MySQL Group Replication plugin issues with 5.7.8-rc2

Well the new things are cool to test and learn. But it is not possible every time, to have smooth testing process. if you can’t get right software on your hand.

So there are great articles about this new plugin here you can follow all of them: Group Replication Topics

I must say that, plugin available for download as source code and as for Oracle Linux 6 x86_64 from ->

So if you want to try it with MySQL 5.7.8-rc2 on Ubuntu you should compile it with MySQL. But you will not be able to compile due to well known ‘boost’ dependency -> see BUG #78600

UPDATE to BUG 78600:

Pedro Gomes clarified the reason of failed compiling process. There must not be any “spaces” between cmake options specified with -DMYSQL_SERVER_CMAKE_ARGS=””. So we have working cmake command as follows:

    cmake ..  -DMYSQL_SERVER_SRC_DIR="/home/sh/Sandboxes/mysql-5.7.8-rc" -DMYSQL_SERVER_CMAKE_ARGS="-DMYSQL_DATADIR=/opt/mysql-5.7.8-grouprepl/datadir;-DSYSCONFDIR=/opt/mysql-5.7.8-grouprepl;-DWITH_SSL=system;-DMYSQL_TCP_PORT=3307;-DMYSQL_UNIX_ADDR=/opt/mysql-5.7.8-grouprepl/mysqld.sock;-DDEFAULT_CHARSET=utf8;-DDEFAULT_COLLATION=utf8_general_ci;-DWITH_DEBUG=1;-DCOMPILATION_COMMENT='Group Replication enabled MySQL-5.7.8';-DOPTIMIZER_TRACE=1;-DWITH_ZLIB=system;-DWITH_VALGRIND=1;-DCMAKE_C_FLAGS=-DHAVE_purify;-DCMAKE_CXX_FLAGS=-DHAVE_purify;-DDOWNLOAD_BOOST=1;-DWITH_BOOST=/home/sh/Sandboxes"

But even you have Oracle Linux 6 x86_64 and even you follow topics: 1. Corosync Guide 2. Getting Started with MySQL Group Replication

You will likely get “Segmentation Fault” after running START GROUP_REPLICATION:

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fffc8ef2700 (LWP 3294)]
0x00007ffff625d532 in _int_malloc () from /lib64/
Missing separate debuginfos, use: debuginfo-install corosynclib-1.4.7-2.el6.x86_64
(gdb) bt
#0  0x00007ffff625d532 in _int_malloc () from /lib64/
#1  0x00007ffff625e991 in malloc () from /lib64/
#2  0x00007ffff6acf0bd in operator new(unsigned long) () from /usr/lib64/
#3  0x00007fffc8f5b2ab in Certifier::Certifier (this=0x7fffbc051d20)
    at /export/home/pb2/build/sb_0-16452762-1441960761.59/release-0.5.0-export-8447366/BIN/BUILD/mysql-server/plugin/group_replication/src/
#4  0x00007fffc8f6bb36 in Certification_handler::initialize (this=0x7fffbc0507e0)
    at /export/home/pb2/build/sb_0-16452762-1441960761.59/release-0.5.0-export-8447366/BIN/BUILD/mysql-server/plugin/group_replication/src/handlers/
#5  0x00007fffc8f634d7 in configure_pipeline (pipeline=0x7fffbc051a80, handler_list=0x7fffbc0506f0, num_handlers=3)
    at /export/home/pb2/build/sb_0-16452762-1441960761.59/release-0.5.0-export-8447366/BIN/BUILD/mysql-server/plugin/group_replication/src/
#6  0x00007fffc8f6364d in get_pipeline (pipeline_type=<value optimized out>, pipeline=0x7fffbc051a80)
    at /export/home/pb2/build/sb_0-16452762-1441960761.59/release-0.5.0-export-8447366/BIN/BUILD/mysql-server/plugin/group_replication/src/
#7  0x00007fffc8f554b0 in Applier_module::setup_applier_module (this=0x7fffbc051920, pipeline_type=STANDARD_GROUP_REPLICATION_PIPELINE, reset_logs=false, 
    stop_timeout=31536000, group_sidno=2)
    at /export/home/pb2/build/sb_0-16452762-1441960761.59/release-0.5.0-export-8447366/BIN/BUILD/mysql-server/plugin/group_replication/src/
#8  0x00007fffc8f63eca in configure_and_start_applier_module ()
    at /export/home/pb2/build/sb_0-16452762-1441960761.59/release-0.5.0-export-8447366/BIN/BUILD/mysql-server/plugin/group_replication/src/
#9  0x00007fffc8f657df in plugin_group_replication_start ()
    at /export/home/pb2/build/sb_0-16452762-1441960761.59/release-0.5.0-export-8447366/BIN/BUILD/mysql-server/plugin/group_replication/src/
#10 0x00000000016927c9 in Group_replication_handler::start (this=0x378f2d0) at /home/full_datadir/mysql-5.7.8-rc/sql/
#11 0x0000000001692b81 in group_replication_start () at /home/full_datadir/mysql-5.7.8-rc/sql/
#12 0x000000000149739c in mysql_execute_command (thd=0x7fffbc007180) at /home/full_datadir/mysql-5.7.8-rc/sql/
#13 0x000000000149e15b in mysql_parse (thd=0x7fffbc007180, parser_state=0x7fffc8ef14a0) at /home/full_datadir/mysql-5.7.8-rc/sql/
#14 0x0000000001492dec in dispatch_command (thd=0x7fffbc007180, com_data=0x7fffc8ef1cd0, command=COM_QUERY)
    at /home/full_datadir/mysql-5.7.8-rc/sql/
#15 0x00000000014917f3 in do_command (thd=0x7fffbc007180) at /home/full_datadir/mysql-5.7.8-rc/sql/
#16 0x00000000015c9042 in handle_connection (arg=0x36c1a50) at /home/full_datadir/mysql-5.7.8-rc/sql/conn_handler/
#17 0x0000000001c56c41 in pfs_spawn_thread (arg=0x37d1990) at /home/full_datadir/mysql-5.7.8-rc/storage/perfschema/
#18 0x00007ffff7bc79d1 in start_thread () from /lib64/
#19 0x00007ffff62ccb6d in clone () from /lib64/

For further reading refer to related fresh BUG report -> #78627

It is really cool to help community to improve Open Source projects. So go on and test by your own, report interesting things and ofcourse contact with community members. They are all open to discussion 🙂

Using GDB, investigating segmentation fault in MySQL

In previous article, we have covered some errors and issues with using MySQL in “disk full” environment. Where there was no space left on device.(See here: Testing Disk Full Conditions)

Today’s scenario is -> Starting MySQL with GTID/binary log enabled, in 0 space left Linux(CentOS 6.5) environment.

If you hit a bug or problem, general rule for helping community to fix it is to provide as much information as possible. Especially useful is to give gdb output from coredump. To get coredump you can read this wonderful article Hunting-The-Core

Now let’s explore our situation. Because our segfault is detected while starting MySQL, it is not possible to attach PID to GDB and also using strace. Our my.cnf file:

log_bin = /opt/mysql/datadir/mysql-bin 
log_bin_index = /opt/mysql/datadir/mysql-bin 
sync_binlog = 1 
binlog_format = row 
gtid-mode = on 
log_slave_updates = 1 
enforce-gtid-consistency = true

Starting MySQL:

[root@localhost ~]# /opt/mysql/bin/mysqld_safe --defaults-file=/opt/mysql/my.cnf --user=mysql --datadir=/opt/mysql/datadir --socket=/opt/mysql/datadir/mysqld-new.sock --pid-file=/home/error_log_dir/ --port=3307 --log-error=/home/error_log_dir/error.err & 
[1] 2849 
[root@localhost ~]# 150427 06:31:42 mysqld_safe Logging to '/home/error_log_dir/error.err'. 150427 06:31:42 mysqld_safe Starting mysqld daemon with databases from /opt/mysql/datadir /opt/mysql/bin/mysqld_safe: line 166: 3110 Segmentation fault (core dumped) nohup /opt/mysql/bin/mysqld
--plugin-dir=/opt/mysql/lib/plugin --user=mysql     
--port=3307 < /dev/null >> /home/error_log_dir/error.err 2>&1 
150427 06:32:07 mysqld_safe mysqld from pid file /home/error_log_dir/ ended 

3110 Segmentation fault (core dumped) -> We have core dump. Using gdb with coredump:

[root@localhost coredumps]# gdb /opt/mysql/bin/mysqld core.3110 
BFD: Warning: /home/coredumps/core.3110 is truncated: expected core file size >= 803807232, found: 697573376. 
[New Thread 3110] 
[New Thread 3111] 
Cannot access memory at address 0x7f5ec00ff168 
Cannot access memory at address 0x7f5ec00ff168 
Cannot access memory at address 0x7f5ec00ff168 
Reading symbols from /lib64/
Reading symbols from /usr/lib/debug/lib64/ done. 
Loaded symbols for /lib64/ Failed to read a valid object file image from memory. 
Core was generated by `/opt/mysql/bin/mysqld --defaults-file=/opt/mysql/my.cnf --basedir=/opt/mysql --'. Program terminated with signal 11, Segmentation fault. #0 0x00007f5ebfccd8ac in ?? () 

(gdb) bt #0 0x00007f5ebfccd8ac in ?? () Cannot access memory at address 0x7fffb0aa89b8 

(gdb) bt full #0 0x00007f5ebfccd8ac in ?? () No symbol table info available. Cannot access memory at address 0x7fffb0aa89b8 

Such information is not sufficient further analysis, that’s why you should try to run MySQL start command with-in GDB as follows:

[root@localhost error_log_dir]# gdb /opt/mysql/bin/mysqld 
(gdb) run --defaults-file=/home/error_log_dir/my.cnf --basedir=/opt/mysql --datadir=/opt/mysql/datadir --plugin-dir=/opt/mysql/lib/plugin --user=mysql --log-error=/home/error_log_dir/error.err --pid-file=/home/error_log_dir/ --socket=/opt/mysql/datadir/mysqld-new.sock --port=3307 . . 
Program received signal SIGSEGV, Segmentation fault. 0x0000000000000000 in ?? () . . 

(gdb) bt 
    #0 0x0000000000000000 in ?? () 
    #1 0x0000000000ae6242 in my_printf_warning (format=0x1026f08 "Disk is full writing '%s' (Errcode: %d - %s). Waiting for someone to free space...") at /root/mysql-5.6.24/mysys/my_error.c:260 #2 0x0000000000ac9052 in wait_for_free_space (filename=0x1fe7ee0 "/opt/mysql/datadir/mysql-bin.~rec~", errors=0) at /root/mysql-5.6.24/mysys/errors.c:115 
#3 0x0000000000af1ac7 in my_write (Filedes=19, Buffer=0x1964d00 "/opt/mysql/datadir/mysql-bin.000003n", Count=36, MyFlags=52) at /root/mysql-5.6.24/mysys/my_write.c:89 
#4 0x0000000000acd5ae in inline_mysql_file_write (src_file=0x1027708 "/root/mysql-5.6.24/mysys/mf_iocache.c", src_line=1788, file=19, buffer=0x1964d00 "/opt/mysql/datadir/mysql-bin.000003n", count=36, flags=52) at /root/mysql-5.6.24/include/mysql/psi/mysql_file.h:1141 
#5 0x0000000000ad078c in my_b_flush_io_cache (info=0x183c1a8, need_append_buffer_lock=0) at /root/mysql-5.6.24/mysys/mf_iocache.c:1787 
#6 0x0000000000a7132b in MYSQL_BIN_LOG::sync_purge_index_file (this=0x183b400) at /root/mysql-5.6.24/sql/ 
#7 0x0000000000a6e206 in MYSQL_BIN_LOG::open_binlog (this=0x183b400, log_name=0x190d130 "/opt/mysql/datadir/mysql-bin", new_name=0x0, io_cache_type_arg=WRITE_CACHE, max_size_arg=1073741824, null_created_arg=false, need_lock_index=true, need_sid_lock=true, extra_description_event=0x0) at /root/mysql-5.6.24/sql/ 
#8 0x000000000063ad8e in init_server_components () at /root/mysql-5.6.24/sql/ 
#9 0x000000000063b6e7 in mysqld_main (argc=19, argv=0x186de68) at /root/mysql-5.6.24/sql/ 
#10 0x000000000062fc74 in main (argc=10, argv=0x7fffffffe3d8) at /root/mysql-5.6.24/sql/ ###################### 

(gdb) bt full 
#0 0x0000000000000000 in ?? () No symbol table info available. 
#1 0x0000000000ae6242 in my_printf_warning (format=0x1026f08 "Disk is full writing '%s' (Errcode: %d - %s). Waiting for someone to free space...") at /root/mysql-5.6.24/mysys/my_error.c:260 args = {{gp_offset = 32, fp_offset = 48, overflow_arg_area = 0x7fffffffd8a0, reg_save_area = 0x7fffffffd7e0}} wbuff = "Disk is full writing '/opt/mysql/datadir/mysql-bin.~rec~' (Errcode: 28 - No space left on device). Waiting for someone to free space...0033032737737737717700002103413773673771770000340267376367377177000027133224u00000000Zn33636737717700000000000000000000/35!3663771770000C00000000000000f223!36637717700000100000000000000P31!3663771770000LC_"... _db_stack_frame_ = {func = 0x102c53c "my_write", file = 0x102c518 "/root/mysql-5.6.24/mysys/my_write.c", level = 2147483654, prev = 0x7fffffffd9f0} 
#2 0x0000000000ac9052 in wait_for_free_space (filename=0x1fe7ee0 "/opt/mysql/datadir/mysql-bin.~rec~", errors=0) at /root/mysql-5.6.24/mysys/errors.c:115 errbuf = "No space left on device003252425700350000002303240201000000002723240201000000000033137737734000000 ܆01000000003400000006000000 ܆0100000000@3313773773771770000[3462570000000000 ܆010000000000܆0123000000<305020100000000303050201000000" 
#3 0x0000000000af1ac7 in my_write (Filedes=19, Buffer=0x1964d00 "/opt/mysql/datadir/mysql-bin.000003n", Count=36, MyFlags=52) at /root/mysql-5.6.24/mysys/my_write.c:89 writtenbytes = 18446744073709551615 sum_written = 0 errors = 0 initial_count = 36 _db_stack_frame_ = {func = 0x1027c7b "my_b_flush_io_cache", file = 0x1027708 "/root/mysql-5.6.24/mysys/mf_iocache.c", level = 2147483653, prev = 0x7fffffffdb10}  

From know developers should be able to see exact code line, for further examination. For further reading(to see “bt full” full output) refer related BUG report: #76852 It is already verified.