14699590921
        cpu_nsec_idle                   1302005686348634
        cpu_nsec_intr                   10345655014135
        cpu_nsec_kernel                 81405829122846
        cpu_nsec_user                   384278971412372

Here’s an “interesting” design decision I maybe should have mentioned earlier. If you set sys_fields to an empty list, you get all the cpu:n:sys kstats.

You may feel this is a terrible, counter-intuitive decision, and I wouldn’t blame you, but it feels right to me. If you actually want to specify “no stats”, put something like ["none"] as your field list. Or disable the plugin.

Here is a chart of some of those sys metrics, along with the Wavefront WQL queries which generate it. Hover over the points to see the extra dimensions, or tags, or labels, or whatever you prefer to call them.

WQL> rate(sum(ts("dev.telegraf.cpu.nsec.*"), metrics)) / 4e7
WQL> mavg(10m, rate(sum(ts("dev.telegraf.cpu.nsec.*"))) / 4e7)

The first query sums the different types of CPU usage presented by the kstats across all the cores. Dividing by number of cores × 1e7 gives me a percentage.

The second query (the flatter blue line) is the moving average of all CPU usage across all cores.

We could omit the sum() and get per-core usage, if we cared about that. If you aren’t interested in DTrace or interrupt usage – which you likely aren’t — omit them from the Telegraf config and save yourself some point rate. Pretty standard stuff.

It might be more interesting to look at a per-zone breakdown. To turn this on, set zone_cpu_stats to true, and you’ll get something like this.

WQL> rate(sum(ts("dev.telegraf.cpu.zone.*"), name)) / 4e7

This is a largely idle system: the spikes are Puppet running in each zone, with the global burbling along running things, and it looks like something maxed out a core in cube-ws for about five minutes. You get system and user times for each zone, but here I’ve summed them for a “total CPU per zone” metric.

Turning on cpu_info_stats looks at the cpu_info. It produces a single metric at the moment: the current speed of the VCPU, tagged with some other, potentially useful, information.

WQL> ts("dev.telegraf.cpu.info.speed")

Disk Health

Next, alphabetically, is the disk health plugin. This uses kstats in the device_error class. Let’s have a look:

$ kstat -c device_error -i3
module: sderr                           instance: 3
name:   sd3,err                         class:    device_error
        crtime                          33.030081552
        Device Not Ready                0
        Hard Errors                     0
        Illegal Request                 0
        Media Error                     0
        No Device                       0
        Predictive Failure Analysis     0
        Product                         Samsung SSD 860 9
        Recoverable                     0
        Revision                        1B6Q
        Serial No                       S3Z2NB1K728477N
        Size                            500107862016
        snaptime                        2112679.332420447
        Soft Errors                     0
        Transport Errors                0
        Vendor                          ATA

There are two things to notice here. First, a lot of the values are not numeric. If you try to turn these into metrics, you’ll have a bad time. So choose wisely. Secondly, what’s with those names? Capital letters and spaces?

The plugin makes some effort to improve this. You specify your fields using the real kstat names, but the plugin will camelCase them into hardErrors and illegalRequest and so-on. If any of the string-valued stats look useful, you can turn them into tags.

The choice to output raw values also makes sense here, because you’re probably if you’re measuring the rate of disk errors, you’ve got real issues. Better to know cumulatively how many there have been.

Here’s where the “not specifying anything gets you everything” approach makes more sense. You may not know in advance what device IDs your disks will get, so by using a blank value, you’ll get metrics about them all, wherever they land. Add more disks, get more metrics.

Here’s my config, which checks disk health every ten minutes.

[[inputs.illumos_disk_health]]
  interval = "10m"
  fields = ["Hard Errors", "Soft Errors", "Transport Errors", "Illegal Request"]
  tags = ["Vendor", "Serial No", "Product", "Revision"]
  devices = []

Here is a disk dying in agony. Please excuse the screwy “size” tag: that bug is fixed now. The metric path is different from the others because these are production metrics. The alert ends because the disk was taken out of the pool.

WQL> ts("diskHealth.transportErrors", serialNo="WD-WCC7K3ZVCRH6")

FMA

The illumos_fma collector shells out to fmstat(1m) and fmadm(1m), turning their output into numbers. I don’t think there’s a huge amount of value in the fmstat metrics, though they do give a little insight into how FMA actually works. I don’t collect them now.

I do, however, collect, and alert off, the fma.fmadm.faults metric. Anything non-zero here ain’t good.

For each FMA error, it sees, the collector will produce a point whose tags are a breakdown of the fault FMRI. A fault of zfs://pool=big/vdev=3706b5d93e20f727 will therefore generate a point with a constant value of 1 and tags of module = zfs, pool = big, and vdev = 3706b5d93e20f727. Put these in a table and they’re a pretty useful metric. Sadly, Wavefront won’t let me share tables with you.

IO

The IO plugin looks at the disk kstat class which, on my machines at least, breaks down into sd (device level) and zfs (pool level) statistics.

$ kstat -c disk -m zfs
module: zfs                             instance: 0
name:   rpool                           class:    disk
        crtime                          33.040698445
        nread                           89256141824
        nwritten                        4917084512256
        rcnt                            0
        reads                           12924589
        rlastupdate                     2283599909215801
        rlentime                        93260596443424
        rtime                           22778143997056
        snaptime                        2283600.200850278
        wcnt                            0
        wlastupdate                     2283599909180201
        wlentime                        1382360339824286
        writes                          134488141
        wtime                           17956052528931
...
$ kstat -c disk -m sd
module: sd                              instance: 6
name:   sd6                             class:    disk
        crtime                          38.500260610
        nread                           4403392102
        nwritten                        63619379200
        rcnt                            0
        reads                           617284
        rlastupdate                     779318097724680
        rlentime                        6037614078523
        rtime                           3660651799956
        snaptime                        2283628.843277697
        wcnt                            0
        wlastupdate                     779318095367423
        wlentime                        2103813659369
        writes                          153664
        wtime                           685893661939
...

The config looks like this

[[illumos_io]]
  fields = ["reads", "nread", "writes", "nwritten"]
  modules = ["sd", "zfs"]
  ## Report on the following devices, inside the above modules. Specifying none reports on all.
  #devices = ["sd0"]

You can select zfs and/or sd; you can select any devices (the kstat name) and, as usual, selecting none gets you all of them. You can also select the kstat fields you wish to collect, and they’re emitted as raw values, so you’ll likely need to get your rate() on.

WQL> rate(ts("dev.telegraf.io.nwritten", module="sd"))

You can see from that that I have mirrored disks. Here’s the same view by pool, which probably makes more sense.

WQL> rate(ts("dev.telegraf.io.nwritten", module="zfs"))

Memory

The memory plugin takes its info from a number of sources, all of which are optional. Here’s the config:

[[inputs.illumos_memory]]
 swap_on = true
 swap_fields = ["allocated", "reserved", "used", "available"]
 extra_on = true
 extra_fields = ["kernel", "arcsize", "freelist"]
 vminfo_on = true
 vminfo_fields = ["freemem", "swap_alloc", "swap_avail", "swap_free", "swap_resv"]
 cpuvm_on =true
 cpuvm_fields = ["pgin", "anonpgin", "pgpgin", "pgout", "anonpgout", "pgpgout",
                 "swapin", "swapout", "pgswapin", "pgswapout"]
 cpuvm_aggregate = true

swap (as in on and fields) uses the output of swap -s, turning the numbers into bytes.

WQL> ts("dev.telegraf.memory.swap.*")

vminfo looks at the unix:0:vminfo kstat, and converts the values it finds there, which are in pages, into bytes.

WQL> ts("dev.telegraf.memory.vminfo.*")

cpuvm uses the cpu:n:vm kstats:

# kstat cpu:0:vm
module: cpu                             instance: 0
name:   vm                              class:    misc
        anonfree                        1556497
        anonpgin                        91181
        anonpgout                       691806
        as_fault                        2808009691
        cow_fault                       456075696
        crtime                          34.408122794
        dfree                           2198350
        execfree                        39764
        execpgin                        1
        execpgout                       1526
        fsfree                          602089
        fspgin                          530327
        fspgout                         377473
        hat_fault                       0
        kernel_asflt                    0
        maj_fault                       160708
        pgfrec                          374000423
        pgin                            161053
        pgout                           88551
        pgpgin                          621509
        pgpgout                         1070805
        pgrec                           374000476
        pgrrun                          887
        pgswapin                        0
        pgswapout                       0
        prot_fault                      1300095547
        rev                             0
        scan                            88740494
        snaptime                        2371429.653330849
        softlock                        22753
        swapin                          0
        swapout                         0
        zfod                            1610062468

Choose whichever fields you think will be useful. Per-CPU information of this level seemed excessive to me, so I added the cpuvm_aggregate switch, which adds everything together and puts them under an aggregate metric path. I use these numbers to look for paging and swapping.

WQL> ts("dev.telegraf.memory.cpuVm.vm.aggregate.*")

Finally, there are the extra fields, which look for the size of the kernel, ZFS ARC, and the freelist. These are all kstats, but they’re gauge values, so there’s no need to process them further.

WQL> ts("dev.telegraf.memory.arcsize")
WQL> ts("dev.telegraf.memory.kernel")
WQL> ts("dev.telegraf.memory.freelist")

Network

The network plugin tries to be at least a little smart. If you hover over this chart and look at the legend you’ll see it’s collecting network metrics for all VNICs, and attempting to add meaningful tags to them.

WQL> rate(ts("dev.telegraf.net.obytes64"))

It can work out the zone, by running dlamd(1m) each time it is invoked, and mapping the VNIC name to the zone. Whilst it’s doing that it also tries to get stuff like the link speed and the name of the underlying NIC. It’s not very good with etherstubs, and it wouldn’t have a clue about anything any more advanced than you see here. Like all these plugins, it does what I wanted and goes no further.

NFS

The NFS server and client plugins expose metrics in the kstat nfs modules. Here you run up against a limitation of kstats. So far as I can tell, zones keep their own kstat views, so Telegraf running in the global zone cannot monitor the NFS activity – server or client – in a local zone. I suppose I could do something horrible, like zlogin into the NGZ and parse the output of kstat(1m), but doing things cleanly, it’s not possible. So if NGZ NFS is a big thing to you, you’re stuck using per-zone Telegrafs.

You can choose which NFS protocol versions you require, and then you just pick your kstats like all the other plugins. The NFS version is a tag.

WQL> rate(ts("dev.telegraf.nfs.server.*", nfsVersion="v4"))

Packages

This just counts the number of packages which can be upgraded. It works in a pkg(5) or pkgin zone, but can’t see other zones. I plan to make it able to see into NGZs from the global, but I haven’t got round to it yet.

Here you can see me upgrading my dev server.

WQL> ts("dev.telegraf.packages.upgradeable")
WQL> events(name="patch cube")

The caveat here is that something needs to continually refresh the package cache. For me, Puppet does that as part of its normal duties.

SMF

This shells out to svcs(1m) to give you an overview of the health of your SMF services. It runs svcs with the -Z flag, via pfexec, which, assuming the user running Telegraf has the file_dac_search privilege, lets it see the states of services in all non-global zones. Here’s just one NGZ, seen from the global. You can, of course, specify which zones you’re interested in, and specifying none gets you the lot.

WQL> ts("dev.telegraf.smf.states", zone="cube-pkgsrc")

You can also get more detailed breakdowns of errant services. Normally I present this data as a table, but that won’t work here.

WQL> ts("dev.telegraf.smf.errors", zone="cube-pkgsrc")

If you don’t want the detailed service view, or you’re worried applying service names as tags will cause high cardinality, you can set generate_details = false and not get these metrics.

ZFS ARC

This plugin just presents the stats you get from kstat -m zfs -n arcstats. There are too many of those to list here, and I don’t run this plugin as I don’t have anything with a ZFS ARC right now so you don’t even get a chart. Sorry!

Zones

The zones plugin gathers the uptime and the age of every zone on the box. The former comes from the zones boottime kstat, and the latter is worked out by looking when the relevant file in /etc/zones was modified. I haven’t found uptime enormously useful, but I like the age stat because I like to exercise my infrastructure creation, and it shows me any zones that haven’t been rebuilt in too long.

Each point on these metric paths comes with a bunch of tags like brand, IP type and status. Filtering and grouping on these can turn up lots of useful and interesting data.

I display this as a pie chart, but Wavefront can’t share those either.

WQL> count(ts("dev.telegraf.zones.status"), brand)

Zpool

Zpool is another run-external-program cop-out. For starters it parses zpool list, and offers up the various fields as numbers. Here you can see me alerting off >80% capacity.

WQL> ts("dev.telegraf.zpool.cap")

There’s a synthetic “health” metric too. This converts the health of the pool to a number. I put the mapping in my chart annotation:

0 = ONLINE, 1 = DEGRADED, 2 = SUSPENDED, 3 = UNAVAIL, 4 = unknown

and as you can see from this chart, I alert off non-zero values. Here’s an errant pool being fixed:

WQL> ts("dev.telegraf.zpool.status")

You can also turn on “status” metrics. This takes the output of zpool status -pv <pool> and turns it into numbers. As well as counting the errors in each device of the pool, it also plots the time since the last successful scrub (for easy alerting off not-scrubbed-in-forever pools), and plots the time of a resilver scrub. The actual elapsed time probably isn’t so useful, but it being non-zero certainly can be.

Here’s a pool being scrubbed. The purple line (left axis) is the time since it was scrubbed, the blue line (right axis) the time spent scrubbing.

WQL> ts("zpool.status.scrubTime", name="rpool")
WQL> ts("zpool.status.timeSinceScrub", name="rpool")

Making it Work

The repo has full instructions on how to build a version of Telegraf with these plugins installed, and there’s everything you need to run it under SMF.

The Future

I have a couple more plugins not quite ready for production. One mimics prstat to give you charts of resource consumption by process; another is specifically written to run inside a SmartOS NGZ, reporting mostly on the proportions of allocated resources currently being consumed.

I think I currently measure everything I’m interested in, but I see telemetry as a work forever in progress, and I constantly refine not only my alerts and dashboards, but also my metric collection.

If you wish to improve these plugins, or add more, please do fork the repo and raise a PR. If you find bugs, or wish improvements that you aren’t able to make yourself, open an issue and I’ll have a look.

  1. Actually, the first thing a lot of people seem to look for is load average, but if you think that’s a good way to monitor a system, look elsewhere. 

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