應用報錯中，我們需要從獲取到一些關鍵的信息點，死鎖等情況說明，可以通過show engine innodb status中獲取
mysql>show engine innodb status
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| Type | Name | Status |
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| InnoDB | |
=====================================
2016-05-12 08:52:28 2b6142bc7700 INNODB MONITOR OUTPUT
=====================================
Per second averages calculated from the last 50 seconds //最近50秒內每2秒的平均值
-----------------
BACKGROUND THREAD //backgroup 線程
-----------------
srv_master_thread loops: 1332198 srv_active, 0 srv_shutdown, 64396 srv_idle
srv_master_thread log flush and writes: 1396594
----------
SEMAPHORES // 信號
----------
OS WAIT ARRAY INFO: reservation count 118146 //os wait 的信息 ，reservation count 表示InnoDB產生了多少次OS WAIT
OS WAIT ARRAY INFO: signal count 186714 // 進行OS WAIT線程，接收到多少次信號(single)被喚醒，如果這個single數值越大，幾十萬或者幾百萬，可能是很多I/0等待或者是InnoDB爭用問題(關於爭用問題可能與OS調度有關，可以嘗試減少innodb_thread_concurrency參數)
Mutex spin waits 1664035, rounds 4276317, OS waits 20348 // Mutex spin線程無法獲取鎖而進入Spin wait ,rounds是spin wait 進行輪詢檢查mutextes的次數，os wait 線程放棄spin-wait 進入掛起狀態
RW-shared spins 302454, rounds 11667281, OS waits 69050 //RW-shared 共享鎖，
RW-excl spins 83942, rounds 4021896, OS waits 28377 // RW-excl 排他鎖
Spin rounds per wait: 2.57 mutex, 38.58 RW-shared, 47.91 RW-excl
// 備註：要明白Innodb如何處理互斥量(Mutexes)，以及什麼是兩步獲得鎖(two-step approach)。首先進程，
試圖獲得一個鎖，如果此鎖被它人佔用。它就會執行所謂的spin wait,即所謂循環的查詢”鎖被釋放了嗎？”。
如果在循環過程中，一直未得到鎖釋放的信息，則其轉入OS WAIT，即所謂線程進入掛起(suspended)狀態。
直到鎖被釋放後，通過信號(singal)喚醒線程
Spin wait的消耗遠小於OS waits。Spinwait利用cpu的空閒時間，檢查鎖的狀態，
OS Wait會有所謂content switch，從CPU內核中換出當前執行線程以供其它線程使用。
你可以通過innodb_sync_spin_loops參數來平衡spin wait和os wait
------------------------
LATEST DETECTED DEADLOCK
------------------------
2016-05-11 18:52:09 2b6677e07700 //死鎖發生的時間
*** (1) TRANSACTION:
TRANSACTION 495116414, ACTIVE 0.092 sec fetching rows
mysql tables in use 1, locked 1
LOCK WAIT 14 lock struct(s), heap size 6544, 20 row lock(s), undo log entries 6
LOCK BLOCKING MySQL thread id: 870003 block 876753
MySQL thread id 876753, OS thread handle 0x2b6685903700, query id 315677415 10.168.152.132 dsc Searching rows for update
update aaaa
set xxx=xxx+(-1)
where id=412 and xxx+(-1)>=0 //顯示第一個死鎖的的第一個事務
*** (1) WAITING FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 558 page no 5 n bits 144 index `idx_aaaa_unique` of table `test`.`aaaa` trx id 495116414 lock_mode X locks rec but not gap waiting
Record lock, heap no 17 PHYSICAL RECORD: n_fields 23; compact format; info bits 0
// 以上表示死鎖發生時事務1等待的鎖，事務想獲得aaaa表的idx_aaaa_unique索引對應的X排他鎖(Innodb的鎖是與索引相關)
0: len 8; hex 8000000000000001; asc ;;
1: len 2; hex 5748; asc WH;;
2: len 8; hex 800000000000004b; asc K;;
3: len 8; hex 8000000000000002; asc ;;
4: len 8; hex 8000000000002725; asc '%;;
5: len 8; hex 8000000000000215; asc ;;
6: len 2; hex 5a50; asc ZP;;
7: len 8; hex 4231363033313441; asc B160314A;;
8: len 6; hex 00001d82e06a; asc j;;
9: len 7; hex 1d00000235151a; asc 5 ;;
10: len 8; hex 800000000000019c; asc ;;
11: len 8; hex 8000000000000000; asc ;;
12: len 5; hex 9998da0000; asc ;;
13: len 5; hex 999f5a0000; asc Z ;;
14: len 10; hex 5a303230323032303031; asc Z020202001;;
15: len 12; hex e5b9bfe4b89ce5b9bfe5b79e; asc ;;
16: len 4; hex 80001b2f; asc /;;
17: len 7; hex 80000000000000; asc ;;
18: len 23; hex 50555243484153455f4f524445525f494e5f53544f434b; asc PURCHASE_ORDER_IN_STOCK;;
19: len 22; hex 53493230313630343136303030303136333531313735; asc SI20160416000016351175;;
20: len 5; hex 99992b1384; asc + ;;
21: SQL NULL;
22: len 5; hex 99994d7c8d; asc M| ;;
*** (2) TRANSACTION: // 事務2的狀態
TRANSACTION 495116394, ACTIVE 0.246 sec fetching rows
mysql tables in use 1, locked 1
17 lock struct(s), heap size 2936, 18 row lock(s), undo log entries 21
MySQL thread id 870003, OS thread handle 0x2b6677e07700, query id 315677426 10.168.152.132 dsc Searching rows for update
update aaaa
set xxx=xxx+(-2)
where id=430 and xxx+(-2)>=0
*** (2) HOLDS THE LOCK(S): // 表示事務2獲得的鎖
RECORD LOCKS space id 558 page no 5 n bits 144 index `idx_aaaa_unique` of table `test`.`aaaa` trx id 495116394 lock_mode X locks rec but not gap
Record lock, heap no 17 PHYSICAL RECORD: n_fields 23; compact format; info bits 0
0: len 8; hex 8000000000000001; asc ;;
1: len 2; hex 5748; asc WH;;
2: len 8; hex 800000000000004b; asc K;;
3: len 8; hex 8000000000000002; asc ;;
4: len 8; hex 8000000000002725; asc '%;;
5: len 8; hex 8000000000000215; asc ;;
6: len 2; hex 5a50; asc ZP;;
7: len 8; hex 4231363033313441; asc B160314A;;
8: len 6; hex 00001d82e06a; asc j;;
9: len 7; hex 1d00000235151a; asc 5 ;;
10: len 8; hex 800000000000019c; asc ;;
11: len 8; hex 8000000000000000; asc ;;
12: len 5; hex 9998da0000; asc ;;
13: len 5; hex 999f5a0000; asc Z ;;
14: len 10; hex 5a303230323032303031; asc Z020202001;;
15: len 12; hex e5b9bfe4b89ce5b9bfe5b79e; asc ;;
16: len 4; hex 80001b2f; asc /;;
17: len 7; hex 80000000000000; asc ;;
18: len 23; hex 50555243484153455f4f524445525f494e5f53544f434b; asc PURCHASE_ORDER_IN_STOCK;;
19: len 22; hex 53493230313630343136303030303136333531313735; asc SI20160416000016351175;;
20: len 5; hex 99992b1384; asc + ;;
21: SQL NULL;
22: len 5; hex 99994d7c8d; asc M| ;;
Record lock, heap no 59 PHYSICAL RECORD: n_fields 23; compact format; info bits 0
0: len 8; hex 8000000000000001; asc ;;
1: len 2; hex 5748; asc WH;;
2: len 8; hex 800000000000004b; asc K;;
3: len 8; hex 8000000000000002; asc ;;
4: len 8; hex 800000000000276a; asc 'j;;
5: len 8; hex 80000000000002c2; asc ;;
6: len 2; hex 5a50; asc ZP;;
7: len 9; hex 423136303231374341; asc B160217CA;;
8: len 6; hex 00001d82e06a; asc j;;
9: len 7; hex 1d00000235169f; asc 5 ;;
10: len 8; hex 80000000000001db; asc ;;
11: len 8; hex 8000000000000000; asc ;;
12: len 5; hex 9998a20000; asc ;;
13: len 5; hex 99a2600000; asc ` ;;
14: len 10; hex 5a303230323032303031; asc Z020202001;;
15: len 12; hex e5b9bfe4b89ce5b9bfe5b79e; asc ;;
16: len 4; hex 80000772; asc r;;
17: len 7; hex 80000000000000; asc ;;
18: len 23; hex 50555243484153455f4f524445525f494e5f53544f434b; asc PURCHASE_ORDER_IN_STOCK;;
19: len 22; hex 53493230313630343136303030303137333630353531; asc SI20160416000017360551;;
20: len 5; hex 99992b1385; asc + ;;
21: SQL NULL;
22: len 5; hex 99994d7c8d; asc M| ;;
*** (2) WAITING FOR THIS LOCK TO BE GRANTED: // 表示事務2等待的鎖
RECORD LOCKS space id 558 page no 4 n bits 152 index `idx_aaaa_unique` of table `test`.`aaaa` trx id 495116394 lock_mode X locks rec but not gap waiting
Record lock, heap no 63 PHYSICAL RECORD: n_fields 23; compact format; info bits 0
0: len 8; hex 8000000000000001; asc ;;
1: len 2; hex 5748; asc WH;;
2: len 8; hex 800000000000004b; asc K;;
3: len 8; hex 8000000000000002; asc ;;
4: len 8; hex 8000000000000065; asc e;;
5: len 8; hex 80000000000000a8; asc ;;
6: len 2; hex 5a50; asc ZP;;
7: len 9; hex 423136303232314b41; asc B160221KA;;
8: len 6; hex 00001d82e07e; asc ~;;
9: len 7; hex 2b000001d920ad; asc + ;;
10: len 8; hex 80000000000001c8; asc ;;
11: len 8; hex 8000000000000000; asc ;;
12: len 5; hex 9998aa0000; asc ;;
13: len 5; hex 99a2680000; asc h ;;
14: len 10; hex 5a303230323032303031; asc Z020202001;;
15: len 12; hex e5b9bfe4b89ce5b9bfe5b79e; asc ;;
16: len 4; hex 80000b14; asc ;;
17: len 7; hex 80000000000000; asc ;;
18: len 23; hex 50555243484153455f4f524445525f494e5f53544f434b; asc PURCHASE_ORDER_IN_STOCK;;
19: len 22; hex 53493230313630343136303030303137333630353531; asc SI20160416000017360551;;
20: len 5; hex 99992b1385; asc + ;;
21: SQL NULL;
22: len 5; hex 99994d7c8d; asc M| ;;
*** WE ROLL BACK TRANSACTION (1) // 表示選擇了哪個事務回滾，避免無限期死鎖等待
// innodb有一個內在的死鎖檢測工具，當死鎖超過一定時間後，會回滾其中一個事務,innodb_lock_wait_timeout
可配置死鎖等待超時時間
------------
TRANSACTIONS // 包含了InnoDB事務(transaction)的統計信息
------------
Trx id counter 495910498 // 當前的transaction id ,這是個系統變量，隨着每次新的transaction產生而增加
Purge done for trx's n:o < 495910389 undo n:o < 0 state: running but idle //正在進行清空的操作操作的transaction ID
History list length 2606 // 記錄了undo spaces 內unpurged 的事務個數
//Purge的原則就是記錄沒有被其它事務繼續使用了
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 329193748744296, not started
MySQL thread id 909825, OS thread handle 0x2b6142bc7700, query id 325773092 10.143.34.172 dsc init
show engine innodb status
---TRANSACTION 329193658413160, not started
MySQL thread id 909832, OS thread handle 0x2b667d881700, query id 325773024 10.168.108.146 dsc cleaning up
.....此處省略...
---TRANSACTION 329194102134888, not started
MySQL thread id 886232, OS thread handle 0x2b6686c40700, query id 325769275 10.252.160.92 dsc cleaning up
--------
FILE I/O // 顯示了I/O Helper thread d的狀態，包含一些統計信息
--------
I/O thread 0 state: waiting for i/o request (insert buffer thread)
I/O thread 1 state: waiting for i/o request (log thread)
I/O thread 2 state: waiting for i/o request (read thread)
I/O thread 3 state: waiting for i/o request (read thread)
I/O thread 4 state: waiting for i/o request (read thread)
I/O thread 5 state: waiting for i/o request (read thread)
I/O thread 6 state: waiting for i/o request (write thread)
I/O thread 7 state: waiting for i/o request (write thread)
I/O thread 8 state: waiting for i/o request (write thread)
I/O thread 9 state: waiting for i/o request (write thread) // 以上顯示了I/O Helper thread的狀態
Pending normal aio reads: 0 [0, 0, 0, 0] , aio writes: 0 [0, 0, 0, 0] ,
ibuf aio reads: 0, log i/o's: 0, sync i/o's: 0
Pending flushes (fsync) log: 0; buffer pool: 0 // 顯示各個I/O Helper thread的pending operations,pending的log和buffer pool thread的fsync()調用
2531032 OS file reads, 61115257 OS file writes, 51279005 OS fsyncs //顯示了reads writes fsync() 調用次數
0.00 reads/s, 0 avg bytes/read, 46.64 writes/s, 39.30 fsyncs/s
-------------------------------------
INSERT BUFFER AND ADAPTIVE HASH INDEX
-------------------------------------
Ibuf: size 1, free list len 3606, seg size 3608, 38466 merges
// seg size 表示當前插入緩衝的大小爲3608*16KB，大約爲57728KB。free list len代表了空閒列表的長度，merges 表示合併次數
merged operations:
insert 34642, delete mark 1008134, delete 0 //insert 插入的記錄數，delete mark 打上的標記,delete 刪除的次數
discarded operations:
insert 0, delete mark 0, delete 0
AHI PARTITION 1: Hash table size 4980539, node heap has 161 buffer(s)
AHI PARTITION 2: Hash table size 4980539, node heap has 90 buffer(s)
AHI PARTITION 3: Hash table size 4980539, node heap has 225 buffer(s)
AHI PARTITION 4: Hash table size 4980539, node heap has 352 buffer(s)
AHI PARTITION 5: Hash table size 4980539, node heap has 3556 buffer(s)
AHI PARTITION 6: Hash table size 4980539, node heap has 4393 buffer(s)
AHI PARTITION 7: Hash table size 4980539, node heap has 3052 buffer(s)
AHI PARTITION 8: Hash table size 4980539, node heap has 145 buffer(s)
26.62 hash searches/s, 51.78 non-hash searches/s
---
LOG // 記錄了transaction log 子系統的信息
---
Log sequence number 264509449071 //顯示當前log sequence number表示有多少字節寫入到log文件內
Log flushed up to 264509449064 //顯示已經被flushed(寫入磁盤)的logs
Pages flushed up to 264509446093
Last checkpoint at 264509412298 //顯示最後一個checkpoint 的logs
0 pending log flushes, 0 pending chkp writes
27332545 log i/o's done, 16.22 log i/o's/second // 顯示pending log 的統計信息
----------------------
BUFFER POOL AND MEMORY
----------------------
Total memory allocated 20653670400; in additional pool allocated 0 // 顯示分配給innodb 的內存大小，以及additional pool 使用的大小 (0表示沒有使用)
Dictionary memory allocated 1905658
Buffer pool size 1228800 // buffer pool size > database pages 因爲buffer pool size 還會存放lock index hash index 等一些其他系統信息
Free buffers 8192
Database pages 1208634
Old database pages 445992
Modified db pages 8
Pending reads 0 //顯示了pending的reads 和writes
Pending writes: LRU 0, flush list 0, single page 0 // 顯示InnoDB讀寫和創建的頁面(pages)
Pages made young 842882, not young 127112054
0.00 youngs/s, 0.00 non-youngs/s
Pages read 2637230, created 729565, written 30484675
0.00 reads/s, 0.34 creates/s, 24.06 writes/s
Buffer pool hit rate 1000 / 1000, young-making rate 0 / 1000 not 0 / 1000 //顯示buffer pool 的命中率
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 1208634, unzip_LRU len: 0
I/O sum[9624]:cur[0], unzip sum[0]:cur[0]
----------------------
INDIVIDUAL BUFFER POOL INFO
----------------------
---BUFFER POOL 0
Buffer pool size 153600
Free buffers 1024
Database pages 151095
Old database pages 55755
Modified db pages 2
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 32021, not young 15238551
0.00 youngs/s, 0.00 non-youngs/s
Pages read 326672, created 90881, written 6387155
0.00 reads/s, 0.00 creates/s, 4.80 writes/s
Buffer pool hit rate 1000 / 1000, young-making rate 0 / 1000 not 0 / 1000
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 151095, unzip_LRU len: 0
I/O sum[1203]:cur[0], unzip sum[0]:cur[0]
---BUFFER POOL 1
Buffer pool size 153600
Free buffers 1024
Database pages 151061
Old database pages 55742
Modified db pages 0
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 32063, not young 15503760
0.00 youngs/s, 0.00 non-youngs/s
Pages read 327353, created 91471, written 978265
0.00 reads/s, 0.00 creates/s, 0.24 writes/s
Buffer pool hit rate 1000 / 1000, young-making rate 0 / 1000 not 0 / 1000
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 151061, unzip_LRU len: 0
I/O sum[1203]:cur[0], unzip sum[0]:cur[0]
---BUFFER POOL 2
Buffer pool size 153600
Free buffers 1024
Database pages 151107
Old database pages 55759
Modified db pages 0
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 32746, not young 14789866
0.00 youngs/s, 0.00 non-youngs/s
Pages read 328273, created 91339, written 4147582
0.00 reads/s, 0.00 creates/s, 3.50 writes/s
Buffer pool hit rate 1000 / 1000, young-making rate 0 / 1000 not 0 / 1000
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 151107, unzip_LRU len: 0
I/O sum[1203]:cur[0], unzip sum[0]:cur[0]
---BUFFER POOL 3
Buffer pool size 153600
Free buffers 1024
Database pages 151088
Old database pages 55752
Modified db pages 0
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 31950, not young 15539726
0.00 youngs/s, 0.00 non-youngs/s
Pages read 329629, created 91566, written 2998238
0.00 reads/s, 0.00 creates/s, 1.68 writes/s
Buffer pool hit rate 1000 / 1000, young-making rate 0 / 1000 not 0 / 1000
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 151088, unzip_LRU len: 0
I/O sum[1203]:cur[0], unzip sum[0]:cur[0]
---BUFFER POOL 4
Buffer pool size 153600
Free buffers 1024
Database pages 151063
Old database pages 55743
Modified db pages 1
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 323393, not young 17803631
0.00 youngs/s, 0.00 non-youngs/s
Pages read 337003, created 90967, written 3974291
0.00 reads/s, 0.08 creates/s, 4.38 writes/s
Buffer pool hit rate 1000 / 1000, young-making rate 0 / 1000 not 0 / 1000
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 151063, unzip_LRU len: 0
I/O sum[1203]:cur[0], unzip sum[0]:cur[0]
---BUFFER POOL 5
Buffer pool size 153600
Free buffers 1024
Database pages 151066
Old database pages 55744
Modified db pages 3
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 323468, not young 18135650
0.00 youngs/s, 0.00 non-youngs/s
Pages read 335789, created 90992, written 3382034
0.00 reads/s, 0.26 creates/s, 3.04 writes/s
Buffer pool hit rate 1000 / 1000, young-making rate 0 / 1000 not 0 / 1000
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 151066, unzip_LRU len: 0
I/O sum[1203]:cur[0], unzip sum[0]:cur[0]
---BUFFER POOL 6
Buffer pool size 153600
Free buffers 1024
Database pages 151073
Old database pages 55747
Modified db pages 2
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 34315, not young 15008240
0.00 youngs/s, 0.00 non-youngs/s
Pages read 324769, created 91064, written 5580181
0.00 reads/s, 0.00 creates/s, 4.66 writes/s
Buffer pool hit rate 1000 / 1000, young-making rate 0 / 1000 not 0 / 1000
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 151073, unzip_LRU len: 0
I/O sum[1203]:cur[0], unzip sum[0]:cur[0]
---BUFFER POOL 7
Buffer pool size 153600
Free buffers 1024
Database pages 151081
Old database pages 55750
Modified db pages 0
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 32926, not young 15092630
0.00 youngs/s, 0.00 non-youngs/s
Pages read 327742, created 91285, written 3036929
0.00 reads/s, 0.00 creates/s, 1.76 writes/s
Buffer pool hit rate 1000 / 1000, young-making rate 0 / 1000 not 0 / 1000
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 151081, unzip_LRU len: 0
I/O sum[1203]:cur[0], unzip sum[0]:cur[0]
--------------
ROW OPERATIONS //顯示了row operations 及其他一些統計信息
--------------
0 queries inside InnoDB, 0 queries in queue //顯示了有多少個線程在InnoDB內核
52 read views open inside InnoDB // 有多少個read view 被打開，一個read view 是一致性保證MVCC "snapshot"
Main thread process no. 46196, id 47719070582528, state: sleeping //顯示內核main thread的狀態信息。
Number of rows inserted 35803330, updated 3181469, deleted 14015545, read 7740416065
12.48 inserts/s, 0.68 updates/s, 0.30 deletes/s, 3005.82 reads/s
----------------------------
END OF INNODB MONITOR OUTPUT
============================
上面的兩個死鎖還是很簡單就能處理的，分析這個表的時候，發現，研發在設計之時，忘記設置主鍵ID，而innodb存儲引擎在這種情況下，會導致update的過程中，將當前
表進行表鎖，從而出現了死鎖的情況
解決方法：查看錶結構，統計表數據，因爲數據量不大，增加主鍵ID，解決問題。