asmhatreandClaude Sonnet 5
e478eafda3
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
63 lines
1.7 KiB
Bash
Executable File
63 lines
1.7 KiB
Bash
Executable File
#!/usr/bin/env bash
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# Shared paths and settings for every script in this directory. Source this, don't run it.
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export EC_DB_TCP_PORT="${EC_DB_TCP_PORT:-9092}"
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export EC_DB_NAME="${EC_DB_NAME:-expand-contract}"
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EC_DB_BASE_DIR="${EC_DB_BASE_DIR:-/tmp/ec-demo/db}"
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EC_RUN_DIR="${EC_RUN_DIR:-/tmp/ec-demo}"
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EC_LOG_DIR="$EC_RUN_DIR/logs"
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EC_PID_DIR="$EC_RUN_DIR/pids"
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EC_PHASE_FILE="$EC_RUN_DIR/phase.txt"
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EC_LOAD_SUMMARY="$EC_RUN_DIR/load-summary.txt"
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PORT_A=8081
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PORT_B=8082
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MODULE_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
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JAR="$MODULE_DIR/target/db-migrations-expand-contract-1.0.0.jar"
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CP_FILE="$MODULE_DIR/cp.txt"
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mkdir -p "$EC_LOG_DIR" "$EC_PID_DIR" "$EC_DB_BASE_DIR"
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wait_db_server() {
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local tries="${1:-40}"
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for i in $(seq 1 "$tries"); do
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if (echo > "/dev/tcp/localhost/$EC_DB_TCP_PORT") >/dev/null 2>&1; then
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return 0
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fi
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sleep 0.25
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done
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echo "H2 TCP server on port $EC_DB_TCP_PORT never came up" >&2
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return 1
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}
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set_phase() {
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echo -n "$1" > "$EC_PHASE_FILE"
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echo "[phase] $1"
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}
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wait_healthy() {
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local port="$1"
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local tries="${2:-40}"
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for i in $(seq 1 "$tries"); do
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code=$(curl -s -o /dev/null -w '%{http_code}' "http://localhost:$port/actuator/health" || true)
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if [ "$code" = "200" ]; then
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return 0
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fi
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sleep 0.5
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done
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echo "instance on port $port never became healthy" >&2
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return 1
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}
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wait_down() {
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local port="$1"
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local tries="${2:-20}"
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for i in $(seq 1 "$tries"); do
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code=$(curl -s -o /dev/null -w '%{http_code}' --max-time 1 "http://localhost:$port/actuator/health" || true)
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if [ "$code" != "200" ]; then
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return 0
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fi
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sleep 0.3
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done
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return 1
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}
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