Impossible Query Demo

Impossible Query Demo

A 60-second marketing demo that proves HeliosProxy can survive a primary database failure mid-transaction with zero errors and zero data loss.

What This Proves

• Transaction Replay (TR) buffers in-flight transactions and replays them on a new primary after failover.
• The client sees a successful COMMIT even though the original primary was killed with SIGKILL while the transaction was open.
• Failover detection + promotion + replay happens in under 15 seconds.

Prerequisites

• Docker and Docker Compose
• psql (PostgreSQL client) installed locally
• curl and python3 (for admin API output formatting)

How to Run

# Interactive mode (pauses between steps for live demos)
./demo.sh

# Automatic mode (runs straight through)
./demo.sh --auto

What Happens

1. A 2-node PostgreSQL cluster starts (1 primary + 1 streaming standby)
2. HeliosProxy connects to both nodes with Transaction Replay enabled
3. A client opens a transaction through the proxy: BEGIN, INSERT, UPDATE
4. The primary is killed with docker kill (simulating hardware failure)
5. The client issues COMMIT — HeliosProxy detects the failure, promotes the standby, and replays the buffered transaction on the new primary
6. COMMIT succeeds. A SELECT confirms the data exists.

Expected Output

• Steps 1-3: Cluster starts, transaction opens normally
• Step 4: Primary is killed
• Step 6: COMMIT succeeds (typically within 2-10 seconds)
• Step 7: SELECT returns the inserted order and updated inventory
• Step 9: Summary shows zero errors, zero data loss

What to Look For

• The commit latency — how long the client waited for the replay to complete
• The proxy logs (docker compose logs heliosproxy) show the failover detection, standby promotion, and transaction replay in real-time
• After failover, the admin API (/nodes) shows the former standby as the new primary

Cleanup

The demo cleans up automatically on exit. To clean up manually:

docker compose down -v --remove-orphans