Shulou(Shulou.com)06/01 Report--

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Background:

MySQL-5.7.12, debian 8-core 16G virtual machine, the business reported a large number of database errors at a certain point in time, and then returned to normal.

Scene:

After the developer checked the log, he found that at some point in time, the application disconnected all connections to the database, and a few seconds later it was restored.

At the same time, the memory utilization of the monitoring system has dropped abnormally.

After the 3min received the message of the alarm system, the memory utilization rate was 82%.

Analysis:

The first judgment is that the problem of the network caused the disconnection of the application layer, but the sudden drop in memory usage will not be caused by the network.

Check the log of MySQL and find that crash has occurred in the MySQL instance. The relevant error messages are as follows:

Click (here) to collapse or open

07:42:44 UTC-mysqld got signal 11; This could be because you hit a bug. It is also possible that this binaryor one of the libraries it was linked against is corrupt, improperly built,or misconfigured. This error can also be caused by malfunctioning hardware.Attempting to collect some information that could help diagnose the problem.As this is a crash and something is definitely wrong, the informationcollection process might fail.key_buffer_size=8388608read_buffer_size=16777216max_used_connections=29max_threads=5000thread_count=32connection_count=22It is possible that mysqld could use up tokey_buffer_size + (read_buffer_size + sort_buffer_size) * max_threads= 245834871 K bytes of memoryHope that is ok; if not, decrease some variables in the equation.Thread pointer: 0x7f607c0072c0Attempting backtrace. You can use the following information to find outwhere mysqld died. If you see no messages after this Something wentterribly wrong...stack_bottom = 7f6141b36e80 thread_stack 0x40000/usr/sbin/mysqld (my_print_stacktrace+0x2c) [0xe77fec] / usr/sbin/mysqld (handle_fatal_signal+0x459) [0x7a7019] / lib/x86_64-linux-gnu/libpthread.so.0 (+ 0xf8d0) [0x7f643257a8d0] / usr/sbin/mysqld (_ ZN16Partition_helper25handle_ordered_index_scanEPh+0x5c) [0xbbabec] / usr/sbin/mysqld (_ ZN7handler13ha_index_lastEPh+0x1b0) [0x7f4410] / usr/sbin/mysqld (_ Z14join_read_lastP7QEP) _ TAB+0x65) [0xc1f605] / usr/sbin/mysqld (_ Z10sub_selectP4JOINP7QEP_TABb+0x11b) [0xc25e4b] / usr/sbin/mysqld (_ ZN4JOIN4execEv+0x3b8) [0xc1ea78] / usr/sbin/mysqld (_ Z12handle_queryP3THDP3LEXP12Query_resultyy+0x238) [0xc8e408] / usr/sbin/ mysqld [0x770ccf] / usr/sbin/mysqld (_ Z21mysql_execute_commandP3THDb+0x3403) [0xc51103] / usr/sbin/mysqld (_ Z11mysql_parseP3THDP12Parser_state+0x3ad) [0xc531bd] / usr/sbin/mysqld (_ Z16dispatch_commandP3THDPK8COM_DATA19enum_server_command+0x817) [0xc53a47] / usr/ Sbin/mysqld (_ Z10do_commandP3THD+0x18f) [0xc54faf] / usr/sbin/mysqld (handle_connection+0x278) [0xd108d8] / usr/sbin/mysqld (pfs_spawn_thread+0x1b4) [0xe90784] / lib/x86_64-linux-gnu/libpthread.so.0 (+ 0x80a4) [0x7f64325730a4] / lib/x86_64-linux-gnu/libc.so.6 (clone+0x6d) [0x7f6430e1b87d] Trying to get some variables.Some pointers may be invalid and cause the dump to abort.Query (7f607c015ad0): select * from test where time > = '2016-07- 29 00 and time='2016-07-29 00 and time='2016-07-29 00 and time 00 and time

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