OSMC 2018 | It’s all about the… containers! by Claudio Kuenzler

... !It’s all about the containers
Monitoring containers 2018OSMC Nuremberg @ClaudioKuenzler
How to integrateHow to integrate
modern containersmodern containers
in a classicalin a classical
system monitoringsystem monitoring

!Brace for impact
What are containers?
- A real world comparison
- Brief introduction?
LXC
LXC – System Containers
- Short Introduction
- Monitoring System Containers
- check_lxc
(Application) Containers
- Quick Introduction
- Monitoring Challenges
- Rancher (2)
- check_rancher2

This guy
… is called Claudio Kuenzler
… lives in Switzerland
… reports to a master process, co-managing two forks
… works at NZZ Media Group and co-founded Infiniroot.com
… is @Napsty on Github and @ClaudioKuenzler on Twitter
… runs a blog at claudiokuenzler.com
… started using Nagios® in 2006, discovered #monitoringlove
… maintains several monitoring plugins, best known are:
check_esxi_hardware, check_smart, check_equallogic
… been using containers since 2012

?What are containers
?

20 feet standard container (1 TEU)
~ 20 feet long (6.1m)
~ 8 feet wide (2.4m)
~ 8 feet high (2.5m)
~ 33 m3 volume
40 feet standard container (= 2 TEU)
~ 40 feet long (12.2m)
~ 8 feet wide (2.4m)
~ 8 feet high (2.5m)
~ 67 m3 volume
TEU = Twenty feet equivalent unit
' !That s a container

!They stack up
By stacking containers together:
- Efficiency (use of space)
- Stability (they don't wobble around)
- Security (for on board staff)

In a perfect world
The current largest container vessel, the “OOCL Hong
Kong”, holds a capacity of 21’413 TEU.

The world is not perfect

When we talk containers, do we mean…?
- Linux Containers (LXC) – aka System Containers → Lightweight VM
- (Docker) Containers – aka Application Containers → Single process (mostly)
Virtualization on process level
- The hard truth: a container is a process
- Processes started inside a container are (obviously) child processes
- Containers use the same Kernel as the host (process, remember?)
- Direct hardware access through Kernel (no hardware virtualization)
- Resource allocation/limits using cgroups
?Again… What are containers

Containers are believed to be “new” but are actually “old” in the Unix world
- FreeBSD “Jails” exist since FreeBSD 4.0 (2000)
- Solaris “Zones” exist since Solaris 10 (2004)
- OpenVZ “Containers” exist since 2005
- Linux Containers (LXC) exist since 2007
First developped at IBM, now maintained by Canonical (Ubuntu)
AKA System Containers (to distinguish from Docker containers)
- Docker Containers (based on liblxc) exist since 2013
Since 2014 with own library (libcontainer)
AKA Application Containers
- containerd container runtime (since 2015) of Docker Inc.
In 2017 Docker Inc donated containerd to CNCF
...A brief history

LXC – Linux Containers

LXC – Linux Containers
- Can be compared to a classical virtual machine w/o hardware virtualization
- Dedicated virtual nic (bridged veth by default), full network access
- Dedicated file system (rootfs)
- Dedicated namespaces for isolation
- cannot see processes of the host
- neither of other containers on the same hosts
- Dedicated init system
- Basically: A super fast VM! (Fast creation, fast boot)
- Install monitoring agents/daemons as you would do on a VM

root@container:~# ps auxf
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root     27207  0.1  0.0  20068  4036 ?        Ss   21:21   0:00 /bin/bash
root     27274  0.0  0.0  38308  3348 ?        R+   21:21   0:00  _ ps auxf
root         1  0.0  0.0 204336  6660 ?        Ss   Sep03   0:09 /sbin/init
root        16  0.0  0.2 374092 267440 ?       Ss   Sep03   1:53 /lib/systemd/systemd
journald
root        35  0.0  0.0  29664  2820 ?        Ss   Sep03   0:03 /usr/sbin/cron f
root        36  0.0  0.0 250116  3492 ?        Ssl  Sep03   3:21 /usr/sbin/rsyslogd n
nagios      71  0.0  0.0  23916  4196 ?        Ss   Sep03   0:03 /usr/sbin/nrpe c
/etc/nagios/nrpe.cfg f
root        75  0.0  0.0  12668  1644 pts/3    Ss+  Sep03   0:00 /sbin/agetty noclear
tty4 linux
tty1 linux
tty3 linux
[...]
LXC – Monitoring processes
→ Use check_procs !

root@container:~# df h x cgroup
Filesystem             Type         Size  Used Avail Use% Mounted on
/dev/vgdata/irczsrvc03 ext4          25G   17G  6.5G  73% /
none                   tmpfs        492K     0  492K   0% /dev
proc                   proc            0     0     0     /proc
proc                   proc            0     0     0     /proc/sys/net
proc                   proc            0     0     0     /proc/sys
proc                   proc            0     0     0     /proc/sysrqtrigger
sysfs                  sysfs           0     0     0     /sys
sysfs                  sysfs           0     0     0     /sys
sysfs                  sysfs           0     0     0     /sys/devices/virtual/net
sysfs                  sysfs           0     0     0     /sys/devices/virtual/net
fusectl                fusectl         0     0     0     /sys/fs/fuse/connections
devpts                 devpts          0     0     0     /dev/console
devpts                 devpts          0     0     0     /dev/pts
devpts                 devpts          0     0     0     /dev/tty1
tmpfs                  tmpfs         60G     0   60G   0% /dev/shm
tmpfs                  tmpfs         60G  169M   59G   1% /run
tmpfs                  tmpfs        5.0M     0  5.0M   0% /run/lock
tmpfs                  tmpfs         60G     0   60G   0% /sys/fs/cgroup
mqueue                 mqueue          0     0     0     /dev/mqueue
binfmt_misc            binfmt_misc     0     0     0     /proc/sys/fs/binfmt_misc
hugetlbfs              hugetlbfs       0     0     0     /dev/hugepages
( )LXC – Monitoring flesystem s
→ Use check_disk !

root@host:~# free m
              total        used        free      shared  buff/cache   available
Mem:         120869        7296       46183        2839       67390      109749
Swap:         15258           0       15258
root@container:~# free m
Mem:         120869        7296       46182        2839       67390      109748
Swap:         15258           0       15258
LXC – Monitoring memory
That’s the same!
- Container sees total capacity and used memory of host
- Not able to determine own memory usage within container
- Therefore do not use monitoring plugin inside container (e.g. check_mem)

Above: Host
Below: Container
LXC – Monitoring memory
- Same memory usage
- Same CPU load
- Same uptime
- Tasks (procs) differ

LXC – Monitoring memory ( )LXCFS
Above: Host
Below: Container
- Still same CPU load
- But memory usage differs
- Uptime now differs, too
- Tasks (procs) differ
- lxcfs virtualizes parts of
/proc inside the container
- lxcfs package in Ubuntu is
recommended when
installing liblxc1 (since LXC
2.x)
- In Debian, needs to be
installed manually

root@host:~# free m
Mem:           3945         229        2894           0         821        3470
Swap:          3814           0        3814
root@container:~# free m
Mem:           3945          93        3663           0         187        3851
Swap:          3814           0        3814
LXC – Monitoring memory ( )LXCFS
Used is not the same anymore!
- Able to show own memory usage inside container
- Container still sees total memory capacity of host
- However: Misleading “available” calculation because not all consumers seen
- If you run a memory check within the container, use “used” column only
That’s wrong!
X

LXC – Monitoring CPU usage
- Container will always see host usage
- Currently not possible to have a “different” view inside container
- (Clumsy) Approach: Compare jiffies on the host
- Example for time spent on system CPU (kernel space) in 5s:
12215974 – 12215646 = 328
- Compared with the host’s jiffies, gives an idea about the container usage
- Future: Possible to monitor CPU usage inside container with cgroups → soon
root@host:~# lxccgroup n container cpuacct.stat
user 41618658
system 12215646
root@host:~# sleep 5
root@host:~# lxccgroup n container cpuacct.stat
user 41619791
system 12215974

LXC – Using check_lxc
- check_lxc is a monitoring (workaround) plugin executed on the LXC host
- Uses cgroup values for memory and cpu checks (lxc-cgroup)
- Checks container autostart configuration
- Correctly monitors memory usage of container(s), incl. Swap
- Gives an idea about container cpu usage
root@host:~# /usr/lib/nagios/plugins/check_lxc.sh n container01 t auto
LXC AUTOSTART OK
root@host:~# /usr/lib/nagios/plugins/check_lxc.sh n container01 t mem
LXC container01 OK Used Memory: 571 MB|mem=598769664B;0;0;0;0
root@host:~# /usr/lib/nagios/plugins/check_lxc.sh n container01 t cpu
LXC container01 OK CPU Usage: 27%|cpu=27%;;;0;0
root@host:~# /usr/lib/nagios/plugins/check_lxc.sh n container99 t cpu
LXC container99 OK CPU Usage: 3%|cpu=3%;;;0;0

2LXC – check_lxc in Icinga
- Deploy checks of LXC containers with “apply” rules
- Example: Define a custom variable “containers” on the host object:
- Apply rule (here used with nrpe remote check):
object Host "lxchost01" {
  import "generichost"
  address = "192.168.100.101"
[…]
  # Containers running on this host
  vars.containers = [ "container01", "container02", "container99" ]
}
apply Service "LXC Memory " for (container in host.vars.containers) {
  import "genericservice"
  check_command = "nrpe"
  vars.nrpe_command = "check_lxc"
  vars.nrpe_arguments = [ container, "mem" ]
  assign where host.address && host.vars.containers
}

2LXC – check_lxc in Icinga
- All (defined) containers are monitored
- Not much config changes needed
- Quick overview which container uses
→ most memory
→ most cpu
- check_lxc is still in development
→ contributions welcome

LXC – Recap
- Can “mostly” be monitored the same way as a classical host or VM
- Some resources must be monitored from “outside” (= on the LXC host)
- CPU resource monitoring might soon work from “inside”, too!
Monitoring... Where? Example Plugin
Processes Inside check_procs
Filesystem Inside check_disk
Network IO Inside check_netio
Memory usage Outside check_lxc
CPU usage Outside check_lxc
Disk IO Outside check_diskio

Application Containers

( )Application Containers AC
- Single process application running in a container (supposed to be)
- Stateless (no data stored inside container)
- Dedicated virtual nic (veth by default), NATted network access (expose)
- Dedicated file system (aufs or overlayfs by default, share the capacity)
- Dedicated namespaces for isolation
- cannot see processes of the host
- neither of other containers on the same hosts
- No init system – Just a process to start, remember?
- Great for quickly scaling up redundant applications (behind a LB)
- We rarely hear “Docker” anymore these days. Kubernetes! containerd!

AC – Monitoring challenges
- No additional software/daemons “allowed” (single process, remember?)
- No direct network access (NAT via host bridge, iptables)
- Expose ports? Yes, but workaroundish and legacy (→ Ingress)
- Standalone Docker means a lot of manual work (→ use Orchestration)
- Stop treating application containers as a classical host/network object
- Think of it as a process, not a host

/AC – Management w Rancher
- Rancher is a “management layer” on top of the orchestration layer
→ Container Runtime → Orchestration (e.g. Kubernetes) → Rancher
- Intuitive user interface and a flexible HTTP API (→ CI/CD!)
- Rancher was chosen after >1y of internal Docker research, comparisons, tests
- Since Q3 2017 in production with total >1200 containers (Oct 18)
- Rancher 1.x uses Cattle orchestration
- Rancher 2.x is relatively new (April 2018), built on Kubernetes orchestration
- Rancher 2.x Working on Test + Staging environments, soon first Prod env
- Need to monitor the Rancher 2.x environments!
PS: No, I’m not affiliated with Rancher! Just a community user.

/AC – Management w Rancher

!AC – Healthchecks ( )Kubernetes
- The container (pod) can be monitored using readiness and liveness probes
- readinessProbe: Detect when the application is ready (e.g. startup delay)
- livenessProbe: Detect failures in application (e.g. http error)
- Allows multiple kind of probes:
- Run a command (e.g. cat /tmp/healthy) → exit 0 = OK
- HTTP Check (e.g. GET /health on port 8080) → Status 2xx/3xx = OK
- TCP Check (e.g. establish connection to port 8080) → Established = OK

2AC – Healthcheck in Rancher

AC – Healthcheck in kubectl
$ kubectl describe pod nginxtestpfbwm namespace gamma insecureskiptlsverify=true
Name:           nginxtestpfbwm
Namespace:      gamma
Node:           mhradoi02t/192.168.254.62
Start Time:     Tue, 02 Oct 2018 21:16:09 +0200
Labels:         controllerrevisionhash=3146803588
                podtemplategeneration=4
                workload.user.cattle.io/workloadselector=daemonSetgammanginxtest
Annotations:    cni.projectcalico.org/podIP: 10.42.1.118/32
Status:         Running
IP:             10.42.1.118
Controlled By:  DaemonSet/nginxtest
Containers:
  nginxtest:
    Container ID:   docker://93c32c0f3eaf34f939347206c5e7151eac60efb14ef4a464fb3c82fa5cbde659
    Image:          nginx
    Image ID:       docker
pullable://nginx@sha256:e8ab8d42e0c34c104ac60b43ba60b19af08e19a0e6d50396bdfd4cef0347ba83
    Port:           <none>
    Host Port:      <none>
    State:          Running
      Started:      Tue, 02 Oct 2018 21:16:12 +0200
    Ready:          True
    Restart Count:  0
    Liveness:       httpget http://:80/ delay=10s timeout=2s period=2s #success=1 #failure=3
    Readiness:      httpget http://:80/ delay=10s timeout=2s period=2s #success=2 #failure=3
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from defaulttoken9nbfr (ro)
Conditions:
  Type           Status
  Initialized    True
  Ready          True
  PodScheduled   True
[...]

AC – Healthcheck in Rancher API
$ curl s u tokenxxxxx:longsecretpass https://rancher2.example.com/v3/project/cr8ss7:p
85rmm/pods/gamma:nginxtestpfbwm |jshon |more
{
[...]
   "name": "nginxtest",
   "privileged": false,
   "readOnly": false,
   "readinessProbe": {
    "failureThreshold": 3,
    "initialDelaySeconds": 10,
    "path": "/",
    "periodSeconds": 2,
    "port": 80,
    "scheme": "HTTP",
    "successThreshold": 2,
    "tcp": false,
    "timeoutSeconds": 2,
    "type": "/v3/project/schemas/probe"
   },
   "resources": {
    "type": "/v3/project/schemas/resourceRequirements"
   },
   "restartCount": 0,
   "runAsNonRoot": false,
   "state": "running",
   "stdin": true,
   "stdinOnce": false,
[...]

2AC – Using check_rancher
- check_rancher2 is a monitoring plugin which uses Rancher 2’s API
- Can run anywhere (requires http/https connection to API)
- Checks status of:
- Cluster(s)
- Project(s)
- Workload(s) (→ Services)
- Pod(s) (→ Containers)
- Consider the API endpoint as the “host”, check types as its services
- Future (hopefully):
- Workload or Pod usage (cpu, memory, network statistics)
depends on https://github.com/rancher/rancher/issues/14230

2AC – check_rancher example
- Workload stuck in “removing”
- New workload (importer) already active
- Monitoring needs to alert me about this!

2AC – check_rancher example
$ ./check_rancher2.sh H rancher2.example.com U token
xxxxx P longsecretpass S t pod p cr8ss7:p85rmm o
importer8bf85dcc9r5rtn n gamma
CHECK_RANCHER2 CRITICAL Pod importer8bf85dcc9r5rtn is
removing|'pod_active'=0;;;; 'pod_error'=1;;;;
- Plugin connects to Rancher 2 API using the information from the parameters:
-H: API Host/DNS/IP
-U: User-ID (token-xxxxx)
-P: Password for User-ID
-S: Use SSL (https)
-t: Use “pod” check type
-p: Project name (contains cluster ID, too)
-o: Pod name (optional)
-n: Namespace

Application Containers – Recap
- It’s not only Docker anymore → containerd (+ runc, kata) as container engine
- An application container is not a classical host
- Think of it as an application/process
- Use orchestration/container management (Kubernetes, Rancher, OpenShift, ...)
- Set up health checks → Healthchecks are your monitoring go go!
- Monitor these health checks using orchestration/management API’s
(Rancher2: check_rancher2)
- There might also be plugins which use kubectl locally → go out and explore!

References and links
- Lost at sea: https://gcaptain.com/number-of-containers-lost-at-sea-falling-survey-shows/
- LXC: https://linuxcontainers.org/
- cgroup-v1: https://www.kernel.org/doc/Documentation/cgroup-v1/
- cgroup-v2: https://www.kernel.org/doc/Documentation/cgroup-v2.txt
- Docker: https://www.docker.com/
- Kubernetes: https://kubernetes.io/
- containerd: https://containerd.io/
- Rancher: https://rancher.com/
- check_lxc: https://claudiokuenzler.com/monitoring-plugins/check_lxc.php
- check_rancher2: https://claudiokuenzler.com/monitoring-plugins/check_rancher2.php

Thank you
[[ $questions eq 0 ]] && exit 0

OSMC 2018 | It’s all about the… containers! by Claudio Kuenzler

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