draft

Author: xuniq

doc/platform/sharding/vshard_admin.rst

@@ -594,7 +594,7 @@ In this case:
 
   A write request can be executed repeatedly without a check in two cases:
   - The request is idempotent.
-  - It's known for sure that the previous request errored before executing any write operations.
+  - It's known for sure that the previous request raised an error before executing any write operations.
     For example, ER_READONLY was thrown by the server.
     In this case, we know that the request couldn't complete due to server in read-only mode.
 
@@ -603,6 +603,11 @@ In this case:
 To ensure that the write requests (INSERT, UPDATE, UPSERT, and autoincrement) are idempotent,
 you should implement a check that the request is applied for the first time.
 
+..  note::
+
+    There is no built-in deduplication check in Tarantool.
+    Currently, deduplication can be only implemented by the user in the application code.
+
 For example, when you add a new tuple to a space, you can use a unique insert ID to check the request.
 In the example below within a single transaction:
 

doc/reference/reference_rock/vshard/vshard_router.rst

@@ -132,7 +132,14 @@ Router public API
         * ``timeout`` — a request timeout, in seconds. If the ``router`` cannot identify a
           shard with the specified ``bucket_id``, it will retry until the timeout is reached.
 
-        * ``request_timeout``  — timeout in seconds
+        * ``request_timeout`` (since ``vshard`` 0.1.28) — timeout in seconds that serves as a protection against hung replicas.
+          The parameter is used in the read requests only (``mode=read``).
+          It is necessary to pass the ``request_timeout`` and ``timeout`` parameters together, with the following requirement:
+          ``timeout > request_timeout``.
+
+          The ``timeout``parameter controls how much time a single request attempt may take.
+          When this time is over (the ``TimedOut`` error is raised), router retries the request on the next replica as long
+          as the ``timeout`` value is not elapsed.
 
         * other :ref:`net.box options <net_box-options>`, such as ``is_async``,
           ``buffer``, ``on_push`` are also supported.
@@ -211,6 +218,17 @@ Router public API
         * ``timeout`` — a request timeout, in seconds.If the ``router`` cannot identify a
           shard with the specified ``bucket_id``, it will retry until the timeout is reached.
 
+.. vshard_request_timeout_note_start
+
+        * ``request_timeout`` (since ``vshard`` 0.1.28) — timeout in seconds that serves as a protection against hung replicas.
+          It is necessary to pass the ``request_timeout`` and ``timeout`` parameters together, with the following requirement:
+          ``timeout > request_timeout``.
+          The ``timeout``parameter controls how much time a single request attempt may take.
+          When this time is over (the ``TimedOut`` error is raised), router retries the request on the next replica as long
+          as the ``timeout`` value is not elapsed.
+
+.. vshard_request_timeout_note_end
+
         * other :ref:`net.box options <net_box-options>`, such as ``is_async``,
           ``buffer``, ``on_push`` are also supported.
 
@@ -283,6 +301,17 @@ Router public API
         * ``timeout`` — a request timeout, in seconds. If the ``router`` cannot identify a
           shard with the specified ``bucket_id``, it will retry until the timeout is reached.
 
+          ..  include:: /reference/reference_rock/vshard/vshard_router.rst
+              :start-after: vshard_request_timeout_note_start
+              :end-before: vshard_request_timeout_note_end
+
+        * ``request_timeout`` (since ``vshard`` 0.1.28) — timeout in seconds that serves as a protection against hung replicas.
+          It is necessary to pass the ``request_timeout`` and ``timeout`` parameters together, with the following requirement:
+          ``timeout > request_timeout``.
+          The ``timeout``parameter controls how much time a single request attempt may take.
+          When this time is over (the ``TimedOut`` error is raised), router retries the request on the next replica as long
+          as the ``timeout`` value is not elapsed.
+
         * other :ref:`net.box options <net_box-options>`, such as ``is_async``,
           ``buffer``, ``on_push`` are also supported.