docker monitoring CPU and memory usage

you can run "top" on the host machine, or even better use "docker stats":

docker stats https://docs.docker.com/engine/reference/commandline/stats/#usage

CONTAINER           CPU %               MEM USAGE / LIMIT       MEM %               NET I/O               BLOCK I/O             PIDS
481ab8c0e8c3        0.00%               1.152 MiB / 15.51 GiB   0.01%               57.44 kB / 34.53 kB   10.06 MB / 4.096 kB   3
335eac0388c6        0.10%               575.2 MiB / 15.51 GiB   3.62%               37.72 kB / 1.296 kB   98.64 MB / 172 kB     45
57adda2fc2ca        0.08%               851.3 MiB / 15.51 GiB   5.36%               6.311 MB / 1.029 MB   152.3 MB / 258 kB     91
58d783dd5b7e        0.09%               849.8 MiB / 15.51 GiB   5.35%               9.961 MB / 2.459 MB   157.1 MB / 266.2 kB   88
f935787e6800        0.10%               2.03 GiB / 15.51 GiB    13.09%              227.9 MB / 36.82 MB   357.7 MB / 311.3 kB   114
a6996fee63aa        184.91%             653.8 MiB / 15.51 GiB   4.12%               876 B / 1.296 kB      100.8 MB / 0 B        92

"docker top" seems to be a misnomer, it's more similar to "ps"

docker top 481ab8c0e8c3

UID                 PID                 PPID                C                   STIME               TTY                 TIME                CMD
root                21277               21262               0                   Jan30               ?                   00:00:00            /bin/bash /opt/jboss/wildfly/bin/standalone.sh -b 0.0.0.0 -bmanagement 0.0.0.0
root                21309               21277               0                   Jan30               ?                   00:00:00            /bin/bash /usr/local/bin/ssh-start
root                21312               21309               0                   Jan30               ?                   00:00:00            /usr/sbin/sshd -D

It's good to set LIMITS on the MEMORY and CPU a container can use:

https://docs.docker.com/engine/admin/resource_constraints/#limit-a-containers-access-to-memory

docker run -it --cpus=".5" ubuntu /bin/bash