如果您得到“too many connections”错误信息,并且想要了解正在发生的情况,本语句是非常有用的。MySQL保留一个额外的连接,让拥有SUPER权限的 账户使用,以确保管理员能够随时连接和检查系统(假设您没有把此权限给予所有的用户)。
mysql> show full processlist; +---------+-------------+--------------------+----------------+-------------+-------+-----------------------------------------------------------------------+-----------------------+ | Id | User | Host | db | Command | Time | State | Info | +---------+-------------+--------------------+----------------+-------------+-------+-----------------------------------------------------------------------+-----------------------+ | 1056536 | replication | 192.168.6.91:38417 | NULL | Binlog Dump | 33759 | Master has sent all binlog to slave; waiting for binlog to be updated | NULL | | 1107067 | miaohr | 192.168.6.81:32024 | NULL | Query | 0 | NULL | show full processlist | | 1107182 | miaohr | 192.168.6.91:44217 | hr_db_business | Sleep | 1 | | NULL | +---------+-------------+--------------------+----------------+-------------+-------+-----------------------------------------------------------------------+-----------------------+
mysql> show status; +------------------------------------------+----------------------+ | Variable_name | Value | +------------------------------------------+----------------------+ | Aborted_clients | 777 | | Aborted_connects | 16 | | Binlog_cache_disk_use | 532 | | Binlog_cache_use | 8333221 | | Binlog_stmt_cache_disk_use | 0 | | Binlog_stmt_cache_use | 18732 | | Bytes_received | 303 | | Bytes_sent | 12460 | | Com_admin_commands | 0 | | 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 | 0 | | Com_change_master | 0 | | Com_check | 0 | | Com_checksum | 0 | | Com_commit | 0 | | Com_create_db | 0 | | Com_create_event | 0 | | Com_create_function | 0 | | Com_create_index | 0 | | Com_create_procedure | 0 | | Com_create_server | 0 | | Com_create_table | 0 | | Com_create_trigger | 0 | | Com_create_udf | 0 | | Com_create_user | 0 | | Com_create_view | 0 | | Com_dealloc_sql | 0 | | Com_delete | 0 | | 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 | 0 | | Com_insert_select | 0 | | Com_install_plugin | 0 | | Com_kill | 0 | | Com_load | 0 | | Com_lock_tables | 0 | | 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 | 1 | | Com_set_option | 0 | | Com_signal | 0 | | Com_show_authors | 0 | | Com_show_binlog_events | 0 | | Com_show_binlogs | 0 | | Com_show_charsets | 0 | | Com_show_collations | 0 | | Com_show_contributors | 0 | | Com_show_create_db | 0 | | Com_show_create_event | 0 | | Com_show_create_func | 0 | | Com_show_create_proc | 0 | | Com_show_create_table | 0 | | Com_show_create_trigger | 0 | | Com_show_databases | 0 | | 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 | 0 | | Com_show_function_status | 0 | | Com_show_grants | 0 | | Com_show_keys | 0 | | Com_show_master_status | 0 | | Com_show_open_tables | 0 | | Com_show_plugins | 0 | | Com_show_privileges | 0 | | Com_show_procedure_status | 0 | | Com_show_processlist | 6 | | 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 | 2 | | Com_show_storage_engines | 0 | | Com_show_table_status | 0 | | Com_show_tables | 0 | | Com_show_triggers | 0 | | Com_show_variables | 0 | | Com_show_warnings | 0 | | Com_slave_start | 0 | | Com_slave_stop | 0 | | Com_stmt_close | 0 | | Com_stmt_execute | 0 | | Com_stmt_fetch | 0 | | Com_stmt_prepare | 0 | | Com_stmt_reprepare | 0 | | Com_stmt_reset | 0 | | Com_stmt_send_long_data | 0 | | Com_truncate | 0 | | Com_uninstall_plugin | 0 | | Com_unlock_tables | 0 | | Com_update | 0 | | Com_update_multi | 0 | | 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 | 1107216 | | Created_tmp_disk_tables | 0 | | Created_tmp_files | 564 | | Created_tmp_tables | 0 | | Delayed_errors | 0 | | Delayed_insert_threads | 0 | | Delayed_writes | 0 | | Flush_commands | 1 | | Handler_commit | 0 | | Handler_delete | 0 | | Handler_discover | 0 | | Handler_prepare | 0 | | Handler_read_first | 0 | | Handler_read_key | 0 | | Handler_read_last | 0 | | Handler_read_next | 0 | | Handler_read_prev | 0 | | Handler_read_rnd | 0 | | Handler_read_rnd_next | 0 | | Handler_rollback | 0 | | Handler_savepoint | 0 | | Handler_savepoint_rollback | 0 | | Handler_update | 0 | | Handler_write | 0 | | Innodb_buffer_pool_pages_data | 376178 | | Innodb_buffer_pool_bytes_data | 4261109760 | | Innodb_buffer_pool_pages_dirty | 0 | | Innodb_buffer_pool_bytes_dirty | 0 | | Innodb_buffer_pool_pages_flushed | 4419408 | | Innodb_buffer_pool_pages_free | 0 | | Innodb_buffer_pool_pages_misc | 18446744073709437581 | | Innodb_buffer_pool_pages_total | 262143 | | Innodb_buffer_pool_read_ahead_rnd | 0 | | Innodb_buffer_pool_read_ahead | 506357 | | Innodb_buffer_pool_read_ahead_evicted | 49891 | | Innodb_buffer_pool_read_requests | 3550554620 | | Innodb_buffer_pool_reads | 8777938 | | Innodb_buffer_pool_wait_free | 0 | | Innodb_buffer_pool_write_requests | 159577779 | | Innodb_data_fsyncs | 13359191 | | Innodb_data_pending_fsyncs | 0 | | Innodb_data_pending_reads | 0 | | Innodb_data_pending_writes | 0 | | Innodb_data_read | 133311885312 | | Innodb_data_reads | 9323868 | | Innodb_data_writes | 17580993 | | Innodb_data_written | 163731449856 | | Innodb_dblwr_pages_written | 4419408 | | Innodb_dblwr_writes | 119202 | | Innodb_have_atomic_builtins | ON | | Innodb_log_waits | 0 | | Innodb_log_write_requests | 39730223 | | Innodb_log_writes | 12957426 | | Innodb_os_log_fsyncs | 13004841 | | Innodb_os_log_pending_fsyncs | 0 | | Innodb_os_log_pending_writes | 0 | | Innodb_os_log_written | 25546702336 | | Innodb_page_size | 16384 | | Innodb_pages_created | 539547 | | Innodb_pages_read | 9323581 | | Innodb_pages_written | 4419408 | | Innodb_row_lock_current_waits | 0 | | Innodb_row_lock_time | 26866245 | | Innodb_row_lock_time_avg | 1367 | | Innodb_row_lock_time_max | 55497 | | Innodb_row_lock_waits | 19649 | | Innodb_rows_deleted | 15511 | | Innodb_rows_inserted | 1868056 | | Innodb_rows_read | 1657696248 | | Innodb_rows_updated | 7778106 | | Innodb_truncated_status_writes | 0 | | Key_blocks_not_flushed | 0 | | Key_blocks_unused | 26773 | | Key_blocks_used | 19 | | Key_read_requests | 67555 | | Key_reads | 19 | | Key_write_requests | 69364 | | Key_writes | 11544 | | Last_query_cost | 0.000000 | | Max_used_connections | 436 | | Not_flushed_delayed_rows | 0 | | Open_files | 99 | | Open_streams | 0 | | Open_table_definitions | 327 | | Open_tables | 1301 | | Opened_files | 22851 | | Opened_table_definitions | 0 | | Opened_tables | 0 | | 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 | 3426 | | Qcache_free_memory | 38784160 | | Qcache_hits | 9223399 | | Qcache_inserts | 3505151 | | Qcache_lowmem_prunes | 0 | | Qcache_not_cached | 400457 | | Qcache_queries_in_cache | 19336 | | Qcache_total_blocks | 42289 | | Queries | 27883378 | | Questions | 9 | | Rpl_status | AUTH_MASTER | | Select_full_join | 0 | | Select_full_range_join | 0 | | Select_range | 0 | | Select_range_check | 0 | | Select_scan | 0 | | Slave_heartbeat_period | 0.000 | | Slave_open_temp_tables | 0 | | Slave_received_heartbeats | 0 | | Slave_retried_transactions | 0 | | Slave_running | OFF | | Slow_launch_threads | 30 | | Slow_queries | 0 | | Sort_merge_passes | 0 | | Sort_range | 0 | | Sort_rows | 0 | | Sort_scan | 0 | | 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 | 13127661 | | Table_locks_waited | 648 | | Tc_log_max_pages_used | 0 | | Tc_log_page_size | 0 | | Tc_log_page_waits | 6 | | Threads_cached | 7 | | Threads_connected | 2 | | Threads_created | 54593 | | Threads_running | 2 | | Uptime | 651324 | | Uptime_since_flush_status | 651324 | +------------------------------------------+----------------------+ 312 rows in set (0.01 sec)
Uptime 服务器工作了多少秒。
查看配置参数:
SHOW VARIABLES LIKE '%timeout%'
Variable_name Value ------------------------------------------------- ------------------------------------------------------------------------------------------------------------------------ auto_increment_increment 1 auto_increment_offset 1 autocommit ON automatic_sp_privileges ON back_log 384 basedir /usr big_tables OFF binlog_cache_size 1048576 binlog_direct_non_transactional_updates OFF binlog_format MIXED binlog_stmt_cache_size 32768 bulk_insert_buffer_size 67108864 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 /usr/share/mysql/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 10 datadir /var/lib/mysql/ 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 error_count 0 event_scheduler OFF expire_logs_days 30 external_user flush OFF flush_time 0 foreign_key_checks ON ft_boolean_syntax + -><()~*:""&| ft_max_word_len 84 ft_min_word_len 4 ft_query_expansion_limit 20 ft_stopword_file (built-in) general_log OFF general_log_file /var/lib/mysql/VM84.log group_concat_max_len 1024 have_compress YES have_crypt YES 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 VM84 identity 0 ignore_builtin_innodb OFF init_connect init_file init_slave innodb_adaptive_flushing ON innodb_adaptive_hash_index ON innodb_additional_mem_pool_size 16777216 innodb_autoextend_increment 8 innodb_autoinc_lock_mode 1 innodb_buffer_pool_instances 1 innodb_buffer_pool_size 4294967296 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 ON innodb_flush_log_at_trx_commit 2 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 16777216 innodb_log_file_size 536870912 innodb_log_files_in_group 2 innodb_log_group_home_dir ./ 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 0 innodb_thread_sleep_delay 10000 innodb_use_native_aio ON innodb_use_sys_malloc ON innodb_version 5.5.36 innodb_write_io_threads 4 insert_id 0 interactive_timeout 300 join_buffer_size 8388608 keep_files_on_create OFF key_buffer_size 33554432 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 last_insert_id 0 lc_messages en_US lc_messages_dir /usr/share/mysql/ lc_time_names en_US license GPL local_infile ON lock_wait_timeout 31536000 locked_in_memory OFF log OFF log_bin ON log_bin_trust_function_creators OFF log_error /var/lib/mysql/VM84.err log_output FILE log_queries_not_using_indexes OFF log_slave_updates OFF log_slow_queries ON log_warnings 1 long_query_time 2.000000 low_priority_updates OFF lower_case_file_system OFF lower_case_table_names 0 max_allowed_packet 16777216 max_binlog_cache_size 18446744073709547520 max_binlog_size 1073741824 max_binlog_stmt_cache_size 18446744073709547520 max_connect_errors 1024 max_connections 2048 max_delayed_threads 20 max_error_count 64 max_heap_table_size 67108864 max_insert_delayed_threads 20 max_join_size 18446744073709551615 max_length_for_sort_data 1024 max_long_data_size 16777216 max_prepared_stmt_count 16382 max_relay_log_size 0 max_seeks_for_key 18446744073709551615 max_sort_length 1024 max_sp_recursion_depth 0 max_tmp_tables 32 max_user_connections 0 max_write_lock_count 18446744073709551615 metadata_locks_cache_size 1024 min_examined_row_limit 0 multi_range_count 256 myisam_data_pointer_size 6 myisam_max_sort_file_size 21474836480 myisam_mmap_size 18446744073709551615 myisam_recover_options DEFAULT myisam_repair_threads 1 myisam_sort_buffer_size 536870912 myisam_stats_method nulls_unequal myisam_use_mmap OFF net_buffer_length 16384 net_read_timeout 30 net_retry_count 10 net_write_timeout 60 new OFF old OFF old_alter_table OFF old_passwords OFF open_files_limit 65535 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 /var/run/mysqld/mysqld.pid plugin_dir /usr/lib64/mysql/plugin/ port 3306 preload_buffer_size 32768 profiling OFF profiling_history_size 15 protocol_version 10 proxy_user pseudo_slave_mode OFF pseudo_thread_id 2634591 query_alloc_block_size 8192 query_cache_limit 2097152 query_cache_min_res_unit 4096 query_cache_size 67108864 query_cache_type ON query_cache_wlock_invalidate OFF query_prealloc_size 8192 rand_seed1 0 rand_seed2 0 range_alloc_block_size 4096 read_buffer_size 2097152 read_only OFF read_rnd_buffer_size 16777216 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 84 skip_external_locking ON skip_name_resolve ON skip_networking OFF skip_show_database OFF slave_compressed_protocol OFF slave_exec_mode STRICT slave_load_tmpdir /tmp slave_max_allowed_packet 1073741824 slave_net_timeout 3600 slave_skip_errors 1032,1062 slave_transaction_retries 10 slave_type_conversions slow_launch_time 2 slow_query_log ON slow_query_log_file /var/lib/mysql/VM84-slow.log socket /var/lib/mysql/mysql.sock sort_buffer_size 8388608 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 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 CST table_definition_cache 400 table_open_cache 2048 thread_cache_size 8 thread_concurrency 16 thread_handling one-thread-per-connection thread_stack 262144 time_format %H:%i:%s time_zone SYSTEM timed_mutexes OFF timestamp 1408104399 tmp_table_size 67108864 tmpdir /tmp transaction_alloc_block_size 8192 transaction_prealloc_size 4096 tx_isolation REPEATABLE-READ unique_checks ON updatable_views_with_limit YES version 5.5.36-log version_comment MySQL Community Server (GPL) by Remi version_compile_machine x86_64 version_compile_os Linux wait_timeout 28800 warning_count 0