Nagios script for checking AWS reservation usage full coverage. Will alert on any wasted reservation capacity. Support latest feature from AWS - instance types inter-family conversion, includes tables with all the data. Doesn't work with region specific reservations.

check_wasted_aws_reserv.sh

#!/bin/bash
# tested with aws-cli/1.11.123 Python/2.7.9 Linux/3.16.0-4-amd64 botocore/1.5.86
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

#set -x

family_conversion="Type      Factor
nano      1
micro     2
small     4
medium    8
large     16
xlarge    32
2xlarge   64
4xlarge   128
8xlarge   256
10xlarge  320
16xlarge  512
32xlarge  1024"

# based on table at http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ri-modifying.html#ri-modification-instancemove
# multiplied by 4 for natural numbers (nano is 0.25)
convert_family(){
        sed 's#\.nano# 0.25#; s#\.micro# 0.5#; s#\.small# 1#; s#\.medium# 2#; s#\.large# 4#; s#\.xlarge# 8#; s#\.2xlarge# 16#; s#\.4xlarge# 32#; s#\.8xlarge# 64#; s#\.10xlarge# 80#; s#\.16xlarge# 128#; s#\.32xlarge# 256#;' |\
        awk '{A[$1]+=$2*$3*4}; END {for (i in A) print i, A[i]}' | sort
}

print_table(){
        (
                echo "$1 Instances Reserved Potential Waste Status"
                join -o 1.1 1.2 2.2 -a 1 -a 2 -e 0 <(echo "$2") <(echo "$3") |\
                        awk '{if ($3>$2) {$5=$3-$2; $4=0} else {$5="0"; $4=$2-$3}; if ($5==0) {$6="OK"} else {$6="Alert"}; print $0}'
        ) | column -t
}
#example:
#       Type                         Instances  Reserved  Potential  Waste  Status
#       dedicated/Linux/c4.large     5          5         0          0      OK
#       dedicated/Linux/c4.xlarge    6          6         0          0      OK
#       dedicated/Linux/m3.large     1          0         1          0      OK

ins_count_raw=`aws ec2 describe-instances | jq -r '.Reservations[].Instances[] | "\(.State.Name) \(.Placement.Tenancy) \(.Platform) \(.InstanceType)"' | awk '$1=="running"{if ($3=="null") $3="Linux"; print $2"/"$3"/"$4}' | sort | uniq -c | awk '{print $2, $1}' | sort`
#exmple:
#       5 dedicated/null/c4.large
#       1 dedicated/windows/m4.xlarge
#       3 default/null/m4.large

#echo "$ins_count_raw"
#echo ---

if [ -z "$ins_count_raw" ]; then
        echo "Can't get instance list"
        exit 2
fi

ins_count_family=`echo "$ins_count_raw" | convert_family`
#example:
#       dedicated/null/c4 272
#       dedicated/windows/m4 32
#       default/null/m4 48

#echo "$ins_count_family"
#echo ---

res_count_raw=`aws ec2 describe-reserved-instances | jq -r '.ReservedInstances[] | "\(.State) \(.InstanceCount) \(.InstanceTenancy) \(.ProductDescription) \(.InstanceType)"' | awk '$1=="active"{if ($4=="Linux/UNIX") $4="Linux"; print $3"/"$4"/"$5" "$2}' | sort`
#example:
#       9 dedicated/Linux/m3.medium
#       5 dedicated/Linux/c4.large
#       2 default/Linux/m3.medium

#echo "$res_count_raw"
#echo ---

res_count_family=`echo "$res_count_raw" | convert_family`
#example:
#       dedicated/Linux/c4 272
#       dedicated/Linux/m3 72
#       default/Linux/c4 16

#echo "$res_count_family"
#echo ---

family_table=`print_table "Family" "$ins_count_family" "$res_count_family"`
type_table=`print_table "Type" "$ins_count_raw" "$res_count_raw"`

if echo "$family_table" | sed 1d | grep -q "Alert"; then
        msg="Found wasted reservation"
        ec=2
else
        msg="Reservations are in full use"
        ec=0
fi

echo "$msg
<pre>
Count by instance type family (converted to nano):
$family_table
* alerts are based on this table only
* counts are noirmailzed to nano for inter family conversion

Count by specific instance type:
$type_table
* count for specific instance types
* alerts here are not crucial

Instance size conversion table (for reference):
$family_conversion
* conversion table for all types sizes
* based http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ri-modifying.html#ri-modification-instancemove
* multiplied by 4 for natural numbers (nano is originaly 0.25)
</pre>
"

exit "$ec"