Health Endpoint for DAB Engine

src/Config/Converters/DataSourceConverterFactory.cs

@@ -47,7 +47,7 @@ public DataSourceConverter(bool replaceEnvVar)
 
         public override DataSource? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
         {
-            DataSource dataSource = new(DatabaseType.MSSQL, string.Empty, null);
+            DataSource dataSource = new(DatabaseType.MSSQL, string.Empty, null, null);
             if (reader.TokenType is JsonTokenType.StartObject)
             {
 
@@ -114,6 +114,18 @@ public DataSourceConverter(bool replaceEnvVar)
                                     dataSource = dataSource with { Options = optionsDict };
                                     break;
                                 }
+                            case "health":
+                                if (reader.TokenType == JsonTokenType.Null)
+                                {
+                                    dataSource = dataSource with { Health = null };
+                                }
+                                else
+                                {
+                                    DabHealthCheckConfig health = JsonSerializer.Deserialize<DabHealthCheckConfig>(ref reader, options) ?? new();
+                                    dataSource = dataSource with { Health = health };
+                                }
+
+                                break;
                             default:
                                 throw new JsonException($"Unexpected property {propertyName} while deserializing DataSource.");
                         }

src/Config/ObjectModel/DataSource.cs

@@ -12,7 +12,12 @@ namespace Azure.DataApiBuilder.Config.ObjectModel;
 /// <param name="DatabaseType">Type of database to use.</param>
 /// <param name="ConnectionString">Connection string to access the database.</param>
 /// <param name="Options">Custom options for the specific database. If there are no options, this could be null.</param>
-public record DataSource(DatabaseType DatabaseType, string ConnectionString, Dictionary<string, object?>? Options)
+/// <param name="Health">Health check configuration for the database. In case null, follow old format of health check.</param>
+public record DataSource(
+    DatabaseType DatabaseType,
+    string ConnectionString,
+    Dictionary<string, object?>? Options,
+    DabHealthCheckConfig? Health = null)
 {
     /// <summary>
     /// Converts the <c>Options</c> dictionary into a typed options object.

src/Config/ObjectModel/Entity.cs

@@ -19,6 +19,7 @@ namespace Azure.DataApiBuilder.Config.ObjectModel;
 /// <param name="Mappings">Defines mappings between database fields and GraphQL and REST fields.</param>
 /// <param name="Cache">Defines whether to allow caching for a read operation's response and
 /// how long that response should be valid in the cache.</param>
+/// <param name="Health">Defines the health check configuration for the entity.</param>
 public record Entity
 {
     public const string PROPERTY_PATH = "path";
@@ -31,6 +32,7 @@ public record Entity
     public Dictionary<string, string>? Mappings { get; init; }
     public Dictionary<string, EntityRelationship>? Relationships { get; init; }
     public EntityCacheOptions? Cache { get; init; }
+    public DabHealthCheckConfig? Health { get; init; }
 
     [JsonIgnore]
     public bool IsLinkingEntity { get; init; }
@@ -44,6 +46,7 @@ public Entity(
         Dictionary<string, string>? Mappings,
         Dictionary<string, EntityRelationship>? Relationships,
         EntityCacheOptions? Cache = null,
+        DabHealthCheckConfig? Health = null,
         bool IsLinkingEntity = false)
     {
         this.Source = Source;
@@ -53,6 +56,7 @@ public Entity(
         this.Mappings = Mappings;
         this.Relationships = Relationships;
         this.Cache = Cache;
+        this.Health = Health;
         this.IsLinkingEntity = IsLinkingEntity;
     }
 

src/Config/ObjectModel/HealthCheck/DabConfigurationDetails.cs

@@ -0,0 +1,18 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+namespace Azure.DataApiBuilder.Config.ObjectModel
+{
+    /// <summary>
+    /// The health report of the DAB Enigne.
+    /// </summary>
+    public record DabConfigurationDetails
+    {
+        public bool Rest { get; init; }
+        public bool GraphQL { get; init; }
+        public bool Caching { get; init; }
+        public bool Telemetry { get; init; }
+        public HostMode Mode { get; init; }
+        public required string DabSchema { get; init; }
+    }
+}

src/Config/ObjectModel/HealthCheck/DabHealthCheckConfig.cs

@@ -0,0 +1,20 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using System.Text.Json.Serialization;
+
+namespace Azure.DataApiBuilder.Config.ObjectModel;
+
+public record DabHealthCheckConfig
+{
+    public bool Enabled { get; set; } // Default value: false
+    public string? Moniker { get; set; }
+    public string? Query { get; set; } // "query: "SELECT TOP 1 1"
+
+    [JsonPropertyName("threshold-ms")]
+    public int? ThresholdMs { get; set; } // (Default: 10000ms)
+    public string Role { get; set; } = "*"; // "roles": ["anonymous", "authenticated"] (Default: *)
+
+    [JsonPropertyName("max-dop")]
+    public int MaxDop { get; set; } = 1; // Parallelized streams to run Health Check (Default: 1)
+}

src/Config/ObjectModel/HealthCheck/DabHealthCheckReport.cs

@@ -0,0 +1,45 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using System.Text.Json.Serialization;
+
+namespace Azure.DataApiBuilder.Config.ObjectModel
+{
+    [JsonConverter(typeof(JsonStringEnumConverter))]
+    public enum HealthStatus
+    {
+        Healthy,
+        Unhealthy
+    }
+
+    /// <summary>
+    /// The health report of the DAB Enigne.
+    /// </summary>
+    public record DabHealthCheckReport
+    {
+        /// <summary>
+        /// The health status of the service.
+        /// </summary>
+        public HealthStatus HealthStatus { get; init; }
+
+        /// <summary>
+        /// The version of the service.
+        /// </summary>
+        public string? Version { get; set; }
+
+        /// <summary>
+        /// The name of the dab service.
+        /// </summary>
+        public string? AppName { get; set; }
+
+        /// <summary>
+        /// The configuration details of the dab service.
+        /// </summary>
+        public DabConfigurationDetails? DabConfigurationDetails { get; set; }
+
+        /// <summary>
+        /// The health check results of the dab service.
+        /// </summary>
+        public DabHealthCheckResults? HealthCheckResults { get; set; }
+    }
+}

src/Config/ObjectModel/HealthCheck/DabHealthCheckResults.cs

@@ -0,0 +1,29 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+namespace Azure.DataApiBuilder.Config.ObjectModel
+{
+    /// <summary>
+    /// The health report of the DAB Enigne.
+    /// </summary>
+    public record DabHealthCheckResults
+    {
+        public List<HealthCheckResultEntry>? DataSourceHealthCheckResults { get; init; }
+        public List<HealthCheckResultEntry>? EntityHealthCheckResults { get; init; }
+    }
+
+    public class HealthCheckResultEntry
+    {
+        public string? Name { get; init; }
+        public HealthStatus HealthStatus { get; init; }
+        public string? Description { get; init; }
+        public string? Exception { get; init; }
+        public ResponseTimeData? ResponseTimeData { get; init; }
+    }
+
+    public class ResponseTimeData
+    {
+        public int? ResponseTimeMs { get; init; }
+        public int? MaxAllowedResponseTimeMs { get; init; }
+    }
+}

src/Config/ObjectModel/HostMode.cs

@@ -1,8 +1,11 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
+using System.Text.Json.Serialization;
+
 namespace Azure.DataApiBuilder.Config.ObjectModel;
 
+[JsonConverter(typeof(JsonStringEnumConverter))]
 public enum HostMode
 {
     Development,

src/Config/ObjectModel/RuntimeOptions.cs

@@ -15,6 +15,7 @@ public record RuntimeOptions
     public TelemetryOptions? Telemetry { get; init; }
     public EntityCacheOptions? Cache { get; init; }
     public PaginationOptions? Pagination { get; init; }
+    public DabHealthCheckConfig? Health { get; init; }
 
     [JsonPropertyName("log-level")]
     public LogLevelOptions? LoggerLevel { get; init; }

src/Service.Tests/dab-config.MsSql.json

@@ -3728,4 +3728,4 @@
       }
     }
   }
-}
+}

src/Service/HealthCheck/EnhancedFormat/EnhancedHealthReportResponseWriter.cs

@@ -0,0 +1,87 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using System.IO;
+using System.Text.Json;
+using System.Threading.Tasks;
+using Azure.DataApiBuilder.Config.ObjectModel;
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+using Microsoft.Extensions.Logging;
+
+namespace Azure.DataApiBuilder.Service.HealthCheck
+{
+    /// <summary>
+    /// Creates a JSON response for the health check endpoint using the provided health report.
+    /// If the response has already been created, it will be reused.
+    /// </summary>
+    public class EnhancedHealthReportResponseWriter
+    {
+        // Dependencies
+        private ILogger? _logger;
+        private HealthCheckUtlity _healthCheckUtlity;
+
+        // Constants
+        private const string JSON_CONTENT_TYPE = "application/json; charset=utf-8";
+
+        public EnhancedHealthReportResponseWriter(ILogger<HealthReportResponseWriter>? logger, HealthCheckUtlity healthCheckUtlity)
+        {
+            _logger = logger;
+            _healthCheckUtlity = healthCheckUtlity;
+        }
+
+        /* {
+        "runtime" : {
+            "health" : {
+                "enabled": true, (default: true)
+                "cache-ttl": 5, (optional default: 5)
+                "max-dop": 5, (optional default: 1)
+                "roles": ["anonymous", "authenticated"] (optional default: *)
+            }
+        },            
+        {
+        "data-source" : {
+            "health" : {
+                "moniker": "sqlserver", (optional default: NULL) 
+                "enabled": true, (default: true)
+                "query": "SELECT TOP 1 1", (option)
+                "threshold-ms": 100 (optional default: 10000)
+            }
+        },
+        {
+        "<entity-name>": {
+            "health": {
+                "enabled": true, (default: true)
+                "filter": "Id eq 1" (optional default: null),
+                "first": 1 (optional default: 1),
+                "threshold-ms": 100 (optional default: 10000)
+            }
+        } */
+        /// <summary>
+        /// Function provided to the health check middleware to write the response.
+        /// </summary>
+        /// <param name="context">HttpContext for writing the response.</param>
+        /// <param name="healthReport">Result of health check(s).</param>
+        /// <param name="config">Result of health check(s).</param>
+        /// <returns>Writes the http response to the http context.</returns>
+        public Task WriteResponse(HttpContext context, HealthReport healthReport, RuntimeConfig config)
+        {
+            context.Response.ContentType = JSON_CONTENT_TYPE;
+            LogTrace("Writing health report response.");
+            DabHealthCheckReport dabHealthCheckReport = _healthCheckUtlity.GetHealthCheckResponse(healthReport, config);
+            return context.Response.WriteAsync(JsonSerializer.Serialize(dabHealthCheckReport, options: new JsonSerializerOptions { WriteIndented = true, DefaultIgnoreCondition = System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingNull }));
+        }
+
+        /// <summary>
+        /// Logs a trace message if a logger is present and the logger is enabled for trace events.
+        /// </summary>
+        /// <param name="message">Message to emit.</param>
+        private void LogTrace(string message)
+        {
+            if (_logger is not null && _logger.IsEnabled(LogLevel.Trace))
+            {
+                _logger.LogTrace(message);
+            }
+        }
+    }
+}