CSHARP-2862: Check that max pool size is never less than min pool size in connection string

src/MongoDB.Driver/Core/Configuration/ConnectionString.cs

@@ -963,6 +963,11 @@ string ProtectConnectionString(string connectionString)
                 var protectedString = Regex.Replace(connectionString, @"(?<=://)[^/]*(?=@)", "<hidden>");
                 return protectedString;
             }
+
+            if (_minPoolSize > _maxPoolSize)
+            {
+                throw new MongoConfigurationException("MaxPoolSize should be >= MinPoolSize.");
+            }
         }
 
         private void ParseOption(string name, string value)
@@ -1055,7 +1060,7 @@ private void ParseOption(string name, string value)
                     {
                         throw new MongoConfigurationException("Multiple proxyHost options are not allowed.");
                     }
-                    
+
                     _proxyHost = value;
                     if (_proxyHost.Length == 0)
                     {

tests/MongoDB.Driver.Tests/Core/Configuration/ConnectionStringTests.cs

@@ -1320,6 +1320,25 @@ public void Invalid_srvMaxHosts_configuration_should_throw(string connectionStri
             exception.Should().BeOfType<MongoConfigurationException>();
         }
 
+        [Theory]
+        [InlineData("mongodb://localhost?maxPoolSize=5&minPoolSize=10", true)]
+        [InlineData("mongodb://localhost?maxPoolSize=10&minPoolSize=10", false)]
+        [InlineData("mongodb://localhost?maxPoolSize=10&minPoolSize=5", false)]
+        [InlineData("mongodb://localhost?maxPoolSize=10", false)]
+        public void MaxPoolSize_less_than_MinPoolSize_should_throw(string connectionString, bool shouldThrow)
+        {
+            var exception = Record.Exception(() => new ConnectionString(connectionString));
+
+            if (shouldThrow)
+            {
+                exception.Should().BeOfType<MongoConfigurationException>();
+            }
+            else
+            {
+                exception.Should().BeNull();
+            }
+        }
+
         [Fact]
         public void When_calling_resolve_on_a_srv_connection_string()
         {

tests/MongoDB.Driver.Tests/MongoClientSettingsTests.cs

@@ -88,7 +88,7 @@ public void TestClone()
             var connectionString =
                 "mongodb://user1:password1@somehost/?appname=app;" +
                 "connect=direct;connectTimeout=123;ipv6=true;heartbeatInterval=1m;heartbeatTimeout=2m;localThreshold=128;loadBalanced=false;" +
-                "maxConnecting=3;maxIdleTime=124;maxLifeTime=125;maxPoolSize=126;minPoolSize=127;readConcernLevel=majority;" +
+                "maxConnecting=3;maxIdleTime=124;maxLifeTime=125;maxPoolSize=127;minPoolSize=126;readConcernLevel=majority;" +
                 "readPreference=secondary;readPreferenceTags=a:1,b:2;readPreferenceTags=c:3,d:4;socketTimeout=129;" +
                 "serverMonitoringMode=Stream;serverSelectionTimeout=20s;ssl=true;sslVerifyCertificate=false;waitqueuesize=130;waitQueueTimeout=131;" +
                 "w=1;fsync=true;journal=true;w=2;wtimeout=131;gssapiServiceName=other;tlsInsecure=true";
@@ -586,7 +586,7 @@ public void TestFromUrl()
             var connectionString =
                 "mongodb://user1:password1@somehost/?appname=app1;authSource=db;authMechanismProperties=CANONICALIZE_HOST_NAME:true;" +
                 "compressors=zlib,snappy;zlibCompressionLevel=9;connectTimeout=123;directConnection=true;ipv6=true;heartbeatInterval=1m;heartbeatTimeout=2m;loadBalanced=false;localThreshold=128;" +
-                "maxConnecting=3;maxIdleTime=124;maxLifeTime=125;maxPoolSize=126;minPoolSize=127;readConcernLevel=majority;" +
+                "maxConnecting=3;maxIdleTime=124;maxLifeTime=125;maxPoolSize=127;minPoolSize=126;readConcernLevel=majority;" +
                 "readPreference=secondary;readPreferenceTags=a:1,b:2;readPreferenceTags=c:3,d:4;retryReads=false;retryWrites=true;socketTimeout=129;" +
                 "serverMonitoringMode=Stream;serverSelectionTimeout=20s;tls=true;sslVerifyCertificate=false;waitqueuesize=130;waitQueueTimeout=131;" +
                 "w=1;fsync=true;journal=true;w=2;wtimeout=131;gssapiServiceName=other" +
@@ -686,7 +686,7 @@ public void TestFromUrlTlsInsecure()
 
         [Theory]
         [InlineData(0, int.MaxValue)]
-        [InlineData(126, 126)]
+        [InlineData(127, 127)]
         public void TestFromUrlWithMaxPoolSize(int inputValue, int expectedValue)
         {
             var connectionString = $"mongodb://the-next-generation/?maxPoolSize={inputValue}";

tests/MongoDB.Driver.Tests/MongoUrlBuilderTests.cs

@@ -81,8 +81,8 @@ public void TestAll()
                 MaxConnecting = 3,
                 MaxConnectionIdleTime = TimeSpan.FromSeconds(2),
                 MaxConnectionLifeTime = TimeSpan.FromSeconds(3),
-                MaxConnectionPoolSize = 4,
-                MinConnectionPoolSize = 5,
+                MaxConnectionPoolSize = 5,
+                MinConnectionPoolSize = 4,
                 Password = "password",
                 ReadConcernLevel = ReadConcernLevel.Majority,
                 ReadPreference = readPreference,
@@ -138,8 +138,8 @@ public void TestAll()
                 "maxConnecting=3",
                 "maxIdleTime=2s",
                 "maxLifeTime=3s",
-                "maxPoolSize=4",
-                "minPoolSize=5",
+                "maxPoolSize=5",
+                "minPoolSize=4",
                 "serverMonitoringMode=Poll",
                 "serverSelectionTimeout=10s",
                 "socketTimeout=7s",
@@ -177,8 +177,8 @@ public void TestAll()
                 Assert.Equal(TimeSpan.FromSeconds(2), builder.MaxConnectionIdleTime);
                 Assert.Equal(TimeSpan.FromSeconds(3), builder.MaxConnectionLifeTime);
                 Assert.Equal(3, builder.MaxConnecting);
-                Assert.Equal(4, builder.MaxConnectionPoolSize);
-                Assert.Equal(5, builder.MinConnectionPoolSize);
+                Assert.Equal(4, builder.MinConnectionPoolSize);
+                Assert.Equal(5, builder.MaxConnectionPoolSize);
                 Assert.Equal("password", builder.Password);
                 Assert.Equal(ReadConcernLevel.Majority, builder.ReadConcernLevel);
                 Assert.Equal(readPreference, builder.ReadPreference);

tests/MongoDB.Driver.Tests/MongoUrlTests.cs

@@ -23,7 +23,6 @@
 using MongoDB.Driver.Core.Servers;
 using MongoDB.TestHelpers.XunitExtensions;
 using Xunit;
-
 namespace MongoDB.Driver.Tests
 {
     [Trait("Category", "ConnectionString")]
@@ -172,8 +171,8 @@ public void TestAll()
                 MaxConnecting = 3,
                 MaxConnectionIdleTime = TimeSpan.FromSeconds(2),
                 MaxConnectionLifeTime = TimeSpan.FromSeconds(3),
-                MaxConnectionPoolSize = 4,
-                MinConnectionPoolSize = 5,
+                MaxConnectionPoolSize = 5,
+                MinConnectionPoolSize = 4,
                 Password = "password",
                 ReadConcernLevel = ReadConcernLevel.Majority,
                 ReadPreference = readPreference,
@@ -223,8 +222,8 @@ public void TestAll()
                 "maxConnecting=3",
                 "maxIdleTime=2s",
                 "maxLifeTime=3s",
-                "maxPoolSize=4",
-                "minPoolSize=5",
+                "maxPoolSize=5",
+                "minPoolSize=4",
                 "serverMonitoringMode=Poll",
                 "serverSelectionTimeout=10s",
                 "socketTimeout=7s",
@@ -260,8 +259,8 @@ public void TestAll()
                 Assert.Equal(3, url.MaxConnecting);
                 Assert.Equal(TimeSpan.FromSeconds(2), url.MaxConnectionIdleTime);
                 Assert.Equal(TimeSpan.FromSeconds(3), url.MaxConnectionLifeTime);
-                Assert.Equal(4, url.MaxConnectionPoolSize);
-                Assert.Equal(5, url.MinConnectionPoolSize);
+                Assert.Equal(5, url.MaxConnectionPoolSize);
+                Assert.Equal(4, url.MinConnectionPoolSize);
                 Assert.Equal("password", url.Password);
                 Assert.Equal(ReadConcernLevel.Majority, url.ReadConcernLevel);
                 Assert.Equal(readPreference, url.ReadPreference);