MySQL读取联合表时读取通信数据包超时

Question

我有两台服务器（所罗门和宁静）。
两台服务器都是 Windows Server (2012 & 2016)、IIS、PHP (5.6.31)、MySQL (5.5)。

在所罗门上，我设置了几个联合表，指向宁静表。我在 solomon 上设置了一个用户，专门用于连接到这些联合表。

帐户分布在两台服务器上。我的用户帐户一半在 solomon 上，一半在 serenity 上。但是，所有用户的登录页面都很平静。这是为了让 serenity 服务器可以检查该用户应该被定向到哪个服务器，然后重定向到 solomon 或 serenity 上的密码页面。所以通过这种方式，所有用户都经历了宁静，但并非所有用户都留在那里。

但是，在 solomon 上运行的其他一些脚本确实会检查这些联合表，因此即使用户已经通过 solomon，该站点仍在查询这些联合表，从而达到了平静。

据我所知，这应该不是问题，但在平静中我在 mysqlerror.log 中收到很多警告，如下所示：（用户名、数据库名和 IP 地址被混淆）

180430 16:21:00 [Warning] Aborted connection 24784 to db: 'dbname_blah' user: 'federated_user_blah' host: 'xxx.xxx.xx.xx' (Got timeout reading communication packets)

在所罗门我没有收到这些警告。此外，这些警告中有 95% 提到了联合用户，即使我 99% 的查询是使用不同的用户完成的。所以这就是为什么我怀疑这是联合表/用户的问题。

我不会太担心，除了我在宁静方面遇到了很多问题，我怀疑这可能与此有关。今天我的数据库崩溃了，我不得不重新启动服务器。很多愤怒的顾客。

其他症状

在过去的几个月里，我遇到了似乎是并发连接限制的问题，因为我有几个脚本循环遍历多行数据（通常在 50 到 200 之间）并使用 ajax 为每一行调用发送电子邮件脚本，或者在另一种情况下计算小时数。有时，这些循环脚本不会执行循环中的所有调用，而是会以 500 个错误结束，特别是当循环中有很多行（比如超过 100 行）时。较小的循环（如 50 条记录）通常没有问题。

然而，根据微软的说法，IIS 中不再有任何并发​​连接限制。

网站上的超时 有时并非我的所有 sql 语句都能够在页面加载时完成执行。他们只是超时并且不返回任何行。然后当我刷新页面时，它们通常会加载，但如果加载时间超过几秒钟，我知道会有一些语句超时。

MySQL Workbench 中的超时 如果我尝试在 MySQL Workbench中执行长时间运行的查询，它总是会在 10 到 12 秒之间超时。所以如果我想一次选择或删除超过 30,000 行，它通常会超时，所以我总是必须限制我正在处理的行数。

备份失败 另外，我的备份一直在使用 MySQLDump 失败。尝试备份相当大的表时，它们总是失败。较小的表没有问题，但它无法备份这个包含 700 万行约 600 MB 数据的大表。

空闲线程 几周前，服务器运行得非常慢，我意识到有数百个空闲的数据库线程一直存在并且没有消亡。我通过将 wait_timeout 设置为 20 秒来解决这个问题，但这似乎更像是一个补丁而不是解决方案。

打开文件限制 当我将 open-files-limit=4096 添加到 my.ini 时，我遇到了另一个问题，因为这是根据我为尝试解决我遇到的这些问题而调整的另一个设置所推荐的。然而，添加 open-files-limit=4096 是一个很大的错误，因为这几乎杀死了服务器。一旦我发表评论，它就又开始正常工作了。

到目前为止，我已经“修复”了所有这些问题，但我觉得我没有解决所有这些问题的根本原因，只是修补它们。

最重要的是，我知道我的服务器有问题，我怀疑这可能都与我在 mysqlerror.log 中不断看到的这个警告有关。任何人都可以解释为什么我可能会收到此警告消息？会不会是dns的问题？权限问题？MySQL 中的错误？

我应该指出我的服务器都很忙。每个每秒执行数千个选择语句。

我的整个 my.ini 文件（我删除了注释以保持简短）

[client]
port=3306

[mysql]
default-character-set=UTF8

[mysqld]
federated

ft_min_word_len = 3
log_warnings = 2
log_error=c:\inetpub\wwwroot\mysqlerror.log
connect_timeout = 40
wait_timeout = 40  
max_allowed_packet = 500M
net_read_timeout = 600
net_write_timeout = 600
port=3306

basedir="C:/Program Files/MySQL/MySQL Server 5.5/"
datadir="C:/ProgramData/MySQL/MySQL Server 5.5/Data/"
character-set-server=UTF8
default-storage-engine=INNODB
sql-mode="STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION"

max_connections=1500
query_cache_size=50M
table_cache=2000
tmp_table_size=256M
thread_cache_size=64

myisam_max_sort_file_size=100G
myisam_sort_buffer_size=69M
key_buffer_size=384M
read_buffer_size=1MB
read_rnd_buffer_size=256K
sort_buffer_size=256K

innodb_additional_mem_pool_size=3M
innodb_flush_log_at_trx_commit=0
innodb_log_buffer_size=32M
innodb_buffer_pool_size=20G
innodb_log_file_size=256M
innodb_thread_concurrency=66
innodb_log_files_in_group = 2
innodb_log_group_home_dir = "C:/Program Files/MySQL/MySQL Server 5.5/data"
query_cache_type = 1

[mysqld_safe]
log_warnings = 2
log_error=c:\inetpub\wwwroot\mysqlerror.log

显示全球状态

Aborted_clients 8050
Aborted_connects    5119
Binlog_cache_disk_use   0
Binlog_cache_use    0
Binlog_stmt_cache_disk_use  0
Binlog_stmt_cache_use   0
Bytes_received  99146740665
Bytes_sent  1312788340530
Com_admin_commands  642
Com_assign_to_keycache  0
Com_alter_db    0
Com_alter_db_upgrade    0
Com_alter_event 0
Com_alter_function  0
Com_alter_procedure 0
Com_alter_server    0
Com_alter_table 0
Com_alter_tablespace    0
Com_analyze 0
Com_begin   0
Com_binlog  0
Com_call_procedure  0
Com_change_db   2451188
Com_change_master   0
Com_check   0
Com_checksum    0
Com_commit  0
Com_create_db   8
Com_create_event    0
Com_create_function 0
Com_create_index    0
Com_create_procedure    0
Com_create_server   0
Com_create_table    5
Com_create_trigger  0
Com_create_udf  0
Com_create_user 0
Com_create_view 0
Com_dealloc_sql 0
Com_delete  2298884
Com_delete_multi    0
Com_do  0
Com_drop_db 0
Com_drop_event  0
Com_drop_function   0
Com_drop_index  0
Com_drop_procedure  0
Com_drop_server 0
Com_drop_table  0
Com_drop_trigger    0
Com_drop_user   0
Com_drop_view   0
Com_empty_query 0
Com_execute_sql 0
Com_flush   0
Com_grant   0
Com_ha_close    0
Com_ha_open 0
Com_ha_read 0
Com_help    0
Com_insert  80433
Com_insert_select   3662
Com_install_plugin  0
Com_kill    143
Com_load    0
Com_lock_tables 796
Com_optimize    0
Com_preload_keys    0
Com_prepare_sql 0
Com_purge   0
Com_purge_before_date   0
Com_release_savepoint   0
Com_rename_table    0
Com_rename_user 0
Com_repair  0
Com_replace 0
Com_replace_select  0
Com_reset   0
Com_resignal    0
Com_revoke  0
Com_revoke_all  0
Com_rollback    0
Com_rollback_to_savepoint   0
Com_savepoint   0
Com_select  28145718
Com_set_option  2449199
Com_signal  0
Com_show_authors    0
Com_show_binlog_events  0
Com_show_binlogs    0
Com_show_charsets   1
Com_show_collations 1
Com_show_contributors   0
Com_show_create_db  0
Com_show_create_event   0
Com_show_create_func    1900
Com_show_create_proc    0
Com_show_create_table   428
Com_show_create_trigger 3
Com_show_databases  622
Com_show_engine_logs    0
Com_show_engine_mutex   0
Com_show_engine_status  0
Com_show_events 0
Com_show_errors 0
Com_show_fields 624
Com_show_function_status    381
Com_show_grants 0
Com_show_keys   12
Com_show_master_status  620
Com_show_open_tables    166496
Com_show_plugins    0
Com_show_privileges 0
Com_show_procedure_status   381
Com_show_processlist    352275
Com_show_profile    0
Com_show_profiles   0
Com_show_relaylog_events    0
Com_show_slave_hosts    0
Com_show_slave_status   0
Com_show_status 33924
Com_show_storage_engines    1
Com_show_table_status   9631732
Com_show_tables 427
Com_show_triggers   481
Com_show_variables  779
Com_show_warnings   0
Com_slave_start 0
Com_slave_stop  0
Com_stmt_close  3543
Com_stmt_execute    3543
Com_stmt_fetch  0
Com_stmt_prepare    3543
Com_stmt_reprepare  0
Com_stmt_reset  0
Com_stmt_send_long_data 0
Com_truncate    0
Com_uninstall_plugin    0
Com_unlock_tables   760
Com_update  190582
Com_update_multi    112
Com_xa_commit   0
Com_xa_end  0
Com_xa_prepare  0
Com_xa_recover  0
Com_xa_rollback 0
Com_xa_start    0
Compression OFF
Connections 4902222
Created_tmp_disk_tables 2044232
Created_tmp_files   16985
Created_tmp_tables  19170929
Delayed_errors  0
Delayed_insert_threads  0
Delayed_writes  0
Flush_commands  1
Handler_commit  30519874
Handler_delete  29441
Handler_discover    0
Handler_prepare 0
Handler_read_first  80100
Handler_read_key    3399084113
Handler_read_last   4209
Handler_read_next   402859087
Handler_read_prev   70204318
Handler_read_rnd    447590174
Handler_read_rnd_next   1384408509
Handler_rollback    30345
Handler_savepoint   0
Handler_savepoint_rollback  0
Handler_update  2708725
Handler_write   954512657
Innodb_buffer_pool_pages_data   165761
Innodb_buffer_pool_bytes_data   2715828224
Innodb_buffer_pool_pages_dirty  12
Innodb_buffer_pool_bytes_dirty  196608
Innodb_buffer_pool_pages_flushed    824631
Innodb_buffer_pool_pages_free   1126267
Innodb_buffer_pool_pages_misc   18692
Innodb_buffer_pool_pages_total  1310720
Innodb_buffer_pool_read_ahead_rnd   0
Innodb_buffer_pool_read_ahead   59353
Innodb_buffer_pool_read_ahead_evicted   0
Innodb_buffer_pool_read_requests    1411093916
Innodb_buffer_pool_reads    102643
Innodb_buffer_pool_wait_free    0
Innodb_buffer_pool_write_requests   2315658
Innodb_data_fsyncs  162458
Innodb_data_pending_fsyncs  0
Innodb_data_pending_reads   0
Innodb_data_pending_writes  0
Innodb_data_read    2682212352
Innodb_data_reads   163586
Innodb_data_writes  967117
Innodb_data_written 1404415488
Innodb_dblwr_pages_written  824631
Innodb_dblwr_writes 25129
Innodb_have_atomic_builtins ON
Innodb_log_waits    0
Innodb_log_write_requests   214508
Innodb_log_writes   97683
Innodb_os_log_fsyncs    112195
Innodb_os_log_pending_fsyncs    0
Innodb_os_log_pending_writes    0
Innodb_os_log_written   145280512
Innodb_page_size    16384
Innodb_pages_created    2314
Innodb_pages_read   163447
Innodb_pages_written    824631
Innodb_row_lock_current_waits   0
Innodb_row_lock_time    48
Innodb_row_lock_time_avg    0
Innodb_row_lock_time_max    15
Innodb_row_lock_waits   59
Innodb_rows_deleted 29441
Innodb_rows_inserted    83161
Innodb_rows_read    3180508723
Innodb_rows_updated 138346
Innodb_truncated_status_writes  0
Key_blocks_not_flushed  0
Key_blocks_unused   319666
Key_blocks_used 36
Key_read_requests   2183276
Key_reads   24
Key_write_requests  28603
Key_writes  0
Last_query_cost 0.000000
Max_used_connections    243
Not_flushed_delayed_rows    0
Open_files  2
Open_streams    0
Open_table_definitions  155
Open_tables 116
Opened_files    8196208
Opened_table_definitions    162
Opened_tables   12879
Performance_schema_cond_classes_lost    0
Performance_schema_cond_instances_lost  0
Performance_schema_file_classes_lost    0
Performance_schema_file_handles_lost    0
Performance_schema_file_instances_lost  0
Performance_schema_locker_lost  0
Performance_schema_mutex_classes_lost   0
Performance_schema_mutex_instances_lost 0
Performance_schema_rwlock_classes_lost  0
Performance_schema_rwlock_instances_lost    0
Performance_schema_table_handles_lost   0
Performance_schema_table_instances_lost 0
Performance_schema_thread_classes_lost  0
Performance_schema_thread_instances_lost    0
Prepared_stmt_count 0
Qcache_free_blocks  5902
Qcache_free_memory  17741584
Qcache_hits 631937988
Qcache_inserts  27096342
Qcache_lowmem_prunes    4224427
Qcache_not_cached   1048077
Qcache_queries_in_cache 12188
Qcache_total_blocks 32437
Queries 683199489
Questions   683165600
Rpl_status  AUTH_MASTER
Select_full_join    873441
Select_full_range_join  1591
Select_range    18162680
Select_range_check  0
Select_scan 10081022
Slave_heartbeat_period  0.000
Slave_open_temp_tables  0
Slave_received_heartbeats   0
Slave_retried_transactions  0
Slave_running   OFF
Slow_launch_threads 0
Slow_queries    174
Sort_merge_passes   15942
Sort_range  1874836
Sort_rows   91682277
Sort_scan   7671476
Ssl_accept_renegotiates 0
Ssl_accepts 0
Ssl_callback_cache_hits 0
Ssl_cipher  
Ssl_cipher_list 
Ssl_client_connects 0
Ssl_connect_renegotiates    0
Ssl_ctx_verify_depth    0
Ssl_ctx_verify_mode 0
Ssl_default_timeout 0
Ssl_finished_accepts    0
Ssl_finished_connects   0
Ssl_session_cache_hits  0
Ssl_session_cache_misses    0
Ssl_session_cache_mode  NONE
Ssl_session_cache_overflows 0
Ssl_session_cache_size  0
Ssl_session_cache_timeouts  0
Ssl_sessions_reused 0
Ssl_used_session_cache_entries  0
Ssl_verify_depth    0
Ssl_verify_mode 0
Ssl_version 
Table_locks_immediate   63848411
Table_locks_waited  4
Tc_log_max_pages_used   0
Tc_log_page_size    0
Tc_log_page_waits   0
Threads_cached  63
Threads_connected   14
Threads_created 1124
Threads_running 1
Uptime  186389
Uptime_since_flush_status   186389

显示全局变量；

auto_increment_increment    1
auto_increment_offset   1
autocommit  ON
automatic_sp_privileges ON
back_log    50
basedir C:/Program Files/MySQL/MySQL Server 5.5/
big_tables  OFF
binlog_cache_size   32768
binlog_direct_non_transactional_updates OFF
binlog_format   STATEMENT
binlog_stmt_cache_size  32768
bulk_insert_buffer_size 8388608
character_set_client    utf8
character_set_connection    utf8
character_set_database  utf8
character_set_filesystem    binary
character_set_results   utf8
character_set_server    utf8
character_set_system    utf8
character_sets_dir  C:\Program Files\MySQL\MySQL Server 5.5\share\charsets\
collation_connection    utf8_general_ci
collation_database  utf8_general_ci
collation_server    utf8_general_ci
completion_type NO_CHAIN
concurrent_insert   AUTO
connect_timeout 40
datadir C:\ProgramData\MySQL\MySQL Server 5.5\Data\
date_format %Y-%m-%d
datetime_format %Y-%m-%d %H:%i:%s
default_storage_engine  InnoDB
default_week_format 0
delay_key_write ON
delayed_insert_limit    100
delayed_insert_timeout  300
delayed_queue_size  1000
div_precision_increment 4
engine_condition_pushdown   ON
event_scheduler OFF
expire_logs_days    0
flush   OFF
flush_time  1800
foreign_key_checks  ON
ft_boolean_syntax   + -><()~*:""&|
ft_max_word_len 84
ft_min_word_len 3
ft_query_expansion_limit    20
ft_stopword_file    (built-in)
general_log OFF
general_log_file    C:\ProgramData\MySQL\MySQL Server 5.5\Data\Serenity.log
group_concat_max_len    1024
have_compress   YES
have_crypt  NO
have_csv    YES
have_dynamic_loading    YES
have_geometry   YES
have_innodb YES
have_ndbcluster NO
have_openssl    DISABLED
have_partitioning   YES
have_profiling  YES
have_query_cache    YES
have_rtree_keys YES
have_ssl    DISABLED
have_symlink    YES
hostname    Serenity
ignore_builtin_innodb   OFF
init_connect    
init_file   
init_slave  
innodb_adaptive_flushing    ON
innodb_adaptive_hash_index  ON
innodb_additional_mem_pool_size 3145728
innodb_autoextend_increment 8
innodb_autoinc_lock_mode    1
innodb_buffer_pool_instances    1
innodb_buffer_pool_size 21474836480
innodb_change_buffering all
innodb_checksums    ON
innodb_commit_concurrency   0
innodb_concurrency_tickets  500
innodb_data_file_path   ibdata1:10M:autoextend
innodb_data_home_dir    
innodb_doublewrite  ON
innodb_fast_shutdown    1
innodb_file_format  Antelope
innodb_file_format_check    ON
innodb_file_format_max  Antelope
innodb_file_per_table   OFF
innodb_flush_log_at_trx_commit  0
innodb_flush_method 
innodb_force_load_corrupted OFF
innodb_force_recovery   0
innodb_io_capacity  200
innodb_large_prefix OFF
innodb_lock_wait_timeout    50
innodb_locks_unsafe_for_binlog  OFF
innodb_log_buffer_size  33554432
innodb_log_file_size    268435456
innodb_log_files_in_group   2
innodb_log_group_home_dir   C:\Program Files\MySQL\MySQL Server 5.5\data
innodb_max_dirty_pages_pct  75
innodb_max_purge_lag    0
innodb_mirrored_log_groups  1
innodb_old_blocks_pct   37
innodb_old_blocks_time  0
innodb_open_files   300
innodb_print_all_deadlocks  OFF
innodb_purge_batch_size 20
innodb_purge_threads    0
innodb_random_read_ahead    OFF
innodb_read_ahead_threshold 56
innodb_read_io_threads  4
innodb_replication_delay    0
innodb_rollback_on_timeout  OFF
innodb_rollback_segments    128
innodb_spin_wait_delay  6
innodb_stats_method nulls_equal
innodb_stats_on_metadata    ON
innodb_stats_sample_pages   8
innodb_strict_mode  OFF
innodb_support_xa   ON
innodb_sync_spin_loops  30
innodb_table_locks  ON
innodb_thread_concurrency   66
innodb_thread_sleep_delay   10000
innodb_use_native_aio   ON
innodb_use_sys_malloc   ON
innodb_version  5.5.45
innodb_write_io_threads 4
interactive_timeout 28800
join_buffer_size    131072
keep_files_on_create    OFF
key_buffer_size 402653184
key_cache_age_threshold 300
key_cache_block_size    1024
key_cache_division_limit    100
large_files_support ON
large_page_size 0
large_pages OFF
lc_messages en_US
lc_messages_dir C:\Program Files\MySQL\MySQL Server 5.5\share\
lc_time_names   en_US
license GPL
local_infile    ON
lock_wait_timeout   31536000
log OFF
log_bin OFF
log_bin_trust_function_creators OFF
log_error   c:\inetpub\wwwroot\mysqlerror.log
log_output  FILE
log_queries_not_using_indexes   OFF
log_slave_updates   OFF
log_slow_queries    OFF
log_warnings    2
long_query_time 10.000000
low_priority_updates    OFF
lower_case_file_system  ON
lower_case_table_names  1
max_allowed_packet  524288000
max_binlog_cache_size   18446744073709547520
max_binlog_size 1073741824
max_binlog_stmt_cache_size  18446744073709547520
max_connect_errors  10
max_connections 1500
max_delayed_threads 20
max_error_count 64
max_heap_table_size 16777216
max_insert_delayed_threads  20
max_join_size   18446744073709551615
max_length_for_sort_data    1024
max_long_data_size  524288000
max_prepared_stmt_count 16382
max_relay_log_size  0
max_seeks_for_key   4294967295
max_sort_length 1024
max_sp_recursion_depth  0
max_tmp_tables  32
max_user_connections    0
max_write_lock_count    4294967295
metadata_locks_cache_size   1024
min_examined_row_limit  0
multi_range_count   256
myisam_data_pointer_size    6
myisam_max_sort_file_size   107374182400
myisam_mmap_size    18446744073709551615
myisam_recover_options  OFF
myisam_repair_threads   1
myisam_sort_buffer_size 72351744
myisam_stats_method nulls_unequal
myisam_use_mmap OFF
named_pipe  OFF
net_buffer_length   16384
net_read_timeout    600
net_retry_count 10
net_write_timeout   600
new OFF
old OFF
old_alter_table OFF
old_passwords   OFF
open_files_limit    9548
optimizer_prune_level   1
optimizer_search_depth  62
optimizer_switch    index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,engine_condition_pushdown=on
performance_schema  OFF
performance_schema_events_waits_history_long_size   10000
performance_schema_events_waits_history_size    10
performance_schema_max_cond_classes 80
performance_schema_max_cond_instances   1000
performance_schema_max_file_classes 50
performance_schema_max_file_handles 32768
performance_schema_max_file_instances   10000
performance_schema_max_mutex_classes    200
performance_schema_max_mutex_instances  1000000
performance_schema_max_rwlock_classes   30
performance_schema_max_rwlock_instances 1000000
performance_schema_max_table_handles    100000
performance_schema_max_table_instances  50000
performance_schema_max_thread_classes   50
performance_schema_max_thread_instances 1000
pid_file    C:\ProgramData\MySQL\MySQL Server 5.5\Data\Serenity.pid
plugin_dir  C:\Program Files\MySQL\MySQL Server 5.5\lib\plugin\
port    3306
preload_buffer_size 32768
profiling   OFF
profiling_history_size  15
protocol_version    10
query_alloc_block_size  8192
query_cache_limit   1048576
query_cache_min_res_unit    4096
query_cache_size    52428800
query_cache_type    ON
query_cache_wlock_invalidate    OFF
query_prealloc_size 8192
range_alloc_block_size  4096
read_buffer_size    1048576
read_only   OFF
read_rnd_buffer_size    262144
relay_log   
relay_log_index 
relay_log_info_file relay-log.info
relay_log_purge ON
relay_log_recovery  OFF
relay_log_space_limit   0
report_host 
report_password 
report_port 3306
report_user 
rpl_recovery_rank   0
secure_auth OFF
secure_file_priv    
server_id   0
shared_memory   OFF
shared_memory_base_name MYSQL
skip_external_locking   ON
skip_name_resolve   OFF
skip_networking OFF
skip_show_database  OFF
slave_compressed_protocol   OFF
slave_exec_mode STRICT
slave_load_tmpdir   C:\Windows\TEMP
slave_max_allowed_packet    1073741824
slave_net_timeout   3600
slave_skip_errors   OFF
slave_transaction_retries   10
slave_type_conversions  
slow_launch_time    2
slow_query_log  OFF
slow_query_log_file C:\ProgramData\MySQL\MySQL Server 5.5\Data\Serenity-slow.log
socket  MySQL
sort_buffer_size    262144
sql_auto_is_null    OFF
sql_big_selects ON
sql_big_tables  OFF
sql_buffer_result   OFF
sql_log_bin ON
sql_log_off OFF
sql_low_priority_updates    OFF
sql_max_join_size   18446744073709551615
sql_mode    STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
sql_notes   ON
sql_quote_show_create   ON
sql_safe_updates    OFF
sql_select_limit    18446744073709551615
sql_slave_skip_counter  0
sql_warnings    OFF
ssl_ca  
ssl_capath  
ssl_cert    
ssl_cipher  
ssl_key 
storage_engine  InnoDB
stored_program_cache    256
sync_binlog 0
sync_frm    ON
sync_master_info    0
sync_relay_log  0
sync_relay_log_info 0
system_time_zone    Eastern Daylight Time
table_definition_cache  400
table_open_cache    2000
thread_cache_size   64
thread_concurrency  10
thread_handling one-thread-per-connection
thread_stack    262144
time_format %H:%i:%s
time_zone   SYSTEM
timed_mutexes   OFF
tmp_table_size  268435456
tmpdir  C:\Windows\TEMP
transaction_alloc_block_size    8192
transaction_prealloc_size   4096
tx_isolation    REPEATABLE-READ
unique_checks   ON
updatable_views_with_limit  YES
version 5.5.45
version_comment MyS

    

Answer 1

我现在意识到，当空闲线程被 wait_timeout 杀死时，就会发生此错误。换句话说，如果 wait_timeout 设置为 40 并且空闲线程停留长达 40 秒，一旦达到 40 秒并被终止，就会记录错误： \xe2\x80\x9c读取通信数据包超时\xe2\ x80\x9d。

\n\n

通常，避免线程被 wait_timeout 杀死的方法是在不再需要连接时在脚本中调用 mysql_close() 。

\n\n

不幸的是，这不适用于通过联合表进行的查询。因此，当在联合表上执行查询时，它在其他服务器上创建的连接不会被 mysql_close() 终止。（这就是为什么我有这么多空闲连接，以及为什么它们只会被 wait_timeout 杀死）

\n