Allocate a server extension structure for slave_stats_daemon

Summary:
Without allocating the server extension structure, 8.0.20 instances were crashing. This structure maintains compression context information.

Moved

`mysql_extension_set_server_extn(mysql, &mi->server_extn);`

to method `configure_master_connection_options` which is common to both slave stats daemon and replication io thread.

Now both threads will be setting the structure properly.

Reviewed By: hermanlee

Differential Revision: D27486594

include/mysql_com_server.h

@@ -56,9 +56,9 @@ struct compression_attributes {
 };
 
 typedef struct NET_SERVER {
-  before_header_callback_fn m_before_header;
-  after_header_callback_fn m_after_header;
-  void *m_user_data;
+  before_header_callback_fn m_before_header{nullptr};
+  after_header_callback_fn m_after_header{nullptr};
+  void *m_user_data{nullptr};
   struct compression_attributes compression;
   mysql_compress_context compress_ctx;
   bool timeout_on_full_packet;

mysql-test/r/slave_stats_daemon.result

@@ -156,6 +156,38 @@ select now() - max(timestamp) <= 1 as less_than_1_sec_old_most_recent_stats from
 less_than_1_sec_old_most_recent_stats
 1
 ########################################################################################################
+### Case 3.6: Test for 8.0.20 crashes. Make sure secondary does not crash when slave_compressed_protocol = 1 
+########################################################################################################
+set @@GLOBAL.write_stats_frequency=1;
+set @@GLOBAL.write_stats_count=10;
+select sleep(2);
+sleep(2)
+0
+select count(*) > 0 as stats_samples_collected from performance_schema.replica_statistics;
+stats_samples_collected
+1
+include/stop_slave.inc
+set @@GLOBAL.slave_compressed_protocol=1;
+include/start_slave.inc
+select sleep(2);
+sleep(2)
+0
+select 1;
+1
+1
+select sleep(2);
+sleep(2)
+0
+select now() - max(timestamp) <= 1 as less_than_1_sec_old_most_recent_stats from performance_schema.replica_statistics;
+less_than_1_sec_old_most_recent_stats
+1
+create table t(a int) engine=innodb;
+insert into t values(1);
+drop table t;
+include/stop_slave.inc
+set @@GLOBAL.slave_compressed_protocol=0;
+include/start_slave.inc
+########################################################################################################
 ### Case 4: Promote slave to master and master to slave. Old master(new slave) should be able to send
 ### stats to new master(old slave)
 ########################################################################################################

mysql-test/t/slave_stats_daemon.test

@@ -160,6 +160,45 @@ select sleep(2);
 # Master should be receiving stats every second and it's most recent stat should not be more than 1 sec old
 select now() - max(timestamp) <= 1 as less_than_1_sec_old_most_recent_stats from performance_schema.replica_statistics;
 
+--echo ########################################################################################################
+--echo ### Case 3.6: Test for 8.0.20 crashes. Make sure secondary does not crash when slave_compressed_protocol = 1 
+--echo ########################################################################################################
+connection slave;
+set @@GLOBAL.write_stats_frequency=1;
+
+connection master;
+set @@GLOBAL.write_stats_count=10;
+select sleep(2);
+select count(*) > 0 as stats_samples_collected from performance_schema.replica_statistics;
+
+connection slave;
+-- source include/stop_slave.inc
+set @@GLOBAL.slave_compressed_protocol=1;
+-- source include/start_slave.inc
+
+## make sure secondary does not crash
+select sleep(2);
+select 1;
+
+# Master should be receiving stats every second and it's most recent stat should not be more than 1 sec old
+connection master;
+select sleep(2);
+select now() - max(timestamp) <= 1 as less_than_1_sec_old_most_recent_stats from performance_schema.replica_statistics;
+
+# Generate some traffic on primary to make sure replication I/O channel is fine
+create table t(a int) engine=innodb;
+insert into t values(1);
+
+
+# reset
+connection master;
+drop table t;
+--sync_slave_with_master
+connection slave;
+-- source include/stop_slave.inc
+set @@GLOBAL.slave_compressed_protocol=0;
+-- source include/start_slave.inc
+
 --echo ########################################################################################################
 --echo ### Case 4: Promote slave to master and master to slave. Old master(new slave) should be able to send
 --echo ### stats to new master(old slave)

sql/slave_stats_daemon.cc

@@ -25,6 +25,7 @@
 #include <mysql.h>
 #include <mysql/psi/mysql_thread.h>
 #include <mysql_com.h>
+#include <sql_common.h>
 #include <sql_string.h>
 
 #include "sql/log.h"
@@ -66,7 +67,8 @@ static bool connected_to_master = false;
   @retval false otherwise.
 */
 static bool safe_connect_slave_stats_thread_to_master(MYSQL *&mysql,
-                                                      Master_info *active_mi) {
+                                                      Master_info *active_mi,
+                                                      NET_SERVER *server_extn) {
   if (mysql != nullptr) {
     mysql_close(mysql);
   }
@@ -85,7 +87,7 @@ static bool safe_connect_slave_stats_thread_to_master(MYSQL *&mysql,
   if (active_mi->get_password(pass, &password_size)) {
     return false;
   }
-
+  mysql_extension_set_server_extn(mysql, server_extn);
   if (!mysql_real_connect(mysql, active_mi->host, active_mi->get_user(), pass,
                           0, active_mi->port, 0, 0)) {
     return false;
@@ -104,6 +106,13 @@ static void *handle_slave_stats_daemon(void *arg MY_ATTRIBUTE((unused))) {
   slave_stats_daemon_thread = my_thread_self();
 
   MYSQL *mysql = nullptr;
+  // allocate server extension structure
+  NET_SERVER server_extn;
+  server_extn.m_user_data = nullptr;
+  server_extn.m_before_header = nullptr;
+  server_extn.m_after_header = nullptr;
+  server_extn.compress_ctx.algorithm = MYSQL_UNCOMPRESSED;
+
   Master_info *active_mi;
   while (true) {
     mysql_mutex_lock(&LOCK_slave_stats_daemon);
@@ -150,8 +159,8 @@ static void *handle_slave_stats_daemon(void *arg MY_ATTRIBUTE((unused))) {
       // successful, try again in next cycle
 
       if (!connected_to_master) {
-        connected_to_master =
-            safe_connect_slave_stats_thread_to_master(mysql, active_mi);
+        connected_to_master = safe_connect_slave_stats_thread_to_master(
+            mysql, active_mi, &server_extn);
         if (connected_to_master) {
           DBUG_PRINT("info",
                      ("Slave Stats Daemon: connected to master '%s@%s:%d'",