Add db-migrations-expand-contract: zero-downtime schema migrations proven with a real 4-deploy rolling run

Companion code for Zero-Downtime Database Migrations: Expand-Contract in Practice with Spring Boot: a full expand/migrate-writes/migrate-reads/contract sequence run as an actual rolling deploy across two live replicas, with a load generator sending continuous HTTP traffic through all four deploys (99.98% success, every residual error traced to a root cause rather than left unexplained). Findings include a real NOT NULL constraint trap in the expand migration, a backfill-window bug in the read switch, H2's AUTO_SERVER=TRUE single-point-of-failure behavior under a rolling restart, the drain-before-SIGTERM fix needed to close a health-check gap during graceful shutdown, and H2 silently discarding a concurrently committed INSERT during an ALTER TABLE ADD/DROP COLUMN rebuild - confirmed, by primary source, to be an H2-specific behavior rather than a property of the technique itself. Co-Authored-By: Claude Sonnet 5 <[email protected]> Claude-Session: https://claude.ai/code/session_019Fb7vW8vLyLKngBc4R3huA
2026-09-16 19:22:48 +00:00
parent 22c30d4a5b
commit e478eafda3
60 changed files with 3561 additions and 0 deletions
@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+set -euo pipefail
+DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "$DIR/env.sh"
+
+PID_FILE="$EC_PID_DIR/db-server.pid"
+if [ -f "$PID_FILE" ]; then
+    PID="$(cat "$PID_FILE")"
+    if kill -0 "$PID" 2>/dev/null; then
+        kill -9 "$PID"
+        echo "stopped H2 TCP server (pid $PID)"
+    fi
+    rm -f "$PID_FILE"
+fi