We're getting too many connections errors in normal conditions, so I'm assuming it's a configuration issue. Four webservers, not using persistant connections partly because that triggers to the too many connections error too quickly. See more about PHP and persistant connections at PHP/mySQL: how to debug a 'too many connections' error?
The machine is hosted on Amazon. Some web servers are not in the same AZ as the DB. 1a->1d.
Strangely, the hardcoded value of max_connections is 400, but sets it to 214 on restart. I am able to change that global from mysql client back to 400. But going beyond seems excessive.
From SHOW STATUS:
| Connections | 38587 |
| Max_used_connections | 31 |
The app is PHP (fcgi/apache).
Our database size is about 54G. The machine has 36Gigs ram. Free tells me there is 13G free, even including all ram used for cache/buffers. When I tried to give 32G to "innodb_buffer_pool_size" MySQL failed to start because of mmap running out of allocatable memory. The buffer pool is currently at 22G.
The output of mysqltuner mentioned bufferpool size, and join_buffer_size - which is not in the config below.
This is Percona 5.5.
I've also set a http://jeremy.zawodny.com/blog/archives/011421.html max_connect_errors=1844674407370954751
Debugging mysql too many connections problem
max_used_connections is 21 in output of SHOW STATUS.
max_user_connections is set to 0 ... no limit.
Edit: Could this be related to the open file/page limit on Linux systems?
Config file:
#
# The MySQL database server configuration file.
#
# You can copy this to one of:
# - "/etc/mysql/my.cnf" to set global options,
# - "~/.my.cnf" to set user-specific options.
#
# One can use all long options that the program supports.
# Run program with --help to get a list of available options and with
# --print-defaults to see which it would actually understand and use.
#
# For explanations see
# http://dev.mysql.com/doc/mysql/en/server-system-variables.html
# This will be passed to all mysql clients
# It has been reported that passwords should be enclosed with ticks/quotes
# escpecially if they contain "#" chars...
# Remember to edit /etc/mysql/debian.cnf when changing the socket location.
[client]
port = 3306
socket = /var/run/mysqld/mysqld.sock
# Here is entries for some specific programs
# The following values assume you have at least 32M ram
# This was formally known as [safe_mysqld]. Both versions are currently parsed.
[mysqld_safe]
socket = /var/run/mysqld/mysqld.sock
# bl server specific HIGH PRIORITY
nice = -5
[mysqld]
#
# * Basic Settings
#
#
# * IMPORTANT
# If you make changes to these settings and your system uses apparmor, you may
# also need to also adjust /etc/apparmor.d/usr.sbin.mysqld.
#
user = mysql
socket = /var/run/mysqld/mysqld.sock
port = 3306
basedir = /usr
datadir = /var/lib/mysql
tmpdir = /tmp
skip-external-locking
#
# Instead of skip-networking the default is now to listen only on
# localhost which is more compatible and is not less secure.
#bind-address = 127.0.0.1
#
# * Fine Tuning
#
key_buffer = 64M
max_allowed_packet = 128M
thread_stack = 192K
thread_cache_size = 18
# This replaces the startup script and checks MyISAM tables if needed
# the first time they are touched
myisam-recover = BACKUP
max_connections = 400
table_cache = 512M
tmp_table_size = 512M
max_heap_table_size = 512M
#http://jeremy.zawodny.com/blog/archives/011421.html
max_connect_errors=1844674407370954751
connect_timeout=15
#thread_concurrency = 10
#
# * Query Cache Configuration
#
query_cache_limit = 64M
query_cache_size = 2048M
#
# * Logging and Replication
#
# Both location gets rotated by the cronjob.
# Be aware that this log type is a performance killer.
# As of 5.1 you can enable the log at runtime!
#general_log_file = /var/log/mysql/mysql.log
#general_log = 1
log_error = /var/log/mysql/error.log
# Here you can see queries with especially long duration
log_slow_queries = /var/log/mysql/mysql-slow.log
long_query_time = 1
#log-queries-not-using-indexes
#
# The following can be used as easy to replay backup logs or for replication.
# note: if you are setting up a replication slave, see README.Debian about
# other settings you may need to change.
server-id = 1
#http://dev.mysql.com/doc/refman/5.1/en/binary-log.html
log_bin = /var/log/mysql/mysql-bin.log
expire_logs_days = 3
max_binlog_size = 200M
#binlog_do_db = include_database_name
#binlog_ignore_db = include_database_name
#
# * InnoDB
#
# InnoDB is enabled by default with a 10MB datafile in /var/lib/mysql/.
# Read the manual for more InnoDB related options. There are many!
#### InnoDB ## use the precompiled shared library
#ignore_builtin_innodb
#plugin-load=innodb=ha_innodb_plugin.so;innodb_trx=ha_innodb_plugin.so;innodb_locks=ha_innodb_plugin.so;innodb_lock_waits=ha_innodb_plugin.so;innodb_cmp=ha_innodb_plugin.so;innodb_cmp_reset=ha_innodb_plugin.so;innodb_cmpmem=ha_innodb_plugin.so;innodb_cmpmem_reset=ha_innodb_plugin.so
#http://dev.mysql.com/doc/refman/5.1/en/innodb-parameters.html
innodb_thread_concurrency = 10
# Uncomment the following if you are using InnoDB tables
innodb_data_home_dir = /var/lib/mysql/
innodb_data_file_path = ibdata1:10M:autoextend
innodb_log_group_home_dir = /var/lib/mysql/
# You can set .._buffer_pool_size up to 50 - 80 %
# of RAM but beware of setting memory usage too high
innodb_buffer_pool_size = 22000M
innodb_additional_mem_pool_size = 256M
# Set .._log_file_size to 25 % of buffer pool size
innodb_log_file_size = 1024M
innodb_log_buffer_size = 256M
innodb_flush_log_at_trx_commit = 1
innodb_lock_wait_timeout = 50
innodb_flush_method=O_DIRECT
default-storage-engine=InnoDB
innodb_file_per_table=1
innodb_file_format=barracuda
innodb_strict_mode=1
# * Security Features
#
# Read the manual, too, if you want chroot!
# chroot = /var/lib/mysql/
#
# For generating SSL certificates I recommend the OpenSSL GUI "tinyca".
#
# ssl-ca=/etc/mysql/cacert.pem
# ssl-cert=/etc/mysql/server-cert.pem
# ssl-key=/etc/mysql/server-key.pem
[mysqldump]
quick
quote-names
max_allowed_packet = 64M
[mysql]
#no-auto-rehash # faster start of mysql but no tab completition
[isamchk]
key_buffer = 64M
#
# * IMPORTANT: Additional settings that can override those from this file!
# The files must end with '.cnf', otherwise they'll be ignored.
#
!includedir /etc/mysql/conf.d/
SHOW STATUS
mysql> SHOW STATUS ;
+------------------------------------------+-------------+
| Variable_name | Value |
+------------------------------------------+-------------+
| Aborted_clients | 0 |
| Aborted_connects | 1 |
| Binlog_cache_disk_use | 43 |
| Binlog_cache_use | 13919 |
| Binlog_stmt_cache_disk_use | 0 |
| Binlog_stmt_cache_use | 95 |
| Bytes_received | 3177 |
| Bytes_sent | 135644 |
[com_* truncated]
| Com_show_status | 2 |
| Com_show_storage_engines | 0 |
| Com_show_table_statistics | 0 |
| Com_show_table_status | 0 |
| Com_show_tables | 1 |
| Com_show_temporary_tables | 0 |
| Com_show_thread_statistics | 0 |
| Com_show_triggers | 0 |
| Com_show_user_statistics | 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 | 14529 |
| Created_tmp_disk_tables | 0 |
| Created_tmp_files | 29 |
| Created_tmp_tables | 2 |
| Delayed_errors | 0 |
| Delayed_insert_threads | 0 |
| Delayed_writes | 0 |
| Flashcache_enabled | OFF |
| 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 | 143 |
| Handler_rollback | 0 |
| Handler_savepoint | 0 |
| Handler_savepoint_rollback | 0 |
| Handler_update | 0 |
| Handler_write | 141 |
| Innodb_adaptive_hash_cells | 45653879 |
| Innodb_adaptive_hash_heap_buffers | 2078 |
| Innodb_adaptive_hash_hash_searches | 6808835 |
| Innodb_adaptive_hash_non_hash_searches | 1390813 |
| Innodb_background_log_sync | 4350 |
| Innodb_buffer_pool_pages_data | 128339 |
| Innodb_buffer_pool_pages_dirty | 56 |
| Innodb_buffer_pool_pages_flushed | 43003 |
| Innodb_buffer_pool_pages_LRU_flushed | 0 |
| Innodb_buffer_pool_pages_free | 1277581 |
| Innodb_buffer_pool_pages_made_not_young | 0 |
| Innodb_buffer_pool_pages_made_young | 80 |
| Innodb_buffer_pool_pages_misc | 2079 |
| Innodb_buffer_pool_pages_old | 47395 |
| Innodb_buffer_pool_pages_total | 1407999 |
| Innodb_buffer_pool_read_ahead_rnd | 0 |
| Innodb_buffer_pool_read_ahead | 7542 |
| Innodb_buffer_pool_read_ahead_evicted | 0 |
| Innodb_buffer_pool_read_requests | 275698257 |
| Innodb_buffer_pool_reads | 117954 |
| Innodb_buffer_pool_wait_free | 0 |
| Innodb_buffer_pool_write_requests | 156336 |
| Innodb_checkpoint_age | 10748 |
| Innodb_checkpoint_max_age | 1738160825 |
| Innodb_checkpoint_target_age | 1683843300 |
| Innodb_data_fsyncs | 30470 |
| Innodb_data_pending_fsyncs | 0 |
| Innodb_data_pending_reads | 0 |
| Innodb_data_pending_writes | 0 |
| Innodb_data_read | 2090881024 |
| Innodb_data_reads | 127629 |
| Innodb_data_writes | 69275 |
| Innodb_data_written | 1439578624 |
| Innodb_dblwr_pages_written | 43003 |
| Innodb_dblwr_writes | 700 |
| Innodb_deadlocks | 0 |
| Innodb_dict_tables | 143 |
| Innodb_have_atomic_builtins | ON |
| Innodb_history_list_length | 2394 |
| Innodb_ibuf_discarded_delete_marks | 0 |
| Innodb_ibuf_discarded_deletes | 0 |
| Innodb_ibuf_discarded_inserts | 0 |
| Innodb_ibuf_free_list | 1385 |
| Innodb_ibuf_merged_delete_marks | 285 |
| Innodb_ibuf_merged_deletes | 18 |
| Innodb_ibuf_merged_inserts | 2521 |
| Innodb_ibuf_merges | 2235 |
| Innodb_ibuf_segment_size | 1387 |
| Innodb_ibuf_size | 1 |
| Innodb_log_waits | 0 |
| Innodb_log_write_requests | 37129 |
| Innodb_log_writes | 24787 |
| Innodb_lsn_current | 73821527998 |
| Innodb_lsn_flushed | 73821527998 |
| Innodb_lsn_last_checkpoint | 73821517250 |
| Innodb_master_thread_1_second_loops | 4290 |
| Innodb_master_thread_10_second_loops | 427 |
| Innodb_master_thread_background_loops | 27 |
| Innodb_master_thread_main_flush_loops | 27 |
| Innodb_master_thread_sleeps | 4289 |
| Innodb_max_trx_id | 49591271 |
| Innodb_mem_adaptive_hash | 399297584 |
| Innodb_mem_dictionary | 92552066 |
| Innodb_mem_total | 23699456000 |
| Innodb_mutex_os_waits | 262 |
| Innodb_mutex_spin_rounds | 9713 |
| Innodb_mutex_spin_waits | 5692 |
| Innodb_oldest_view_low_limit_trx_id | 49591190 |
| Innodb_os_log_fsyncs | 25225 |
| Innodb_os_log_pending_fsyncs | 0 |
| Innodb_os_log_pending_writes | 0 |
| Innodb_os_log_written | 30232064 |
| Innodb_page_size | 16384 |
| Innodb_pages_created | 856 |
| Innodb_pages_read | 127483 |
| Innodb_pages_written | 43003 |
| Innodb_purge_trx_id | 49591179 |
| Innodb_purge_undo_no | 0 |
| Innodb_row_lock_current_waits | 0 |
| Innodb_current_row_locks | 0 |
| Innodb_row_lock_time | 0 |
| Innodb_row_lock_time_avg | 0 |
| Innodb_row_lock_time_max | 0 |
| Innodb_row_lock_waits | 1 |
| Innodb_rows_deleted | 720 |
| Innodb_rows_inserted | 4710 |
| Innodb_rows_read | 331834870 |
| Innodb_rows_updated | 8203 |
| Innodb_s_lock_os_waits | 9507 |
| Innodb_s_lock_spin_rounds | 286903 |
| Innodb_s_lock_spin_waits | 9919 |
| Innodb_truncated_status_writes | 0 |
| Innodb_x_lock_os_waits | 288 |
| Innodb_x_lock_spin_rounds | 9739 |
| Innodb_x_lock_spin_waits | 147 |
| Key_blocks_not_flushed | 0 |
| Key_blocks_unused | 53585 |
| Key_blocks_used | 24 |
| Key_read_requests | 22116 |
| Key_reads | 0 |
| Key_write_requests | 14076 |
| Key_writes | 0 |
| Last_query_cost | 0.000000 |
| Max_used_connections | 21 |
| Not_flushed_delayed_rows | 0 |
| Open_files | 56 |
| Open_streams | 0 |
| Open_table_definitions | 178 |
| Open_tables | 250 |
| Opened_files | 85241 |
| 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 | 15802 |
| Qcache_free_memory | 2090180712 |
| Qcache_hits | 333110 |
| Qcache_inserts | 250475 |
| Qcache_lowmem_prunes | 0 |
| Qcache_not_cached | 61087 |
| Qcache_queries_in_cache | 30167 |
| Qcache_total_blocks | 76233 |
| Queries | 695077 |
| Questions | 142 |
| Rpl_status | AUTH_MASTER |
| Select_full_join | 0 |
| Select_full_range_join | 0 |
| Select_range | 0 |
| Select_range_check | 0 |
| Select_scan | 2 |
| 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 | 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 | 401832 |
| Table_locks_waited | 0 |
| Tc_log_max_pages_used | 0 |
| Tc_log_page_size | 0 |
| Tc_log_page_waits | 0 |
| Threads_cached | 10 |
| Threads_connected | 11 |
| Threads_created | 21 |
| Threads_running | 2 |
| Uptime | 4357 |
| Uptime_since_flush_status | 4357 |
| binlog_commits | 14014 |
| binlog_group_commits | 14013 |
+------------------------------------------+-------------+
370 rows in set (0.00 sec)
mysql> SHOW STATUS WHERE Variable_name LIKE '%con%';
+----------------------------------------+-------+
| Variable_name | Value |
+----------------------------------------+-------+
| Aborted_connects | 1 |
| Com_show_contributors | 0 |
| Connections | 38587 |
| Innodb_master_thread_1_second_loops | 10818 |
| Innodb_master_thread_10_second_loops | 1077 |
| Max_used_connections | 31 |
| Performance_schema_cond_classes_lost | 0 |
| Performance_schema_cond_instances_lost | 0 |
| Ssl_client_connects | 0 |
| Ssl_connect_renegotiates | 0 |
| Ssl_finished_connects | 0 |
| Threads_connected | 8 |
+----------------------------------------+-------+
12 rows in set (0.00 sec)
We have a separate database we use for sessions which was configured to use persistant connections from PHP, and that's where the error message was coming from.
Turning off persistant connections may turn out to be the answer after all. The above comes from not being able to find anything unusually bad with the configuration for the main database.