pantheon-ai/cfn-behavior-validator
Creates test stacks, analyzes CloudFormation events, and compares actual vs documented update behavior to validate whether resource property changes trigger replacement or in-place updates. Use when: a user wants to test if a CFN property change causes resource replacement; when investigating stack update behavior or "Update requires" documentation accuracy; when validating whether a workaround (e.g. hash-based logical IDs) is actually necessary; when questioning UpdateRequiresReplacement behavior for immutable properties; when empirical evidence is needed before an architectural decision involving CDK or CloudFormation stack updates.
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watch-cfn-events.shscripts/
#!/usr/bin/env bash
# CloudFormation Event Watcher
# Watches CloudFormation events in real-time during stack updates
set -euo pipefail
STACK_NAME="${1:-}"
WATCH_INTERVAL="${2:-5}"
if [ -z "$STACK_NAME" ]; then
echo "Usage: $0 <stack-name> [watch-interval-seconds]"
echo ""
echo "Example: $0 LctMonitoringStack-ST 5"
exit 1
fi
echo "Watching CloudFormation events for stack: $STACK_NAME"
echo "Refresh interval: ${WATCH_INTERVAL} seconds"
echo "Press Ctrl+C to stop"
echo ""
echo "----------------------------------------"
LAST_TIMESTAMP=""
while true; do
# Get latest events
EVENTS=$(aws cloudformation describe-stack-events \
--stack-name "$STACK_NAME" \
--max-items 20 \
--query 'StackEvents[*].[Timestamp,LogicalResourceId,ResourceType,ResourceStatus,ResourceStatusReason]' \
--output text 2>/dev/null || echo "")
if [ -z "$EVENTS" ]; then
echo "No events found or stack doesn't exist"
sleep "$WATCH_INTERVAL"
continue
fi
# Filter events newer than last seen
NEW_EVENTS=$(echo "$EVENTS" | while read -r line; do
TIMESTAMP=$(echo "$line" | awk '{print $1}')
if [ -z "$LAST_TIMESTAMP" ] || [[ "$TIMESTAMP" > "$LAST_TIMESTAMP" ]]; then
echo "$line"
fi
done)
if [ -n "$NEW_EVENTS" ]; then
echo "$NEW_EVENTS" | while read -r line; do
TIMESTAMP=$(echo "$line" | awk '{print $1"T"$2}')
RESOURCE=$(echo "$line" | awk '{print $3}')
TYPE=$(echo "$line" | awk '{print $4}')
STATUS=$(echo "$line" | awk '{print $5}')
REASON=$(echo "$line" | cut -d$'\t' -f6-)
# Color code based on status
case "$STATUS" in
*COMPLETE*)
COLOR="\033[0;32m" # Green
;;
*FAILED* | *ROLLBACK*)
COLOR="\033[0;31m" # Red
;;
*IN_PROGRESS*)
COLOR="\033[0;33m" # Yellow
;;
*)
COLOR="\033[0m" # No color
;;
esac
printf "${COLOR}%-20s %-30s %-25s %-20s %s\033[0m\n" \
"$TIMESTAMP" "$RESOURCE" "$TYPE" "$STATUS" "$REASON"
done
# Update last timestamp
LAST_TIMESTAMP=$(echo "$NEW_EVENTS" | head -1 | awk '{print $1}')
fi
sleep "$WATCH_INTERVAL"
done