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
37 lines
982 B
Plaintext
37 lines
982 B
Plaintext
=========================================================================
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Deploy 1 (EXPAND): additive column + backfill, Stage 1 code untouched
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=========================================================================
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captured: 2026-09-16T19:20:56.676919361Z
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-- schema before Deploy 1 --
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COLUMN_NAME
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-----------
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ID
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NAME
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EMAIL
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CREATED_AT
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(4 rows)
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-- schema after Deploy 1 (email_address added) --
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COLUMN_NAME
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-------------
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ID
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NAME
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EMAIL
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CREATED_AT
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EMAIL_ADDRESS
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(5 rows)
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-- Ada's row was backfilled by the migration itself --
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NAME | EMAIL | EMAIL_ADDRESS
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-------------+------------------+-----------------
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Ada Lovelace | [email protected] | [email protected]
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(1 row)
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-- Stage 1's original INSERT still works, unmodified, after the migration --
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NAME | EMAIL | EMAIL_ADDRESS
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-------------+--------------------+--------------
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Grace Hopper | [email protected] | NULL
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(1 row)
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