Cherry-pick #15845 to 7.x: SQL module now supports key/value mode

[jsoriano]

Cherry-pick of PR #15845 to 7.x branch. Original message:

What does this PR do?

This PR allows to SQL generic module to send events correctly when the query return results in the way of key/values format.

Why is it important?

Because there are some querys like mysql SHOW STATUS that display the results in a key/value format so they need to be scanned in a different way, being the key the first column of the response and the value the second one of the response.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works

How to test this PR locally

Having a mysql database, enable and configure que sql module with console as output, variable mode and query SHOW STATUS.

For example

- module: sql
  metricsets:
    - query
  period: 10s
  hosts: ["root:secret@tcp(127.0.0.1:3306)/"]

  driver: "mysql"
  sql_query: "SHOW STATUS"
  sql_response_format: variable

Running metricbeat -e you will see only one event with all key/value pairs:

...
 "metrics": {
      "numeric": {
        "com_alter_tablespace": 0,
        "com_drop_event": 0,
        "com_admin_commands": 1,
        "slow_queries": 0,
        "com_show_tables": 0,
        "innodb_buffer_pool_read_ahead_rnd": 0,
        "com_delete": 0,
        "innodb_data_reads": 784,
        "handler_read_first": 0,
        "com_reset": 0,
        "innodb_row_lock_current_waits": 0,
        "com_show_keys": 0,
        "performance_schema_digest_lost": 0,
        "qcache_hits": 0,
        "select_scan": 0,
        "performance_schema_locker_lost": 0,
        "performance_schema_stage_classes_lost": 0,
        "com_xa_commit": 0,
        "com_purge_before_date": 0,
        "performance_schema_accounts_lost": 0,
        "com_rollback_to_savepoint": 0,
        "binlog_cache_disk_use": 0,
        "key_blocks_not_flushed": 0,
        "com_change_master": 0,
        "innodb_buffer_pool_bytes_data": 7.487488e+06,
        "sort_range": 0,
        "ssl_sessions_reused": 0,
        "threads_running": 1,
        "innodb_buffer_pool_pages_dirty": 0,
        "queries": 21,
        "com_show_storage_engines": 0,
        "handler_discover": 0,
        "ssl_callback_cache_hits": 0,
        "innodb_data_pending_reads": 0,
        "com_begin": 0,
        "com_show_engine_mutex": 0,
        "max_used_connections": 1,
        "com_show_profiles": 0,
        "com_show_procedure_status": 0,
        "com_drop_view": 0,
        "handler_savepoint": 0,
        "performance_schema_session_connect_attrs_lost": 0,
        "qcache_lowmem_prunes": 0,
        "handler_rollback": 0,
        "com_show_master_status": 0,
        "ssl_verify_mode": 0,
        "flush_commands": 1,
        "connections": 8,
        "com_show_collations": 0,
        "handler_commit": 0,
        "com_show_create_proc": 0,
        "com_stmt_reprepare": 0,
        "com_purge": 0,
        "com_do": 0,
        "com_show_procedure_code": 0,
        "handler_read_last": 0,
        "com_savepoint": 0,
        "innodb_available_undo_logs": 128,
        "com_show_engine_logs": 0,
        "handler_read_rnd": 0,
        "com_rename_user": 0,
        "handler_write": 0,
        "performance_schema_mutex_instances_lost": 0,
        "com_stmt_fetch": 0,
        "com_create_user": 0,
        "innodb_buffer_pool_pages_total": 8191,
        "binlog_cache_use": 0,
        "com_show_profile": 0,
        "com_checksum": 0,
        "not_flushed_delayed_rows": 0,
        "performance_schema_statement_classes_lost": 0,
        "connection_errors_peer_address": 0,
        "com_help": 0,
        "last_query_cost": 0,
        "com_rename_table": 0,
        "com_show_slave_status": 0,
        "questions": 1,
        "binlog_stmt_cache_disk_use": 0,
        "com_insert": 0,
        "com_stmt_send_long_data": 0,
        "com_show_status": 1,
        "connection_errors_tcpwrap": 0,
        "ssl_default_timeout": 0,
        "ssl_session_cache_overflows": 0,
        "performance_schema_file_instances_lost": 0,
        "performance_schema_file_handles_lost": 0,
        "com_release_savepoint": 0,
        "com_select": 0,
        "com_xa_rollback": 0,
        "innodb_log_write_requests": 1,
        "innodb_buffer_pool_write_requests": 1,
        "performance_schema_table_handles_lost": 0,
        "com_repair": 0,
        "com_xa_end": 0,
        "com_show_events": 0,
        "innodb_buffer_pool_read_ahead": 0,
        "handler_update": 0,
        "ssl_session_cache_misses": 0,
        "innodb_data_pending_fsyncs": 0,
        "performance_schema_table_instances_lost": 0,
        "com_show_create_trigger": 0,
        "com_show_table_status": 0,
        "opened_files": 115,
        "innodb_buffer_pool_reads": 458,
        "innodb_pages_written": 1,
        "qcache_inserts": 0,
        "innodb_os_log_pending_writes": 0,
        "innodb_buffer_pool_read_requests": 19969,
        "innodb_buffer_pool_pages_flushed": 1,
        "innodb_buffer_pool_pages_data": 457,
        "innodb_rows_deleted": 0,
        "innodb_data_writes": 5,
        "key_blocks_used": 0,
        "connection_errors_select": 0,
        "tc_log_max_pages_used": 0,
        "com_show_relaylog_events": 0,
        "com_create_procedure": 0,
        "ssl_ctx_verify_mode": 0,
        "com_show_open_tables": 0,
        "performance_schema_file_classes_lost": 0,
        "com_grant": 0,
        "table_open_cache_hits": 0,
        "com_show_engine_status": 0,
        "com_show_plugins": 0,
        "com_alter_db": 0,
        "prepared_stmt_count": 0,
        "ssl_session_cache_hits": 0,
        "com_stmt_close": 0,
        "bytes_received": 105,
        "innodb_log_writes": 1,
        "qcache_free_memory": 1.031352e+06,
        "performance_schema_socket_instances_lost": 0,
        "sort_scan": 0,
        "com_create_table": 0,
        "handler_read_next": 0,
        "com_slave_start": 0,
        "qcache_not_cached": 0,
        "com_drop_server": 0,
        "com_set_option": 0,
        "aborted_clients": 0,
        "open_files": 16,
        "table_open_cache_overflows": 0,
        "ssl_session_cache_timeouts": 0,
        "handler_read_rnd_next": 0,
        "innodb_rows_read": 0,
        "created_tmp_disk_tables": 0,
        "ssl_accepts": 0,
        "com_alter_event": 0,
        "binlog_stmt_cache_use": 0,
        "com_analyze": 0,
        "key_read_requests": 0,
        "com_truncate": 0,
        "table_locks_waited": 0,
        "bytes_sent": 100,
        "ssl_verify_depth": 0,
        "com_dealloc_sql": 0,
        "ssl_finished_connects": 0,
        "com_stmt_reset": 0,
        "key_reads": 0,
        "com_alter_user": 0,
        "connection_errors_max_connections": 0,
        "com_kill": 0,
        "table_open_cache_misses": 0,
        "performance_schema_mutex_classes_lost": 0,
        "select_full_join": 0,
        "key_writes": 0,
        "com_drop_procedure": 0,
        "com_revoke": 0,
        "com_show_function_status": 0,
        "ssl_accept_renegotiates": 0,
        "opened_table_definitions": 0,
        "opened_tables": 0,
        "com_show_databases": 0,
        "innodb_data_pending_writes": 0,
        "performance_schema_rwlock_classes_lost": 0,
        "com_update_multi": 0,
        "innodb_row_lock_time_avg": 0,
        "innodb_buffer_pool_bytes_dirty": 0,
        "innodb_row_lock_time": 0,
        "innodb_page_size": 16384,
        "handler_external_lock": 0,
        "innodb_data_fsyncs": 5,
        "com_lock_tables": 0,
        "com_xa_prepare": 0,
        "uptime_since_flush_status": 135,
        "com_show_create_table": 0,
        "threads_cached": 0,
        "com_call_procedure": 0,
        "innodb_truncated_status_writes": 0,
        "delayed_errors": 0,
        "com_show_privileges": 0,
        "qcache_queries_in_cache": 0,
        "com_change_db": 0,
        "com_show_grants": 0,
        "com_stmt_execute": 0,
        "aborted_connects": 0,
        "com_show_warnings": 0,
        "com_drop_user": 0,
        "com_optimize": 0,
        "performance_schema_cond_instances_lost": 0,
        "com_replace": 0,
        "com_show_function_code": 0,
        "performance_schema_users_lost": 0,
        "com_alter_table": 0,
        "com_empty_query": 0,
        "innodb_log_waits": 0,
        "com_rollback": 0,
        "innodb_row_lock_waits": 0,
        "com_prepare_sql": 0,
        "innodb_buffer_pool_pages_free": 7731,
        "com_show_create_event": 0,
        "com_alter_procedure": 0,
        "com_create_index": 0,
        "delayed_insert_threads": 0,
        "com_insert_select": 0,
        "threads_connected": 1,
        "com_show_create_db": 0,
        "slave_open_temp_tables": 0,
        "com_resignal": 0,
        "sort_merge_passes": 0,
        "com_check": 0,
        "handler_prepare": 0,
        "com_flush": 0,
        "qcache_free_blocks": 1,
        "innodb_buffer_pool_pages_misc": 3,
        "created_tmp_tables": 0,
        "ssl_session_cache_size": 0,
        "com_get_diagnostics": 0,
        "com_show_charsets": 0,
        "com_update": 0,
        "com_create_udf": 0,
        "com_show_triggers": 0,
        "com_uninstall_plugin": 0,
        "table_locks_immediate": 70,
        "com_load": 0,
        "com_show_binlogs": 0,
        "last_query_partial_plans": 0,
        "innodb_rows_inserted": 0,
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        "com_unlock_tables": 0,
        "ssl_used_session_cache_entries": 0,
        "com_show_variables": 0,
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        "com_xa_start": 0,
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        "com_drop_table": 0,
        "innodb_os_log_written": 1024,
        "created_tmp_files": 6,
        "com_drop_trigger": 0,
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        "performance_schema_rwlock_instances_lost": 0,
        "com_revoke_all": 0,
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        "com_show_fields": 0,
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        "sort_rows": 0,
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        "innodb_dblwr_pages_written": 1,
        "performance_schema_cond_classes_lost": 0,
        "com_create_trigger": 0,
        "com_show_create_func": 0,
        "slow_launch_threads": 0,
        "com_binlog": 0,
        "innodb_os_log_pending_fsyncs": 0,
        "uptime": 135,
        "tc_log_page_size": 0,
        "ssl_finished_accepts": 0,
        "com_alter_server": 0,
        "open_table_definitions": 67,
        "ssl_client_connects": 0,
        "com_drop_function": 0,
        "com_ha_open": 0,
        "innodb_buffer_pool_read_ahead_evicted": 0,
        "com_delete_multi": 0,
        "key_write_requests": 0,
        "com_ha_close": 0,
        "select_range": 0,
        "delayed_writes": 0,
        "com_ha_read": 0,
        "com_xa_recover": 0,
        "ssl_ctx_verify_depth": 0,
        "innodb_pages_created": 0,
        "com_commit": 0,
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        "handler_read_prev": 0,
        "tc_log_page_waits": 0,
        "com_show_slave_hosts": 0,
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        "com_signal": 0,
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        "com_stmt_prepare": 0,
        "com_alter_function": 0,
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        "handler_delete": 0,
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        "innodb_pages_read": 457,
        "innodb_data_written": 34816,
        "innodb_data_read": 9.670656e+06,
        "select_range_check": 0,
        "innodb_buffer_pool_wait_free": 0,
        "key_blocks_unused": 6698,
        "com_show_processlist": 0
      },
      "string": {
        "ssl_version": "",
        "slave_received_heartbeats": "",
        "innodb_have_atomic_builtins": "ON",
        "ssl_server_not_after": "",
        "slave_heartbeat_period": "",
        "ssl_server_not_before": "",
        "innodb_buffer_pool_dump_status": "not started",
        "innodb_buffer_pool_load_status": "not started",
        "slave_retried_transactions": "",
        "slave_last_heartbeat": "",
        "rsa_public_key": "",
        "ssl_session_cache_mode": "NONE",
        "ssl_cipher": "",
        "compression": "OFF",
        "ssl_cipher_list": "",
        "slave_running": "OFF"
      }
...

This PR introduces a new configuration option called sql_response_format with 2 available values:

• table: This is the current behaviour
• variable: This is to indicate when the response format is like a key/value table

Any other value will exit with an error. The configuration option and their values were suggested in the issue #15770

Related issues

• Closes Add "key/value" mode for SQL module #15770