From e7917f8270981b47669966ed34c2a23f5c1e5d64 Mon Sep 17 00:00:00 2001
From: Bradley Grainger <bgrainger@gmail.com>
Date: Fri, 17 Nov 2023 07:07:43 -0800
Subject: [PATCH] Send a MySQL ping packet by default. Fixes #2031

Users can opt in to setting a command that will be executed on the server, but the default is now a more efficient ping.
---
 .../MySqlHealthCheckBuilderExtensions.cs      |  9 ++++----
 src/HealthChecks.MySql/MySqlHealthCheck.cs    | 23 +++++++++++++------
 .../MySqlHealthCheckOptions.cs                |  3 +--
 3 files changed, 21 insertions(+), 14 deletions(-)

diff --git a/src/HealthChecks.MySql/DependencyInjection/MySqlHealthCheckBuilderExtensions.cs b/src/HealthChecks.MySql/DependencyInjection/MySqlHealthCheckBuilderExtensions.cs
index 09e2fac106..0b755f37bd 100644
--- a/src/HealthChecks.MySql/DependencyInjection/MySqlHealthCheckBuilderExtensions.cs
+++ b/src/HealthChecks.MySql/DependencyInjection/MySqlHealthCheckBuilderExtensions.cs
@@ -10,14 +10,13 @@ namespace Microsoft.Extensions.DependencyInjection;
 public static class MySqlHealthCheckBuilderExtensions
 {
     private const string NAME = "mysql";
-    internal const string HEALTH_QUERY = "SELECT 1;";
 
     /// <summary>
     /// Add a health check for MySQL databases.
     /// </summary>
     /// <param name="builder">The <see cref="IHealthChecksBuilder"/>.</param>
     /// <param name="connectionString">The MySQL connection string to be used.</param>
-    /// <param name="healthQuery">The query to be executed.</param>
+    /// <param name="healthQuery">The optional query to be executed. If this is <c>null</c>, a MySQL "ping" packet will be sent to the server instead of a query.</param>
     /// <param name="configure">An optional action to allow additional MySQL specific configuration.</param>
     /// <param name="name">The health check name. Optional. If <c>null</c> the type name 'mysql' will be used for the name.</param>
     /// <param name="failureStatus">
@@ -30,7 +29,7 @@ public static class MySqlHealthCheckBuilderExtensions
     public static IHealthChecksBuilder AddMySql(
         this IHealthChecksBuilder builder,
         string connectionString,
-        string healthQuery = HEALTH_QUERY,
+        string? healthQuery = null,
         Action<MySqlConnection>? configure = null,
         string? name = default,
         HealthStatus? failureStatus = default,
@@ -45,7 +44,7 @@ public static IHealthChecksBuilder AddMySql(
     /// </summary>
     /// <param name="builder">The <see cref="IHealthChecksBuilder"/>.</param>
     /// <param name="connectionStringFactory">A factory to build the MySQL connection string to use.</param>
-    /// <param name="healthQuery">The query to be executed.</param>
+    /// <param name="healthQuery">The optional query to be executed. If this is <c>null</c>, a MySQL "ping" packet will be sent to the server instead of a query.</param>
     /// <param name="configure">An optional action to allow additional MySQL specific configuration.</param>
     /// <param name="name">The health check name. Optional. If <c>null</c> the type name 'mysql' will be used for the name.</param>
     /// <param name="failureStatus">
@@ -58,7 +57,7 @@ public static IHealthChecksBuilder AddMySql(
     public static IHealthChecksBuilder AddMySql(
         this IHealthChecksBuilder builder,
         Func<IServiceProvider, string> connectionStringFactory,
-        string healthQuery = HEALTH_QUERY,
+        string? healthQuery = null,
         Action<MySqlConnection>? configure = null,
         string? name = default,
         HealthStatus? failureStatus = default,
diff --git a/src/HealthChecks.MySql/MySqlHealthCheck.cs b/src/HealthChecks.MySql/MySqlHealthCheck.cs
index fb7f433193..8bb4b3b4a7 100644
--- a/src/HealthChecks.MySql/MySqlHealthCheck.cs
+++ b/src/HealthChecks.MySql/MySqlHealthCheck.cs
@@ -13,7 +13,6 @@ public class MySqlHealthCheck : IHealthCheck
     public MySqlHealthCheck(MySqlHealthCheckOptions options)
     {
         Guard.ThrowIfNull(options.ConnectionString, true);
-        Guard.ThrowIfNull(options.CommandText, true);
         _options = options;
     }
 
@@ -27,13 +26,23 @@ public async Task<HealthCheckResult> CheckHealthAsync(HealthCheckContext context
             _options.Configure?.Invoke(connection);
             await connection.OpenAsync(cancellationToken).ConfigureAwait(false);
 
-            using var command = connection.CreateCommand();
-            command.CommandText = _options.CommandText;
-            object? result = await command.ExecuteScalarAsync(cancellationToken).ConfigureAwait(false);
+            if (_options.CommandText is { } commandText)
+            {
+                using var command = connection.CreateCommand();
+                command.CommandText = _options.CommandText;
+                object? result = await command.ExecuteScalarAsync(cancellationToken).ConfigureAwait(false);
 
-            return _options.HealthCheckResultBuilder == null
-                ? HealthCheckResult.Healthy()
-                : _options.HealthCheckResultBuilder(result);
+                return _options.HealthCheckResultBuilder == null
+                    ? HealthCheckResult.Healthy()
+                    : _options.HealthCheckResultBuilder(result);
+            }
+            else
+            {
+                var success = await connection.PingAsync(cancellationToken).ConfigureAwait(false);
+                return _options.HealthCheckResultBuilder is null
+                    ? (success ? HealthCheckResult.Healthy() : new HealthCheckResult(context.Registration.FailureStatus)) :
+                    _options.HealthCheckResultBuilder(success);
+            }
         }
         catch (Exception ex)
         {
diff --git a/src/HealthChecks.MySql/MySqlHealthCheckOptions.cs b/src/HealthChecks.MySql/MySqlHealthCheckOptions.cs
index d8a1f073d7..47d2629620 100644
--- a/src/HealthChecks.MySql/MySqlHealthCheckOptions.cs
+++ b/src/HealthChecks.MySql/MySqlHealthCheckOptions.cs
@@ -1,4 +1,3 @@
-using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Diagnostics.HealthChecks;
 using MySqlConnector;
 
@@ -17,7 +16,7 @@ public class MySqlHealthCheckOptions
     /// <summary>
     /// The query to be executed.
     /// </summary>
-    public string CommandText { get; set; } = MySqlHealthCheckBuilderExtensions.HEALTH_QUERY;
+    public string? CommandText { get; set; }
 
     /// <summary>
     /// An optional action executed before the connection is opened in the health check.