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
19 lines
1.1 KiB
Plaintext
19 lines
1.1 KiB
Plaintext
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-- after Deploy 0 (Stage 1 / Stage 1) --
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{"appStage":1,"columns":["ID","NAME","EMAIL","CREATED_AT"],"rowCount":0,"rowsWithEmail":0}
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-- after Deploy 1 (schema expanded, both replicas still Stage 1) --
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{"appStage":1,"columns":["ID","NAME","EMAIL","CREATED_AT","EMAIL_ADDRESS"],"rowCount":1212,"rowsWithEmail":1212,"rowsWithEmailAddress":1184}
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-- after Deploy 2 (both replicas Stage 2, dual-write live) --
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{"appStage":2,"columns":["ID","NAME","EMAIL","CREATED_AT","EMAIL_ADDRESS"],"rowCount":4218,"rowsWithEmail":4218,"rowsWithEmailAddress":2561}
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-- after Deploy 3 (both replicas Stage 3, reading email_address) --
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{"appStage":3,"columns":["ID","NAME","EMAIL","CREATED_AT","EMAIL_ADDRESS"],"rowCount":7547,"rowsWithEmail":7547,"rowsWithEmailAddress":6115}
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-- after Deploy 4a (both replicas Stage 4, email column still present but unused) --
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{"appStage":4,"columns":["ID","NAME","EMAIL","CREATED_AT","EMAIL_ADDRESS"],"rowCount":10642,"rowsWithEmail":9653,"rowsWithEmailAddress":9212}
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-- after Deploy 4b (email column dropped) --
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{"appStage":4,"columns":["ID","NAME","CREATED_AT","EMAIL_ADDRESS"],"rowCount":11806,"rowsWithEmailAddress":10374}
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