Replication Issues: Never purge logs before slave catches them!!

1. Restore backed up binary logs in Master.
2. Modify mysql-bin.index file in Master to make binary logs “visible”
3. Reset slave to restart replication information.
4. Restart replication.

1. Customer doesn't have enough space in default folder to restore all deleted binary logs (about 250GB) so they had to mount a NFS folder.
2. There isn't a good documented way to refresh cached information about binary logs reported with SHOW BINARY LOGS statement.
3. Easy one.
4. Easy one.

1. Once we had the list of each recovered binary log (wich was from mysql-bin.002671 to mysql-bin.002877) we moved to next step.
2. We modified mysql-bin.index file to include lost binaries. After finish it looks this way:

mysql> show binary logs;
 +------------------+------------+
 | Log_name | File_size |
 +------------------+------------+
 | mysql-bin.002671 | 1073742130 |
 | mysql-bin.002672 | 1073741934 |
 | mysql-bin.002673 | 1073742001 |
 | mysql-bin.002674 | 1073742857 |
 | mysql-bin.002675 | 1073741944 |
 ...and so on

Continuing changes: 
 mysql> change master to master_host ='xxxx.xxxxxx.xxx', master_user='repl', master_password='pwd', master_log_file='mysql-bin.002671', master_log_pos=1073741674;
 
 Query OK, 0 rows affected (0.16 sec)
 mysql> START SLAVE;
 Query OK, 0 rows affected (0.00 sec)
 mysql> show slave status\G
 *************************** 1. row ***************************
 Slave_IO_State:
 Master_Host: oxxxx.xxxxxx.xxx
 Master_User: repl
 Master_Port: 3306
 Connect_Retry: 60
 Master_Log_File: mysql-bin.002671
 Read_Master_Log_Pos: 1073741674
 Relay_Log_File: xxxxxxxxxxxx-relay-bin.000001
 Relay_Log_Pos: 98
 Relay_Master_Log_File: mysql-bin.002671
 Slave_IO_Running: No
 Slave_SQL_Running: Yes
 Replicate_Do_DB:
 Replicate_Ignore_DB:
 Replicate_Do_Table:
 Replicate_Ignore_Table:
 Replicate_Wild_Do_Table:
 Replicate_Wild_Ignore_Table:
 Last_Errno: 0
 Last_Error:
 Skip_Counter: 0
 Exec_Master_Log_Pos: 1073741674
 Relay_Log_Space: 98
 Until_Condition: None
 Until_Log_File:
 Until_Log_Pos: 0
 Master_SSL_Allowed: No
 Master_SSL_CA_File:
 Master_SSL_CA_Path:
 Master_SSL_Cert:
 Master_SSL_Cipher:
 Master_SSL_Key:
 Seconds_Behind_Master: NULL
 1 row in set (0.00 sec)

-- void MYSQL_LOG::new_file(bool need_lock)
 {
  char new_name[FN_REFLEN], *new_name_ptr, *old_name;
  enum_log_type save_log_type;
 
  DBUG_ENTER("MYSQL_LOG::new_file");
  if (!is_open())
  {
  DBUG_PRINT("info",("log is closed"));
  DBUG_VOID_RETURN;
  }
 
  if (need_lock)
  pthread_mutex_lock(&LOCK_log);
  pthread_mutex_lock(&LOCK_index);
 
  safe_mutex_assert_owner(&LOCK_log);
  safe_mutex_assert_owner(&LOCK_index);
 
  /*
  if binlog is used as tc log, be sure all xids are "unlogged",
  so that on recover we only need to scan one - latest - binlog file
  for prepared xids. As this is expected to be a rare event,
  simple wait strategy is enough. We're locking LOCK_log to be sure no
  new Xid_log_event's are added to the log (and prepared_xids is not
  increased), and waiting on COND_prep_xids for late threads to
  catch up.
  */
  if (prepared_xids)
  {
  tc_log_page_waits++;
  pthread_mutex_lock(&LOCK_prep_xids);
  while (prepared_xids)
  pthread_cond_wait(&COND_prep_xids, &LOCK_prep_xids);
  pthread_mutex_unlock(&LOCK_prep_xids);
  }
 
  /* Reuse old name if not binlog and not update log */
  new_name_ptr= name;
 
  /*
  If user hasn't specified an extension, generate a new log name
  We have to do this here and not in open as we want to store the
  new file name in the current binary log file.
  */
  if (generate_new_name(new_name, name))
  goto end;
  new_name_ptr=new_name;
 
  if (log_type == LOG_BIN)
  {
  if (!no_auto_events)
  {
  /*
  We log the whole file name for log file as the user may decide
  to change base names at some point.
  */
  THD *thd = current_thd; /* may be 0 if we are reacting to SIGHUP */
  Rotate_log_event r(thd,new_name+dirname_length(new_name),
  0, LOG_EVENT_OFFSET, 0);
  r.write(&log_file);
  bytes_written += r.data_written;
  }
  /*
  Update needs to be signalled even if there is no rotate event
  log rotation should give the waiting thread a signal to
  discover EOF and move on to the next log.
  */
  signal_update();
  }
  old_name=name;
  save_log_type=log_type;
  name=0; // Don't free name
 close(LOG_CLOSE_TO_BE_OPENED | LOG_CLOSE_INDEX);
 
  /*
  Note that at this point, log_type != LOG_CLOSED (important for is_open()).
  */
 
  /*
  new_file() is only used for rotation (in FLUSH LOGS or because size >
  max_binlog_size or max_relay_log_size).
  If this is a binary log, the Format_description_log_event at the beginning of
  the new file should have created=0 (to distinguish with the
  Format_description_log_event written at server startup, which should
  trigger temp tables deletion on slaves.
  */
 
  /* reopen index binlog file, BUG#34582 */
  if (!open_index_file(index_file_name, 0))
  open(old_name, save_log_type, new_name_ptr,
  io_cache_type, no_auto_events, max_size, 1);
  my_free(old_name,MYF(0));
 
 end:
  if (need_lock)
  pthread_mutex_unlock(&LOCK_log);
  pthread_mutex_unlock(&LOCK_index);
 
  DBUG_VOID_RETURN;
 }

1. Moved the last log that slaves catches ( mysql-bin.002671) to it's original position.
2. Modified again the mysql-bin.index to point this file to proper path.
3. Perform FLUSH LOGS and FLUSH PRIVILEGES command to force server to refresh the information about binary logs and clients.
4. Went to slave and restart replication (and cross fingers of course)