handle SystemOverloadedError on command errors

Author: blink1073

pymongo/asynchronous/topology.py

@@ -868,6 +868,8 @@ async def _handle_error(self, address: _Address, err_ctx: _ErrorContext) -> None
             # as Unknown and request an immediate check of the server.
             # Otherwise, we clear the connection pool, mark the server as
             # Unknown and request an immediate check of the server.
+            if error.has_error_label("SystemOverloadedError"):
+                return
             if hasattr(error, "code"):
                 err_code = error.code
             else:

pymongo/synchronous/topology.py

@@ -866,6 +866,8 @@ def _handle_error(self, address: _Address, err_ctx: _ErrorContext) -> None:
             # as Unknown and request an immediate check of the server.
             # Otherwise, we clear the connection pool, mark the server as
             # Unknown and request an immediate check of the server.
+            if error.has_error_label("SystemOverloadedError"):
+                return
             if hasattr(error, "code"):
                 err_code = error.code
             else:

test/discovery_and_monitoring/unified/backpressure-hello-command-error.json

@@ -0,0 +1,150 @@
+{
+  "description": "backpressure hello-command-error",
+  "schemaVersion": "1.4",
+  "runOnRequirements": [
+    {
+      "minServerVersion": "4.4.7",
+      "serverless": "forbid",
+      "topologies": [
+        "single",
+        "replicaset",
+        "sharded"
+      ]
+    }
+  ],
+  "createEntities": [
+    {
+      "client": {
+        "id": "setupClient",
+        "useMultipleMongoses": false
+      }
+    }
+  ],
+  "initialData": [
+    {
+      "collectionName": "backpressure hello-command-error",
+      "databaseName": "sdam-tests",
+      "documents": []
+    }
+  ],
+  "tests": [
+    {
+      "description": "hello command error with backpressure label does not clear the pool",
+      "operations": [
+        {
+          "name": "createEntities",
+          "object": "testRunner",
+          "arguments": {
+            "entities": [
+              {
+                "client": {
+                  "id": "client",
+                  "useMultipleMongoses": false,
+                  "observeEvents": [
+                    "serverHeartbeatSucceededEvent",
+                    "poolClearedEvent",
+                    "poolReadyEvent",
+                    "commandStartedEvent"
+                  ],
+                  "uriOptions": {
+                    "retryWrites": false,
+                    "heartbeatFrequencyMS": 10000,
+                    "serverMonitoringMode": "poll",
+                    "directConnection": true,
+                    "appname": "backpressureCommandErrorHandshakeTest"
+                  }
+                }
+              },
+              {
+                "database": {
+                  "id": "database",
+                  "client": "client",
+                  "databaseName": "sdam-tests"
+                }
+              },
+              {
+                "collection": {
+                  "id": "collection",
+                  "database": "database",
+                  "collectionName": "backpressure hello-command-error"
+                }
+              }
+            ]
+          }
+        },
+        {
+          "name": "waitForEvent",
+          "object": "testRunner",
+          "arguments": {
+            "client": "client",
+            "event": {
+              "serverHeartbeatSucceededEvent": {}
+            },
+            "count": 1
+          }
+        },
+        {
+          "name": "failPoint",
+          "object": "testRunner",
+          "arguments": {
+            "client": "setupClient",
+            "failPoint": {
+              "configureFailPoint": "failCommand",
+              "mode": "alwaysOn",
+              "data": {
+                "failCommands": [
+                  "hello",
+                  "isMaster"
+                ],
+                "appName": "backpressureCommandErrorHandshakeTest",
+                "closeConnection": false,
+                "errorCode": 9001,
+                "errorLabels": [
+                  "SystemOverloadedError"
+                ]
+              }
+            }
+          }
+        },
+        {
+          "name": "insertMany",
+          "object": "collection",
+          "arguments": {
+            "documents": [
+              {
+                "_id": 1
+              },
+              {
+                "_id": 2
+              }
+            ]
+          },
+          "expectError": {
+            "isError": true
+          }
+        }
+      ],
+      "expectEvents": [
+        {
+          "client": "client",
+          "eventType": "cmap",
+          "events": [
+            {
+              "poolReadyEvent": {}
+            }
+          ]
+        },
+        {
+          "client": "client",
+          "eventType": "sdam",
+          "ignoreExtraEvents": false,
+          "events": [
+            {
+              "serverHeartbeatSucceededEvent": {}
+            }
+          ]
+        }
+      ]
+    }
+  ]
+}

test/discovery_and_monitoring/unified/backpressure-network-error-fail.json

@@ -36,7 +36,7 @@
   ],
   "tests": [
     {
-      "description": "Apply backpressure on network connection errors during connection establishment",
+      "description": "apply backpressure on network connection errors during connection establishment",
       "operations": [
         {
           "name": "createEntities",

test/discovery_and_monitoring/unified/backpressure-network-timeout-fail.json

@@ -36,7 +36,7 @@
   ],
   "tests": [
     {
-      "description": "Apply backpressure on network timeout error during connection establishment",
+      "description": "apply backpressure on network timeout error during connection establishment",
       "operations": [
         {
           "name": "createEntities",