(Initially reported in https://forum.piwik.org/t/piwik-3-0-3-breaks-mysql-group-replication/23796 )

When MySQL 5.7.17 is running in group replication (a high-availability feature introduced in MySQL 5.7.17), all tables are required to have a primary key. Installing Piwik 3.0.3 on MySQL 5.7.17 running in a group replication breaks the group because all of the Piwik tables do not contain a primary key. The solution is to add a primary key to the three Piwik tables that do not contain primary keys:

• piwik_log_profiling
• piwik_plugin_setting
• piwik_site_setting

If possible, please make this change in Piwik 3.0.4 so we may continue with our high-availability setup. Thanks in advance.

Reference: https://dev.mysql.com/doc/refman/5.7/en/group-replication-requirements.html
"Primary Keys. Every table that is to be replicated by the group must have an explicit primary key defined. Primary keys play an extremely important role in determining which transactions conflict by identifying exactly which rows each transaction has modified."