SERVER-37837 Get rid of TransactionReaper (Part 1)

This change gets rid of the TransactionReaper's usage of the
ReplicationCoordinator for checking whether it is primary or not and
makes the LogicalSessionCache joinable on shutdown.

It also removes the TransactionReaper's grouping per-shard optimization
and moves it all under SessionCollectionSharded.

1 files changed, 75 insertions, 0 deletions

diff --git a/src/mongo/db/logical_session_cache.idl b/src/mongo/db/logical_session_cache.idl
new file mode 100644
index 00000000000..3294df14378
--- /dev/null
+++ b/src/mongo/db/logical_session_cache.idl
@@ -0,0 +1,75 @@
+# Copyright (C) 2019-present MongoDB, Inc.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the Server Side Public License, version 1,
+# as published by MongoDB, Inc.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# Server Side Public License for more details.
+#
+# You should have received a copy of the Server Side Public License
+# along with this program. If not, see
+# <http://www.mongodb.com/licensing/server-side-public-license>.
+#
+# As a special exception, the copyright holders give permission to link the
+# code of portions of this program with the OpenSSL library under certain
+# conditions as described in each individual source file and distribute
+# linked combinations including the program with the OpenSSL library. You
+# must comply with the Server Side Public License in all respects for
+# all of the code used other than as permitted herein. If you modify file(s)
+# with this exception, you may extend this exception to your version of the
+# file(s), but you are not obligated to do so. If you do not wish to do so,
+# delete this exception statement from your version. If you delete this
+# exception statement from all source files in the program, then also delete
+# it in the license file.
+#
+
+global:
+  cpp_namespace: "mongo"
+
+server_parameters:
+
+  logicalSessionRefreshMillis:
+    description: The interval (in milliseconds) at which the cache refreshes its logical session
+                 records against the main session store.
+    set_at: startup
+    cpp_vartype: int
+    cpp_varname: logicalSessionRefreshMillis
+    default: 300000
+
+  maxSessions:
+    description: The maximum number of sessions that can be cached.
+    set_at: startup
+    cpp_vartype: int
+    cpp_varname: maxSessions
+    default: 1000000
+
+  disableLogicalSessionCacheRefresh:
+    description: Disable the logical session cache refresh (for testing only).
+    set_at: startup
+    cpp_vartype: bool
+    cpp_varname: disableLogicalSessionCacheRefresh
+    default: false
+
+  TransactionRecordMinimumLifetimeMinutes:
+    # The minimum lifetime for a transaction record is how long it has to have lived on the server
+    # before we'll consider it for cleanup. This is effectively the window for how long it is
+    # permissible for a mongos to hang before we're willing to accept a failure of the retryable
+    # writes subsystem.
+    #
+    # Specifically, we imagine that a client connects to one mongos on a session and performs a
+    # retryable write after which that mongos hangs. Then the client connects to a new mongos on the
+    # same session and successfully executes its write.  After a day passes, the session will time
+    # out, cleaning up the retryable write. Then the original mongos wakes up, vivifies the session
+    # and executes the write (because all records of the session + transaction have been deleted).
+    #
+    # So the write is performed twice, which is unavoidable without losing session vivification
+    # and/or requiring synchronized clocks all the way out to the client.  In lieu of that we
+    # provide a weaker guarantee after the minimum transaction lifetime.
+    description: The minimum lifetime for a transaction record.
+    set_at: startup
+    cpp_vartype: int
+    cpp_varname: gTransactionRecordMinimumLifetimeMinutes
+    default: 30