PIDP-775 HealthCheck endpoints for PlrIntake (#421)

* Liveness and readiness endpoint

* nl

---------

Co-authored-by: James Hollinger <39168456+james-hollinger@users.noreply.github.com>

backend/services.plr-intake/Infrastructure/HealthChecks/HealthCheckTag.cs

@@ -0,0 +1,23 @@
+
+namespace PlrIntake.Infrastructure.HealthChecks;
+
+public class HealthCheckTag
+{
+    /// <summary>
+    /// Represents a "liveness" check.
+    /// A service that fails a liveness check is considered to be unrecoverable and has to be restarted by the orchestrator.
+    /// </summary>
+    public static readonly HealthCheckTag Liveness = new("liveness");
+
+    /// <summary>
+    /// Represents a "readiness" check.
+    /// A service that fails a readiness check is considered to be unable to serve traffic temporarily.
+    /// </summary>
+    public static readonly HealthCheckTag Readiness = new("readiness");
+
+    public string Value { get; }
+
+    private HealthCheckTag(string value) => this.Value = value;
+
+    public static implicit operator string(HealthCheckTag type) => type.Value;
+}

backend/services.plr-intake/Startup.cs

@@ -1,6 +1,8 @@
 namespace PlrIntake;
 
 using FluentValidation.AspNetCore;
+using HealthChecks.ApplicationStatus.DependencyInjection;
+using Microsoft.AspNetCore.Diagnostics.HealthChecks;
 using Microsoft.EntityFrameworkCore;
 using Serilog;
 using SoapCore;
@@ -11,6 +13,7 @@ namespace PlrIntake;
 using PlrIntake.Data;
 using PlrIntake.Features;
 using PlrIntake.Features.Intake;
+using PlrIntake.Infrastructure.HealthChecks;
 
 public class Startup
 {
@@ -40,7 +43,9 @@ public void ConfigureServices(IServiceCollection services)
         services.AddSoapServiceOperationTuner(new IntakeServiceOperationTuner(config));
         services.AddSoapCore();
 
-        services.AddHealthChecks();
+        services.AddHealthChecks()
+            .AddApplicationStatus(tags: new[] { HealthCheckTag.Liveness.Value })
+            .AddNpgSql(config.ConnectionStrings.PlrDatabase, tags: new[] { HealthCheckTag.Readiness.Value });
     }
 
     private PlrIntakeConfiguration InitializeConfiguration(IServiceCollection services)
@@ -85,7 +90,14 @@ public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
         {
             endpoints.UseSoapEndpoint<IIntakeService>("/api/PLRHL7", intakeBinding, SoapSerializer.XmlSerializer);
             endpoints.MapControllers();
-            endpoints.MapHealthChecks("/health/liveness").AllowAnonymous();
+            endpoints.MapHealthChecks("/health/liveness", new HealthCheckOptions
+            {
+                Predicate = registration => registration.Tags.Contains(HealthCheckTag.Liveness)
+            }).AllowAnonymous();
+            endpoints.MapHealthChecks("/health/readiness", new HealthCheckOptions
+            {
+                Predicate = registration => registration.Tags.Contains(HealthCheckTag.Readiness)
+            }).AllowAnonymous();
         });
     }
 }

backend/services.plr-intake/plr-intake.csproj

@@ -6,6 +6,7 @@
     <RootNamespace>PlrIntake</RootNamespace>
   </PropertyGroup>
   <ItemGroup>
+    <PackageReference Include="AspNetCore.HealthChecks.ApplicationStatus" Version="6.0.0" />
     <PackageReference Include="AspNetCore.HealthChecks.NpgSql" Version="6.0.2" />
     <PackageReference Include="DomainResult" Version="2.0.0" />
     <PackageReference Include="FluentValidation" Version="10.3.6" />