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
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+#!/usr/bin/env bash
+# Runs the standalone migration.MigrationCli against the live database - no app
+# restart, no app deploy. Usage: migrate.sh <target|latest>
+set -euo pipefail
+DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "$DIR/env.sh"
+
+TARGET="${1:-latest}"
+java -cp "$MODULE_DIR/target/classes:$(cat "$CP_FILE")" \
+    com.ankurm.expandcontract.migration.MigrationCli --target="$TARGET"