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DRIVERS-1819 Snapshot session sends readConcern with all commands even writes #1033

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Merged
merged 7 commits into from
Jun 30, 2021
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DRIVERS-1819 Snapshot session sends readConcern with all commands even writes #1033

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6bd7f45
DRIVERS-1819 Writes are not allowed in snapshot sessions
ShaneHarvey Jun 29, 2021
166e7bb
DRIVERS-1819 Add tests for unsupported operations
ShaneHarvey Jun 29, 2021
884cc09
DRIVERS-1819 Send readConcern with all commands even writes
ShaneHarvey Jun 29, 2021
cb8bf31
DRIVERS-1819 fix runCommand typo
ShaneHarvey Jun 30, 2021
bd38e85
DRIVERS-1819 Skip insert/update/delete tests on sharded clusters due …
ShaneHarvey Jun 30, 2021
20920bd
DRIVERS-1819 Fix listCollections in runCommand test
ShaneHarvey Jun 30, 2021
380340a
DRIVERS-1819 Describe write error behavior more explicitly
ShaneHarvey Jun 30, 2021
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17 changes: 14 additions & 3 deletions source/sessions/snapshot-sessions.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -3,13 +3,13 @@ Snapshot Reads Specification
============================

:Spec Title: Snapshot Reads Specification (See the registry of specs)
:Spec Version: 1.1
:Spec Version: 1.2
:Author: Boris Dogadov
:Advisors: Jeff Yemin, A. Jesse Jiryu Davis, Judah Schvimer
:Status: Draft (Could be Draft, Accepted, Rejected, Final, or Replaced)
:Type: Standards
:Minimum Server Version: 5.0
:Last Modified: 15-Jun-2021
:Last Modified: 29-Jun-2021

.. contents::

Expand Down Expand Up @@ -192,6 +192,7 @@ Server Errors
=============
1. The server may reply to read commands with a ``SnapshotTooOld`` error if the client's ``atClusterTime`` value is not available in the server's history.
2. The server will return ``InvalidOptions`` error if both ``atClusterTime`` and ``afterClusterTime`` options are set to true.
3. The server will return ``InvalidOptions`` error if the command does not support readConcern.level "snapshot".

Snapshot read commands
======================
Expand All @@ -211,7 +212,7 @@ by specifying ``readConcern`` with ``snapshot`` level field, and store it as ``s
}
}

For subsequent reads from same snapshot driver MUST send the ``snapshotTime`` saved in
For subsequent reads in the same session, the driver MUST send the ``snapshotTime`` saved in
the ``ClientSession`` as the value of the ``atClusterTime`` field of the
``readConcern`` with ``snapshot`` level field:

Expand All @@ -233,6 +234,15 @@ Lists of commands that support snapshot reads:
2. aggregate
3. distinct

Sending readConcern to the server on all commands
=================================================

Drivers MUST set the readConcern ``level`` and ``atClusterTime`` fields (as
outlined above) on all commands in a snapshot session even commands like
insert and update that do not accept a readConcern. This ensures the server
will return an error for invalid operations, such as writes, within a session
configured for snapshot reads.

Requires MongoDB 5.0+
=====================

Expand Down Expand Up @@ -277,3 +287,4 @@ Changelog

:2021-06-15: Initial version.
:2021-06-28: Raise client side error on < 5.0.
:2021-06-29: Send readConcern with all snapshot session commands.
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