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
50 lines
2.1 KiB
Java
50 lines
2.1 KiB
Java
package com.ankurm.expandcontract;
|
|
|
|
import com.ankurm.expandcontract.customer.CustomerService;
|
|
import org.junit.jupiter.api.Test;
|
|
import org.junit.jupiter.api.io.TempDir;
|
|
|
|
import java.nio.file.Path;
|
|
import java.sql.Connection;
|
|
import java.sql.DriverManager;
|
|
|
|
import static org.assertj.core.api.Assertions.assertThat;
|
|
|
|
/**
|
|
* Deploy 2 (MIGRATE WRITES): Stage 2 code writes every create and update to both
|
|
* columns. This is the deploy that makes Deploy 3's read switch safe later - if this
|
|
* one is wrong, nothing downstream can be trusted. See docs/04-the-dual-write.md.
|
|
*/
|
|
class DualWriteConsistencyTest {
|
|
|
|
@Test
|
|
void createAndUpdatePopulateBothColumnsIdentically(@TempDir Path tmp) throws Exception {
|
|
Path db = tmp.resolve("dual-write");
|
|
TestSupport.migrateTo(db, "2");
|
|
Transcript t = Transcript.start("04-dual-write-consistency",
|
|
"Deploy 2 (MIGRATE WRITES): Stage 2 writes land in both columns");
|
|
|
|
CustomerService stage2 = new CustomerService(TestSupport.jdbcClient(db), 2);
|
|
long id = stage2.create("Margaret Hamilton", "[email protected]");
|
|
|
|
try (Connection conn = DriverManager.getConnection(TestSupport.jdbcUrl(db), "sa", "")) {
|
|
t.section("after create()");
|
|
String row = DbDump.table(conn, "select name, email, email_address from customers where id = " + id);
|
|
t.line(row);
|
|
assertThat(row).contains("[email protected]");
|
|
assertThat(row.indexOf("[email protected]")).isNotEqualTo(row.lastIndexOf("[email protected]"));
|
|
}
|
|
|
|
stage2.updateEmail(id, "[email protected]");
|
|
|
|
try (Connection conn = DriverManager.getConnection(TestSupport.jdbcUrl(db), "sa", "")) {
|
|
t.section("after updateEmail() - the old value is gone from BOTH columns, not just one");
|
|
String row = DbDump.table(conn, "select name, email, email_address from customers where id = " + id);
|
|
t.line(row);
|
|
assertThat(row).contains("[email protected]").doesNotContain("[email protected]");
|
|
}
|
|
|
|
t.write();
|
|
}
|
|
}
|