Monitor available entropy

[gerardocorea]

Required for all PRs:

• Signed CLA.
• Associated README.md updated.
• Has appropriate unit tests.

[danielnelson]

closes #2647

[danielnelson]

Let's just call it entropy_avail to match what is in proc.

[kyzh]

Is there anything that I can do to help this PR to be merged and shipped ?
I could bake a cake, but I'm a long way away from SF to deliver it to your office.

[hanej]

I have something like this to collect entropy in the mean time.

telegraf.conf

[[inputs.exec]]
commands = ["/etc/telegraf/collectors/collect_*.sh"]
data_format = "influx"
timeout = "10s"

shell script

#!/bin/bash

LOCATION=/etc/ansible/facts.d/location.fact

if [ ! -f $LOCATION ]; then
    exit 1
fi

DC=$($LOCATION | grep datacenter | awk '{print $2}' | sed -r 's/"(.*)".*/\1/')
ENV=$($LOCATION | grep '"environment"' | awk '{print $2}' | sed -r 's/"(.*)".*/\1/')
HOST=$(hostname -s)

if [ -z $DC ] || [ -z $ENV ]; then
    exit 1
fi

if [ ! -f /proc/sys/kernel/random/entropy_avail ]; then
    exit 1
fi

VALUE=$(cat /proc/sys/kernel/random/entropy_avail)

echo "system,dc=${DC},env=${ENV},host=${HOST} entropy=${VALUE}"

[danielnelson]

@gerardocorea92 Do you think you could fix the unit test?

[gerardocorea]

@danielnelson pushed commit to fix CircleCI testing.