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According to Valgrind, InnoDB is writing uninitialized data to redo log:
./mtr --valgrind sql_sequence.next
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Stack traces vary, but they have log_write_up_to() in common:
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10.3 19bb7fdcd6e68aca6e41a2e30ffb3c2ad1d14cb6
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sql_sequence.next 'innodb' [ fail ] Found warnings/errors in server log file!
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Test ended at 2018-04-03 10:15:24
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line
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==21186== Thread 10:
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==21186== Syscall param pwrite64(buf) points to uninitialised byte(s)
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==21186== at 0x4E4A6CF: pwrite (pwrite64.c:29)
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==21186== by 0xD8FBEE: SyncFileIO::execute(IORequest const&) (os0file.cc:1596)
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==21186== by 0xD93BF6: os_file_io(IORequest const&, int, void*, unsigned long, unsigned long, dberr_t*) (os0file.cc:4847)
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==21186== by 0xD9413E: os_file_pwrite(IORequest const&, int, unsigned char const*, unsigned long, unsigned long, dberr_t*) (os0file.cc:4931)
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==21186== by 0xD942B1: os_file_write_func(IORequest const&, char const*, int, void const*, unsigned long, unsigned long) (os0file.cc:4962)
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==21186== by 0xD974CF: os_aio_func(IORequest&, unsigned long, char const*, pfs_os_file_t, void*, unsigned long, unsigned long, bool, fil_node_t*, void*) (os0file.cc:6606)
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==21186== by 0x1017530: pfs_os_aio_func(IORequest&, unsigned long, char const*, pfs_os_file_t, void*, unsigned long, unsigned long, bool, fil_node_t*, void*, char const*, unsigned int) (os0file.ic:255)
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==21186== by 0x102692A: fil_io(IORequest const&, bool, page_id_t const&, page_size_t const&, unsigned long, unsigned long, void*, void*, bool) (fil0fil.cc:4632)
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==21186== by 0xD6B841: log_group_write_buf(log_group_t*, unsigned char*, unsigned long, unsigned long, unsigned long, unsigned long) (log0log.cc:1023)
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==21186== by 0xD6C459: log_write_up_to(unsigned long, bool) (log0log.cc:1270)
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The reason is that the tail of the first buffer is not being initialized.
This should also affect MariaDB 10.2, even though I was unable to repeat the problem there. By default, innodb_log_write_ahead_size=8192 already in 10.2.
The following patch fixes the problem:
diff --git a/storage/innobase/log/log0log.cc b/storage/innobase/log/log0log.cc
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index 7da66c04c18..68d15665b04 100644
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--- a/storage/innobase/log/log0log.cc
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+++ b/storage/innobase/log/log0log.cc
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@@ -1235,6 +1235,9 @@ log_write_up_to(
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log_group_set_fields(&log_sys->log, log_sys->write_lsn);
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log_mutex_exit();
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+ /* Erase the end of the last log block. */
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+ memset(write_buf + end_offset, 0, ~end_offset & OS_FILE_LOG_BLOCK_SIZE);
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/* Calculate pad_size if needed. */
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pad_size = 0;
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if (write_ahead_size > OS_FILE_LOG_BLOCK_SIZE) {
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