DRIVERS-1912 Clarify maxWireVersion check for maxStalenessSeconds (#1064)

Author: kevinAlbs

source/max-staleness/max-staleness.rst

@@ -10,7 +10,7 @@ Max Staleness
 :Status: Accepted
 :Type: Standards
 :Last Modified: April 6, 2021
-:Version: 1.4
+:Version: 1.4.1
 
 .. contents::
 
@@ -484,8 +484,12 @@ Therefore, this spec *also* requires that maxStalenessSeconds is at least 90:
 All servers must have wire version 5 to support maxStalenessSeconds
 -------------------------------------------------------------------
 
-Clients are required to throw an error if maxStalenessSeconds is set,
-and any server in the topology has maxWireVersion less than 5.
+Clients with minWireVersion < 5 MUST throw an error if maxStalenessSeconds is set,
+and any available server in the topology has maxWireVersion less than 5.
+
+An available server is defined in the `Server Selection
+<../server-selection/server-selection.rst#terms>`_
+specification.
 
 Servers began reporting lastWriteDate in wire protocol version 5,
 and clients require some or all servers' lastWriteDate in order to
@@ -593,6 +597,7 @@ Changes
 =======
 
 2021-09-08: Updated tests to support driver removal of support for server versions older than 3.6.
+2021-09-03: Clarify that wire version check only applies to available servers.
 2021-04-06: Updated to use hello command.
 2016-09-29: Specify "no max staleness" in the URI with "maxStalenessMS=-1"
 instead of "maxStalenessMS=0".

source/max-staleness/tests/ReplicaSetNoPrimary/OneKnownTwoUnavailable.json

@@ -0,0 +1,60 @@
+{
+  "topology_description": {
+    "type": "ReplicaSetNoPrimary",
+    "servers": [
+      {
+        "address": "a:27017",
+        "type": "PossiblePrimary",
+        "avg_rtt_ms": 5,
+        "maxWireVersion": 0
+      },
+      {
+        "address": "b:27017",
+        "type": "Unknown",
+        "avg_rtt_ms": 5,
+        "maxWireVersion": 0
+      },
+      {
+        "address": "c:27017",
+        "type": "RSSecondary",
+        "maxWireVersion": 6,
+        "avg_rtt_ms": 5,
+        "lastWrite": {
+          "lastWriteDate": {
+            "$numberLong": "1"
+          }
+        }
+      }
+    ]
+  },
+  "read_preference": {
+    "mode": "Nearest",
+    "maxStalenessSeconds": 120
+  },
+  "suitable_servers": [
+    {
+      "address": "c:27017",
+      "type": "RSSecondary",
+      "maxWireVersion": 6,
+      "avg_rtt_ms": 5,
+      "lastWrite": {
+        "lastWriteDate": {
+          "$numberLong": "1"
+        }
+      }
+    }
+  ],
+  "in_latency_window": [
+    {
+      "address": "c:27017",
+      "type": "RSSecondary",
+      "maxWireVersion": 6,
+      "avg_rtt_ms": 5,
+      "lastWrite": {
+        "lastWriteDate": {
+          "$numberLong": "1"
+        }
+      }
+    }
+  ]
+}

source/max-staleness/tests/ReplicaSetNoPrimary/OneKnownTwoUnavailable.yml

@@ -0,0 +1,28 @@
+# Clients ignore Unknown/PossiblePrimary servers even when read preference has maxStalenessSeconds
+topology_description:
+  type: ReplicaSetNoPrimary
+  servers:
+  - &1
+    address: a:27017
+    type: PossiblePrimary
+    avg_rtt_ms: 5
+    maxWireVersion: 0
+  - &2
+    address: b:27017
+    type: Unknown
+    avg_rtt_ms: 5
+    maxWireVersion: 0
+  - &3
+    address: c:27017
+    type: RSSecondary
+    maxWireVersion: 6
+    avg_rtt_ms: 5
+    lastWrite: {lastWriteDate: {$numberLong: "1"}}
+read_preference:
+  mode: Nearest
+  maxStalenessSeconds: 120
+suitable_servers:
+- *3
+in_latency_window:
+- *3
+

source/server-selection/server-selection.rst

@@ -10,7 +10,7 @@ Server Selection
 :Status: Accepted
 :Type: Standards
 :Last Modified: 2021-05-13
-:Version: 1.13.2
+:Version: 1.13.3
 
 .. contents::
 
@@ -456,9 +456,9 @@ mongos MUST reject a read with ``maxStalenessSeconds`` that is not a positive in
 mongos MUST reject a read if ``maxStalenessSeconds`` is less than smallestMaxStalenessSeconds,
 with error code 160 (SERVER-24421).
 
-During server selection,
-drivers (but not mongos) MUST raise an error if ``maxStalenessSeconds`` is a positive number,
-and any server's ``maxWireVersion`` is less than 5. [#]_
+During server selection, drivers (but not mongos) with ``minWireVersion`` < 5
+MUST raise an error if ``maxStalenessSeconds`` is a positive number, and any
+available server's ``maxWireVersion`` is less than 5. [#]_
 
 After filtering servers according to ``mode``, and before filtering with ``tag_sets``,
 eligibility MUST be determined from ``maxStalenessSeconds`` as follows:
@@ -1232,7 +1232,7 @@ selection`_::
                 throw invalid wire protocol range error with details
 
             if maxStalenessSeconds is set:
-                if any server's maxWireVersion < 5:
+                if client minWireVersion < 5 and any available server's maxWireVersion < 5:
                     client.lock.release()
                     throw error
 
@@ -1317,7 +1317,7 @@ The following is pseudocode for `single-threaded server selection`_::
                 throw invalid wire version range error with details
 
             if maxStalenessSeconds is set:
-                if any server's maxWireVersion < 5:
+                if client minWireVersion < 5 and any available server's maxWireVersion < 5:
                     throw error
 
                 if topologyDescription.type in (ReplicaSetWithPrimary, ReplicaSetNoPrimary):
@@ -1789,6 +1789,8 @@ References
 Changes
 =======
 
+2021-09-03: Clarify that wire version check only applies to available servers.
+
 2015-06-26: Updated single-threaded selection logic with "stale" and serverSelectionTryOnce.
 
 2015-08-10: Updated single-threaded selection logic to ensure a scan always