BUG in mysql-threshold_resultset_size, queries become slow above a specific value

[MichalisDBA]

Hello @renecannao

We are using ProxySQL latest version 2.7.1.

We found a bug when setting mysql-threshold_resultset_size variable.

If you set it to 536870912 bytes (512MB), even a simple query that returns 10 rows, becomes very slow to get the response back.

If you set the variable again to 536870911 (the above value -1), the same query returns data instantly.

Every value equals or above 536870912 makes every query to return data very slow to the client.

+----------------------------------------------------------------------+--------------------------------------------------------------------+
| variable_name                                                        | variable_value                                                     |
+----------------------------------------------------------------------+--------------------------------------------------------------------+
| admin-stats_credentials                                              | stats:stats                                                        |
| admin-stats_mysql_connections                                        | 60                                                                 |
| admin-stats_mysql_connection_pool                                    | 60                                                                 |
| admin-stats_mysql_query_cache                                        | 60                                                                 |
| admin-stats_mysql_query_digest_to_disk                               | 0                                                                  |
| admin-stats_system_cpu                                               | 60                                                                 |
| admin-stats_system_memory                                            | 60                                                                 |
| admin-telnet_admin_ifaces                                            | (null)                                                             |
| admin-telnet_stats_ifaces                                            | (null)                                                             |
| admin-refresh_interval                                               | 2000                                                               |
| admin-read_only                                                      | false                                                              |
| admin-vacuum_stats                                                   | true                                                               |
| admin-version                                                        | 2.7.1-16-g2726c27                                                  |
| admin-cluster_check_interval_ms                                      | 1000                                                               |
| admin-cluster_check_status_frequency                                 | 10                                                                 |
| admin-cluster_mysql_query_rules_diffs_before_sync                    | 3                                                                  |
| admin-cluster_mysql_servers_diffs_before_sync                        | 3                                                                  |
| admin-cluster_mysql_users_diffs_before_sync                          | 3                                                                  |
| admin-cluster_proxysql_servers_diffs_before_sync                     | 3                                                                  |
| admin-cluster_mysql_variables_diffs_before_sync                      | 3                                                                  |
| admin-cluster_admin_variables_diffs_before_sync                      | 3                                                                  |
| admin-cluster_ldap_variables_diffs_before_sync                       | 3                                                                  |
| admin-cluster_mysql_query_rules_save_to_disk                         | true                                                               |
| admin-cluster_mysql_servers_save_to_disk                             | true                                                               |
| admin-cluster_mysql_users_save_to_disk                               | true                                                               |
| admin-cluster_proxysql_servers_save_to_disk                          | true                                                               |
| admin-cluster_mysql_variables_save_to_disk                           | true                                                               |
| admin-cluster_admin_variables_save_to_disk                           | true                                                               |
| admin-cluster_ldap_variables_save_to_disk                            | true                                                               |
| admin-cluster_mysql_servers_sync_algorithm                           | 1                                                                  |
| admin-checksum_mysql_query_rules                                     | true                                                               |
| admin-checksum_mysql_servers                                         | true                                                               |
| admin-checksum_mysql_users                                           | true                                                               |
| admin-checksum_mysql_variables                                       | true                                                               |
| admin-checksum_admin_variables                                       | true                                                               |
| admin-checksum_ldap_variables                                        | true                                                               |
| admin-restapi_enabled                                                | false                                                              |
| admin-restapi_port                                                   | 6070                                                               |
| admin-web_enabled                                                    | false                                                              |
| admin-web_port                                                       | 6080                                                               |
| admin-web_verbosity                                                  | 0                                                                  |
| admin-prometheus_memory_metrics_interval                             | 61                                                                 |
| admin-coredump_generation_interval_ms                                | 30000                                                              |
| admin-coredump_generation_threshold                                  | 10                                                                 |
| admin-ssl_keylog_file                                                |                                                                    |
| admin-admin_credentials                                              | admin:admin;proxysql_cluster:Pe!569nzG@6NCqe@4J;logrotate:3q#Eh4aJ |
| admin-cluster_username                                               | proxysql_cluster                                                   |
| admin-cluster_password                                               | Pe!569nzG@6NCqe@4J                                                 |
| admin-mysql_ifaces                                                   | 0.0.0.0:6032                                                       |
| mysql-default_charset                                                | utf8                                                               |
| mysql-default_collation_connection                                   | utf8_general_ci                                                    |
| mysql-shun_on_failures                                               | 5                                                                  |
| mysql-shun_recovery_time_sec                                         | 10                                                                 |
| mysql-unshun_algorithm                                               | 0                                                                  |
| mysql-query_retries_on_failure                                       | 1                                                                  |
| mysql-client_host_cache_size                                         | 0                                                                  |
| mysql-client_host_error_counts                                       | 0                                                                  |
| mysql-connect_retries_delay                                          | 1                                                                  |
| mysql-connection_delay_multiplex_ms                                  | 0                                                                  |
| mysql-connection_max_age_ms                                          | 0                                                                  |
| mysql-connect_timeout_client                                         | 10000                                                              |
| mysql-connect_timeout_server_max                                     | 10000                                                              |
| mysql-enable_client_deprecate_eof                                    | true                                                               |
| mysql-enable_server_deprecate_eof                                    | true                                                               |
| mysql-enable_load_data_local_infile                                  | false                                                              |
| mysql-eventslog_filename                                             |                                                                    |
| mysql-eventslog_filesize                                             | 104857600                                                          |
| mysql-eventslog_default_log                                          | 0                                                                  |
| mysql-eventslog_format                                               | 1                                                                  |
| mysql-handle_unknown_charset                                         | 1                                                                  |
| mysql-free_connections_pct                                           | 20                                                                 |
| mysql-connection_warming                                             | false                                                              |
| mysql-session_idle_ms                                                | 1                                                                  |
| mysql-have_ssl                                                       | true                                                               |
| mysql-log_mysql_warnings_enabled                                     | false                                                              |
| mysql-monitor_enabled                                                | true                                                               |
| mysql-monitor_connect_timeout                                        | 600                                                                |
| mysql-monitor_ping_max_failures                                      | 3                                                                  |
| mysql-monitor_ping_timeout                                           | 1000                                                               |
| mysql-monitor_aws_rds_topology_discovery_interval                    | 0                                                                  |
| mysql-monitor_read_only_max_timeout_count                            | 3                                                                  |
| mysql-monitor_replication_lag_group_by_host                          | false                                                              |
| mysql-monitor_replication_lag_interval                               | 10000                                                              |
| mysql-monitor_replication_lag_timeout                                | 1000                                                               |
| mysql-monitor_replication_lag_count                                  | 1                                                                  |
| mysql-monitor_groupreplication_healthcheck_interval                  | 5000                                                               |
| mysql-monitor_groupreplication_healthcheck_timeout                   | 800                                                                |
| mysql-monitor_groupreplication_healthcheck_max_timeout_count         | 3                                                                  |
| mysql-monitor_groupreplication_max_transactions_behind_count         | 3                                                                  |
| mysql-monitor_groupreplication_max_transactions_behind_for_read_only | 1                                                                  |
| mysql-monitor_galera_healthcheck_interval                            | 5000                                                               |
| mysql-monitor_galera_healthcheck_timeout                             | 800                                                                |
| mysql-monitor_galera_healthcheck_max_timeout_count                   | 3                                                                  |
| mysql-monitor_replication_lag_use_percona_heartbeat                  |                                                                    |
| mysql-monitor_query_interval                                         | 60000                                                              |
| mysql-monitor_query_timeout                                          | 100                                                                |
| mysql-monitor_slave_lag_when_null                                    | 60                                                                 |
| mysql-monitor_threads_min                                            | 8                                                                  |
| mysql-monitor_threads_max                                            | 128                                                                |
| mysql-monitor_threads_queue_maxsize                                  | 128                                                                |
| mysql-monitor_local_dns_cache_ttl                                    | 300000                                                             |
| mysql-monitor_local_dns_cache_refresh_interval                       | 60000                                                              |
| mysql-monitor_local_dns_resolver_queue_maxsize                       | 128                                                                |
| mysql-monitor_wait_timeout                                           | true                                                               |
| mysql-monitor_writer_is_also_reader                                  | true                                                               |
| mysql-tcp_keepalive_time                                             | 120                                                                |
| mysql-use_tcp_keepalive                                              | true                                                               |
| mysql-automatic_detect_sqli                                          | false                                                              |
| mysql-firewall_whitelist_enabled                                     | false                                                              |
| mysql-firewall_whitelist_errormsg                                    | Firewall blocked this query                                        |
| mysql-throttle_connections_per_sec_to_hostgroup                      | 1000000                                                            |
| mysql-multiplexing                                                   | true                                                               |
| mysql-log_unhealthy_connections                                      | true                                                               |
| mysql-enforce_autocommit_on_reads                                    | false                                                              |
| mysql-autocommit_false_not_reusable                                  | false                                                              |
| mysql-autocommit_false_is_transaction                                | false                                                              |
| mysql-hostgroup_manager_verbose                                      | 1                                                                  |
| mysql-binlog_reader_connect_retry_msec                               | 3000                                                               |
| mysql-threshold_query_length                                         | 524288                                                             |
| mysql-threshold_resultset_size                                       | 536870912                                                          |
| mysql-query_digests_max_query_length                                 | 65000                                                              |
| mysql-query_digests_grouping_limit                                   | 3                                                                  |
| mysql-query_digests_groups_grouping_limit                            | 10                                                                 |
| mysql-query_rules_fast_routing_algorithm                             | 1                                                                  |
| mysql-throttle_max_bytes_per_second_to_client                        | 0                                                                  |
| mysql-throttle_ratio_server_to_client                                | 0                                                                  |
| mysql-max_stmts_per_connection                                       | 20                                                                 |
| mysql-max_stmts_cache                                                | 10000                                                              |
| mysql-mirror_max_concurrency                                         | 16                                                                 |
| mysql-mirror_max_queue_length                                        | 32000                                                              |
| mysql-default_max_latency_ms                                         | 1000                                                               |
| mysql-query_processor_iterations                                     | 0                                                                  |
| mysql-query_processor_regex                                          | 1                                                                  |
| mysql-set_query_lock_on_hostgroup                                    | 1                                                                  |
| mysql-set_parser_algorithm                                           | 2                                                                  |
| mysql-reset_connection_algorithm                                     | 2                                                                  |
| mysql-auto_increment_delay_multiplex                                 | 5                                                                  |
| mysql-auto_increment_delay_multiplex_timeout_ms                      | 10000                                                              |
| mysql-long_query_time                                                | 1000                                                               |
| mysql-query_cache_size_MB                                            | 256                                                                |
| mysql-query_cache_soft_ttl_pct                                       | 0                                                                  |
| mysql-query_cache_handle_warnings                                    | 0                                                                  |
| mysql-poll_timeout_on_failure                                        | 100                                                                |
| mysql-server_capabilities                                            | 569867                                                             |
| mysql-keep_multiplexing_variables                                    | tx_isolation,transaction_isolation,version                         |
| mysql-default_authentication_plugin                                  | mysql_native_password                                              |
| mysql-kill_backend_connection_when_disconnect                        | true                                                               |
| mysql-client_session_track_gtid                                      | true                                                               |
| mysql-session_idle_show_processlist                                  | true                                                               |
| mysql-show_processlist_extended                                      | 0                                                                  |
| mysql-query_digests                                                  | true                                                               |
| mysql-query_digests_lowercase                                        | false                                                              |
| mysql-query_digests_replace_null                                     | false                                                              |
| mysql-query_digests_no_digits                                        | false                                                              |
| mysql-query_digests_normalize_digest_text                            | false                                                              |
| mysql-query_digests_keep_comment                                     | false                                                              |
| mysql-parse_failure_logs_digest                                      | false                                                              |
| mysql-servers_stats                                                  | true                                                               |
| mysql-default_reconnect                                              | true                                                               |
| mysql-ssl_p2s_ca                                                     |                                                                    |
| mysql-ssl_p2s_capath                                                 |                                                                    |
| mysql-ssl_p2s_cert                                                   |                                                                    |
| mysql-ssl_p2s_key                                                    |                                                                    |
| mysql-ssl_p2s_cipher                                                 |                                                                    |
| mysql-ssl_p2s_crl                                                    |                                                                    |
| mysql-ssl_p2s_crlpath                                                |                                                                    |
| mysql-init_connect                                                   |                                                                    |
| mysql-ldap_user_variable                                             |                                                                    |
| mysql-add_ldap_user_comment                                          |                                                                    |
| mysql-default_session_track_gtids                                    | OFF                                                                |
| mysql-connpoll_reset_queue_length                                    | 50                                                                 |
| mysql-min_num_servers_lantency_awareness                             | 1000                                                               |
| mysql-aurora_max_lag_ms_only_read_from_replicas                      | 2                                                                  |
| mysql-stats_time_backend_query                                       | false                                                              |
| mysql-stats_time_query_processor                                     | false                                                              |
| mysql-query_cache_stores_empty_result                                | true                                                               |
| mysql-data_packets_history_size                                      | 0                                                                  |
| mysql-handle_warnings                                                | 1                                                                  |
| mysql-evaluate_replication_lag_on_servers_load                       | 1                                                                  |
| mysql-proxy_protocol_networks                                        |                                                                    |
| mysql-threads                                                        | 4                                                                  |
| mysql-max_connections                                                | 2048                                                               |
| mysql-default_query_delay                                            | 0                                                                  |
| mysql-default_query_timeout                                          | 36000000                                                           |
| mysql-have_compress                                                  | true                                                               |
| mysql-poll_timeout                                                   | 2000                                                               |
| mysql-default_schema                                                 | information_schema                                                 |
| mysql-stacksize                                                      | 1048576                                                            |
| mysql-connect_timeout_server                                         | 3000                                                               |
| mysql-monitor_history                                                | 600000                                                             |
| mysql-monitor_read_only_interval                                     | 1500                                                               |
| mysql-monitor_read_only_timeout                                      | 500                                                                |
| mysql-ping_interval_server_msec                                      | 120000                                                             |
| mysql-ping_timeout_server                                            | 500                                                                |
| mysql-commands_stats                                                 | true                                                               |
| mysql-sessions_sort                                                  | true                                                               |
| mysql-connect_retries_on_failure                                     | 10                                                                 |
| mysql-interfaces                                                     | 0.0.0.0:3306                                                       |
| mysql-monitor_username                                               | proxysql_monitor                                                   |
| mysql-monitor_password                                               | zVkJ!L5FGKXlsp3hO5                                                 |
| mysql-server_version                                                 | 5.7.30                                                             |
| mysql-monitor_connect_interval                                       | 2000                                                               |
| mysql-monitor_ping_interval                                          | 2000                                                               |
| mysql-auditlog_filename                                              | proxysql-1_audit.log                                               |
| mysql-auditlog_filesize                                              | 1048576000                                                         |
| mysql-max_allowed_packet                                             | 16777216                                                           |
| mysql-max_transaction_idle_time                                      | 43200000                                                           |
| mysql-max_transaction_time                                           | 43200000                                                           |
| mysql-wait_timeout                                                   | 28800000                                                           |
| mysql-query_digests_track_hostname                                   | true                                                               |
| mysql-query_digests_max_digest_length                                | 10240                                                              |
| mysql-verbose_query_error                                            | true                                                               |
+----------------------------------------------------------------------+--------------------------------------------------------------------+

[MichalisDBA]

I attach a screen record

firefox_FVwb3QRlXb.mp4