MySQL报错Can not connect to MySQL server. Too many connections，报错，很明确，与MySQL的连接数满了。
首先我们先查看下数据线程池的一些数据
查看最大连接数
mysqladmin -uroot -p processlist
一般这个时候会提醒你连接数已经够多了，你已经进入不了数据库了，所有还是使用你当前的客户端工具查看吧
SHOW PROCESSLIST;SHOW STATUS;SHOW VARIABLES LIKE "max_connections";
1.SHOW PROCESSLIST查看当前数据库连接
如果是root帐号，你能看到所有用户的当前连接。如果是其它普通帐号，只能看到自己占用的连接。
show processlist;只列出前100条，如果想全列出请使用show full processlist;
2.SHOW VARIABLES LIKE “max_connections” 查看最大连接数Threads_connected;
3.show status可查看当前已连接的数量
Variable_nameValueAborted_clients1750Aborted_connects271Binlog_cache_disk_use0Binlog_cache_use0Binlog_stmt_cache_disk_use0Binlog_stmt_cache_use0Bytes_received39810Bytes_sent321179Com_admin_commands0Com_assign_to_keycache0Com_alter_db0Com_alter_db_upgrade0Com_alter_event0Com_alter_function0Com_alter_procedure0Com_alter_server0Com_alter_table2Com_alter_tablespace0Com_alter_user0Com_analyze0Com_begin0Com_binlog0Com_call_procedure0Com_change_db11Com_change_master0Com_check0Com_checksum0Com_commit0Com_create_db0Com_create_event0Com_create_function0Com_create_index0Com_create_procedure0Com_create_server0Com_create_table7Com_create_trigger0Com_create_udf0Com_create_user0Com_create_view0Com_dealloc_sql0Com_delete0Com_delete_multi0Com_do0Com_drop_db0Com_drop_event0Com_drop_function0Com_drop_index0Com_drop_procedure0Com_drop_server0Com_drop_table2Com_drop_trigger0Com_drop_user0Com_drop_view0Com_empty_query0Com_execute_sql0Com_flush0Com_get_diagnostics0Com_grant0Com_ha_close0Com_ha_open0Com_ha_read0Com_help0Com_insert41Com_insert_select0Com_install_plugin0Com_kill0Com_load0Com_lock_tables0Com_optimize0Com_preload_keys0Com_prepare_sql0Com_purge0Com_purge_before_date0Com_release_savepoint0Com_rename_table0Com_rename_user0Com_repair0Com_replace0Com_replace_select0Com_reset0Com_resignal0Com_revoke0Com_revoke_all0Com_rollback0Com_rollback_to_savepoint0Com_savepoint0Com_select69Com_set_option55Com_signal0Com_show_binlog_events0Com_show_binlogs0Com_show_charsets4Com_show_collations4Com_show_create_db5Com_show_create_event0Com_show_create_func0Com_show_create_proc0Com_show_create_table29Com_show_create_trigger0Com_show_databases5Com_show_engine_logs0Com_show_engine_mutex0Com_show_engine_status0Com_show_events0Com_show_errors0Com_show_fields31Com_show_function_code0Com_show_function_status5Com_show_grants0Com_show_keys31Com_show_master_status0Com_show_open_tables0Com_show_plugins0Com_show_privileges0Com_show_procedure_code0Com_show_procedure_status5Com_show_processlist7Com_show_profile0Com_show_profiles12Com_show_relaylog_events0Com_show_slave_hosts0Com_show_slave_status0Com_show_status36Com_show_storage_engines0Com_show_table_status12Com_show_tables10Com_show_triggers5Com_show_variables33Com_show_warnings0Com_slave_start0Com_slave_stop0Com_stmt_close0Com_stmt_execute0Com_stmt_fetch0Com_stmt_prepare0Com_stmt_reprepare0Com_stmt_reset0Com_stmt_send_long_data0Com_truncate0Com_uninstall_plugin0Com_unlock_tables0Com_update87Com_update_multi0Com_xa_commit0Com_xa_end0Com_xa_prepare0Com_xa_recover0Com_xa_rollback0Com_xa_start0CompressionONConnection_errors_accept0Connection_errors_internal0Connection_errors_max_connections1370Connection_errors_peer_address0Connection_errors_select0Connection_errors_tcpwrap0Connections12310Created_tmp_disk_tables103Created_tmp_files13110Created_tmp_tables309Delayed_errors0Delayed_insert_threads0Delayed_writes0Flush_commands1Handler_commit142Handler_delete0Handler_discover0Handler_external_lock316Handler_mrr_init0Handler_prepare0Handler_read_first28Handler_read_key726Handler_read_last0Handler_read_next0Handler_read_prev0Handler_read_rnd192Handler_read_rnd_next5482Handler_rollback0Handler_savepoint0Handler_savepoint_rollback0Handler_update516Handler_write5064Innodb_buffer_pool_dump_statusnot startedInnodb_buffer_pool_load_statusnot startedInnodb_buffer_pool_pages_data3845Innodb_buffer_pool_bytes_data62996480Innodb_buffer_pool_pages_dirty0Innodb_buffer_pool_bytes_dirty0Innodb_buffer_pool_pages_flushed301814Innodb_buffer_pool_pages_free4218Innodb_buffer_pool_pages_misc128Innodb_buffer_pool_pages_total8191Innodb_buffer_pool_read_ahead_rnd0Innodb_buffer_pool_read_ahead127Innodb_buffer_pool_read_ahead_evicted0Innodb_buffer_pool_read_requests126411955Innodb_buffer_pool_reads3187Innodb_buffer_pool_wait_free0Innodb_buffer_pool_write_requests612176Innodb_data_fsyncs397006Innodb_data_pending_fsyncs0Innodb_data_pending_reads0Innodb_data_pending_writes0Innodb_data_read54480896Innodb_data_reads3598Innodb_data_writes552289Innodb_data_written10014147584Innodb_dblwr_pages_written301814Innodb_dblwr_writes70817Innodb_have_atomic_builtinsONInnodb_log_waits0Innodb_log_write_requests68955Innodb_log_writes108688Innodb_os_log_fsyncs179512Innodb_os_log_pending_fsyncs0Innodb_os_log_pending_writes0Innodb_os_log_written88069120Innodb_page_size16384Innodb_pages_created525Innodb_pages_read3320Innodb_pages_written301814Innodb_row_lock_current_waits0Innodb_row_lock_time0Innodb_row_lock_time_avg0Innodb_row_lock_time_max0Innodb_row_lock_waits0Innodb_rows_deleted91Innodb_rows_inserted9110Innodb_rows_read298911691Innodb_rows_updated108767Innodb_num_open_files276Innodb_truncated_status_writes0Innodb_available_undo_logs128Key_blocks_not_flushed0Key_blocks_unused6698Key_blocks_used0Key_read_requests0Key_reads0Key_write_requests0Key_writes0Last_query_cost10.499000Last_query_partial_plans1Max_used_connections215Not_flushed_delayed_rows0Open_files46Open_streams0Open_table_definitions358Open_tables395Opened_files44624Opened_table_definitions8Opened_tables2Performance_schema_accounts_lost0Performance_schema_cond_classes_lost0Performance_schema_cond_instances_lost0Performance_schema_digest_lost0Performance_schema_file_classes_lost0Performance_schema_file_handles_lost0Performance_schema_file_instances_lost0Performance_schema_hosts_lost0Performance_schema_locker_lost0Performance_schema_mutex_classes_lost0Performance_schema_mutex_instances_lost0Performance_schema_rwlock_classes_lost0Performance_schema_rwlock_instances_lost0Performance_schema_session_connect_attrs_lost0Performance_schema_socket_classes_lost0Performance_schema_socket_instances_lost0Performance_schema_stage_classes_lost0Performance_schema_statement_classes_lost0Performance_schema_table_handles_lost0Performance_schema_table_instances_lost0Performance_schema_thread_classes_lost0Performance_schema_thread_instances_lost0Performance_schema_users_lost0Prepared_stmt_count0Qcache_free_blocks1Qcache_free_memory1031352Qcache_hits0Qcache_inserts0Qcache_lowmem_prunes0Qcache_not_cached1389061Qcache_queries_in_cache0Qcache_total_blocks1Queries2094615Questions511Rsa_public_keySelect_full_join0Select_full_range_join0Select_range0Select_range_check0Select_scan213Slave_heartbeat_periodSlave_last_heartbeatSlave_open_temp_tables0Slave_received_heartbeatsSlave_retried_transactionsSlave_runningOFFSlow_launch_threads0Slow_queries0Sort_merge_passes0Sort_range0Sort_rows351Sort_scan20Ssl_accept_renegotiates0Ssl_accepts0Ssl_callback_cache_hits0Ssl_cipherSsl_cipher_listSsl_client_connects0Ssl_connect_renegotiates0Ssl_ctx_verify_depth0Ssl_ctx_verify_mode0Ssl_default_timeout0Ssl_finished_accepts0Ssl_finished_connects0Ssl_server_not_afterSsl_server_not_beforeSsl_session_cache_hits0Ssl_session_cache_misses0Ssl_session_cache_modeNONESsl_session_cache_overflows0Ssl_session_cache_size0Ssl_session_cache_timeouts0Ssl_sessions_reused0Ssl_used_session_cache_entries0Ssl_verify_depth0Ssl_verify_mode0Ssl_versionTable_locks_immediate863932Table_locks_waited0Table_open_cache_hits1411Table_open_cache_misses1Table_open_cache_overflows0Tc_log_max_pages_used0Tc_log_page_size0Tc_log_page_waits0Threads_cached9Threads_connected162Threads_created1193Threads_running1Uptime887001Uptime_since_flush_status887001
Aborted_clients 由于客户没有正确关闭连接已经死掉，已经放弃的连接数量。
Aborted_connects 尝试已经失败的MySQL服务器的连接的次数。
Connections 试图连接MySQL服务器的次数。
Created_tmp_tables 当执行语句时，已经被创造了的隐含临时表的数量。
Delayed_insert_threads 正在使用的延迟插入处理器线程的数量。
Delayed_writes 用INSERT DELAYED写入的行数。
Delayed_errors 用INSERT DELAYED写入的发生某些错误(可能重复键值)的行数。
Flush_commands 执行FLUSH命令的次数。
Handler_delete 请求从一张表中删除行的次数。
Handler_read_first 请求读入表中第一行的次数。
Handler_read_key 请求数字基于键读行。
Handler_read_next 请求读入基于一个键的一行的次数。
Handler_read_rnd 请求读入基于一个固定位置的一行的次数。
Handler_update 请求更新表中一行的次数。
Handler_write 请求向表中插入一行的次数。
Key_blocks_used 用于关键字缓存的块的数量。
Key_read_requests 请求从缓存读入一个键值的次数。
Key_reads 从磁盘物理读入一个键值的次数。
Key_write_requests 请求将一个关键字块写入缓存次数。
Key_writes 将一个键值块物理写入磁盘的次数。
Max_used_connections 同时使用的连接的最大数目。
Not_flushed_key_blocks 在键缓存中已经改变但是还没被清空到磁盘上的键块。
Not_flushed_delayed_rows 在INSERT DELAY队列中等待写入的行的数量。
Open_tables 打开表的数量。
Open_files 打开文件的数量。
Open_streams 打开流的数量(主要用于日志记载）
Opened_tables 已经打开的表的数量。
Questions 发往服务器的查询的数量。
Slow_queries 要花超过long_query_time时间的查询数量。
Threads_connected 当前打开的连接的数量。
Threads_running 不在睡眠的线程数量。
Uptime 服务器工作了多少秒。
当前已经连接的数量如果达到最大连接数，再启动项目肯定就连接不上了，下一篇我会编辑下处理的办法。
