How to Add a ‘STOP ALL SLAVES’ Command to MySQL 5.6 Source Code

Background

The feature originates from the book Expert MySQL , which describes the internals of MySQL 5.6.x. The goal is to add a new high‑availability command STOP ALL SLAVES that can be issued on the master and propagated to all slaves via the binary log.

Source reference

Original article: https://mysql.az/2016/10/31/playing-with-mysql-source-code-adding-stop-all-slaves-command/

Step‑by‑step source modifications (MySQL 5.6.32)

Update sql/lex.h Add a new token entry for the command, keeping the symbol array alphabetically ordered.

Extend sql/sql_cmd.h Insert a new enum value SQLCOM_STOP_SLAVES into the enum_sql_command list.

Add token to the parser Edit sql/sql_yacc.yy and insert the token SLAVES at the appropriate location (lines 1539‑1540).

Update %type definitions Modify lines 1855‑1856 in sql/sql_yacc.yy to include the new token.

Extend the command list Use the ‘|’ operator to add the new rule in the command list (lines 2079‑2080).

Map token to enum in the parser In sql/sql_parse.cc , add a case that sets the command type to SQLCOM_STOP_SLAVES (lines 8114‑8115).

Write a binlog event Insert logic in sql/sql_parse.cc (lines 3159‑3160) to emit a STOP SLAVE IO_THREAD event when the new command is executed, ensuring the action is replicated.

Register status variable Modify sql/mysqld.cc at lines 3571‑3572 to add the new command to the status‑variable array (replace struct show_var_st with SHOW_VAR ).

Compilation

Build MySQL from source using CMake and Make. For detailed installation steps see https://mysql.az/2015/08/18/installing-mysql-from-source-cmake-issues/. Resolve any compilation errors (e.g., missing my_ok(thd) call) by applying the suggested fix.

Testing

Deploy a master‑two‑slave cluster with MySQL Sandbox. After recompiling, execute STOP ALL SLAVES on the master. The command succeeds and each slave reports the expected stopped state.

Conclusion

By extending the lexical analyzer, command enumeration, YACC grammar, parser switch, binlog writer, and status‑variable registration, the new STOP ALL SLAVES command becomes a first‑class MySQL feature, allowing administrators to halt replication on all slaves with a single statement.