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MySQL semi-sync settings
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MySQL semi-sync settings

MySQL semi-sync settings affect the performance of the database cluster. When you create a MySQL semi-sync database cluster, the values for all settings are set automatically. The values are selected to ensure high cluster performance and vary depending on the cluster configuration and MySQL semi-sync version.

If the automatic values are not suitable for your application, set your own values at cluster creation or change settings in an already created cluster.

For your information

We recommend that you change the settings only when necessary — incorrect values can reduce cluster performance. When scaling the cluster, some settings are automatically replaced with valid values.

View list of settings⁠

See a detailed description of the settings in official MySQL documentation.

You can view a list of settings that can be changed by cluster creation or customization.

If you have changed settings, you can see a list of all changes.

  1. In control panel go to Cloud platform → Databases.
  2. Open the cluster page → tab Settings.
  3. In the block DBMS settings displays the previously changed settings — name and value.

Change settings⁠

For your information

Changing some parameters in the settings causes the databases in the cluster to reboot — the cluster may be unavailable during this time. These settings depend on the MySQL semi-sync version — check them out list.

  1. In control panel go to Cloud platform → Databases.
  2. Open the cluster page → tab Settings.
  3. In the block DBMS settings click Modify and specify the new values.
  4. Click Save.

List of settings that require a reboot⁠

  • innodb_adaptive_hash_index_parts;
  • innodb_autoinc_lock_mode;
  • innodb_buffer_pool_instances;
  • innodb_buffer_pool_pool_load_at_startup;
  • innodb_commit_concurrency;
  • innodb_flush_method;
  • innodb_ft_cache_size;
  • innodb_ft_max_token_size;
  • innodb_ft_min_token_size;
  • innodb_ft_total_cache_size;
  • innodb_ft_sort_pll_degree;
  • innodb_log_buffer_size (except MySQL sync 8);
  • innodb_log_file_size;
  • innodb_page_cleaners;
  • innodb_purge_threads;
  • innodb_read_io_threads;
  • innodb_rollback_on_timeout;
  • innodb_sort_buffer_size;
  • innodb_sync_array_size;
  • innodb_write_io_threads;
  • max_digest_length;
  • table_open_cache_instances;
  • thread_pool_size;
  • thread_stack.

Settings when scaling a cluster⁠

Any DBMS parameter has the limits of acceptable values. When cluster scaling (configuration change) values of some settings are automatically changed to valid values so that the cluster can operate.

When the cluster is scaled up and moves to status ACTIVEyou'll be able to set the new values — change settings.

A list of settings that change values when the cluster is scaled:

innodb_buffer_pool_size, innodb_log_file_size, innodb_buffer_pool_instances, thread_pool_size, max_heap_table_size, tmp_table_size, temptable_max_ram

CHARSET and COLLATION⁠

MySQL semi-sync uses the following encoding (CHARSET) utf8mb4.

The sorting algorithm (COLLATION) is used as a sorting algorithm:

  • in MySQL semi-sync 5.7 — utf8mb4_general_ci
  • in MySQL semi-sync 8 — utf8mb4_0900_ai_ci

You can change the CHARSET and COLLATION values when creating objects.