Update files after the review

Author: xuniq

doc/reference/reference_lua/box_events/system_events.rst

@@ -19,6 +19,12 @@ The events are available from the beginning as non-:ref:`MP_NIL <box_protocol-no
 If a watcher subscribes to a system event before it has been broadcast,
 it receives an empty table for the event value.
 
+The event is generated when there is a change in any of the values listed in the event.
+For example, see the parameters in the ``box.id`` event below -- ``id``, ``instance_uuid``, and ``replicaset_uuid``.
+Suppose the ``ìd`` value (``box.info.id``) has changed.
+This triggers the ``box.info`` event, which states that the value of ``box.info.id`` has changed,
+while ``box.info.uuid`` and ``box.info.cluster.uuid`` remain the same.
+
 box.id
 ~~~~~~
 
@@ -100,25 +106,11 @@ Usage example
 ..  code-block:: lua
 
     local conn = net.box.connect(URI)
+    local log = require('log')
     -- Subscribe to updates of key 'box.id'
     local w = conn:watch('box.id', function(key, value)
         assert(key == 'box.id')
-        -- do something with value
-    end)
-    -- or subscribe to updates of key 'box.status'
-    w = conn:watch('box.status', function(key, value)
-        assert(key == 'box.status')
-        -- do something with value
-    end)
-    -- or subscribe to updates of key 'box.election'
-    w = conn:watch('box.election', function(key, value)
-        assert(key == 'box.election')
-        -- do something with value
-    end)
-    -- or subscribe to updates of key 'box.schema'
-    w = conn:watch('box.schema', function(key, value)
-        assert(key == 'box.schema')
-        -- do something with value
+        log.info("The box.id value is '%s'", value)
     end)
 
 If you want to unregister the watcher when it's no longer needed, use the following command:

doc/reference/reference_lua/box_events/watch.rst

@@ -21,7 +21,7 @@ box.watch()
         In this case, the watcher remains registered.
         It is okay to discard the result of ``watch`` function if the watcher will never be unregistered.
 
-    **Example:**
+    **Examples:**
 
     ..  code-block:: lua
 
@@ -33,6 +33,24 @@ box.watch()
             -- do something with value
         end)
 
+    Server:
+
+    ..  code-block:: lua
+
+        -- Broadcast value 42 for the 'foo' key.
+        box.broadcast('foo', 42)
+
+    Client:
+
+    ..  code-block:: lua
+
+        local conn = net.box.connect(URI)
+        -- Subscribe to updates of the 'foo' key.
+        local w = conn:watch('foo', function(key, value)
+            assert(key == 'foo')
+            -- do something with value
+        end)
+
     If you don't need the watcher anymore, you can unregister it using the command below:
 
     ..  code-block:: lua

doc/reference/reference_lua/net_box.rst

@@ -570,7 +570,7 @@ Below is a list of all ``net.box`` functions.
 
         ..  code-block:: lua
 
-            -- Broadcast value 123 for the key 'foo'.
+            -- Broadcast value 123 for the 'foo' key.
             box.broadcast('foo', 123)
 
         Client: