pt-online-schema-change does not report anything when it waits for slave to replicate new table creation

Bug #1533271 reported by Valerii Kravchuk on 2016-01-12
6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
Percona Toolkit
Undecided
Unassigned

Bug Description

Manual (https://www.percona.com/doc/percona-toolkit/2.1/pt-online-schema-change.html#cmdoption-pt-online-schema-change--max-lag) says:

"The tool waits forever for replicas to stop lagging. If any replica is stopped, the tool waits forever until the replica is started. The data copy continues when all replicas are running and not lagging too much.

The tool prints progress reports while waiting. If a replica is stopped, it prints a progress report immediately, then again at every progress report interval."

On the other hand, manual for --progress option is more clear:

"Print progress reports to STDERR while copying rows."

Progress report or at least some information on what slave is checked for the new table would be useful on the initial stage also, when the table with the new structure is created and we are waiting for it to appear at every slave involved. There is nothing useful to find out the reason for the hang in this case without PTDEBUG=1. With it set we see the following in STDERR:

...
# pt_online_schema_change:8317 44986 Waiting until slave1 replicates the table
# TableParser:3275 44986 Checking `db`.`_t_new`
# TableParser:3279 44986 SHOW TABLES FROM `db` LIKE '\_t\_new'
# TableParser:3293 44986 Table db _t_new exists
# pt_online_schema_change:8317 44986 Waiting until slave2 replicates the table
# TableParser:3275 44986 Checking `db`.`_t_new`
# TableParser:3279 44986 SHOW TABLES FROM `db` LIKE '\_t\_new'
# TableParser:3293 44986 Table db _t_new exists
# pt_online_schema_change:8317 44986 Waiting until slave3 replicates the table
# TableParser:3275 44986 Checking `db`.`_t_new`
# TableParser:3279 44986 SHOW TABLES FROM `db` LIKE '\_t\_new'
# TableParser:3289 44986 Table does not exist
# TableParser:3275 44986 Checking `db`.`_t_new`
# TableParser:3279 44986 SHOW TABLES FROM `db` LIKE '\_t\_new'
# TableParser:3289 44986 Table does not exist
...

Please, write something to STDERR at this stage by default, so that DBA can understand what's happening and what can be the reason for the wait/hang

tags: added: i64224
summary: pt-online-schema-change does not report anything when it waits for slave
- to replicate new table creationhange does not report progress when slave
- lags at new table creation check
+ to replicate new table creation
Changed in percona-toolkit:
status: New → Confirmed
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