MDEV-7257 made a dump thread to read from binlog concurrently with
writers as long as the read bytes are below a water-mark
(MYSQL_BIN_LOG::binlog_end_pos). However it appeared to be possible a
dump thread reader reach out for bytes past the water mark through a
feature of IO_CACHE that fills in the internal buffer and while doing
so it could read what the reader is not supposed to see (the bytes
above MYSQL_BIN_LOG::binlog_end_pos).
The issue is fixed with constraining the IO_CACHE buffer fill to respect
the watermark.
An added unit test proves reading from file is bound to an external
parameter
passed to {IO_CACHE::end_of_file} cache member.
order with Galera and encrypt-tmp-files=1
Problem:- If trans_cache (IO_CACHE) uses encrypted tmp file
then on next DML server will crash.
Case:-
Lets take a case , we have a table t1 , We try to do 2 inserts in t1
1. A really long insert so that trans_cache has to use temp_file
2. Just a small insert
Analysis:- Actually server crashes from inside of galera
library.
/lib64/libc.so.6(abort+0x175)[0x7fb5ba779dc5]
/usr/lib64/galera/libgalera_smm.so(_ZN6galera3FSMINS_9TrxHandle5State...
mysys/stacktrace.c:247(my_print_stacktrace)[0x7fb5a714940e]
sql/signal_handler.cc:160(handle_fatal_signal)[0x7fb5a715c1bd]
sql/wsrep_hton.cc:257(wsrep_rollback)[0x7fb5bcce923a]
sql/wsrep_hton.cc:268(wsrep_rollback)[0x7fb5bcce9368]
sql/handler.cc:1658(ha_rollback_trans(THD*, bool))[0x7fb5bcd4f41a]
sql/handler.cc:1483(ha_commit_trans(THD*, bool))[0x7fb5bcd4f804]
but actual issue is not in galera but in mariadb, because for 2nd
insert we should never call rollback. We are calling rollback because
log_and_order fails it fails because write_cache fails , It fails
because after reinit_io_cache(trans_cache) , my_b_bytes_in_cache says 0
so we look into tmp_file for data , which is obviously wrong since temp
was used for previous insert and it no longer exist.
wsrep_write_cache_inc() reads the IO_CACHE in a loop, filling it with
my_b_fill() until it returns "0 bytes read". Later
MYSQL_BIN_LOG::write_cache() does the same. wsrep_write_cache_inc()
assumes that reading a zero bytes past EOF leaves the old data in the
cache
Solution:- There is two issue in my_b_encr_read
1st we should never equal read_end to info->buffer. I mean this
does not make sense read_end should always point to end of buffer.
2nd For most of the case(apart from async IO_CACHE) info->pos_in_file
should be equal to info->buffer position wrt to temp file , since
in this case we are not changing info->buffer it should remain
unchanged.
These self references were previously used to avoid having to check the
IO_CACHE's type. However, a benchmark shows that on x86 5930k stock,
the type comparison is marginally faster than the double pointer dereference.
For 40 billion my_b_tell calls, the difference is .1 seconds in favor of performing the
type check. (Basically there is no measurable difference)
To prevent bugs from copying the structure using the equals(=) operator,
and having to do the bookkeeping manually, remove these "convenience"
variables.
This is done by splitting variables.errmsg and locale.errmsg to
variables.errmsg_extra and locale.errmsg_extra
The ER() macros in unireg.h now looks more complex than before, but this
isn't critical as most usage of them are with constants and the compiler
will remove most of the test code.
- Removing the "diff_if_only_endspace_difference" argument from
MY_COLLATION_HANDLER::strnncollsp(), my_strnncollsp_simple(),
as well as in the function template MY_FUNCTION_NAME(strnncollsp)
in strcoll.ic
- Removing the "diff_if_only_space_different" from ha_compare_text(),
hp_rec_key_cmp().
- Adding a new function my_strnncollsp_padspace_bin() and reusing
it instead of duplicate code pieces in my_strnncollsp_8bit_bin(),
my_strnncollsp_latin1_de(), my_strnncollsp_tis620(),
my_strnncollsp_utf8_cs().
- Adding more tests for better coverage of the trailing space handling.
- Removing the unused definition of HA_END_SPACE_ARE_EQUAL
1. unused static inline functions are only removed at -xO4,
otherwise test binaries will depend on various mysys
symbols that they don't use. Link test with libmysys.
2. Sphinx - don't instantiate (explicitly) templates before
they're defined. Or, rather, don't instantiate them explicitly at
all.
3. GIS - don't use anonymous unions and structs.
In fact it was error in decimal library (incorrect processing of buffer overflow) invisible from other server parts because of buffer allocation and precision tests.
--encrypt-binlog and --encrypt-tmp-files used to mean
"encrypt XXX if encryption is available, otherwise don't encrypt",
now they mean "encrypt or fail with an error".
Instead of encrypt(src, dst, key, iv) that encrypts all
data in one go, now we have encrypt_init(key,iv),
encrypt_update(src,dst), and encrypt_finish(dst).
This also causes collateral changes in the internal my_crypt.cc
encryption functions and in the encryption service.
There are wrappers to provide the old all-at-once encryption
functionality. But binlog events are often written piecewise,
they'll need the new api.
