Snowflake Connector for .NET

The Snowflake .NET connector supports the the following .NET framework and libraries versions:

• .NET Framework 4.7.2
• .NET Framework 4.7.3
• .NET Core 2.0

Please refer to the Notice section below for information about safe usage of the .NET Driver

Building the Package

Prerequisites

The Snowflake .NET connector supports only Windows.

This project is developed under Visual Studio 2017. Earlier versions of Visual Studio are not supported.

Steps

1. Check out the source code from GitHub:

git clone [email protected]:snowflakedb/snowflake-connector-net snowflake-connector-net

2. Pull down the dependency:

cd snowflake-connector-net
nuget restore

3. Build the solution file

msbuild snowflake-connector-net.sln /p:Configuration=Release

Installing the Package

Package ID for Snowflake Connector for .Net is Snowflake.Data.

Packages can be directly downloaded from nuget.org.

It can also be downloaded using Visual Studio UI (Tools > NuGet Package Manager > Manage NuGet Packages for Solution and search for "Snowflake.Data")

Alternatively, packages can also be downloaded using Package Manager Console:

PM> Install-Package Snowflake.Data

Testing the Connector

Before running tests, create a parameters.json file under Snowflake.Data.Tests\ directory. In this file, specify username, password and account info that tests will run against. Here is a sample parameters.json file

{
  "testconnection": {
    "SNOWFLAKE_TEST_USER": "snowman",
    "SNOWFLAKE_TEST_PASSWORD": "XXXXXXX",
    "SNOWFLAKE_TEST_ACCOUNT": "TESTACCOUNT",
    "SNOWFLAKE_TEST_WAREHOUSE": "TESTWH",
    "SNOWFLAKE_TEST_DATABASE": "TESTDB",
    "SNOWFLAKE_TEST_SCHEMA": "TESTSCHEMA",
    "SNOWFLAKE_TEST_ROLE": "TESTROLE",
    "SNOWFLAKE_TEST_HOST": "testaccount.snowflakecomputing.com"
  }
}

Command Prompt

The build solution file builds the connector and tests binaries. Issue the following command from the command line to run the tests. The test binary is located in the Debug directory if you built the solution file in Debug mode.

cd Snowflake.Data.Tests
dotnet test -f netcoreapp2.0

Tests can also be run under code coverage:

OpenCover.4.6.519\tools\OpenCover.Console.exe -target:"dotnet.exe" -returntargetcode -targetargs:"test -f netcoreapp2.0" -register:user -filter:"+[Snowflake.Data]*" -output:"netcoreapp2.0_coverage.xml" -oldStyle 

Visual Studio 2017

Tests can also be run under Visual Studio 2017. Open the solution file in Visual Studio 2017 and run tests using Test Explorer.

Usage

Create a Connection

To connect to Snowflake, specify a valid connection string composed of key-value pairs separated by semicolons, i.e "<key1>=<value1>;<key2>=<value2>...".

Note: If the keyword or value contains an equal sign (=), you must precede the equal sign with another equal sign. For example, if the keyword is "key" and the value is "value_part1=value_part2", use "key=value_part1==value_part2".

The following table lists all valid connection properties:

The following example demonstrates how to open a connection to Snowflake. This example uses a password for authentication.

using (IDbConnection conn = new SnowflakeDbConnection())
{
    conn.ConnectionString = "account=testaccount;user=testuser;password=XXXXX;db=testdb;schema=testschema";

    conn.Open();
    
    conn.Close();
}

If you are using a different method for authentication, see the examples below:

• Key-pair authentication

  After setting up key-pair authentication, you can specify the private key for authentication in one of the following ways:

  • Specify the file containing an unencrypted private key:

    using (IDbConnection conn = new SnowflakeDbConnection())
    {
        conn.ConnectionString = "account=testaccount;authenticator=snowflake_jwt;user=testuser;private_key_file={pathToThePrivateKeyFile};db=testdb;schema=testschema";
    
        conn.Open();
    
        conn.Close();
    }

    where:

    • {pathToThePrivateKeyFile} is the path to the file containing the unencrypted private key.

  • Specify the file containing an encrypted private key:

    using (IDbConnection conn = new SnowflakeDbConnection())
    {
        conn.ConnectionString = "account=testaccount;authenticator=snowflake_jwt;user=testuser;private_key_file={pathToThePrivateKeyFile};private_key_pwd={passwordForDecryptingThePrivateKey};db=testdb;schema=testschema";
    
        conn.Open();
    
        conn.Close();
    }

    where:

    • {pathToThePrivateKeyFile} is the path to the file containing the unencrypted private key.
    • {passwordForDecryptingThePrivateKey} is the password for decrypting the private key.

  • Specify an unencrypted private key (read from a file):

    using (IDbConnection conn = new SnowflakeDbConnection())
    {
        string privateKeyContent = File.ReadAllText({pathToThePrivateKeyFile}).Replace("=", "==");
    
        conn.ConnectionString = String.Format("account=testaccount;authenticator=snowflake_jwt;user=testuser;private_key={0};db=testdb;schema=testschema", privateKeyContent);
    
        conn.Open();
    
        conn.Close();
    }

    where:

    • {pathToThePrivateKeyFile} is the path to the file containing the unencrypted private key.

• OAuth

  After setting up OAuth, set AUTHENTICATOR=oauth and TOKEN to the OAuth token in the connection string.

  using (IDbConnection conn = new SnowflakeDbConnection())
  {
      conn.ConnectionString = "account=testaccount;user=testuser;authenticator=oauth;token={oauthTokenValue};db=testdb;schema=testschema";
  
      conn.Open();
    
      conn.Close();
  }

  where:

  • {oauthTokenValue} is the oauth token to use for authentication.

• Browser-based SSO

  In the connection string, set AUTHENTICATOR=externalbrowser, and set USER to the login name for your IdP.

  using (IDbConnection conn = new SnowflakeDbConnection())
  {
      conn.ConnectionString = "account=testaccount;authenticator=externalbrowser;user={login_name_for_IdP};db=testdb;schema=testschema";
  
      conn.Open();
  
      conn.Close();
  }

  where:

  • {login_name_for_IdP} is your login name for your IdP.

• Native SSO through Okta

  In the connection string, set AUTHENTICATOR to the URL of the endpoint for your Okta account, and set USER to the login name for your IdP.

  using (IDbConnection conn = new SnowflakeDbConnection())
  {
      conn.ConnectionString = "account=testaccount;authenticator={okta_url_endpoint};user={login_name_for_IdP};db=testdb;schema=testschema";
  
      conn.Open();
  
      conn.Close();
  }

  where:

  • {okta_url_endpoint} is the URL for the endpoint for your Okta account (e.g. https://<okta_account_name>.okta.com).
  • {login_name_for_IdP} is your login name for your IdP.

In v2.0.4 and later releases, you can configure the driver to connect through a proxy server. The following example configures the driver to connect through the proxy server myproxyserver on port 8888. The driver authenticates to the proxy server as the user test with the password test:

using (IDbConnection conn = new SnowflakeDbConnection())
{
    conn.ConnectionString = "account=testaccount;user=testuser;password=XXXXX;db=testdb;schema=testschema;useProxy=true;proxyHost=myproxyserver;proxyPort=8888;proxyUser=test;proxyPassword=test";

    conn.Open();
    
    conn.Close();
}

Using Connection Pools

Instead of creating a connection each time your client application needs to access Snowflake, you can define a cache of Snowflake connections that can be reused as needed. Connection pooling usually reduces the lag time to make a connection. However, it can slow down client failover to an alternative DNS when a DNS problem occurs.

The Snowflake .NET driver provides the following functions for managing connection pools.

The following sample demonstrates how to monitor the size of a connection pool as connections are added and dropped from the pool.

public void TestConnectionPoolClean()
{
  SnowflakeDbConnectionPool.ClearAllPools();
  SnowflakeDbConnectionPool.SetMaxPoolSize(2);
  var conn1 = new SnowflakeDbConnection();
  conn1.ConnectionString = ConnectionString;
  conn1.Open();
  Assert.AreEqual(ConnectionState.Open, conn1.State);

  var conn2 = new SnowflakeDbConnection();
  conn2.ConnectionString = ConnectionString + " retryCount=1";
  conn2.Open();
  Assert.AreEqual(ConnectionState.Open, conn2.State);
  Assert.AreEqual(0, SnowflakeDbConnectionPool.GetCurrentPoolSize());
  conn1.Close();
  conn2.Close();
  Assert.AreEqual(2, SnowflakeDbConnectionPool.GetCurrentPoolSize());
  var conn3 = new SnowflakeDbConnection();
  conn3.ConnectionString = ConnectionString + "  retryCount=2";
  conn3.Open();
  Assert.AreEqual(ConnectionState.Open, conn3.State);

  var conn4 = new SnowflakeDbConnection();
  conn4.ConnectionString = ConnectionString + "  retryCount=3";
  conn4.Open();
  Assert.AreEqual(ConnectionState.Open, conn4.State);

  conn3.Close();
  Assert.AreEqual(2, SnowflakeDbConnectionPool.GetCurrentPoolSize());
  conn4.Close();
  Assert.AreEqual(2, SnowflakeDbConnectionPool.GetCurrentPoolSize());

  Assert.AreEqual(ConnectionState.Closed, conn1.State);
  Assert.AreEqual(ConnectionState.Closed, conn2.State);
  Assert.AreEqual(ConnectionState.Closed, conn3.State);
  Assert.AreEqual(ConnectionState.Closed, conn4.State);
}

Mapping .NET and Snowflake Data Types

The .NET driver supports the following mappings from .NET to Snowflake data types.

Run a Query and Read Data

using (IDbConnection conn = new SnowflakeDbConnection())
{
    conn.ConnectionString = connectionString;
    conn.Open();

    IDbCommand cmd = conn.CreateCommand();
    cmd.CommandText = "select * from t";
    IDataReader reader = cmd.ExecuteReader();

    while(reader.Read())
    {
        Console.WriteLine(reader.GetString(0));
    }

    conn.Close();
}

Note that for a TIME column, the reader returns a System.DateTime value. If you need a System.TimeSpan column, call the getTimeSpan method in SnowflakeDbDataReader. This method was introduced in the v2.0.4 release.

Note that because this method is not available in the generic IDataReader interface, you must cast the object as SnowflakeDbDataReader before calling the method. For example:

TimeSpan timeSpanTime = ((SnowflakeDbDataReader)reader).GetTimeSpan(13);

Bind Parameter

This example shows how bound parameters are converted from C# data types to Snowflake data types. For example, if the data type of the Snowflake column is INTEGER, then you can bind C# data types Int32 or Int16.

This example inserts 3 rows into a table with one column.

using (IDbConnection conn = new SnowflakeDbConnection())
{
    conn.ConnectionString = connectionString;
    conn.Open();

    IDbCommand cmd = conn.CreateCommand();
    cmd.CommandText = "create or replace table T(cola int)";
    int count = cmd.ExecuteNonQuery();
    Assert.AreEqual(0, count);

    IDbCommand cmd = conn.CreateCommand();
    cmd.CommandText = "insert into t values (?), (?), (?)";

    var p1 = cmd.CreateParameter();
    p1.ParameterName = "1";
    p1.Value = 10;
    p1.DbType = DbType.Int32;
    cmd.Parameters.Add(p1);

    var p2 = cmd.CreateParameter();
    p2.ParameterName = "2";
    p2.Value = 10000L;
    p2.DbType = DbType.Int32;
    cmd.Parameters.Add(p2);

    var p3 = cmd.CreateParameter();
    p3.ParameterName = "3";
    p3.Value = (short)1;
    p3.DbType = DbType.Int16;
    cmd.Parameters.Add(p3);

    var count = cmd.ExecuteNonQuery();
    Assert.AreEqual(3, count);

    cmd.CommandText = "drop table if exists T";
    count = cmd.ExecuteNonQuery();
    Assert.AreEqual(0, count);

    conn.Close();
}

Close the Connection

To close the connection, call the Close method of SnowflakeDbConnection.

If you want to avoid blocking threads while the connection is closing, call the CloseAsync method instead, passing in a CancellationToken. This method was introduced in the v2.0.4 release.

Note that because this method is not available in the generic IDbConnection interface, you must cast the object as SnowflakeDbConnection before calling the method. For example:

CancellationTokenSource cancellationTokenSource  = new CancellationTokenSource();
// Close the connection
((SnowflakeDbConnection)conn).CloseAsync(cancellationTokenSource.Token);

Logging

The Snowflake Connector for .NET uses log4net as the logging framework.

Here is a sample app.config file that uses log4net

  <configSections>
    <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net"/>
  </configSections>

  <log4net>
    <appender name="MyRollingFileAppender" type="log4net.Appender.RollingFileAppender">
      <file value="snowflake_dotnet.log" />
      <appendToFile value="true"/>
      <rollingStyle value="Size" />
      <maximumFileSize value="10MB" />
      <staticLogFileName value="true" />
      <maxSizeRollBackups value="10" />
      <layout type="log4net.Layout.PatternLayout">
        <!-- <header value="[DateTime]  [Thread]  [Level]  [ClassName] Message&#13;&#10;" /> -->
        <conversionPattern value="[%date] [%t] [%-5level] [%logger] %message%newline" />
      </layout>
    </appender>

    <root>
      <level value="ALL" />
      <appender-ref ref="MyRollingFileAppender" />
    </root>
  </log4net>

Notice

1. CVE-2019-0820 -
   This CVE has been reported in systems.text.regularexpressions.dll which is used by the regular expressions packages - systems.text.regularexpressions.4.3.1.nupkg. This vulnerability manifests itself ONLY when the following .NET runtime environments are being used:

• v1.0 branch: 1.0 - 1.0.16 (exclusive)

• v1.1 branch: 1.1 - 1.1.13 (exclusive)

• v2.1 branch: 2.1 - 2.1.11 (exclusive)

• v2.2 branch: 2.2 - 2.2.5 (exclusive)

  In order to mitigate this vulnerability, we recommend to update to higher Runtime versions. If you're already running on a .NET Runtime version higher than the ones listed above, you're not going to be affected by this vulnerability.

2. Logging -
   Snowflake has identified an issue on Feb 20, 2020, with our logging code for the .NET drivers in which we write Master and Session tokens in the clear to the debug logs. The debug logs are collected locally on the drive where your programs are running. This issue impacts only those instances where the programs are run with debug flags enabled, i.e. setting the log level value= "Debug” or “All" in the log4Net config

   Under normal conditions, the Master and Session tokens captured in the log files are short-lived for about 4 and 1 hours, respectively. They will expire after the 4-hour window unless explicitly refreshed, in which case they could be refreshed indefinitely.

   If you are using the .NET driver please take the following action:

• Upgrade to the latest version(v1.1.0) as soon as possible.
• Remove all “Debugging” options for any existing .NET drivers in use.
• Delete any logs collected thus far and make sure that all copies are deleted.
• If you cannot upgrade for any reason, please ensure all debugging is disabled
• If you are concerned about a potential compromise, contact Snowflake Customer Support for assistance with invalidating all active sessions/tokens.

3. Global HTTP connection settings -
   Snowflake has identified an issue where the driver is globally enforcing TLS 1.2 and certificate revocation checks with the .NET Driver v1.2.1 and earlier versions.
   Starting with v2.0.0, the driver will set these locally.

   Note that the driver is now targeting .Net framework 4.7.2.
   When upgrading to v2.0.0, you might also need to run "Update-Package -reinstall" to update the dependencies.