[#996] Added MT considerations

1 files changed, 25 insertions, 0 deletions

diff --git a/src/lib/database/database.dox b/src/lib/database/database.dox
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+// Copyright (C) 2020 Internet Systems Consortium, Inc. ("ISC")
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+/**
+ @page libdatabase libkea-database - Kea Database Library
+
+@section databaseMTConsiderations Multi-Threading Consideration for Database
+
+MySQL and PostgreSQL provide connection pools which is used to make
+lease, host and legal log backends thread safe. Cassandra/CQL is
+thread safe by design.
+
+MySQL and PostgreSQL are inter-process safe only when transactions are used
+(including the MySQL auto-transaction mode which includes queries into
+a transaction). For MySQL this means that transactions must be supported
+by the database engine (the engine selection is done in the schema).
+
+Note the InnoDB engine used by Kea for MySQL databases cancels a transaction
+when a deadlock is detected (rare but possible event) and leaves the charge
+to retry the transaction to the caller.
+
+*/