我们先看一下这个报错日志：
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InnoDB: Warning: a long semaphore wait:
--Thread
140593224754944
has waited at btr0cur.c line
528
for
241.00
seconds the semaphore:
X-lock on RW-latch at
0x7fd9142bfcc8
created
in
file dict0dict.c line
1838
a writer (thread id
140570526021376
) has reserved it
in
mode exclusive
number of readers
0
, waiters flag
1
, lock_word:
0
Last time read locked
in
file btr0cur.c line
535
Last time write locked
in
file /pb2/build/sb_0-
10180689
-
1378752874.69
/mysql-
5.5
.
34
/storage/innobase/btr/btr0cur.c line
528
InnoDB: Warning: a long semaphore wait:
--Thread
140570431108864
has waited at btr0cur.c line
528
for
241.00
seconds the semaphore:
X-lock on RW-latch at
0x7fd9142bfcc8
created
in
file dict0dict.c line
1838
a writer (thread id
140570526021376
) has reserved it
in
mode exclusive
number of readers
0
, waiters flag
1
, lock_word:
0
Last time read locked
in
file btr0cur.c line
535
Last time write locked
in
file /pb2/build/sb_0-
10180689
-
1378752874.69
/mysql-
5.5
.
34
/storage/innobase/btr/btr0cur.c line
528
……………………
END OF INNODB MONITOR OUTPUT
============================
InnoDB: ###### Diagnostic info printed to the standard error stream
InnoDB: Error: semaphore wait has lasted >
600
seconds
InnoDB: We intentionally crash the server, because it appears to be hung.
140101
4
:
32
:
58
InnoDB: Assertion failure
in
thread
140570570065664
in
file srv0srv.c line
2502
InnoDB: We intentionally generate a memory trap.
InnoDB: Submit a detailed bug report to http:
//bugs.mysql.com.
InnoDB: If you
get
repeated assertion failures or crashes, even
InnoDB: immediately after the mysqld startup, there may be
InnoDB: corruption
in
the InnoDB tablespace. Please refer to
InnoDB: http:
//dev.mysql.com/doc/refman/5.5/...-recovery.html
InnoDB: about forcing recovery.
20
:
32
:
58
UTC - mysqld got signal
6
;
This could be because you hit a bug. It
is
also possible that
this
binary
or one of the libraries it was linked against
is
corrupt, improperly built,
or misconfigured. This error can also be caused by malfunctioning hardware.
We will
try
our best to scrape up some info that will hopefully help
diagnose the problem, but since we have already crashed,
something
is
definitely wrong and
this
may fail.
key_buffer_size=
16777216
read_buffer_size=
131072
max_used_connections=
608
max_threads=
1600
thread_count=
516
connection_count=
515
It
is
possible that mysqld could
use
up to
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads =
444459
K bytes of memory
Hope that's ok;
if
not, decrease some
var
iables
in
the equation.
Thread pointer:
0x0
Attempting back
trace
. You can
use
the following information to find out
where mysqld died. If you see no messages after
this
, something went
terribly wrong...
stack_bottom =
0
thread_stack
0x30000
/usr/local/mysql/bin/mysqld(my_print_stack
trace
+
0x35
)[
0x7a5f15
]
/usr/local/mysql/bin/mysqld(handle_fatal_signal+
0x403
)[
0x673a13
]
/lib/libpthread.so.
0
(+
0xef60
)[
0x7fde6901cf60
]
/lib/libc.so.
6
(gsignal+
0x35
)[
0x7fde68219165
]
/lib/libc.so.
6
(abort+
0x180
)[
0x7fde6821bf70
]
/usr/local/mysql/bin/mysqld[
0x7ff2ce
]
/lib/libpthread.so.
0
(+
0x68ba
)[
0x7fde690148ba
]
/lib/libc.so.
6
(clone+
0x6d
)[
0x7fde682b602d
]
The manual page at http:
//dev.mysql.com/doc/mysql/en/crashing.html contains
information that should help you find out what
is
causing the crash.
131231
04
:
34
:
11
mysqld_safe
Number
of processes running now:
0
131231
04
:
34
:
11
mysqld_safe mysqld restarted
|
这台机器凌晨MySQL进程崩溃，错误日志里全都是
InnoDB: Warning: a long semaphore wait
--Thread 140570431108864 has waited at btr0cur.c line 528 for 241.00 seconds the semaphore:
X-lock on RW-latch at 0x7fd9142bfcc8 created in file dict0dict.c line 1838
查看监控图（参考25日至31日）
发现spin waits和OS waits等待时间相当高，在手册里查到了这一句话：
|
1
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You can monitor the
use
of the adaptive hash index and the contention
for
its
use
in
the SEMAPHORES section of the output of the SHOW ENGINE INNODB STATUS command. If you see many threads waiting on an RW-latch created
in
btr0sea.c, then it might be useful to disable adaptive hash indexing.
|
|
1
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Sometimes, the read/write lock that guards access to the adaptive hash index can become a source of contention under heavy workloads, such
as
multiple concurrent joins.
|
由于自适应哈希索引造成大量的锁争用，进而堵塞很多进程，最终导致MySQL崩溃重启。
找到原因后，关闭了自适应哈希索引，观察了一天后（参考性能图1月1日），spin waits和OS waits等待时间逐渐减少。
|
1
|
set
global
innodb_adaptive_hash_index = 0;
|
最终病因找到解决之。
参考手册：
附件：http://down.51cto.com/data/2363940
本文转自hcymysql51CTO博客，原文链接：http://blog.51cto.com/hcymysql/1347504，如需转载请自行联系原作者
