Dump dynamo consumption high-water marks from cloudwatch

metrics.sh

#!/bin/bash

# Usage:
#
# $ metrics.sh > dynamo_tables.txt
#
# $ cat dynamo_tables.txt \
#     | tr : ' ' \
#     | sed 's/\./ /' \
#     | sed 's/ =//' \
#     | column -s' ' -t

METRICS=(
  'ConsumedReadCapacityUnits'
  'ConsumedWriteCapacityUnits'
)

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

NOW=$(days_ago 0)

CW_NAMESPACE=AWS/DynamoDB

raw_cw() {
  local dims=$1
  local metric=$2

  aws cloudwatch get-metric-statistics \
    --namespace=$CW_NAMESPACE \
    --period=1200 \
    --start-time=$(days_ago 14) \
    --end-time=$NOW \
    --dimensions ${dims} \
    --metric-name=${metric} \
    --statistics Maximum
}

cw() {
  raw_cw "$1" "$2" \
    | jq '.Datapoints | map(.Maximum) | max'
}

list_indexes() {
  local table=$1

  aws dynamodb describe-table \
    --table-name=${table} \
    | jq -r '.Table | .GlobalSecondaryIndexes[] | .IndexName'
}

# Filter $TABLES as needed!
TABLES=$(aws dynamodb list-tables \
  | jq -r '.TableNames[] | @text'
)

for t in $TABLES; do
  tis=$(list_indexes $t)
  for m in ${METRICS[@]}; do
    echo "$t:__table__.$m = $(cw "Name=TableName,Value=${t}" ${m})"
    for i in $tis; do
      echo "$t:$i.$m = $(cw "Name=TableName,Value=${t} Name=GlobalSecondaryIndexName,Value=${i}" ${m})"
    done
  done
done