Add owner, term, and busy fields.

Author: xuniq

doc/reference/reference_lua/box_info/synchro.rst

@@ -19,8 +19,27 @@ box.info.synchro
 
     *   ``queue``:
 
+        -   ``owner`` -- ID of the replica that owns the synchronous transaction queue.
+            Once the owner instance appears, all other instances become read-only.
+            If the ``owner`` field is ``0``, then every instance is writeable,
+            but it can't create any synchronous transactions.
+            To claim or re-claim the queue, use :ref:`box.ctl.promote() <box_ctl-promote>` on the instance that you want
+            to promote.
+            Since version :doc:`2.10.0 </release/2.10.0>`.
+
+        -   ``term`` -- current queue term.
+            It contains the term of the last ``PROMOTE``.
+            Usually it is equal to :ref:`box.info.election.term <box_info_election>`.
+            However, the queue term value may be less than the corresponding one in election term.
+            It can happen when a new round of elections started, but no one has promoted yet.
+            Since version :doc:`2.10.0 </release/2.10.0>`.
+
         -   ``len`` -- current number of entries that are waiting in the queue.
 
+        -   ``busy`` -- the boolean value is set to ``true`` if there is a synchronous transaction in progress.
+            Until the active transaction is complete, any other incoming synchronous transactions will be delayed.
+            Since version :doc:`2.10.0 </release/2.10.0>`.
+
     *   ``quorum`` -- evaluated value of the
         :ref:`replication_synchro_quorum <cfg_replication-replication_synchro_quorum>` configuration option.
         Since version :doc:`2.5.3 </release/2.5.3>`, the option can be set as a dynamic formula.