MDEV-39006: Galera test failure on galera_3nodes.galera_garbd_backup#5018
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MDEV-39006: Galera test failure on galera_3nodes.galera_garbd_backup#5018hemantdangi-gc wants to merge 1 commit into10.11from
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| DBUG_EXECUTE_IF("sst_force_lsn_advance", | ||
| { | ||
| /* Test-only: write a single FILE_MODIFY redo record so that | ||
| log_sys.get_lsn() advances past | ||
| last_checkpoint_lsn + SIZE_OF_FILE_CHECKPOINT + 8*is_encrypted(). | ||
| A subsequent buf_flush_page_cleaner() wake-up will then enter | ||
| log_checkpoint_low() past its early-return and, absent the | ||
| wsrep_sst_disable_writes gate in buf0flu.cc, fire the | ||
| recv_no_log_write tripwire (debug) or write a FILE_CHECKPOINT | ||
| record to ib_logfile0 (release). With the | ||
| UNIV_LIKELY(!wsrep_sst_disable_writes) check in place this | ||
| extra LSN gets checkpointed past once sst_enable_innodb_writes() | ||
| runs, so it does not survive past the SST window). */ | ||
| skip_verify_checkpoint= true; | ||
| log_sys.latch.wr_lock(); | ||
| mtr_t mtr; | ||
| mtr.start(); | ||
| mtr.log_file_op(FILE_MODIFY, SRV_SPACE_ID_UPPER_BOUND - 1, | ||
| "./mdev39006_fake.ibd"); | ||
| const lsn_t lsn_after_modify= mtr.commit_files(); | ||
| log_sys.latch.wr_unlock(); | ||
| log_write_up_to(lsn_after_modify ? lsn_after_modify : log_sys.get_lsn(), | ||
| true); | ||
| }); |
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This causes a compilation failure on many debug builders, because the low-level member function mtr_t::log_file_op() is not intended to be invoked directly, but only via other functions, such as mtr_t::name_write().
Is there really no other way to trigger this scenario? Could we write a dummy FILE_CHECKPOINT record instead, like innodb_log_file_size_update() does?
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missed that as it run successfully on local.
Thanks for checking issue, I added a dummy function to resolve the issue as mtr_t::name_write() and innodb_log_file_size_update() needed some more changes.
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So this piece of code can be removed?
Issue: sst_disable_innodb_writes() promises no writes to persistent files between Galera donor state and SST release, and most engine subsystems already honour that (purge, dict_stats, encryption thread count, FTS optimizer in fts0opt.cc:2844). The page cleaner did not: buf_flush_page_cleaner()'s set_almost_idle: block ran buf_dblwr.flush_buffered_writes() and log_checkpoint() unconditionally on every wake-up. With LSN advanced past last_checkpoint_lsn (via any prior background mtr - the most common one being a wsrep applier writeset), log_checkpoint_low() then appended a fresh FILE_CHECKPOINT record to ib_logfile0 mid-SST, breaking galera_3nodes.galera_garbd_backup with a --diff_files mismatch. Solution: Add a wsrep_sst_disable_writes gate around those two writes, mirroring the FTS pattern. In non-WSREP builds the flag is a constexpr false and the check compiles away. This closes the page-cleaner leak; other writers (wsrep apply paths, in-flight encryption rotation, ib_buffer_pool dump) are separate concerns and out of scope. Also assert !recv_no_log_write after log_write_up_to() in log_checkpoint_low() so debug builds catch any future write path that slips through.
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I have some improvement requests.
| # (debug) or writes FILE_CHECKPOINT to ib_logfile0 (release). | ||
| SET GLOBAL innodb_max_dirty_pages_pct_lwm=0.0; | ||
| SET GLOBAL innodb_max_dirty_pages_pct=0.0; | ||
| --sleep 2 |
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Is there any other way to see that page cleaner had a change to run? This introduces a race, page cleaner thread might not get change to run during this 2 second wait leading to fact that this test is not testing intended behaviour.
| # recv_no_log_write and resumes normal page-cleaner operation. | ||
| # (raise pct first so the lwm setter does not warn about lwm > pct.) | ||
| SET GLOBAL innodb_max_dirty_pages_pct=99; | ||
| SET GLOBAL debug_dbug = "+d,sst_enable_writes_now"; |
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Should we clear dbug_dbug before setting max_dirty_pages* values?
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| DBUG_EXECUTE_IF("sst_force_lsn_advance", | ||
| { | ||
| /* Test-only: write a single FILE_MODIFY redo record so that | ||
| log_sys.get_lsn() advances past | ||
| last_checkpoint_lsn + SIZE_OF_FILE_CHECKPOINT + 8*is_encrypted(). | ||
| A subsequent buf_flush_page_cleaner() wake-up will then enter | ||
| log_checkpoint_low() past its early-return and, absent the | ||
| wsrep_sst_disable_writes gate in buf0flu.cc, fire the | ||
| recv_no_log_write tripwire (debug) or write a FILE_CHECKPOINT | ||
| record to ib_logfile0 (release). With the | ||
| UNIV_LIKELY(!wsrep_sst_disable_writes) check in place this | ||
| extra LSN gets checkpointed past once sst_enable_innodb_writes() | ||
| runs, so it does not survive past the SST window). */ | ||
| skip_verify_checkpoint= true; | ||
| log_sys.latch.wr_lock(); | ||
| mtr_t mtr; | ||
| mtr.start(); | ||
| mtr.log_file_op(FILE_MODIFY, SRV_SPACE_ID_UPPER_BOUND - 1, | ||
| "./mdev39006_fake.ibd"); | ||
| const lsn_t lsn_after_modify= mtr.commit_files(); | ||
| log_sys.latch.wr_unlock(); | ||
| log_write_up_to(lsn_after_modify ? lsn_after_modify : log_sys.get_lsn(), | ||
| true); | ||
| }); |
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So this piece of code can be removed?
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Issue:
sst_disable_innodb_writes() promises no writes to persistent files between Galera donor state and SST release, and most engine subsystems already honour that (purge, dict_stats, encryption thread count, FTS optimizer in fts0opt.cc:2844). The page cleaner did not: buf_flush_page_cleaner()'s set_almost_idle: block ran buf_dblwr.flush_buffered_writes() and log_checkpoint() unconditionally on every wake-up. With LSN advanced past last_checkpoint_lsn (via any prior background mtr - the most common one being a wsrep applier writeset), log_checkpoint_low() then appended a fresh FILE_CHECKPOINT record to ib_logfile0 mid-SST, breaking
galera_3nodes.galera_garbd_backup with a --diff_files mismatch.
Solution:
Add a wsrep_sst_disable_writes gate around those two writes, mirroring the FTS pattern. In non-WSREP builds the flag is a constexpr false and the check compiles away. This closes the page-cleaner leak; other writers (wsrep apply paths, in-flight encryption rotation, ib_buffer_pool dump) are separate concerns and out of scope.
Also assert !recv_no_log_write after log_write_up_to() in log_checkpoint_low() so debug builds catch any future write path that slips through.