RUST-1531 Improve test coverage for retryable handshake errors (#782)

Author: isabelatkinson

src/coll/options.rs

@@ -975,7 +975,10 @@ pub struct FindOneOptions {
     ///
     /// This options maps to the `maxTimeMS` MongoDB query option, so the duration will be sent
     /// across the wire as an integer number of milliseconds.
-    #[serde(deserialize_with = "bson_util::deserialize_duration_option_from_u64_millis")]
+    #[serde(
+        default,
+        deserialize_with = "bson_util::deserialize_duration_option_from_u64_millis"
+    )]
     pub max_time: Option<Duration>,
 
     /// The inclusive lower bound for a specific index.

src/test/spec/json/retryable-reads/README.rst

@@ -81,17 +81,21 @@ Each YAML file has the following keys:
     the default is all topologies (i.e. ``["single", "replicaset", "sharded",
     "load-balanced"]``).
 
-  - ``serverless``: Optional string. Whether or not the test should be run on
-    serverless instances imitating sharded clusters. Valid values are "require",
-    "forbid", and "allow". If "require", the test MUST only be run on serverless
-    instances. If "forbid", the test MUST NOT be run on serverless instances. If
-    omitted or "allow", this option has no effect.
-
-    The test runner MUST be informed whether or not serverless is being used in
-    order to determine if this requirement is met (e.g. through an environment
-    variable or configuration option). Since the serverless proxy imitates a
-    mongos, the runner is not capable of determining this by issuing a server
-    command such as ``buildInfo`` or ``hello``.
+  - ``serverless``: (optional): Whether or not the test should be run on Atlas
+    Serverless instances. Valid values are "require", "forbid", and "allow". If
+    "require", the test MUST only be run on Atlas Serverless instances. If
+    "forbid", the test MUST NOT be run on Atlas Serverless instances. If omitted
+    or "allow", this option has no effect.
+
+    The test runner MUST be informed whether or not Atlas Serverless is being
+    used in order to determine if this requirement is met (e.g. through an
+    environment variable or configuration option).
+
+    Note: the Atlas Serverless proxy imitates mongos, so the test runner is not
+    capable of determining if Atlas Serverless is in use by issuing commands
+    such as ``buildInfo`` or ``hello``. Furthermore, connections to Atlas
+    Serverless use a load balancer, so the topology will appear as
+    "load-balanced".
 
 - ``database_name`` and ``collection_name``: Optional. The database and
   collection to use for testing.
@@ -116,13 +120,14 @@ Each YAML file has the following keys:
     mongos seed addresses. If ``false`` or omitted, only a single mongos address
     should be specified.
 
-    If ``true``, and the topology type is ``LoadBalanced``, the MongoClient for
-    this test should be initialized with the URI of the load balancer fronting
-    multiple servers. If ``false`` or omitted, the MongoClient for this test
-    should be initialized with the URI of the load balancer fronting a single
-    server.
+    If ``true``, the topology type is ``LoadBalanced``, and Atlas Serverless is
+    not being used, the MongoClient for this test should be initialized with the
+    URI of the load balancer fronting multiple servers. If ``false`` or omitted,
+    the MongoClient for this test should be initialized with the URI of the load
+    balancer fronting a single server.
 
-    ``useMultipleMongoses`` only affects ``Sharded`` and ``LoadBalanced`` topologies.
+    ``useMultipleMongoses`` only affects ``Sharded`` and ``LoadBalanced``
+    topologies (excluding Atlas Serverless).
 
   - ``skipReason``: Optional, string describing why this test should be skipped.
 
@@ -231,6 +236,8 @@ This test requires MongoDB 4.2.9+ for ``blockConnection`` support in the failpoi
 Changelog
 =========
 
+:2022-04-22: Clarifications to ``serverless`` and ``useMultipleMongoses``.
+
 :2022-01-10: Create legacy and unified subdirectories for new unified tests
 
 :2021-08-27: Clarify behavior of ``useMultipleMongoses`` for ``LoadBalanced`` topologies.