Print metrics for DynamoDB table and secondary indexes to show provisioned capacity usage.

dynamodb-usage.sh

#!/bin/bash

set -Eeuf
set -o pipefail

PERIOD=${PERIOD-'3600'}
DAYS_AGO=${DAYS_AGO-'30'}

AWS_DEFAULT_REGION="$1"
shift

export PATH='/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin'
export AWS_DEFAULT_REGION

raw_jq() {
    jq -r "$@"
}

days_ago() {
    local day_count="$1"
    date -u -j -v "-${day_count}d" +'%Y-%m-%dT%H:%M:%SZ'
}

time_now() {
    days_ago 0
}

list_tables() {
    aws dynamodb list-tables | \
        raw_jq '.TableNames[] | @text'
}

list_indexes() {
    local table="$1"
    aws dynamodb describe-table \
        --table-name="${table}" | \
            raw_jq '.Table | .GlobalSecondaryIndexes[] | .IndexName' \
                2>/dev/null || true
}

retrieve_metric() {
    local filter="$1"
    local metric="$2"
    aws cloudwatch get-metric-statistics \
        --namespace='AWS/DynamoDB' \
        --period="${PERIOD}" \
        --start-time="$(days_ago $DAYS_AGO)" \
        --end-time="$(time_now)" \
        --dimensions="${filter}" \
        --metric-name="${metric}" \
        --statistics='Sum' | \
            raw_jq '.Datapoints | map(.Sum) | add // 0'
}

table_metric() {
    local table="$1"
    local metric="$2"
    retrieve_metric "Name=TableName,Value=${table}" "$metric"
}

index_metric() {
    local table="$1"
    local index="$2"
    local metric="$3"
    retrieve_metric "Name=TableName,Value=${table} Name=GlobalSecondaryIndexName,Value=${index}" "$metric"
}

metrics=(
    'ConsumedReadCapacityUnits'
    'ConsumedWriteCapacityUnits'
)

tables=( $(list_tables) )
for table in "${tables[@]}"; do
    indexes=( $(list_indexes "$table") )
    for metric in "${metrics[@]}"; do
        echo "${table}:__table__.${metric} = $(table_metric "$table" "$metric")"
        for index in "${indexes[@]}"; do
            echo "${table}:${index}.${metric} = $(index_metric "$table" "$index" "$metric")"
        done
    done
    echo
done