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
61 lines
1.8 KiB
Java
61 lines
1.8 KiB
Java
package com.ankurm.expandcontract;
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import java.io.IOException;
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import java.io.UncheckedIOException;
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import java.nio.file.Files;
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import java.nio.file.Path;
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import java.nio.file.Paths;
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import java.nio.file.StandardOpenOption;
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import java.time.Instant;
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/**
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* Writes a named transcript under {@code docs/output/} while the test that produced it runs.
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* Every console line quoted in the companion article for this module comes from one of these
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* files, and the file is only ever written by a test assertion - never hand-typed.
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*/
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public final class Transcript {
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private static final Path OUTPUT_DIR = Paths.get("docs", "output");
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private final StringBuilder buffer = new StringBuilder();
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private final String name;
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private Transcript(String name) {
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this.name = name;
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}
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public static Transcript start(String name, String heading) {
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Transcript t = new Transcript(name);
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t.line("=".repeat(Math.min(78, heading.length() + 4)));
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t.line(heading);
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t.line("=".repeat(Math.min(78, heading.length() + 4)));
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t.line("captured: " + Instant.now());
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t.line("");
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return t;
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}
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public Transcript line(String text) {
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buffer.append(text).append(System.lineSeparator());
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System.out.println(text);
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return this;
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}
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public Transcript section(String title) {
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line("");
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line("-- " + title + " --");
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return this;
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}
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public void write() {
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try {
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Files.createDirectories(OUTPUT_DIR);
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Path target = OUTPUT_DIR.resolve(name + ".txt");
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Files.writeString(target, buffer.toString(), StandardOpenOption.CREATE,
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StandardOpenOption.TRUNCATE_EXISTING);
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}
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catch (IOException ex) {
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throw new UncheckedIOException(ex);
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}
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}
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}
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