- Cutover would stall after `lock tables` wait-timeout due do waiting on a channel that would never be written to. This has been identified, reproduced, fixed, confirmed.
- Change of table names. Heres the story:
- Because were testing this even while `pt-online-schema-change` is being used in production, the `_tbl_old` naming convention makes for a collision.
- "old" table name is now `_tbl_del`, "del" standing for "delete"
- ghost table name is now `_tbl_gho`
- when issuing `--test-on-replica`, we keep the ghost table around, and were also briefly renaming original table to "old". Well this collides with a potentially existing "old" table on master (one that hasnt been dropped yet).
`--test-on-replica` uses `_tbl_ght` (ghost-test)
- similar problem with `--execute-on-replica`, and in this case the table doesnt stick around; calling it `_tbl_ghr` (ghost-replica)
- changelog table is now `_tbl_ghc` (ghost-changelog)
- To clarify, I dont want to go down the path of creating "old" tables with 2 or 3 or 4 or 5 or infinite leading underscored. I think this is very confusing and actually not operations friendly. Its OK that the migration will fail saying "hey, you ALREADY have an old table here, why dont you take care of it first", rather than create _yet_another_ `____tbl_old` table. Were always confused on which table it actually is that gets migrated, which is safe to `drop`, etc.
- just after rowcopy completing, just before cutover, during cutover: marking as point in time _of interest_ so as to increase logging frequency.
- Rowcopy time is bounded by copy end-time
- Retries are configurable via `--default-retries` (default: `60`)
- `migrator` notes the hostname
- `applier` and `inspector` note `impliedKey` (`@@hostname` and `@@port`)
- Added lots of code comments
- Adding documentation for "triggerless design"
- Supporting multi-step, safe cut-over phase, where queries are blocked throughout the phase, and worst case scenario is table outage (no data corruption)
- Self-rollsback in case of failure (restored original table)
The idea is that the user is forced to specify the cut-over type they wish to use, given that each type has some drawbacks.
- More data in status hint
- `select count(*)` is deferred till after we validate migration is valid. Also, it is skipped on `--noop`
