MDEV-20220: Merge 5.7 P_S replication table 'replication_applier_status_by_worker

Step1:
=====
Backport 'replication_applier_status_by_worker' from upstream.

Iterate through rpl_parallel_thread_pool and display slave worker thread
specific information as part of 'replication_applier_status_by_worker'
table.

---------------------------------------------------------------------------
|Column Name:           |        Description:                             |
|-------------------------------------------------------------------------|
|                       |                                                 |
|CHANNEL_NAME           | Name of replication channel through which the   |
|                       | transaction is received.                        |
|                       |                                                 |
|THREAD_ID              | Thread_Id as displayed in 'performance_schema.  |
|                       | threads' table for thread with name             |
|                       | 'thread/sql/rpl_parallel_thread'                |
|                       |                                                 |
|                       | THREAD_ID will be NULL when worker threads are  |
|                       | stopped due to an error/force stop              |
|                       |                                                 |
|SERVICE_STATE          | Thread is running or not                        |
|                       |                                                 |
|LAST_SEEN_TRANSACTION  | Last GTID executed by worker                    |
|                       |                                                 |
|LAST_ERROR_NUMBER      | Last Error that occured on a particular worker  |
|                       |                                                 |
|LAST_ERROR_MESSAGE     | Last error specific message                     |
|                       |                                                 |
|LAST_ERROR_TIMESTAMP   | Time stamp of last error                        |
|                       |                                                 |
---------------------------------------------------------------------------

CHANNEL_NAME will be empty when the worker has not processed any
transaction. Channel_name points to valid source channel_name when it is
processing a transaction/event group.

1 files changed, 7 insertions, 0 deletions

diff --git a/sql/rpl_parallel.h b/sql/rpl_parallel.h
index b88e77d5427..49e245176ff 100644
--- a/sql/rpl_parallel.h
+++ b/sql/rpl_parallel.h
@@ -161,6 +161,12 @@ struct rpl_parallel_thread {
   inuse_relaylog *accumulated_ir_last;
   uint64 accumulated_ir_count;
 
+  char channel_name[MAX_CONNECTION_NAME];
+  uint channel_name_length;
+  rpl_gtid last_seen_gtid;
+  int last_error_number;
+  char last_error_message[MAX_SLAVE_ERRMSG];
+  ulonglong last_error_timestamp;
   void enqueue(queued_event *qev)
   {
     if (last_in_queue)
@@ -224,6 +230,7 @@ struct rpl_parallel_thread {
   void batch_free();
   /* Update inuse_relaylog refcounts with what we have accumulated so far. */
   void inuse_relaylog_refcount_update();
+  rpl_parallel_thread();
 };