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
24 lines
1.0 KiB
Bash
Executable File
24 lines
1.0 KiB
Bash
Executable File
#!/usr/bin/env bash
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# Starts one replica on a given port and stage, and waits for it to report healthy.
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# Usage: start-instance.sh <port> <stage>
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set -euo pipefail
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DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
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source "$DIR/env.sh"
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PORT="$1"
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STAGE="$2"
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# -XX:TieredStopAtLevel=1 and a small fixed heap cut this JVM's own startup CPU
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# burst dramatically (C2 compilation and heap sizing are the two biggest costs of a
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# cold Spring Boot start). That matters here specifically because two replicas share
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# a 2-core sandbox: a slow-starting replica can starve its own sibling's health
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# checks long enough to look like an outage that never actually happened - see
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# docs/11-the-load-generator.md.
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nohup java -XX:TieredStopAtLevel=1 -XX:+UseSerialGC -Xms128m -Xmx256m \
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-jar "$JAR" --server.port="$PORT" --app.stage="$STAGE" \
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> "$EC_LOG_DIR/instance-$PORT.log" 2>&1 < /dev/null &
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echo $! > "$EC_PID_DIR/$PORT.pid"
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echo "started stage $STAGE on port $PORT (pid $(cat "$EC_PID_DIR/$PORT.pid"))"
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wait_healthy "$PORT"
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echo "port $PORT healthy"
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