我正在调试一个使用JPA/Hibernate和Postgres (9.6.2)的Java应用程序的奇怪行为。
这个应用程序有3个实体：User, Country, UserEvent。
Hibernate将它们映射到4个表：users, countries, userevent, hibernate_sequences。
User实体拥有版本列(@Version)和一个用于乐观锁定的主题。对于其主键"id"，使用@GeneratedValue(strategy = GenerationType.TABLE)。User表将接收最多的读写操作（最受欢迎的表）。
我创建了一些压力测试来模拟高负载，并在运行它们时注意到Postgres日志中出现了以下错误（请注意导致此错误的更新查询）：
ERROR: deadlock detected
DETAIL: Process 46758 waits for ShareLock on transaction 1580660; blocked by process 46759.
Process 46759 waits for AccessExclusiveLock on tuple (97,26) of relation 17353 of database 16385; blocked by process 46758.
Process 46758: update users set confirmationState=$1, country_iso=$2, dateOfBirth=$3, email=$4, firstName=$5, gender=$6, lastName=$7, lastUsedLocale=$8, middleName=$9, passwordHash=$10, passwordSalt=$11, phone=$12, role=$13, signInState=$14, updated=$15, username=$16, version=$17 where id=$18 and version=$19
Process 46759: update users set confirmationState=$1, country_iso=$2, dateOfBirth=$3, email=$4, firstName=$5, gender=$6, lastName=$7, lastUsedLocale=$8, middleName=$9, passwordHash=$10, passwordSalt=$11, phone=$12, role=$13, signInState=$14, updated=$15, username=$16, version=$17 where id=$18 and version=$19
HINT: See server log for query details.
CONTEXT: while updating tuple (97,26) in relation "users"
我了解Postgres有共享和排他的行、表或索引级别锁。如果以错误的顺序在同一对象上获取它们，可能会导致死锁。
但对于这种情况，为什么使用乐观锁定会导致死锁？我期望在这种情况下一个事务成功，另一个事务返回0个更新。
下面描述了表、FK及其索引：
##################################################################################################
Table "public.users"
Column | Type | Modifiers | Storage | Stats target | Description
-------------------+-----------------------------+-----------+----------+--------------+-------------
id | bigint | not null | plain | |
confirmationstate | character varying(20) | not null | extended | |
created | timestamp without time zone | not null | plain | |
dateofbirth | date | not null | plain | |
email | character varying(255) | not null | extended | |
firstname | character varying(100) | not null | extended | |
gender | character varying(10) | not null | extended | |
lastname | character varying(100) | not null | extended | |
lastusedlocale | character varying(5) | | extended | |
middlename | character varying(100) | | extended | |
passwordhash | bytea | not null | extended | |
passwordsalt | bytea | not null | extended | |
phone | character varying(50) | | extended | |
role | character varying(50) | not null | extended | |
signinstate | character varying(20) | not null | extended | |
updated | timestamp without time zone | not null | plain | |
username | character varying(255) | | extended | |
version | bigint | | plain | |
country_iso | character varying(2) | | extended | |
Indexes:
"users_pkey" PRIMARY KEY, btree (id)
"email_idx" UNIQUE CONSTRAINT, btree (email)
"username_idx" UNIQUE CONSTRAINT, btree (username)
"firstname_idx" btree (firstname)
"lastname_idx" btree (lastname)
"phone_idx" btree (phone)
Foreign-key constraints:
"fk_ghgfskd1hgobolp0fh20i6h14" FOREIGN KEY (country_iso) REFERENCES countries(iso)
Referenced by:
TABLE "userevents" CONSTRAINT "fk_69tm2wh9hkakap0uyjw41c61h" FOREIGN KEY (targetuser_id) REFERENCES users(id)
TABLE "userevents" CONSTRAINT "fk_nov1tso5k93h4m88unjy4f2kl" FOREIGN KEY (user_id) REFERENCES users(id)
##################################################################################################
Table "public.countries"
Column | Type | Modifiers | Storage | Stats target | Description
------------+------------------------+-----------+----------+--------------+-------------
iso | character varying(2) | not null | extended | |
iso3 | character varying(3) | | extended | |
name | character varying(80) | | extended | |
nativename | character varying(150) | | extended | |
numcode | integer | | plain | |
phonecode | integer | not null | plain | |
Indexes:
"countries_pkey" PRIMARY KEY, btree (iso)
"iso3_idx" UNIQUE CONSTRAINT, btree (iso3)
"nativename_idx" btree (nativename)
Referenced by:
TABLE "users" CONSTRAINT "fk_ghgfskd1hgobolp0fh20i6h14" FOREIGN KEY (country_iso) REFERENCES countries(iso)
##################################################################################################
Table "public.userevents"
Column | Type | Modifiers | Storage | Stats target | Description
---------------+-----------------------------+-----------+----------+--------------+-------------
id | bigint | not null | plain | |
data | bytea | | extended | |
ip | character varying(255) | not null | extended | |
time | timestamp without time zone | not null | plain | |
type | character varying(15) | not null | extended | |
url | character varying(2000) | | extended | |
targetuser_id | bigint | | plain | |
user_id | bigint | not null | plain | |
Indexes:
"userevents_pkey" PRIMARY KEY, btree (id)
"usertypetime_idx" btree (user_id, type, "time")
Foreign-key constraints:
"fk_69tm2wh9hkakap0uyjw41c61h" FOREIGN KEY (targetuser_id) REFERENCES users(id)
"fk_nov1tso5k93h4m88unjy4f2kl" FOREIGN KEY (user_id) REFERENCES users(id)
##################################################################################################
Table "public.hibernate_sequences"
Column | Type | Modifiers | Storage | Stats target | Description
------------------------+------------------------+-----------+----------+--------------+-------------
sequence_name | character varying(255) | | extended | |
sequence_next_hi_value | integer | | plain | |
##################################################################################################
编辑1:
pozs先生建议查看带有循环外键的现有问题，并提供有关事务中发生的情况的更多详细信息。 在此模式中没有循环外键，因此我在Postgres中设置了日志记录并尝试隔离问题。
这是引起死锁的2个进程的所有语句的完整日志记录。
进程1 日志:
2017-04-11 12:41:31 PDT 73842 LOG: 00000: execute S_2: BEGIN
2017-04-11 12:41:31 PDT 73842 LOG: 00000: execute S_3: select user0_.id as id1_2_0_, user0_.confirmationState as confirma2_2_0_, user0_.country_iso as country19_2_0_, user0_.created as created3_2_0_, user0_.dateOfBirth as dateOfBi4_2_0_, user0_.email as email5_2_0_, user0_.firstName as firstNam6_2_0_, user0_.gender as gender7_2_0_, user0_.lastName as lastName8_2_0_, user0_.lastUsedLocale as lastUsed9_2_0_, user0_.middleName as middleN10_2_0_, user0_.passwordHash as passwor11_2_0_, user0_.passwordSalt as passwor12_2_0_, user0_.phone as phone13_2_0_, user0_.role as role14_2_0_, user0_.signInState as signInS15_2_0_, user0_.updated as updated16_2_0_, user0_.username as usernam17_2_0_, user0_.version as version18_2_0_, country1_.iso as iso1_0_1_, country1_.iso3 as iso2_0_1_, country1_.name as name3_0_1_, country1_.nativeName as nativeNa4_0_1_, country1_.numCode as numCode5_0_1_, country1_.phoneCode as phoneCod6_0_1_ from users user0_ left outer join countries country1_ on user0_.country_iso=country1_.iso where user0_.id=$1
2017-04-11 12:41:31 PDT 73842 DETAIL: parameters: $1 = '10'
2017-04-11 12:41:31 PDT 73842 LOG: 00000: execute S_10: select country0_.iso as iso1_0_, country0_.iso3 as iso2_0_, country0_.name as name3_0_, country0_.nativeName as nativeNa4_0_, country0_.numCode as numCode5_0_, country0_.phoneCode as phoneCod6_0_ from countries country0_ order by country0_.nativeName, country0_.name
2017-04-11 12:41:31 PDT 73842 LOG: 00000: execute S_4: insert into userEvents (data, ip, targetUser_id, time, type, url, user_id, id) values ($1, $2, $3, $4, $5, $6, $7, $8)
2017-04-11 12:41:31 PDT 73842 DETAIL: parameters: $1 = '\x04545...LONG_BINARY_DATA...d', $2 = '192.168.1.2', $3 = '10', $4 = '2017-04-11 19:41:31.268', $5 = 'UPDATE', $6 = 'http://example.org', $7 = '10', $8 = '201243'
2017-04-11 12:41:31 PDT 73842 LOG: 00000: execute S_7: update users set confirmationState=$1, country_iso=$2, dateOfBirth=$3, email=$4, firstName=$5, gender=$6, lastName=$7, lastUsedLocale=$8, middleName=$9, passwordHash=$10, passwordSalt=$11, phone=$12, role=$13, signInState=$14, updated=$15, username=$16, version=$17 where id=$18 and version=$19
2017-04-11 12:41:31 PDT 73842 DETAIL: parameters: $1 = 'CONFIRMED', $2 = 'IS', $3 = '1984-10-10', $4 = 'email-527785869@example.org', $5 = 's7w7j5cdm1bg', $6 = 'FEMALE', $7 = 'Terrier9', $8 = 'en', $9 = 'Russel', $10 = '\x64..6439', $11 = '\x33...3836', $12 = '+16509876945', $13 = 'USER', $14 = 'ENABLED', $15 = '2017-04-11 19:41:31.268', $16 = 'demouser9', $17 = '547', $18 = '10', $19 = '546'
2017-04-11 12:41:32 PDT 73842 LOG: 00000: process 73842 detected deadlock while waiting for ExclusiveLock on tuple (206,43) of relation 17992 of database 16385 after 1000.114 ms
2017-04-11 12:41:32 PDT 73842 DETAIL: Process holding the lock: 73817. Wait queue: .
2017-04-11 12:41:32 PDT 73842 LOCATION: ProcSleep, proc.c:1415
2017-04-11 12:41:32 PDT 73842 STATEMENT: update users set confirmationState=$1, country_iso=$2, dateOfBirth=$3, email=$4, firstName=$5, gender=$6, lastName=$7, lastUsedLocale=$8, middleName=$9, passwordHash=$10, passwordSalt=$11, phone=$12, role=$13, signInState=$14, updated=$15, username=$16, version=$17 where id=$18 and version=$19
2017-04-11 12:41:32 PDT 73842 ERROR: 40P01: deadlock detected
2017-04-11 12:41:32 PDT 73842 DETAIL: Process 73842 waits for ExclusiveLock on tuple (206,43) of relation 17992 of database 16385; blocked by process 73817.
Process 73817 waits for ShareLock on transaction 2716972; blocked by process 73842.
Process 73842: update users set confirmationState=$1, country_iso=$2, dateOfBirth=$3, email=$4, firstName=$5, gender=$6, lastName=$7, lastUsedLocale=$8, middleName=$9, passwordHash=$10, passwordSalt=$11, phone=$12, role=$13, signInState=$14, updated=$15, username=$16, version=$17 where id=$18 and version=$19
2017-04-11 12:41:32 PDT 73842 HINT: See server log for query details.
2017-04-11 12:41:32 PDT 73842 LOCATION: DeadLockReport, deadlock.c:1140
2017-04-11 12:41:32 PDT 73842 STATEMENT: update users set confirmationState=$1, country_iso=$2, dateOfBirth=$3, email=$4, firstName=$5, gender=$6, lastName=$7, lastUsedLocale=$8, middleName=$9, passwordHash=$10, passwordSalt=$11, phone=$12, role=$13, signInState=$14, updated=$15, username=$16, version=$17 where id=$18 and version=$19
2017-04-11 12:41:32 PDT 73842 ERROR: 25P02: current transaction is aborted, commands ignored until end of transaction block
2017-04-11 12:41:32 PDT 73842 LOCATION: exec_parse_message, postgres.c:1303
2017-04-11 12:41:32 PDT 73842 STATEMENT: SELECT NULL AS TABLE_CAT, n.nspname AS TABLE_SCHEM, c.relname AS TABLE_NAME, CASE n.nspname ~ '^pg_' OR n.nspname = 'information_schema' WHEN true THEN CASE WHEN n.nspname = 'pg_catalog' OR n.nspname = 'information_schema' THEN CASE c.relkind WHEN 'r' THEN 'SYSTEM TABLE' WHEN 'v' THEN 'SYSTEM VIEW' WHEN 'i' THEN 'SYSTEM INDEX' ELSE NULL END WHEN n.nspname = 'pg_toast' THEN CASE c.relkind WHEN 'r' THEN 'SYSTEM TOAST TABLE' WHEN 'i' THEN 'SYSTEM TOAST INDEX' ELSE NULL END ELSE CASE c.relkind WHEN 'r' THEN 'TEMPORARY TABLE' WHEN 'i' THEN 'TEMPORARY INDEX' WHEN 'S' THEN 'TEMPORARY SEQUENCE' WHEN 'v' THEN 'TEMPORARY VIEW' ELSE NULL END END WHEN false THEN CASE c.relkind WHEN 'r' THEN 'TABLE' WHEN 'i' THEN 'INDEX' WHEN 'S' THEN 'SEQUENCE' WHEN 'v' THEN 'VIEW' WHEN 'c' THEN 'TYPE' WHEN 'f' THEN 'FOREIGN TABLE' WHEN 'm' THEN 'MATERIALIZED VIEW' ELSE NULL END ELSE NULL END AS TABLE_TYPE, d.description AS REMARKS FROM pg_catalog.pg_namespace n, pg_catalog.pg_class c LEFT JOIN pg_catalog.pg_description d ON (c.oid = d.objoid AND d.objsubid = 0) LEFT JOIN pg_catalog.pg_class dc ON (d.classoid=dc.oid AND dc.relname='pg_class') LEFT JOIN pg_catalog.pg_namespace dn ON (dn.oid=dc.relnamespace AND dn.nspname='pg_catalog') WHERE c.relnamespace = n.oid AND c.relname LIKE 'PROBABLYNOT' AND (false OR ( c.relkind = 'r' AND n.nspname !~ '^pg_' AND n.nspname <> 'information_schema' ) ) ORDER BY TABLE_TYPE,TABLE_SCHEM,TABLE_NAME
2017-04-11 12:41:32 PDT 73842 LOG: 00000: execute S_11: ROLLBACK
进程 2 日志:
2017-04-11 12:41:31 PDT 73817 LOG: 00000: execute S_2: BEGIN
2017-04-11 12:41:31 PDT 73817 LOG: 00000: execute S_3: select user0_.id as id1_2_0_, user0_.confirmationState as confirma2_2_0_, user0_.country_iso as country19_2_0_, user0_.created as created3_2_0_, user0_.dateOfBirth as dateOfBi4_2_0_, user0_.email as email5_2_0_, user0_.firstName as firstNam6_2_0_, user0_.gender as gender7_2_0_, user0_.lastName as lastName8_2_0_, user0_.lastUsedLocale as lastUsed9_2_0_, user0_.middleName as middleN10_2_0_, user0_.passwordHash as passwor11_2_0_, user0_.passwordSalt as passwor12_2_0_, user0_.phone as phone13_2_0_, user0_.role as role14_2_0_, user0_.signInState as signInS15_2_0_, user0_.updated as updated16_2_0_, user0_.username as usernam17_2_0_, user0_.version as version18_2_0_, country1_.iso as iso1_0_1_, country1_.iso3 as iso2_0_1_, country1_.name as name3_0_1_, country1_.nativeName as nativeNa4_0_1_, country1_.numCode as numCode5_0_1_, country1_.phoneCode as phoneCod6_0_1_ from users user0_ left outer join countries country1_ on user0_.country_iso=country1_.iso where user0_.id=$1
2017-04-11 12:41:31 PDT 73817 DETAIL: parameters: $1 = '10'
2017-04-11 12:41:31 PDT 73817 LOG: 00000: execute S_6: select country0_.iso as iso1_0_0_, country0_.iso3 as iso2_0_0_, country0_.name as name3_0_0_, country0_.nativeName as nativeNa4_0_0_, country0_.numCode as numCode5_0_0_, country0_.phoneCode as phoneCod6_0_0_ from countries country0_ where country0_.iso=$1
2017-04-11 12:41:31 PDT 73817 DETAIL: parameters: $1 = 'JP'
2017-04-11 12:41:31 PDT 73817
2017-04-11 12:41:31 PDT 73817 LOG: 00000: execute S_5: update users set confirmationState=$1, country_iso=$2, dateOfBirth=$3, email=$4, firstName=$5, gender=$6, lastName=$7, lastUsedLocale=$8, middleName=$9, passwordHash=$10, passwordSalt=$11, phone=$12, role=$13, signInState=$14, updated=$15, username=$16, version=$17 where id=$18 and version=$19
2017-04-11 12:41:31 PDT 73817 DETAIL: parameters: $1 = 'CONFIRMED', $2 = 'JP', $3 = '1984-10-10', $4 = 'email465994020@example.org', $5 = '-1kcg4facio48g', $6 = 'FEMALE', $7 = 'Terrier9', $8 = 'en', $9 = 'Russel', $10 = '\x64656d6f7573657270617373776f726439', $11 = '\x33...3836', $12 = '+16509876905', $13 = 'USER', $14 = 'ENABLED', $15 = '2017-04-11 19:41:31.188', $16 = 'demouser9', $17 = '547', $18 = '10', $19 = '546'
2017-04-11 12:41:32 PDT 73842 DETAIL: Process holding the lock: 73817. Wait queue: .
2017-04-11 12:41:32 PDT 73842 DETAIL: Process 73842 waits for ExclusiveLock on tuple (206,43) of relation 17992 of database 16385; blocked by process 73817.
Process 73817 waits for ShareLock on transaction 2716972; blocked by process 73842.
Process 73817: update users set confirmationState=$1, country_iso=$2, dateOfBirth=$3, email=$4, firstName=$5, gender=$6, lastName=$7, lastUsedLocale=$8, middleName=$9, passwordHash=$10, passwordSalt=$11, phone=$12, role=$13, signInState=$14, updated=$15, username=$16, version=$17 where id=$18 and version=$19
2017-04-11 12:41:32 PDT 73817 LOG: 00000: execute S_10: ROLLBACK
第一个流程的步骤如下：
- BEGIN; 开始事务
- SELECT * FROM users WHERE id = 10; 查询id为10的用户
- SELECT * FROM countries; // 不影响问题
- INSERT INTO userEvents (..., user_id, ...) VALUES (..., 10, ...); 插入userEvents记录，其中user_id为10
- UPDATE users SET [..fields to update..] WHERE id = 10 AND version = 546; 更新id为10且版本为546的用户信息
- COMMIT; 提交事务
第二个流程的步骤如下：
- BEGIN; 开始事务
- SELECT * FROM users WHERE id = 10; 查询id为10的用户
- UPDATE users SET [..fields to update..] WHERE id = 10 AND version = 546; 更新id为10且版本为546的用户信息
- COMMIT; 提交事务
是否是因为在第一次事务中先获得了对FK（userEvents.user_id）进行插入的独占锁，然后再获得了对UPDATE（users.id = 10）的独占锁，而在第二次事务中则先获得了对UPDATE（users.id = 10）和（userEvents.user_id）的独占锁导致死锁？
因为当我强制“在INSERT INTO userEvents之前UPDATE users”时，在高负载下不再看到死锁。