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spring-boot-demo/db-migrations-expand-contract/docs/output/11-live-deploy-sequence.txt
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asmhatreandClaude Sonnet 5 e478eafda3 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

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=====================================================================
Zero-downtime expand-contract: live 4-deploy sequence
=====================================================================
19:00:53 captured: 2026-09-16T19:00:53Z
19:00:53 Starting the database as its own standalone process (not owned by either replica)
H2 TCP server up on port 9092 (pid 10861), baseDir /tmp/ec-demo/db
19:00:53 Deploy 0: create schema (V1), start two Stage 1 replicas
=== Before migrate (target=1) ===
00:30:54.634 [main] INFO org.flywaydb.core.FlywayExecutor -- Database: jdbc:h2:tcp://localhost:9092/expand-contract (H2 2.4)
00:30:54.702 [main] WARN org.flywaydb.core.internal.database.base.Database -- Using H2 2.4.240 which is newer than the version Flyway has been verified with. The latest verified version of H2 is 2.3.232.
00:30:54.750 [main] INFO org.flywaydb.core.internal.schemahistory.JdbcTableSchemaHistory -- Schema history table "PUBLIC"."flyway_schema_history" does not exist yet
1 create customer PENDING
2 add email address column ABOVE_TARGET
3 drop email column ABOVE_TARGET
00:30:54.850 [main] INFO org.flywaydb.core.FlywayExecutor -- Database: jdbc:h2:tcp://localhost:9092/expand-contract (H2 2.4)
00:30:54.863 [main] WARN org.flywaydb.core.internal.database.base.Database -- Using H2 2.4.240 which is newer than the version Flyway has been verified with. The latest verified version of H2 is 2.3.232.
00:30:54.874 [main] INFO org.flywaydb.core.internal.schemahistory.JdbcTableSchemaHistory -- Schema history table "PUBLIC"."flyway_schema_history" does not exist yet
00:30:54.877 [main] INFO org.flywaydb.core.internal.command.DbValidate -- Successfully validated 3 migrations (execution time 00:00.007s)
00:30:54.888 [main] INFO org.flywaydb.core.internal.schemahistory.JdbcTableSchemaHistory -- Creating Schema History table "PUBLIC"."flyway_schema_history" ...
00:30:54.940 [main] INFO org.flywaydb.core.internal.command.DbMigrate -- Current version of schema "PUBLIC": << Empty Schema >>
00:30:54.956 [main] INFO org.flywaydb.core.internal.command.DbMigrate -- Migrating schema "PUBLIC" to version "1 - create customer"
00:30:55.018 [main] INFO org.flywaydb.core.internal.command.DbMigrate -- Successfully applied 1 migration to schema "PUBLIC", now at version v1 (execution time 00:00.014s)
=== After migrate ===
00:30:55.055 [main] INFO org.flywaydb.core.FlywayExecutor -- Database: jdbc:h2:tcp://localhost:9092/expand-contract (H2 2.4)
00:30:55.063 [main] WARN org.flywaydb.core.internal.database.base.Database -- Using H2 2.4.240 which is newer than the version Flyway has been verified with. The latest verified version of H2 is 2.3.232.
1 create customer SUCCESS
2 add email address column ABOVE_TARGET
3 drop email column ABOVE_TARGET
Migrations executed: 1, target schema version: 1, success: true
started stage 1 on port 8081 (pid 10946)
port 8081 healthy
started stage 1 on port 8082 (pid 11011)
port 8082 healthy
19:01:02 load generator running against both replicas
19:01:12 baseline soak complete (10s, both replicas on Stage 1)
19:01:12 Deploy 1 (EXPAND): migrating to V2 live - zero app restarts
=== Before migrate (target=2) ===
00:31:13.484 [main] INFO org.flywaydb.core.FlywayExecutor -- Database: jdbc:h2:tcp://localhost:9092/expand-contract (H2 2.4)
00:31:13.607 [main] WARN org.flywaydb.core.internal.database.base.Database -- Using H2 2.4.240 which is newer than the version Flyway has been verified with. The latest verified version of H2 is 2.3.232.
1 create customer SUCCESS
2 add email address column PENDING
3 drop email column ABOVE_TARGET
00:31:13.782 [main] INFO org.flywaydb.core.FlywayExecutor -- Database: jdbc:h2:tcp://localhost:9092/expand-contract (H2 2.4)
00:31:13.801 [main] WARN org.flywaydb.core.internal.database.base.Database -- Using H2 2.4.240 which is newer than the version Flyway has been verified with. The latest verified version of H2 is 2.3.232.
00:31:13.817 [main] INFO org.flywaydb.core.internal.command.DbValidate -- Successfully validated 3 migrations (execution time 00:00.008s)
00:31:13.842 [main] INFO org.flywaydb.core.internal.command.DbMigrate -- Current version of schema "PUBLIC": 1
00:31:13.903 [main] INFO org.flywaydb.core.internal.command.DbMigrate -- Migrating schema "PUBLIC" to version "2 - add email address column"
00:31:14.097 [main] INFO org.flywaydb.core.internal.command.DbMigrate -- Successfully applied 1 migration to schema "PUBLIC", now at version v2 (execution time 00:00.118s)
=== After migrate ===
00:31:14.136 [main] INFO org.flywaydb.core.FlywayExecutor -- Database: jdbc:h2:tcp://localhost:9092/expand-contract (H2 2.4)
00:31:14.174 [main] WARN org.flywaydb.core.internal.database.base.Database -- Using H2 2.4.240 which is newer than the version Flyway has been verified with. The latest verified version of H2 is 2.3.232.
1 create customer SUCCESS
2 add email address column SUCCESS
3 drop email column ABOVE_TARGET
Migrations executed: 1, target schema version: 2, success: true
19:01:19 Deploy 2 (MIGRATE WRITES): rolling restart to Stage 2, replica A first
stopped port 8081 (pid 10946)
started stage 2 on port 8081 (pid 11226)
port 8081 healthy
19:01:29 Deploy 2: replica B
stopped port 8082 (pid 11011)
started stage 2 on port 8082 (pid 11338)
port 8082 healthy
19:01:45 Deploy 3 (MIGRATE READS): rolling restart to Stage 3, replica A first
stopped port 8081 (pid 11226)
started stage 3 on port 8081 (pid 11456)
port 8081 healthy
19:01:55 Deploy 3: replica B
stopped port 8082 (pid 11338)
started stage 3 on port 8082 (pid 11567)
port 8082 healthy
19:02:11 Deploy 4a (CONTRACT code): rolling restart to Stage 4, replica A first
stopped port 8081 (pid 11456)
started stage 4 on port 8081 (pid 11679)
port 8081 healthy
19:02:20 Deploy 4a: replica B
stopped port 8082 (pid 11567)
started stage 4 on port 8082 (pid 11784)
port 8082 healthy
19:02:35 Deploy 4b (CONTRACT schema): migrating to V3 live - drops "email", zero app restarts
=== Before migrate (target=latest) ===
00:32:36.510 [main] INFO org.flywaydb.core.FlywayExecutor -- Database: jdbc:h2:tcp://localhost:9092/expand-contract (H2 2.4)
00:32:36.574 [main] WARN org.flywaydb.core.internal.database.base.Database -- Using H2 2.4.240 which is newer than the version Flyway has been verified with. The latest verified version of H2 is 2.3.232.
1 create customer SUCCESS
2 add email address column SUCCESS
3 drop email column PENDING
00:32:36.669 [main] INFO org.flywaydb.core.FlywayExecutor -- Database: jdbc:h2:tcp://localhost:9092/expand-contract (H2 2.4)
00:32:36.680 [main] WARN org.flywaydb.core.internal.database.base.Database -- Using H2 2.4.240 which is newer than the version Flyway has been verified with. The latest verified version of H2 is 2.3.232.
00:32:36.694 [main] INFO org.flywaydb.core.internal.command.DbValidate -- Successfully validated 3 migrations (execution time 00:00.008s)
00:32:36.707 [main] INFO org.flywaydb.core.internal.command.DbMigrate -- Current version of schema "PUBLIC": 2
00:32:36.726 [main] INFO org.flywaydb.core.internal.command.DbMigrate -- Migrating schema "PUBLIC" to version "3 - drop email column"
00:32:36.795 [main] INFO org.flywaydb.core.internal.command.DbMigrate -- Successfully applied 1 migration to schema "PUBLIC", now at version v3 (execution time 00:00.041s)
=== After migrate ===
00:32:36.811 [main] INFO org.flywaydb.core.FlywayExecutor -- Database: jdbc:h2:tcp://localhost:9092/expand-contract (H2 2.4)
00:32:36.829 [main] WARN org.flywaydb.core.internal.database.base.Database -- Using H2 2.4.240 which is newer than the version Flyway has been verified with. The latest verified version of H2 is 2.3.232.
1 create customer SUCCESS
2 add email address column SUCCESS
3 drop email column SUCCESS
Migrations executed: 1, target schema version: 3, success: true
19:02:46 final soak complete
19:02:46 waiting for the load generator to finish its run...
19:03:04 load generator finished
19:03:11 === deploy sequence complete ===
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