Added PostgreSql health check support

HealthChecks.sln

@@ -1,7 +1,7 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio 15
-VisualStudioVersion = 15.0.26228.9
+VisualStudioVersion = 15.0.27130.2010
 MinimumVisualStudioVersion = 15.0.26228.4
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "samples", "samples", "{E05DCF88-F916-4B61-A5DC-A8344C9E2429}"
 EndProject
@@ -25,6 +25,8 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.AspNet.HealthChec
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "SampleHealthChecker.AspNet", "samples\SampleHealthChecker.AspNet\SampleHealthChecker.AspNet.csproj", "{33FB5967-62C7-4230-B515-780EF63F748E}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Microsoft.Extensions.HealthChecks.PostgreSql", "src\Microsoft.Extensions.HealthChecks.PostgreSql\Microsoft.Extensions.HealthChecks.PostgreSql.csproj", "{207D3914-5E0D-4970-BB5F-0ED5E08A11D0}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -63,6 +65,10 @@ Global
 		{33FB5967-62C7-4230-B515-780EF63F748E}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{33FB5967-62C7-4230-B515-780EF63F748E}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{33FB5967-62C7-4230-B515-780EF63F748E}.Release|Any CPU.Build.0 = Release|Any CPU
+		{207D3914-5E0D-4970-BB5F-0ED5E08A11D0}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{207D3914-5E0D-4970-BB5F-0ED5E08A11D0}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{207D3914-5E0D-4970-BB5F-0ED5E08A11D0}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{207D3914-5E0D-4970-BB5F-0ED5E08A11D0}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -76,5 +82,9 @@ Global
 		{13BE838A-200B-4A68-8F58-3EA3BE3A1A8A} = {F9BA869A-7D5F-420F-9505-2D881F7934A7}
 		{2AE82E1C-6CE1-4755-A332-FA359B7CCE72} = {F9BA869A-7D5F-420F-9505-2D881F7934A7}
 		{33FB5967-62C7-4230-B515-780EF63F748E} = {E05DCF88-F916-4B61-A5DC-A8344C9E2429}
+		{207D3914-5E0D-4970-BB5F-0ED5E08A11D0} = {F9BA869A-7D5F-420F-9505-2D881F7934A7}
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {AB38C3CE-2846-4064-A914-D776DFC8F1E0}
 	EndGlobalSection
 EndGlobal

src/Microsoft.Extensions.HealthChecks.PostgreSql/HealthCheckBuilderPostgreSqlExtensions.cs

@@ -0,0 +1,48 @@
+using System;
+using System.Data;
+using Npgsql;
+
+namespace Microsoft.Extensions.HealthChecks.PostgreSql
+{
+    public static class HealthCheckBuilderPostgreSqlExtensions
+    {
+        public static HealthCheckBuilder AddPostgreSqlCheck(this HealthCheckBuilder builder, string name, string connectionString)
+        {
+            Guard.ArgumentNotNull(nameof(builder), builder);
+
+            return AddPostgreSqlCheck(builder, name, connectionString, builder.DefaultCacheDuration);
+        }
+
+        public static HealthCheckBuilder AddPostgreSqlCheck(this HealthCheckBuilder builder, string name, string connectionString, TimeSpan cacheDuration)
+        {
+            builder.AddCheck($"PostgreSqlCheck({name})", async () =>
+            {
+                try
+                {
+                    using (var connection = new NpgsqlConnection(connectionString))
+                    {
+                        connection.Open();
+                        using (var command = connection.CreateCommand())
+                        {
+                            command.CommandType = CommandType.Text;
+                            command.CommandText = "SELECT 1";
+                            var result = (int)await command.ExecuteScalarAsync().ConfigureAwait(false);
+                            if (result == 1)
+                            {
+                                return HealthCheckResult.Healthy($"PostgreSqlCheck({name}): Healthy");
+                            }
+
+                            return HealthCheckResult.Unhealthy($"PostgreSqlCheck({name}): Unhealthy");
+                        }
+                    }
+                }
+                catch (Exception ex)
+                {
+                    return HealthCheckResult.Unhealthy($"PostgreSqlCheck({name}): Exception during check: {ex.GetType().FullName}");
+                }
+            }, cacheDuration);
+
+            return builder;
+        }
+    }
+}

src/Microsoft.Extensions.HealthChecks.PostgreSql/Microsoft.Extensions.HealthChecks.PostgreSql.csproj

@@ -0,0 +1,20 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>netstandard1.3</TargetFramework>
+    <ApplicationIcon />
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="..\common\Guard.cs" Link="Internal\Guard.cs" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Npgsql" Version="3.2.6" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Microsoft.Extensions.HealthChecks\Microsoft.Extensions.HealthChecks.csproj" />
+  </ItemGroup>
+
+</Project>

src/Microsoft.Extensions.HealthChecks.SqlServer/HealthCheckBuilderSqlServerExtensions.cs

@@ -27,7 +27,7 @@ public static HealthCheckBuilder AddSqlCheck(this HealthCheckBuilder builder, st
                     //TODO: There is probably a much better way to do this.
                     using (var connection = new SqlConnection(connectionString))
                     {
-                        connection.Open();
+                        await connection.OpenAsync();
                         using (var command = connection.CreateCommand())
                         {
                             command.CommandType = CommandType.Text;