Umbraco-CMS/src/Umbraco.Infrastructure/Persistence/DbConnectionExtensions.cs

using System;
using System.Data;
using System.Data.Common;
using Microsoft.Extensions.Logging;
using StackExchange.Profiling.Data;
using Umbraco.Cms.Core;
using Umbraco.Cms.Infrastructure.Persistence.FaultHandling;

namespace Umbraco.Extensions
{
    public static class DbConnectionExtensions
    {
        public static bool IsConnectionAvailable(string connectionString, DbProviderFactory factory)
        {
            var connection = factory?.CreateConnection();

            if (connection == null)
                throw new InvalidOperationException($"Could not create a connection for provider \"{factory}\".");

            connection.ConnectionString = connectionString;
            using (connection)
            {
                return connection.IsAvailable();
            }
        }

        public static bool IsAvailable(this IDbConnection connection)
        {
            try
            {
                connection.Open();
                connection.Close();
            }
            catch (DbException e)
            {
                // Don't swallow this error, the exception is super handy for knowing "why" its not available
                StaticApplicationLogging.Logger.LogWarning(e, "Configured database is reporting as not being available.");
                return false;
            }

            return true;
        }

        /// <summary>
        /// Unwraps a database connection.
        /// </summary>
        /// <remarks>UmbracoDatabase wraps the original database connection in various layers (see
        /// OnConnectionOpened); this unwraps and returns the original database connection.</remarks>
        internal static IDbConnection UnwrapUmbraco(this IDbConnection connection)
        {
            var unwrapped = connection;

            IDbConnection c;
            do
            {
                c = unwrapped;

                if (unwrapped is ProfiledDbConnection profiled)
                {
                    unwrapped = profiled.WrappedConnection;
                }

                if (unwrapped is RetryDbConnection retrying)
                {
                    unwrapped = retrying.Inner;
                }
            }
            while (c != unwrapped);

            return unwrapped;
        }
    }
}